WO2011040986A1

WO2011040986A1 - System and method for offset guidance in pedicle screw stabilization of spinal vertebrae

Info

Publication number: WO2011040986A1
Application number: PCT/US2010/029199
Authority: WO
Inventors: Sherwin Hua
Original assignee: Sherwin Hua
Priority date: 2009-09-30
Filing date: 2010-03-30
Publication date: 2011-04-07

Abstract

An improved system and method for positioning screws and rods to immobilize bones are provided. Specifically, the system and method are optimal for performing transforaminal lumbar interbody fusion (TLIF) and other interbody fusions in the spine. The system involves pedicle screws detachably connected to different types of upwardly extended guidance elements (tabs, blades, strings, wires, towers, etc.) that guide rods down to screws. The guidance elements may be mounted on the inside, outside, or at any position around the screw head. In this manner, the guidance elements for adjacent screws can be offset such that they can intersect without interference to permit introduction through fewer incisions. Locking assemblies and mechanisms are provided to retain the rod in the screw head, including capless locking without a set screw in which the locking mechanism is integrated into the screw head itself for a streamlined procedure.

Description

SYSTEM AND METHOD FOR OFFSET GUIDANCE IN PEDICLE SCREW

STABILIZATION OF SPINAL VERTEBRAE

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to medical devices, systems and methods for bone fixation. Specifically, the invention is directed to stabilize adjoining vertebrae in the cervical, thoracic, and lumbosacral spine. More specifically, the invention is directed to fusion or stabilization of vertebrae in the lumbar spine to alleviate axial back pain. Most specifically, the invention is directed to improving minimally invasive surgical (MIS) approaches to pedicle screw fusion by reducing the number and size of incisions and the size of the medical instruments inserted therein.

Description of the Related Art

[0002] While some lower back conditions can be ameliorated with non-surgical approaches, spinal fusion is recommended for certain conditions when non-surgical approaches fail. Non-surgical approaches include medications, physical therapy, chiropractic treatment, traction, epidural steroid injections, facet blocks or rhizotomy, weight loss, smoking cession, and acupuncture. Conditions that commonly serve as indications for spinal fusion or stabilization surgery can be divided generally into three categories: (i) trauma induced, (ii) curvature, and (iii) degenerative.

[0003] Trauma induced conditions include fractures and ligamentous injuries. Fractures typically result from an unfortunate incident involving an extraneous force or fall but may also arise from pathologic conditions, such as cancer or osteoporosis. Fractures are often compressive in nature and typically lead to a pathological curving of the spine resulting in a loss of the natural lordotic curvature in the lumbar and cervical spine, known as kyphosis. Fractures of the spine also occur with translational or rotational forces perpendicular to the axis of the spine. These forces result in fractures of the facet or pars interarticularis (pars). If the external forces are large enough, vertebrae can collapse resulting in a burst fracture that can injure all 3 columns of the vertebrae (anterior, middle, and posterior columns). Many traumatic injuries can heal without surgery, but unstable injuries that pose a risk for neurologic injury and/or pain require stabilization through a procedure such as fusion.

[0004] A condition called spondylolisthesis characterized by slippage of the spine bones or vertebrae relative to one another can result from fractures of the pars interarticularis (pars fracture) known as spondylolysis. Spondylolisthesis can also develop from malformation of the facet joints by degenerative arthritis as well as congenital malformation and pathologic conditions such as tumors. If the pars on both sides are fractured, then the spinous process and lamina are essentially completely disconnected from the pedicle and vertebral body. This large fragment is called the Gill body. Pars fractures are actually common in people of all ages (often acquired in the teenage years). While, many of these patients are mildly symptomatic and do not require surgery, those with progressive symptoms may require surgical decompression with or without fusion. Spondylolisthesis results in misalignment of the spine and increases the risk of a nerve becoming entrapped. Nerves travel within the spinal canal bounded by the vertebrae and their roots protrude from the curved openings in the sides of the vertebrae called foramina (singular is foramen). These spinal nerves are suspected to be the source of back and radicular pain when they become entrapped or when the nerve endings become irritated by irregular or abrasive motion around a disc, bone, or joint. Spondylolisthesis can also aggravate or be accompanied by degeneration of disc or facet joint which can lead to axial back pain.

[0005J The normal curvature of the lumbar and cervical spine is lordosis, where the posterior aspect of these spinal levels forms a concave curve. The thoracic spine normally has a kyphotic or convex curve. Curvature conditions include straightening of the natural curvature as well as abnormal lordosis, abnormal kyphosis or lateral/ rotational bending called scoliosis. Curvature conditions can occur idiopathically during adolescence, i.e. adolescent idiopathic scoliosis, or develop as a secondary problem in situations where spinal muscle activation is abnormal such as cerebral palsy, spina bifida, or tethered cord syndrome. Abnormal spinal curvature is common in spinal degeneration when the discs and joints degenerate asymmetrically leading to a progressive curvature (scoliosis, kyphosis, or lordosis) as the biomechanics of the spine are disrupted. Curvature conditions also occur after trauma with compression or burst fractures or with ligamentous injury. Additionally, curvature conditions can occur iatrogenically after previous spinal surgery where the anatomy and biomechanics of the spine have been altered. Such situations include the removal of the posterior tension band after laminectomy as well as the alteration of physiologic movement after spinal fusion leading to adjacent level compensation and degeneration. Curvature conditions lead to abnormal biomechanical stress on the discs and facet joints accompanied by compensatory measures such as facet or ligamentous hypertrophy. Patients can develop both axial back pain and radicular pain. In patients who have failed conservative therapy and bracing, surgery can be effective. Surgery in these conditions includes decompression of nerve or spinal cord compression as well as fusion or stabilization. Curvature can be corrected through surgery, and fusion prevents further curvature from developing.

[0006] Degenerative conditions include spinal arthritis and recurrent disc herniation. Spinal arthritis is the most common indication for fusion and. may exist in the form of severe disc degeneration (also called. Degenerative Disc Disease, DDD) or facet disease. Degenerative arthritis can also be a cause of spondylolisthesis in addition to traumatic fractures discussed above. Degenerative conditions are generally accompanied by nerve compression causing radicular pain in the distribution of the nerve^'s receptive field, which usually correlates with and. is manifested in arm or leg pain. Pure nerve compression syndromes such as herniated nucleus pulposus (herniated discs) or foraminal stenosis (narrowing of the side foramina canals through which the nerves pass) can often be treated with decompression without fusion. Pure disc degeneration syndromes can be treated with fusion without decompression of the nerves. However, most commonly disc degeneration occurs in combination with nerve compression causing both axial back pain and radicular limb pain. In these circumstances fusion surgery is combined with nerve decompression surgery.

[0007] Fusion functions to eliminate motion in the disc space and facet joints between adjacent vertebrae. The vertebrae provide the rigid structural framework of the spine and the fibrocartilaginous disc space acts as a cushion or shock-absorber. Degradation of the disc space can distort alignment and alter the biomechanical cushion that the disc affords the adjacent vertebrae. This degradation alters the forces impacted upon the vertebrae and results in axial back pain. Fusion is designed to eliminate movement between adjacent vertebrae by either forming a solid bridge of bone across the disk space and/ or creating new bone formation in the posterolateral space to provide stabilization, rigidity, and strength. Sometimes fusion involves a bone graft taken from another location in the body (i.e. autograft from the iliac crest in the pelvis) or from an external source, i.e. allograft. Physicians commonly refer to the level of a fusion. A single level fusion involves stabilizing the two vertebral bones adjacent to a diseased disc. A two- level fusion involves stabilizing three adjacent vertebral bones spanning two problematic disc spaces. Each vertebra makes contacts (joints) with adjacent vertebrae at three points, the paired facet joints located posteriorly and the intervertebral disc located anteriorly. Thus, lumbar fusion can be directed either at the posterior facet joints or at the anterior interbody/ disc space or both. When an anterior interbody fusion is performed in combination with posterior fusion, the procedure is termed 360° fusion. One commonly used technique of posterolateral fusion is pedicle screw fusion where screws are directed into the pedicle portions and the bodies of adjacent vertebrae and then rods are connected to the screws across the disc spaces. The screws and rods hold the adjacent vertebrae motionless relative to one another and allow the bone graft that is placed either in the interbody (disc) space or in the posterolateral space to grow into solid bone. Conventional pedicle screws and rods are metal, typically titanium (Ti) alloy but have been made from stainless steel as well. Recently rods have been made from a minimally flexible polymer called polyetheretherketone (PEEK).

Interbody fusion Involves placing one or more spacers (typically pre-loaded with bone graft material) within the interbody (disc) space between bony vertebral bodies after the degenerated disc has been cleaned out and removed. Spacers are made from bone grafts, titanium, carbon fiber, or polymers such as PEEK. Interbody fusion can be performed through several approaches including: an anterior approach (anterior lumbar interbody fusion, ALIF), a posterior approach (posterior lumber interbody fusion, PLIF, or transforaminal lumbar interbody fusion, TLIF), or a lateral approach (direct lateral interbody fusion, DLIF™ - Medtronic, or extreme lateral interbody fusion, XLIF™ - Nuvasive). The aim of these approaches is to remove the degenerated disc and replace the disc with material that induces bony fusion. Alternatively the disc can be replaced with an artificial joint/ disc (discussed below). Each of these interbody approaches has advantages and disadvantages. Anterior procedures require a retroperitoneal dissection and risk injury to the large blood vessels anterior to the lumbar vertebrae. Also injury to the nerve plexus anterior to the vertebrae can result in sexual dysfunction. The lateral approach is promising but is limited to the upper and mid lumbar levels (rostral to L5,S 1) because of obstruction by the iliac crest. The posterior interbody approach is more time consuming and typically requires more muscle dissection and retraction. However, the posterior approach allows the placement of the interbody graft, posterior pedicle screw fusion, and decompression of nerves all to occur through the posterior incision(s).

[0009] Although anterior and lateral approaches can be perfomied stand-alone (without posterior instrumentation), many surgeons will back-up or supplement anterior or lateral interbody fusions by placing pedicle screws posteriorly after the interbody cage or graft has been placed. This 360° fusion limits movement more than just an isolated anterior or posterior fusion, and fusion rates are increased. However in AL1F and lateral interbody (DLIF, XL1F) cases, two sets of incisions are required for a 360° fusion.

[0010] The posterior approaches (TL1F and PLIF) allow an interbody fusion, pedicle screw fusion, and neural decompression to be done all through the same posterior incision(s). In the TLIF, a single large interbody spacer is inserted on the side ipsilateral to the patient's symptomatic side after neural decompression is completed, if both sides are symptomatic then decompression is required on both sides. A PLIF is performed by placing two interbody spacers, one on each side. Posterior procedures may be done according to: (i) an invasive open procedure in which a large incision and/or several incisions are made, (ii) a percutaneous approach in which small incisions and/or few incisions are made, and potentially (iii) an endoscopic approach in which small incisions are made and all tools and devices are inserted through portals with visualization provided on an external monitor.

[001 1] As an alternative to fusion, recent advances in interbody stabilization have resulted in the development of artificial disc technology. Artificial discs replace the degenerated discs and allow continued motion at the joint Both cervical and lumbar artificial discs have been developed. Additionally, dynamic stabilization techniques have been developed for the posterior spine. These posterior techniques utilize pedicle screws and a dynamic rod. Typically the dynamic rod has a mechanism to bend under certain loads or forces, thereby absorbing some stress and strain that is applied to the spine. The advantage of dynamic stabilization is that motion is preserved in the spine. However, the durability of these systems may be an issue. In fusions, the bone graft (interbody or posterolateral) eventually fuses the vertebrae eliminating the need for the spinal instrumentation (screws and rods). However in dynamic stabilization, fusion does not occur, so the screws and dynamic rods will always be subjected to the strain and forces of the spine. Over time the possibility of loosening of the pedicle screws or mechanical failure may increase. Sometimes the use of a slightly flexible rod such as a rod made of PEEK may actually increase fusion by reducing stress shielding. Stress shielding occurs when rigid fusion, constructs shield the vertebral bone in contact with the bone graft from the stresses required to form and remodel bone.

Posterior lumber stabilization (fusion and dynamic stabilization) techniques have evolved, into minimally invasive approaches because such minimized exposures reduce patient morbidity and facilitate patients¹ recovery to function. Blood loss and hospital stays are shorter. The process of performing a minimally invasive pedicle screw fusion is the same as that for dynamic stabilization and involves two basic parts. First, screws are placed percutaneously through the pedicle into the vertebral body. For minimally invasive systems, cannulated screws are placed percutaneously over a fluoroscopically (an X-ray that can be seen on a video screen) guided guidance element. Generally, two screws are used on each vertebral body being fused, one on a right side and the other on a left side. The second part of the process involves connecting the screws with a rod and locking the rod and screws together. In dynamic stabilization, the rod or rod-like device (flexible connector) is bendable, but the process of inserting this bendable rod is the same as that for fusion. For example, a rod-like device (flexible connector), like a rod, fits within the screw heads, but may also include an element (a shock absorber, a spring, etc.) that allows some motion. The variations between different minimally invasive systems mostly arise in the method of placing the rod and locking the rod with the screws through a minimal incision.

[0013] Before the intervertebral body spacer is inserted, the damaged or degenerated disc within the disc space must be removed. In the TLIF approach, the disc space is accessed through a facetectomy in which the foramen around the nerve roots is opened with a bone-cutting tool such as an osteotome or a high speed drill. In the PLIF approach, laminectomies or laminotomies are performed to access the disc space. Both TLIF and PLIF allow for decompression of the spinal thecal sac and the nerve roots; however, the facetectomy in a TLIF allows the maximum decompression of the exiting nerve root on that side. With gentle retraction of the thecal sac, the disc space is easily accessed. Then the instruments used for clearing out the degenerated disc may be inserted into the disc space to complete the discectomy.

[ 0014] Following removal of the disc, the surgeon should prepare the bony surfaces, known as the end plates, of the vertebral bodies on each side of the disc that was removed. Peeling off the end plate with a tool such as a curette induces bleeding which stimulates healing and assimilation of the bone graft to be inserted into the interbody space. The spacer or cage that is to be inserted is typically constructed of bone, titanium, carbon fiber, or polymers such as PEEK. The spacer is usually hollow or at least porous to accommodate bone graft material therein. Bone inducing protein such as bone morphogenetic protein (BMP) is also commonly placed within the spacer. After placing the spacer and bone graft, the rods may be inserted into the pedicle screws and the screws can be tightened to lock the rods in place.

[0015] Typically the placement of the percutaneous screws is fairly straight forward. The insertion of the rod through the screw heads and locking of the rod with the screws are the steps that are currently most difficult through a minimal incision. In most of the minimally invasive surgery (MIS) systems used today, a guidance element, such as a wire, is placed percutaneously under fluoroscopic guidance through the pedicle. Percutaneous cannulated drills and screw taps are inserted over the guidance element/wire to prepare the tract through the pedicle and vertebral body for pedicle screw insertion. Dilating tubes and a guidance tube or a retractor system are often used to dilate and hold open the path around the guidance element through skin and muscle to reduce injury to muscle and tissue when pedicle screws and insertion tools are inserted. Pedicle screws are inserted over the guidance elements either with or without passage through a guidance tube/ retractor. In order to place the rod and locking assembly into the screw heads, each screw head is associated with a tower that extends through the skin incision. The tower has to accommodate the rod and locking assemblies so it is typically larger than the m ttx. i xxx viin diameter of the screw head. Once the towers are in place, the rod is then inserted through one of a variety of methods. The leading MIS system is Sextant™ by Medtronic. In this system, the rod is placed by forming a pendulum like mechanism. The two or three towers (for one or two-level fusion, respectively) are coupled together to align the towers, and the rod is swung around through a separate incision superior or inferior to the towers in a pendulum fashion. Once the rod is swung in place, locking caps are placed through the towers and tightened. Alternatively, most of the other systems insert the rod through one of the towers and then turn the rod approximately 90° to capture the other screws in the other towers. Inserting the rod through the screw heads in a minimally invasive system is done blindly, i.e. without direct visualization of the screw head. Thus this process is sometimes tedious and frustrating.

The Sextant™ system and other systems that use towers are hindered by both the number of incisions required and the size of each incision. The use of a separate tower for each screw requires a separate incision for each tower, or a single incision long enough to accommodate two towers. The Sextant™ system also requires an additional incision for the rod, equaling six incisions (three on each side) for a single level fusion and eight incisions for a two level fusion. The other tower systems that use the direct rod insert and. turn mechanism still require one incision for each screw and each incision has to be larger than the size of a tower through which the screws are inserted. Typically, each incision is at least 15mm in length. When the sum of the lengths of all incisions on both sides are totaled, the total length of the current leading minimally invasive systems often are longer than the single midline incision of a traditional "open" approach for a single or two level pedicle screw fusion. [0017] United States Patent No. (hereinafter USP) 7,306,603 entitled "Device and method. for percutaneous placement of lumbar pedicle screws and connecting rods" by Frank H. Boehm, Jr., et al. and assigned to Innovative Spinal Technologies (Mansfield, MA) discloses a system of connecting a rod to the pedicle screws using a pin and recesses within the screw heads. According to this system the rod can pivot about a longitudinal axis of the pin between a first position in which the rod is parallel to the longitudinal axis of the screw (i.e. vertically oriented) and a second position in which the rod is transverse to that axis in order to bridge screws on adjacent vertebrae. USP '603 teaches various guide systems (see FIG. 5 and 6), rod holder systems (see FIG. 8, 9, 10, and 11), and a rod guide system (see FIG. 12) but does not include a sleek, detachable system among them. Rather, the systems illustrated are tower-like with rather bulky dilators (80 and 86 in FIG. 6 and 8), sheaths (81 in FIG. 6), and/or outer housing (120 in FIG. 11 and 12).

[0018] U.S. Patent Application Publication No. (hereinafter US Pub. No.) 20080140075 entitled "Press-On Pedicle Screw Assembly" by Michael D. Ensign and assigned to Alpinespine, LLC (American Fork, Utah) discloses attaching the rod to screw heads indirectly via a tulip assembly. The tulip assembly has a housing with an inner diameter smaller than an inner diameter of the screw head such that it is easily pressed into position upon the screw head. The rod is then placed by attaching directly to the tulip assembly after connecting the assembly to the screw head. The publication mentions using a Kirschner guidance element (or K-gui dance element) for inserting both the pedicle screws and the tulip member (see [0030], [0032], and

[0045]) but does not disclose how the rods are guided into position.

[00 19] US Pub. No. 20080097457 entitled "Pedicle screw systems and methods of assembling/installing the same" by David R. Warnick and unassigned, like US Pub. No. Ό75, also discloses using a tulip assembly as an intervening means to join a rod to the screws. In this system, rather than a press-on locking mechanism, the structure is tightened by rotating an inner member and outer housing of the tulip assembly relative to one another. USP 7,179,261 entitled "Percutaneous access devices and bone anchor assemblies" by Christopher W, Sicvol, et al. and. assigned to Depuy Spine, Inc. describes one of the several tower systems for placement of pedicle screws percutaneously. The patent describes a situation where the angle of the screws intersect, and the towers may interfere with each other. This situation is rather typical in the lordotic lumbar spine, especially the lumbo-sacral (L5, S I) junction. In order to solve this problem, they describe cut-outs in the tubes so that two tubes can intersect. Given that the angles of the vertebrae are variable from patient to patient and the depth of the vertebrae from the skin is also highly variable, the variations on the cutouts would have to be numerous. Additionally, when two tubes intersect at the cutout as shown in Figure 22B in USP '261, the edges of the cutout of one tube interferes or blocks off the lumen of the other tube, and vice versa. This occurs because the muscle and tissue surrounding the tubes will push the tubes together at the section of the cutouts thereby significantly reducing the lumen through which the rod and other elements are inserted. The only way to avoid this interference or blockage of the lumens is to keep the tubes separate which would necessitate a larger incision and would eliminate the need for cutouts in the first place. The present invention would eliminate the need for "cut-outs." The extended tabs or blades do not have a proximal, distal, or any lumen, and the configuration of guidance elements (extended tabs or blades) for screws at adjacent levels allow the tabs to intersect and overlap completely for any patient with any relative geometries. Thus interference between adjacent guidance elements on adjacent vertebrae is not a problem. Also, in the cut-out tubes taught by USP '261, a rod or other element would still have to be inserted through the tube at some point. The cut-out tubes require that the rod (or other inserted element) is oriented longitudinally parallel to the long axis of the tube as it is directed into the body until it reaches a section with side wall openings or slots distal to the cut-out section, at which point it may optionally be turned perpendicularly to the long axis and directed out of the side wall through the opening or slot. In the present invention by using guidance elements such as extended blades or extended tabs (from the screw head), the element that is guided by them and inserted along them (i.e. a rod, a locking assembly etc.) does not have to be inserted through any lumen. When a rod is inserted using the blades, the blades can simply be fed through the outer edges of the rod body, through a retaining element or clasp attached, to the rod. body, or between the outer edges of the rod body and a retaining element (retention thread). Thus, in the present invention it is possible for the inserted rod or other elements to be oriented perpendicular to the long axis or oriented in any other manner during the entire entry pathway. This provides greater flexibility for avoiding interference between adjacent stabilization system pieces and eliminates the need for a surgeon to identify the cutout sections before turning the screw/rod perpendicularly and/or reorienting it. Furthermore, since there are no lumens proximally or distally with the extended tabs/blades in the present invention, blades from adjacent levels may overlap and intersect without the need for cutout therefore allowing all blades to exit a single small minimal incision.

BRIEF SUMMARY OF THE INVENTION

[0021] The present invention is directed towards improving minimally invasive (optionally adaptable for use with the percutaneous or endoscopic approach) TLIF and PLIF approaches and backing up the ALIF, DLIF, and XLIF approaches. TLIF provides several advantages including: (i) stabilization of both the anterior and posterior portions of the spine through one or more posterior incision(s); (ii) the ability to fill with bone graft material a greater volume and diversity of spaces (front disc space with the spacer, amongst the screws and rods on the sides, and in the back of vertebrae) increasing the chances of a successful stabilization through the development and solidification of bone; (iii) the spacer placed within the front disc space maintains the natural interbody disc height to reduce pressure on nerve roots (from bone spurs, thickened, ligaments, etc.); and (iv) enhanced safety because the spinal canal is accessed from one side only and this reduces the risk of pinching, stretching, or otherwise agitating the spinal nerves.

[0022] The invention provides a Microfusion™ product for performing a minimally invasive posterior and/or transforaminal lumbar pedicle screw fusion or stabilization procedure. Hereinafter references to "fusion" implicitly include stabilization which offers somewhat greater motion short of completely fusing the bone. Likewise, hereinafter references to "stabilization" implicitly include fusion. The main situations in which a surgeon can use the Microfusion™ system are similar to the situations in which the Sextant™ system from Medtronic is used. These situations include a minimally invasive TL1F procedure with either: (i) a micro-lumbar interbody fusion, MLIF™, or (ii) mini-open 1 1 IF on the symptomatic side to decompress the neural compression, and a pedicle screw fusion through a minimally invasive incision on the contralateral side. Similarly the Microfusion™ system herein would be used bilaterally in a PLIF approach with the decompression and interbody spacer placement performed bilaterally. Alternatively, the Microfusion™ system is ideal for "backing up" (with a minimal posterior incision) anterior interbody fusions (ALIF) and lateral interbody fusions (XLIF™ and DLIF™). MLIF™ collectively encompasses (i) transforaminal lumbar interbody fusions and stabilizations, (ii) posterior lumbal" interbody fusions and stabilizations, (iii) anterior lumbar interbody fusions and stabilizations, and (iv) lateral, lumbar interbody fusions and. stabilizations through a minimally invasive "micro" approach using the guidance system described herein. Since the lateral fusions are truly minimally invasive, a minimal posterior incision for pedicle screw fusion would be very complementary. Lateral interbody fusions are becoming more popular and more spine companies are coming out with their own lateral interbody fusion systems.

The lumbar spine has a lordotic curvature such that the lowest levels, L4, L5 and SI , have a posteriorly concave orientation or alignment, while the upper levels, L1 -L3, are less lordotic. This curvature sets up a unique situation in which the trajectories through the pedicles (the trajectories to insert the pedicle screws) from L2 to S I are not parallel. Rather, the trajectories commonly intersect at a point around the level of the skin. This configuration is similar to the spokes of a wheel in which the spokes (trajectories) meet at a common center point (a hub). Given that many patients have such a lordotic configuration of the lumbar spine, it is possible to insert pedicle screws through a single incision centered in the middle of the lumbar curvature. However, if each screw required a separate tower (or tube) (as in conventional tower/tube systems) in order for multiple screws to exist simultaneously, then the sum cross sectional area of the towers/tubes does not permit a single small incision. The towers/tubes interfere with each other and get in the way of one another due to their size.

[0024] An alternative method is necessary to in order to minimize the number and size of incisions. Reducing the number and size of incisions minimizes the tissue trauma needed to place pedicle screws for lumbar stabilization or fusion. An ideal system and procedure would take full advantage of the natural curvature of the lumbar spine in order to provide this reduction. However, the apparatus and method of the present invention described and claimed herein are not limited to applications in the lumbar vertebrae and may also find use for fusing, stabilizing, or otherwise treating vertebrae in other regions of the spine.

[0025] One objective of the present invention is to provide a simple method to place two or more pedicle screws through one small hole. This provides a better cosmetic and functional result with just a single skin incision of small size (approximately 1 to 2 cm in length) regardless of the number of screws used.

[0026 ] Another objective of the present invention is to be able to insert, position, and manipulate a rod and a locking assembly through the same small incision in order to lock the rod within the screws. The invention provides novel ways to insert a rod into the heads of pedicle screws and ways to lock the rod within the screws through a single small incision. The method, involves the attachment of one or more flexible yet firm extended blades or extended tabs to each pedicle screw head to be used to guide the rod down to the screw. By using flexible and strong guidance (or guide) elements that do not completely enclose the guided element, the towers/tubes currently used with each screw are not needed. The screws, rods, and locking assemblies can all be placed through a single small incision and yet still be appropriately interconnected within because of the natural lordotic curvature of the lumbar spine. By attaching at least one guidance element on each side of the screw head, the guidance elements assist to align the screw head. The guidance elements also trap or restrict displacement of the rod, forcing it to fit between them and directly into the screw head. [0027] The guidance elements can also be used to guide the locking assemblies down to the screw heads for embodiments in which the locking assembly is not part of the screw head itself (and already down there). In such embodiments, guidance is not needed for the locking assembly because it is built into or part of the screw head. Examples of this latter situation are a hinged door over the rod that swings and snaps into position to hold the rod in place in the screw head, in this situation the built-in locking assembly (on the screw head) is inserted into the pedicle contemporaneously with the screw.

[ 0028] In a preferred embodiment, the locking assembly is also guided down to the screw by small loops placed on the sides of the insertion tools or small holes or slots made in the sides of the insertion tools. The guidance elements (i.e. extended blades or extended tabs) pass through these loops/ holes (the loops pass over the guidance elements) to guide the insertion tools down to the screws to deposit (i.e. drop off or detach) the rods and locking means. In another preferred embodiment, the locking assembly is guided down to the screw by a notched lock and glide mechanism between the locking assembly and the guidance element such as extended blades or tabs. The notched groove on the extended blades traps the locking mechanism into position allowing it to only slide down the blade to fit perfectly into the screw head. Due to the flexibility of the guidance elements, coupled with their ability to possess a high strength while occupying a small volume, several of them can coexist simultaneously even in a small incision. Furthermore, guidance elements that are less flexible such as blades or extended tabs can be offset from one pedicle screw to the other. This offset allows the blades to intersect and crisscross while still allowing the rod and locking mechanism to be placed.

[0029] According to an alternative embodiment, the locking assembly is part of the screw head itself and is therefore deposited when the screw is placed, before the rod arrives, rather than requiring separate guidance and being placed after the rod. For example, the locking assembly (i) may involve turning the screw head to trap the rod and/or (ii) may include elements that snap into place to trap the rod and/or (iii) may include a carved out channel for the rod in the body of the screw head that restricts its motion. According to these embodiments, respectively, the rod may be unlocked, provisionally locked (restrained), or securely locked depending upon (i) the extent or angle of rotation of the screw head about an axis, (ii) the length of extension or extent of flexion, for protruding elements that snap into place, and (iii) the position, of the rod inside grooves of the screw head. The screw head also might have retaining elements including bars, barbs, teeth, balls, etc. that protrude upon activation to trap the rod (or other elements inserted into the screw head) by covering a top surface of the rod and/or mating with the rod's peripheral edges to enclose upon it and stabilize it through friction or physical pressure. This alternative embodiment encompasses modem capless locking assemblies and those without set screws.

[0030] Another alternative embodiment to just narrow or thin, upwardly directed extended guidance elements (tabs or blades) is a hybrid system where each screw is placed through short towers that do not come to the skin surface. Blade or tab extensions are attached to the top of the towers so that the screw, rod, locking assembly, and tools used for insertion, adjustment, locking, compression, distraction, and . removal are guided by the extensions close to the skin but through individual towers close to the bone and pedicle screw. This hybrid system offers both the advantages of the extended blades/tabs in which many guidance elements can overlap in a single incision at the skin level, and the advantages of a tower system are preserved at the bone level. Some surgeons who are comfortable with the tower system but who want the advantages of the blade/tab system may want to use this hybrid system.

[0031] A further objective of the present invention is to reduce patient discomfort and the potential for iatrogenic injury. Providing a system and method designed for use through a single incision assists this purpose. Only one quality incision need be made. With every incision that is made there is at least a small risk of inadvertent injury, including nerve damage, even by a skilled surgeon. However, incising is not the only risky stage of the procedure, nor the only stage capable of causing patient trauma yet having the potential for improvement to reduce these risks and liabilities. Another step of the procedure commonly causing post-surgical patient discomfort and diminished motor/sensory function is placement of the rods within the screws. The extended blades/tabs not only guide the rods to the screws but also function to hold nerves and muscles out of the screw head for easier insertion of the rods and locking assemblies. With nerves and muscles restrained from entering the trajectories along which, the rods are delivered, there is a reduced risk of pinching, tearing, or severing a nerve or muscle.

[0032] Other objectives and advantages of the invention, will be set forth in the description which follows. Implicit modifications of the present invention based on the explicit descriptions will be, at least in part, obvious from the description, or may be learned by practice of the invention. Such subtle, predictable modifications and adaptations are taken to be within the scope of the present invention. Additional advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEW^'S OF THE DRAWING

[0033] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.

[0034] FIG. 1 shows the guidance elements according to a preferred embodiment as offset extended blades/tabs attached to the screw head with the extended blades attached to the outside of one screw head and the inside of another screw head.

[0035] FIG. 2 shows how the offset extended blades/tabs function in operation to intersect/cross without interference as the blades/tabs extending from one screw head pass inside/outside the blades/tabs extending from another adjacent screw head such that the two could pass through the same incision. FIG. 2A is a side view and FIG. 2B is a head-on perspective view.

[0036] FIG. 3 shows another embodiment in which the extended blades/tabs have creases and are divided into foldable panels, straight in FIG. 3A and folding to curve slightly in FIG. 3B. Opening the panels permits the guidance elements to accept the rod, while folding the panels aids in guiding a locking assembly downward toward the screw head after the rod has been inserted. [0037] FIG. 4 shows a preferred embodiment for the screw cap locking assembly in which a screw cap transporter lias an extended or protruded portion to engage with a corresponding recess or slit in a longitudinally extended guidance element or blade. The screw cap transporter is slid down to fit perfectly on top of the screw head such that the screw cap locking assembly is screwed out of the transporter and into the head of the pedicle screw.

[0038] FIG. 5 shows the screw cap and transporter of FIG. 4 in operation, engaging with the recessed longitudinally extended guidance element, to be moved downward to the screw seat, from a perspective looking down from above.

[0039] FIG. 6 shows three additional side views of the screw cap locking assembly and transporter element, with the protrusion engaging with the recessed guidance element, and also demonstrating (right image) how the extended, guidance element and transporter easily detach from the screw head.

[0040] FIG. 7 shows how the upwardly directed extended guidance elements for two adjacent screws are offset from one another such that their respective locking assemblies (screw caps and transporters with protrusions) can be guided down to their respective screw heads simultaneously without interference.

[0041] FIG. 8 shows an alternative arrangement at the base of the longitudinally extended guidance elements in which the guidance elements for one screw (the upper one) are attached to the inside of the screw head, while the elements for the other adjacent screw (the lower one) are attached to the outside of the screw head, such that one set of guide blades (for the upper screw) fits completely within an adjacent set of guide blades (for the lower screw). The guidance elements attached to the inside of the screw head (the upper one) are close enough to allow the screw cap to screw through threads on the blades without a transporter. The widely spaced guidance elements require a transporter to bring the screw cap to the screw head.

[0042] FIG. 9 shows another alternative arrangement at the base of the longitudinally extended guidance elements in which the guidance elements for one screw (the upper one) are attached to the right side of the screw head, while the guidance elements for the other adjacent screw (the lower one) are attached to the left side of the screw head, for a left-left-right-right offset arrangement of the extended guide blades for adjacent screws when intersecting.

[0043] FIG. 10 shows an alternative embodiment for the screw cap locking assembly in which there is a concentric outer screw holder, tlireaded on the outside to engage with corresponding threads on the inside of the extended guide blades, and also threaded on the inside so that the inner screw can be advanced past the holder, further into the screw seat, upon proper positioning over the screw head.

[0044] .FIG. 11 shows a pedicle screw with a tapered shaft directed downwards and with a concave U-shaped screw head and detachable elongated guidance elements directed upwards (one on each side of the head). The elongated guidance elements may attach directly to the screw head (left image) or they may attach to 2 or more short guidance elements on each side of the screw head. This configuration creates a guidance element cage that forces the screw head and the rod to align with each other as the rod is lowered into the seat of the screw head.

[0045] FIG. 12 shows the pedicle screw being inserted into the pedicle portion of a vertebra on the anatomical right side of the central lamina.

[0046] FIG. 13 shows two pedicle screws in position on two adjacent vertebrae on one side of a vertebral column, with the screw shafts buried within the vertebral bones and the U-shaped screw heads protruding from the pedicles' surfaces. Also shown is a rod being guided down (at an angle) to the screw heads, between each of two sets of two guidance elements, one for each screw.

[0047] FIG. 14 shows the rod in a proper final position fully inserted within the screw heads of the pedicle screws in adjacent vertebrae along one side of a vertebral column for a partial (half-finished, the other side having yet to be stabilized) one-level stabilization. The locking assemblies are not shown here but may also be guided by the guidance elements down to the screw heads.

[0048] FIG. 15 shows the guidance elements (for guiding the rods, locking assemblies, etc.) having been detached from the screw heads of the pedicle screws along the anatomical right side of the vertebral column, but with the same screw head-guidance element system still in place on the anatomical left side of the vertebral column ready to accept and guide a rod down to the pedicle screws. The locking assemblies are not shown.

[0049] FIG. 16 shows the second rod in place within the screw heads on the anatomical left side pedicles of the vertebral column, with the detachable screw head guidance elements remaining on only the anatomical left side.

[0050] FIG. 17 shows a preferred embodiment in which the rod also has guidance elements or threads (called rod retention threads) on each, side extending between its longitudinal ends to form a loop with the body of the rod for securing the rod along the screw head guidance elements during placement.

[0051] FIG. 18 shows the rod with retention threads being directed down to two screw heads (one for each longitudinal end of the rod), along screw head guidance elements (corresponding to each side of each pedicle screw head) inserted through the rod retention loop on each side of the rod. The rod retention threads "trap" the guidance elements so that the ends of the rod cannot be pushed out of the screw head.

[0052] FIG. 19 shows a preferred embodiment in which two guidance elements are attached to the top of the screw head, one on each side. Three orientations (left to right) show the process of lowering the rod into the screw head guided by the guidance elements (top row) along with the final position in which the rod is completely within the screw head (bottom row).

[0053] FIG. 20 shows a locking assembly being lowered to attach to the screw head to secure the rod within. An instrument used to lock a locking assembly onto the screw head can also guided by the guidance element but is not shown in this diagram.

[0054] FIG. 21 shows another preferred embodiment in which the guidance elements are connected to flexible strands. The strands are then connected to the top of the screw shaft or the base of the screw head. As the rod is lowered into the screw head, guided by the guidance elements, the flexible strands wrap around the rod. Each strand Is just long enough (approximately half of the circumference of the rod) to wrap around the rod so that the ends of the guidance elements meet together above the rod. [0055] FIG. 22 shows how the threads, as in FIG. 11, can be wrapped around the rod and brought together to guide a cannulated locking assembly (i.e. cap) as well as other cannulated tools (not shown) down to the screw head.

[0056] FIG. 23 shows the insertion of a longer rod through 4 sets of guidance elements attached to 4 pedicle screws in a three level stabilization. The left image shows the guidance elements in a neutral, straight position. The middle and right images show the guidance elements of the two superior vertebrae (L3 and L4) splayed open so thai the rod can be easily tunneled in between the guidance elements.

[0057] FIG. 24 shows a preferred embodiment using a tool to separate the guidance elements deep below the skin surface. In this manner, the skin incision remains small. A "T"- shaped tool with a hinged "T" portion is attached to the guidance elements and slid partially down towards the screw head. As the hinged "T" is opened, the middle section of the guidance elements is separated. This opened window allows the rod to be tunneled in between the guidance elements, especially in instances where the rod and pedicle screw heads are inserted through separate incisions, as shown in FIG. 13 and FIG. 15.

0058] FIG. 25 shows two preferred embodiments of inserting a rod through guidance elements that do not share an incision with the rod. Here the lowest two levels (L5 and SI) do share a single incision but the upper two levels (L3 and L4) have separate incisions. Rod retention threads only span the inferior half of the rod and only capture the guidance elements of the lower two vertebrae (L5 and S I). The superior end of the rod is then pushed through the guidance elements of the upper two vertebrae (middle figure). Alternatively, a thread that is attached to the superior end of the rod can be used to pull the rod through the guidance elements of the upper two vertebrae. This thread can be introduced in between each, set of guidance elements by a large suture needle that is inserted in one incision and is pulled out of the next incision in between the guidance elements.

0059] FIG. 26 shows a preferred embodiment of flanged attachments that help the rod to find the proper orientation to best fit into the screw head. As shown, each attachment is preferably convex in a direction towards the rod so that as the rod approaches the screw head, the entrance to the screw head can accept a large range of angles in which the rod is oriented and still receive the rod. gradually improving the rod's orientation as it gets closer to the seat of the screw head.

[0060] FIG. 27 shows the sequence of lowering a rod into a malaligned screw head (or, alternatively, of lowering a malaligned rod into a properly aligned screw head) using the flanged, attachments as in FIG. 16. The bi-convex nature of the flanged attachments permits the rod to twist and adjust as it is lowered. Otherwise, without the flanged attachments, in a malaligned situation the rod. would hit the edges of the screw head and would not be able to be lowered further. The flanged attachments are shown here as detachable elements on the screw head; however, another preferred embodiment is a flanged and convex shaped rod guide built into the tops of opposing sides of the "U" shaped screw head (i.e. may be integrally part of the screw head interior itself).

[0061] FIG. 28 shows another preferred embodiment in which a guidance element is connected to a screw with break off extended tabs. Extended tabs are used to help reduce the rod into the screw head in cases of malalignment of the screw heads. Extended tabs are removed by snapping them off after the rod is locked in place. A guidance element attached to the extended tab helps to guide the rod and locking assembly into the screw head. The guidance element is removed when the extended tab is removed. Extended tabs that are tapered or triangular in shape also act similarly to the flanged attachments in FIG. 16 and 17 to guide a rod into the seat of a malaligned screw head.

[0062] FIG. 29 shows another preferred embodiment in which a guidance element is connected to a clamp or device that holds the screw head. A preferred embodiment of the clamp or device is composed of at least two parts that can be broken apart after the rod is locked in place so that the pieces of the device can be removed with the guidance element. The clamp or device is attached to the screw before insertion into the bone. The clamp or device is shaped so not to impede the placement of the rod into the seat of the screw head. The parts of the clamp are held together by a thin strand that is cut or snapped apart after the rod is locked in place. The clamp or device is made from metal, polymer, or plastic materials such that no residual is left after the clamp is removed.

[0063] FIG. 30 shows an alternative embodiment for the locking assembly in which the screw head itself forms the locking assembly and no caps or set screws are needed. In this particular alternative embodiment the screw head can be rotated to trap the rod.

DETAILED DESCRIPTION OF THE INVENTION

[0064] The invention involves an improved apparatus and method for guiding at least a screw, a rod, and a locking assembly down to pedicles of the vertebrae and for securing the rod to stabilize the vertebrae. The locking assembly may be built into or attached onto the screw head or be a separate element. Locking assemblies that are separate elements include (but are not limited to) those reliant on caps and set screws. Locking assemblies integrated with the screw head include (but are not limited to) rotatable mechanisms in which a turn of the screw head traps the rod. The locking assembly may be guided down to the screw before or after insertion of the rod depending upon the details of the locking mechanism used to secure the rod. In some cases, the locking assembly is already present on the screw head before the rod is received. In other cases the rod is inserted into the screw head, first and the locking assembly follows.

[0065] The guidance elements for directing the rod, some types of locking assemblies (screw head caps), surgical insertion and manipulation tools, and other components into position are preferably extended tabs or blades. As used herein, extended blades refers to separate elements that attach to the screw head or tabs on the screw head, whereas extended tabs refers to elements that are integrally connected with tabs on the screw head or even the screw itself. The extended tabs or extended blades run from a site adjacent the screw head up through the incision site. They can be curved (along one or more axis) or bent (along one or more axis) to accommodate the cap and other components. The guidance elements may also be curved or bent in order to be offset from adjacent elements such that they do not interfere if/when crossing. The curvature may be a permanent rounded shape or they may be flexibly curveable or comprised of foldable panels (see FIG. 3). The curves and bends may be permanent and pre-formed or adjustable in situ. The extended tabs/blades may also be tapered and/or threaded or notched to assist in stabilizing the cap or other components as they are lowered down to the screw head.

[0066] The blades may be offset from each other so that they do not interfere if/when crossing. They can be offset in any functional manner, including different positions around the screw heads (i.e. for staggered crossing), bending at different positions (i.e. straight to bent), curvatures that are non-intersecting with adjacent elements (blades from adjacent screw head), etc.

[0067] The extended tabs/blades or other guidance elements on adjacent screws should be offset such that they do not interfere with one another when they intersect. Rather, as they cross one another, the extended tabs/blades (or other guidance elements) smoothly pass by one another. Therefore the extended tabs/blades on adjacent screws can be inserted through the same small incision and manipulated within that incision. This may be achieved by tabs/blades, or other guidance elements, on the inside of one screw and the outside of the other screw. Or, in another manner tire tabs/blades for adjacent screws can simply be staggered or misaligned. Another option is for one screw to have a single tab/blade on the medial side while another screw has a single tab/blade on the lateral side. Still another option is for one screw to have extended tabs while the other screw(s) has (have) flexible wire as guidance elements.

[0068] Alternatively, some of the extended guidance elements (tabs, blades, etc.) on some screw heads may be straight while those on. others are bendable or angled, such that the bendable or angled elements cross over the straight ones to exit the body through the same skin level incision.

[0069] The extended tabs/blades or other guidance elements are designed to easily detach from the screw head, upon completion of their functional role of directing rods, caps, instruments, and other components precisely to the screw head. This detachment process may occur by any number of means, including breakoff along a pre- perforated or notched line, burning or melting at the base of the tabs/blades with an instrument, releasing a mechanical clamp, etc. The extended guidance elements (i.e. extended tabs, extended blades, etc.) for adjacent screws may all be attached to their respective screw heads at different positions along the screw head to produce the offset configuration. Alternatively, they may all be attached to their respective screw heads at the same location and bent at different angles to form, different configurations that are offset with respect to one another when crossed. That is, the extended guidance elements may be bent to come out of the screw head at different lateral displacements such that they do not interfere with one another. For a two level fusion, three offset extended guidance elements (tabs, blades, etc.) attached to three adjacent screws is appropriate. For a three level fusion, there would be four offset extended guidance elements attached to four adjacent screws. A four level fusion with five offset extended guidance elements attached to five adjacent screws, potentially all coming through the same skin level incision and crossing at some point is much less likely but might be possible in rare situations.

[ 0070 ] According to a preferred embodiment the extended tabs/blades/arms and wires can work together in a hybrid concept. The first tab attached to the screw head is easily detachable. Additional tabs between the screw head and distal wires protruding from the skin can be added and removed as needed to lengthen or shorten the distance of the guidance trajectory. As used herein, distal is defined as a space farther from a patient's body (which may also be closer to a surgeon's hand, proximal to the hand) and proximal is defined as a space closer to a patient's body (which may also be farther from a surgeon's hand, distal to the hand).

The flexible guidance wires can be used to direct the add-on tab elements during insertion and removal.

[0071] In some embodiments, hinges may exist at the base or along the body of an extended guidance element, proximal or distal to the point at which the guidance element attaches to the screw head. Hinges would permit the guidance element to open up, as necessary, to receive the rod, an instrument, or another component. The hinges may be on either side of the point at which the extended guidance elements join the screw head: the proximal screw head side or the distal extended guidance element side, if the hinges are on the proximal screw head side they will remain after the extended guidance elements are detached. If the hinges are on the distal extended guidance element side they will be removed with the guidance elements. In situations where the guidance elements attach to the screw head througli a mechanical, mechanism the hinge might be integrated into the mechanical mechanism such that detaching the extended guidance elements after they have performed their role disassembles the hinge.

[0072] FIG. 1 shows a preferred embodiment in which the guidance elements 114 are extended blades 114 or extended tabs 114 that connect with the screw head 102 anywhere along it from the inside perimeter/inside wall 115 to the outside perimeter/outside wall 1.16. The extended blades/tabs 114 provide more stability than wires and more flexibility than towers that encompass the rods or other guided elements.

[0073] FIG. 2 shows how the extended blades/tabs 114 are offset 1.15 / 116 such that in operation upon intersection (shown in both FIG. 2A from the side and in FIG. 2B head-on) they smoothly pass one another without interference. As such, adjacent extended blades/tabs 114 can pass through the same skin level incision and be manipulated easily through a range of geometries for final positioning. Further, the same devices can be used generally on all patients with different anatomical dimensions.

[0074] FIG. 3 shows another embodiment in which the extended blades/tabs comprise foldable panels 117 and have creases 118 or hinges such that they can he configured to curve slightly to wrap or partially wrap around a guided element (FIG. 3B). Although three panels (two creases) are shown, more or less panels and creases can be provided. Additionally, although the panels 117 are shown on the inside of the screw head 102, they could also be positioned along the outside 116 of the screw head 102, as shown generally for the guidance elements 114 in FIG. 1 and 2.

[0075] A preferred embodiment of the present inventive system and method is to use one guidance element 103 on each side of a screw head 102 such that there are two guidance elements 103 per screw shaft .101 to securely trap a rod 104 over the screw shaft 101 within the screw head 102. This embodiment is believed to provide the most rod 104 stability for the least volume of stabilizing elements (thereby enabling a very small incision without stressing it). The guidance elements 103 can be part of the screw head as an extension of the screw head itself. Alternatively, the guidance elements 103 can be independent elements attached to the screw head 102 through (i) the guidance element itself, (ii) an extension of the guidance element that is formed of a material that is the same as a material from which the guidance element itself is derived, (iii) a thread material thinner than the guidance element, (iv) a short tower, or (v) an intermediate element including an extensor/extended tab 112, flexible sheet, flange 110, or mechanical device / clamp 113 as discussed further herein, among other possibilities. A single guidance element 103 may be attached to a screw head 102 at a single location or in two or more locations 111 as illustrated in FIG. 11.

[0076] FIG. 4 shows one alternative embodiment for a screw cap placement mechanism as opposed to a simple cap 106 as shown in FIG. 20 and 22. In this alternative embodiment the screw cap portion comparable to 106 (in FIG. 20 and 22) is 119. This is the element that stays on permanently to retain the screw. The remaining portion 120 is a screw cap guidance element to be used with extended blades rather than guiding the cap directly down guidance wires (as in FIG. 20 and 22). The screw cap guidance element 120 has a threaded hole 122 with which the screw cap engages and a protruding portion 121. The protruding portion or extensor element 121 engages with a corresponding cutout 123 in the extended guidance element (blade, tab, arm) 114 as shown in FIG. 5.

[0071] The entire screw cap guidance element 120 can be used to hold the threaded screw cap locking assembly 119 and lead it downward to the screw head 102 using the upwardly directed extended guidance element 114 as a support rail and directional guide. As shown in FIG. 6, when the combination unit (120 and 119) reaches the screw head. 1.02, the screw cap 119 inside can be screwed downward out of the cap . guidance element Ϊ20 into the screw head 102 immediately above the screw within the screw seat. The cap guidance element 120 can then be removed with the extended guidance element 114, for example by simply detaching from the screw head 102 as shown in the right image of FIG. 6. [0078] FIG. 7 illustrates how these screw cap guidance elements 120 work as part of the offset guidance system. In this system, extended guidance elements (blades/arms) 114 for adjacent screws can intersect one another without negative interference. With the extended guidance elements 114 crossed, screw caps 119 can still be led down to each screw head 102 simultaneously by the respective screw cap guidance elements 120 without negative interference. Note how the screw cap guidance element 120 for one screw cap 119 (upper) has its protruding portion 121 engaged with a slot 123 in the left extended guidance element 114 of a first screw head 102, while the other screw cap guidance element 120 for the other screw cap 119 (lower) has its protruding portion 121 engaged with a slot 123 in the right extended guidance element 114 of a second screw head .102. Additionally, FIG. 7 shows one option for the attachment of the extended guidance elements 114 to the screw head 102 in which both extended guidance elements (blades/arms) 114 for the lower screw attach to its outer edges on both the left and right sides (outside/outside orientation 129).

[0079] FIG. 8 shows another option for the attachment of the extended guidance elements

114 to the screw head 102 in which both extended guidance elements (blades/arms) 114 for the upper screw attach to its inner edges on both the left and right sides (inside/inside orientation 130). Thus, a screw head 102 with extended guidance elements (blades/arms) 114 having an inside/inside orientation 130 can fit completely inside another screw head's extended guidance elements .114 that have an outside/outside orientation 129 to cross or intersect in a non- interfering, offset manner. In this arrangement the ordering of blades is: a blade of a first screw; a blade of a second screw; a second blade of the second screw; and a second blade of the first screw.

[0080 ] FIG. 9 shows further options for the attachment of the extended guidance elements

114 to the screw head 102 in which both extended guidance elements (blades/arms) 114 for the upper screw attach to its right edges on both the left and right sides (inside/outside orientation 128). For the lower screw the extended guidance elements (blades/arms) 114 attach to its left edges on both the left and right sides (outside/inside orientation 127). Accordingly, the two sets of extended guidance elements 1.1.4 for these adjacent screws can be made to intersect in a non-interfering, offset manner in which the consecutive arrangement is: a blade of a first screw; a blade of a second screw: a second blade of the first screw; and a second blade of the second screw.

[0081] FIG. 10 shows an alternative screw cap guidance element called a concentric screw cap placer. The concentric screw cap placer 125 has inner threads that engage with the screw cap 119 along with outer threads 1.26 that engage with threads on the inside of the extended guidance elements (blades/arms) 114 (not shown). The extended guidance elements (blade/arms) 114 should have threads at least at the bottom near the screw head 102 to guide this type of screw cap placer more accurately close to the screw head. After placing the screw cap 119 on the screw head 102 above a rod 104 in the seat of the screw head 102, the concentric screw cap placer 125 may be unscrewed out of the body, upward and off of the extended guidance elements 114. Or the extended guidance elements 114 could be detached and the cap placer 125 removed with them. Alternatively, for extra security or support, in some situations the concentric screw cap placer 125 may be left in position above the rod 104 and screw cap 119, even after the extended guidance elements 114 are unscrewed from it and detached.

[0082] FIG. 30 shows an alternative embodiment for the rod locking assembly in which a screw cap 1.19 or set screw and screw placer 1.25 or guidance element 120 (collectively as in FIG. 4 thru FIG. 10 and FIG. 20 and 22) are not necessary. Rather, the locking assembly 124 shown here is part of the screw head 1.02 itself. Integrating the locking assembly 1.24 with the screw head 102 simplifies a surgical procedure by eliminating the step of guiding a separate locking assembly (i.e. 106 as in FIG. 20 and FIG. 22, or 119/120/121 as in FIG. 4 thru FIG. 9, or 119/125/126 as in FIG. 10) down to the screw head 102. Instead, after the rod 104 is placed, the screw head 102 itself (or portions of it 124) can simply by manipulated to lock the rod 104 in position. For example, the screw head 102 might be turned or rotated such that extensions 124 from it trap the rod 104 against its base 102. Alternatively (not shown), portions of the screw head 102 may be manipulated to snap into place around or over the rod 104 or to converge inward to tighten the hold on the rod 104. FIG. 11 shows a first configuration, in which a single guidance element 103 is attached to the screw head 102 (left image), and a second configuration, in which one or more shorter guidance elements 111 are attached to the screw head 102 and also attached to a single elongated guidance element 103 at their other end (center and right images). Multiple short guidance element 111 attached directly to the screw head 102 may provide greater stability for an easier alignment. To accommodate this multiple guidance element configuration 111, insertion instruments having side loops (not shown) through which the guidance element passes also have side loops to accommodate the larger area created by the fanning out configuration of the multiple short guidance elements 111 close to the screw head 102. Thus, the side loop attached near the tip of the insertion tool will be as wide as the screw head to accommodate all the short guidance elements at the screw head. Above the transition zone (from multiple guidance elements 111 to a single guidance element 103) the insertion tool will have smaller side loops that only allow a single guidance element to pass.

In an alternative embodiment there may be a single guidance element 103 on only one side of each screw 101/102 or screw head 102. This embodiment further reduces the volume of stabilizing elements (screw head guidance elements) that must fit through the minimal incision but also reduces rod stability. When only one screw head guidance element 103 is used per pedicle screw 101/102 it is recommended that at least one rod retention thread 10S also be used (see FIG. 17 and 18 for illustration of the rod retention threads 105). The screw head guidance element 103 should be inserted through the loop formed by the rod retention thread 105 along the lateral side of the rod body 104. Rod retention threads 105 can be useful when the rod 104 is bent and the orientation of the bend has to be maintained in a proper direction to match the configuration of the screws. Sometimes a bent rod rotates when inserted and then it doesn't fit into the screw heads because the bend is rotated incorrectly so as not to match up with the orientation of the screw heads. Retention threads can reduce this risk and allow for correction in situ if the upwardly directed extended guidance element is in place properly through the thread. Retention threads are also useful to align a rod to fit into the screw heads when the rod does not have a spherical cross section. For example, the rod can have an oval in cross section so that it is stronger in flexion extension (the long of the oval cross section) than in lateral bending (the shorter axis of the oval cross section). Retention threads can limit rotation and force the rod to sit down into the screw heads.

[0085] in another alternative embodiment, instead, of one or more guidance elements 103, there may be one or more upwardly directed shafts that are not round (not shown) and are attached to a side of the screw head 102. The unique shape of the shaft would prevent insertion tools from turning or rotating around the shaft (i.e. during their descent to approach the screw head 102). Thus any shaft that is not cylindrical would be capable of guiding tools that have a complementary non-cylindrical shaft holder attached to the tool. For example, a shaft that has a cross section of an oval, square, rectangle, triangle, cross, trapezoid, star, or any other shape besides a circle would be able to prevent an insertion tool from rotating around the shaft as long as the insertion tool is equipped with a complementary shaped holder through which the shaft fits precisely. As long as the screw head 102 is multi-axial, there would be some flexibility in moving the shaft around in the incision.

[0086] The screws 101 and screw heads 102 themselves may also have any one of several different vertical and horizontal cross-sections including both circular and non- circular, rectangular-, square, hexagonal, etc. The screws 101 and screw heads 102 are preferably made of a titanium alloy or stainless steel.

[0087] The rods 104 are preferably cylindrical but may alternatively have a non-circular cross-section (triangular, square, hexagonal, etc.) so long as the seat of the screw head 102 is shaped correspondingly to accommodate. The rods 104 are preferably formed of a titanium alloy but may also be made of any other metal (commercially pure titanium, stainless steel, etc.) or a biocompatible minimally flexible polymer such as polyetheretherketone (PEEK). The rods can be uniformly or non-uniformly (same or different degrees of flexion along different axis) rigid, -flexible, or flexible. The rods can be straight or angled and may be pre-bent or bendable in situ. Flexible rods may be formed of a uniform flexible substance such as PEEK or may incorporate a joint in the middle of the rod which bends. Alternatively, cuts in a hollow rod allow bending of the rod similar to a spring. [0088] In some cases other elements, including connectors or T-connectors, can be also introduced, with or without assistance of the upwardly directed extended guidance elements, to cross the spine horizontally and connect two parallel rods to provide additional support.

[0089] In another alternative embodiment there may be more than two guidance elements

103 per pedicle screw 101/102. Preferably, if more than two guidance elements per screw are used, there is at least one guidance element on each side of the screw with more than one guidance element on at least one side. An equal number of guidance elements on each side improves stability and prevents lopsidedness. However, every patient's anatomy is slightly different and when curvature (i.e. scoliosis) and/or other aggravating conditions are present stability during rod 104 insertion may be best achieved by an asymmetric distribution of screw head guidance elements 103 around the perimeter of a screw head 102. in any case, the spinal surgeon is in the best position to make this decision about the appropriate screw head guidance element 103 and rod retention thread 105 set-up to use based on the individual needs of a particular patient.

[0090] The guidance elements 103 on any one screw 101/102 can be placed at various positions around the periphery of a screw (rather than just on the sides) for enhanced stability and control. Screw 101/102 is used to refer to the entire screw including the screw shaft 101 and the screw head 102 collectively. The guidance elements may be uniformly distributed and symmetrical around the periphery or they may be asymmetrical and staggered. For example, having four guidance elements on a screw head (i.e. one guidance element on each edge: north/top, east/right, south/bottom, west/left) ensures that the screw head 102 is oriented along the axis of the rod 104 during transport of the rod through the incision and into a first screw head. Limiting the open regions around the perimeter of a screw head 102 by effectively creating a guidance element cage can also force the rod 104 to turn in the right direction (or force the screw head to turn to accommodate the rod) when it moves from a vertical longitudinal to a transverse lateral orientation after placement of a first end in a first screw head while the other end is being directed for placement in a second screw head. The number of guidance elements, their sizes (i.e. diameters and lengths), shapes, flexibility, and strength may be adjusted to suit a particular procedure in a particular patient based on the incision size to optimize screw stability and facilitate rod alignment while avoiding entanglement of too many guidance elements. Contemplated embodiments include those with from 1 to 10 guidance elements per screw/screw head, especially those with 2 to 4 guidance elements.

Instead of multiple long guidance elements connected to the screw head 102 on each side, a single long guidance element 103 (or thread) is connected to several short guidance elements 111 which in turn are connected to each side of the screw head. Thus, multiple guidance elements 111 are still connected to each screw head 102 but these multiple guidance elements are also connected to one another in an area above the screw head to form single guidance element 103 extending through the incision. These multiple short guidance elements 111 may still function to bound or limit the movement of a rod 104 at least at the base of the screw head 102. The short guidance elements 111 give the advantage of creating a guidance element cage by which the rod 1.04 is forced to sit down into the seat of the screw head 102, The long single guidance element (or thread) 1.03 reduces clutter and confusion at the skin incision that occurs when too many guidance elements are present. The multitude of short guidance elements 1.11 distributed away from the longitudinal entry axis into approximately the same axis along which the rod 104 will ultimately lay also allows the long guidance element 103 and accompanying instruments to adjust the orientation and angle of the screw head 102 in this axis (the rod axis, approximately perpendicular to the longitudinal entry axis used during rod insertion). The screw head 102 is configured to form a concave channel in which the rod 1.04 will eventually come to sit/rest. The concave channel may be U-shaped when a vertical cross-section is taken but any substantially concave shape suited to retain a rod 104 and with dimensions corresponding to those of the rod 104 will work. The upper edges of the screw head 102 itself or those of another intermediate element 110 / 112 / 113 to which it is attached, are configured to receive an incoming rod at a wide range of angles and smoothly direct it into the proper angular configuration to fit into the screw seat. [0092] As an alternative to the screws 101 or the screw heads 102 being attached directly to upwardly directed guidance elements 103 or guide shafts, there may be an intermediary flange, flanged leaflet, sheet 1.10, extensor/extended tab 112, a mechanical clamp/device 113, or other element in between the two. The screw 101/102 or screw head 102 at its outer edges may transform into (integral therewith) or attach to a separate element that is directly attached to the guidance element/shaft 103 such that the screw 101/102 or screw head 102 and the guidance element 103 are indirectly connected. The intermediate element is preferably specially adapted to readily detach from the screw 101/102 or screw head 102 when desirable, such as after securing the rod 104 in proper position and locking it in place. Detachment may be through a snap-off / pop-off mechanical mechanism that might be activated through a push-button on a surgeon's tool; through tearing along a perforation; through cutting, twisting, wagging, burning, heating, radiating, ultrasonically vibrating, electrifying/electrocuting, dissolving, unscrewing, or any other means. In this case with the guidance elements or upward shafts 103 attached directly to the intermediate and readily detachable element 110 / 112 / 113 the guidance elements 103 themselves may be more securely fastened to the intermediate element 110 / 112 / 113. For example, the guidance elements 103 might be soldered or welded to an extensor tab 112 that snaps into/onto and snaps out of/off of a groove or protrusion on the screw head 102. At least a portion of the extensor tab 1.12 may be threaded to mate with a screw 101/102 or screw shaft 101 having corresponding threads or to align a rod 1.04 having some corresponding threads.

[0093] The intermediate element may be in the form of a sheet 110 of a very thin material that is both flexible and can be tensed by pulling or tightening. When pulled tight the sheet 110 functions to guide the rod 1.04 into the seat of the screw head 102. Such material may be rubber.

10094] An intermediate element may be an inwardly tapered flange 110 attached to an inner top edge of the screw head 102 and placed symmetrically about the screw seat in which the rod 104 sits. Such a flange 110 is configured to allow a malaligned rod 104 or screw head. 102 to rotate and adjust relative to one another as the rod is inserted into the seat of the screw head until the two are acceptably aligned. The inwardly tapered sides of the flange 11Θ may take the form, of convexly curved wings 110 that form a channel for the rod 104 between them.

[0095] Alternatively, the intermediate element may be an extensor tab 112 with straight rather than convex sides. Preferably, the tab is triangular which may be formed by removing the corners of an otherwise rectangular tab. The wider base of the triangle may attach to the screw head 102 as shown in FIG. 28.

0096] The function of the screw head 102 or intermediate element 110 / 112 / 113 is to create a channel into which a rod 104 can be easily guided by the upwardly directed guidance element 103/guide shaft. The screw head or intermediate element is adapted to accept a large degree of malalignment of the rod and the screw seat relative to one another and then guide the rod into the screw seat until substantially perfect alignment is achieved. The advantage of this is that the system does not require starting over, pulling out, and reinserting the rod when it turns out the initial positioning is not ideal.

[0097] The guidance elements, threads, and intermediate elements described herein may be attached to the screw or screw head on the outside, on the inside, or through a cannulated portion of the downwardly directed screw shaft 101. Many attachment locations are possible so long as it does not interfere with the ability of the screw shaft 101 to be drilled into the pedicle and the ability of the rod 104 and locking assembly 106 to be received into the seat of the screw head 102.

[0098] The guidance element, thread, or upwardly directed shaft 103 may be attached to the downwardly directed screw shaft 101. the screw head 102, or an intermediate element (i.e. flange, sheet 110, extensor/extended tab 112) with glue, soldering, thread, sutures, string, a mechanical clamp 11.3, etc . . .

[0099] in embodiments in which a mechanical clamp 113 is used to connect the upwardly directed extended guidance element 103 to the screw head 102, the clamp 113 preferably has 2 leaves that are connected under the head 102 or at least below where the rod 104 comes down so as not to impede the path of the rod. After closing the locking assemblies 1.06 to secure the rod 104 in place within the screw head 102, the clamps 113 can be removed. Removing the clamps 113 from the screw head 102 also removes the guidance elements 103 attached to the clamps 113. The clamps 113 may be removed by any means feasible in the limited space including (but not limited to): (i) by breaking the connection (like detaching the extended tabs 112), (ii) by cutting a material that holds the 2 leaves together, (iii) unclamping or unbuckling, and (iv) unvelcro-ing.

[00100] Alternatively, in some embodiments the locking assembly may be part of the clamp 113 such that the clamp is not removed but remains to hold the rod 104 (see FIG. 29). In such situations, the guidance elements 103 only are simply detached from the clamp-locking assembly combination unit.

[OOlOlj Instead of a mechanical clamp with moving parts, the intennediate element (between screw head 102 and guidance elements 103) may also simply be a metal or plastic device that has no moving parts but traps the head 102 securely into it. The intermediate metal or plastic device can be removed by means including (i) snapping a thin center part connecting 2 halves of the device, or (ii) cutting a string that connects 2 parts of the device. If the locking assembly 106 for the rod 104 is distinct from the intermediate metal or plastic device, then the device can be removed along with the guidance elements after the rod is placed. If the locking assembly is integrated with or dependent upon the intermediate metal/plastic device, then the device should stay in place after the guidance elements 103 / 111 only are detached from it.

(00102j In another embodiment illustrated in FIG. 21, the guidance element 103 or an extension thread 107 thereon, can be attached to the area within the screw head 102 where the rod 104 would eventually sit, such as at the base or sides of the screw head and/or to the upper end of the downwardly directed screw shaft 101. For example, the guidance element 103 or its extension 107 may be attached within the cannulated portion of a cannulated screw. By using flexible guidance element or extension thread 107, the guidance element/thread can wrap around the rod 104 as the rod is seated into the screw head 102. The guidance element/thread can then be threaded through cannulated tools and a cannulated locking assembly 106 above the rod. [00103] Optionally, color-coded guidance elements 103 and/or screws 101. may be provided to assist doctors, technicians, and medical personnel in identifying elements, performing the procedure, and monitoring progress during follow-up visits. Alternatively, some other form of visual coding, such as with particular materials and/or only visible under certain conditions may be used to distinguish guidance elements, screws, and other elements (i.e. fluorescent markers, radioactive isotopes, radioopaque markers visible on X-rays, magnetic nanoparticles, etc.). Another alternative or complementary coding means can be sensed by touch (different surface textures) or sound (tactile or auditory) rather than or in addition to visually. The coding could be correlated with right and left sides of the body, medial vs. lateral elements, guidance element/screw sizes, guidance element/screw shapes, guidance element flexibility, and/or guidance element strengths, among other possibilities. This list of variables with which a coding or tagging system may correspond is intended to be illustrative rather than exhaustive. One preferred coding system provides markers or color coding for guidance elements that are intended for the medial side of the rod versus those intended for the lateral side of the rod. This coding would allow for easy separation of the guidance elements 103 when the rod 104 is inserted. This coding would also help the insertion of tools and the locking assembly 106 along the medial side and lateral, side guidance elements 103. Some elements (guidance elements 1.03, screws 101, screw heads 102, rods 104, retention threads 105, locking assemblies 106, etc.) with similar characteristics may be coded in groups such as all medial, side guidance elements being red while all. lateral side guidance elements are green. An alternative variable to code medial and lateral guidance elements is length of the guidance element. Shorter lengths can code for medial while longer lengths code for lateral or vice versa.

[00104] Any locking assembly 106 can be used with the present invention. The precise design of the locking assembly 106 is not important so long as it is configured to retain the rod 104 within the screw head. 102 for a secure and lasting stabilization. Examples of locking assemblies 106 that might be employed include screw-on nuts, press-on caps, fast-drying glue, a tiny swinging gate or door with a latch, a series of elements that can be deployed to ti ghten around the periphery of the rod, etc. [00 105] Since a rod connects two or more separate vertebrae, the rod can first be secured into position, (locked or tightened) though the locking assembly on a first vertebra and then, subsequently on a second vertebra. In some cases after the rod is firmly secured to the screw on the first vertebra, the relative positioning of the vertebrae can be adjusted by the surgeon by moving the vertebrae closer together or farther apart before the rod is secured to the screw on the second, vertebra. With only one side of the rod locked into place the other side of the rod can easily be adjusted in position. For example, the rod can vertically slide forward or backward through the locking assembly until the desired distance spanned by the rod between locking assemblies is obtained.

[00106] The guidance elements 103 can be attached to the screw heads 102 by a number of mechanisms. The retention threads 105 can be attached to the ends of the rods 104 by the same assortment of mechanisms. The simplest attachment mechanism is to solder or glue the guidance element/thread to the screw head/rod. The solder or glue can then be cut or broken off later. Neither the lateral retention threads 105 on the rod 104 nor the upwardly directed extended guidance elements 103 on the screw 101/102, or on the screw head 1.02, are needed after the rod 104 has been securely placed within the screw head 102.

[00 107] The retention threads 105 on the rod 104 that hold it close to the guidance elements

103 as it is guided, into position are preferably made of a flexible material including metal, nitinol, rubber, suture, plastic, polymer, and biodegradable material. The retention thread 105 should be easily removable after the rod 104 has been secured in an aligned position in the seat of the screw head 102 and locked in.

[00108] Alternatively, the guidance element/thread could be threaded into a threaded connector in the side of the screw head/rod so that the guidance element/thread is unscrewed at the end of the case.

[00109] Other embodiments include attaching the guidance element 103/retention thread 105 by dissolvable sutures attached or tied to the screw head 102/rod 104 and to the end. of the guidance element/retention thread with a small loop or grooves in the screw head/rod. Suitable dissolvable suture materials include biocompatible synthetic absorbable materials such as those made primarily of polyglycolic acid (PGA) or other proven compositions. Specific brands of materials include Vicryl™ (from Ethicon), Biovek™ (from Dynek), Visorb™ (from CP Medical), Polysorb™ (from Covidien's Syneture), and Dexon™ (also from Covidien's Syneture). The materials can be tailored to degrade or absorb in an amount of time that coiTesponds with sufficient internal healing to successfully hold the fusion. For example, standard Vicryl™ typically maintains tensile strength for three to four weeks. The materials may also be impregnated with drugs or biomolecules (i.e. triclosan) to accelerate the healing process and prevent infection. When the biodegradation (i.e. bioabsorption, bioerosion. etc.) time for the suture material is too long and the sutures are unnecessary immediately following the procedure the sutures can instead be promptly cut or burned at the end to disconnect the guidance element/retention thread from the screw head/rod.

[001 10] Yet another option for the "guidance element to screw head" or "retention thread to rod" attachment mechanism is to secure using a material that burns, breaks, or dissolves upon the application of current (i.e. radiofrequency current). This option permits the connection to be easily broken by simply passing current through the guidance element or thread. Preferably, the guidance element/retention thread breaks down in response to current applied outside the skin. Alternatively, an insulated guidance element can be used to apply current internally in a targeted and minimally invasive manner. An insulated guidance element would allow the current to pass directly from an external tip (outside the body) to the current-sensitive material at an interior tip near the pedicle screw.

[0011 1] In still another preferred embodiment for attachment, the selected material (i.e. elastic string or rubber) is both flexible and can be tensed by pulling or tightening. The key is to use very thin material that can be both flexible and become tense. These dual properties allow the material to reliably guide the rod and tools down through the small incision without breaking while adapting to share the limited space. Unless it is also biodegradable the flexible, tensile material of string/rubber will need to be cut/broken/burned off or untied from the screw head and guidance element (or rod and retention thread) at the end of the procedure. [00112] Instead of using an intermediary material to connect the guidance element to the screw head and/or to connect the retention thread to the rod, another possibility is for the guidance element and/or retention thread to be formed of the same materials as the intermediary connectors described above. In this situation, it is the guidance element or retention thread that is itself burned or cut at the end of the procedure.

[00113] The final result in all cases is a clean, successful pedicle screw fusion just like that which results from screws and rods used in an open procedure but with a smaller incision and fewer components.

[00114] The material through which the rod-guiding guidance element, is attached to the screw head may be the same material of which the guidance element itself is derived or a separate material. The guidance elements themselves are preferably formed of a biocompatible metal having both strength and durability. In a preferred embodiment, the guidance elements are formed of nitinol (nickel titanium alloy).

[00115] The material through which the retention threads 105 of the rod 104 are attached to the ends of the rod may be the same material of which the retention threads themselves are derived or a separate material The retention threads are preferably formed of a biocompatible metal having both strength and. durability. In a preferred embodiment, the retention threads are formed of nitinol (nickel titanium alloy). Alternatively, another preferred embodiment is for the retention threads of the rod to be made from a biodegradable thread so that it does not have to be removed after placement. Another advantage of thread is that it would not interfere with the rod and cap locking mechanism 106 if it were caught in between the cap 106 and screw head 102 threads.

[001 16] To complement the guidance element guides 1.03, the present invention also provides a special rod 104, with its own retention threads 105, that can fit between the guidance elements. By attaching a small loop or ring at the ends of the rod, two threads can be tied though the loops with good tension along the sides of the rod. This way the guidance elements 1.03 will pass in between the rod 104 and the thread 105 to prevent the rod from slipping out and around the most superior or inferior guidance elements. (See FIG. 17 and 18.) The retention thread 105 may also be attached to the rod by means other than loops or rings at its ends. The rod 104 may have holes or piercings therein for securing the thread to it. The rod may have grooves at its ends with which the thread engages. The thread 105 may be glued on near the ends of the rod. Rod retention threads 105 restrain the rod 104 to riding the guidance elements 103 and. eliminate the risk of internal rod displacement away from the target screw site 102. The retention threads 105 also expedite rod 104 placement into the screws 102/101 to decrease total procedure time.

[00117] The retention thread 105 may take the form a strip or long sheet of material rather than an ordinary thread. The retention thread material should be flexible, strong, and biocompatible.

[00118] The steps for the placement of the pedicle screws and rods for a "Micro open" approach are as follows. First, using fluoroscopy or stereotactic guidance, a single small skin incision 1-4 cm lateral to a midline that will accommodate all pedicle screws is localized. Next, using either a percutaneous Jamshedi/ irschner-guidance element (K-guidance element) approach, a Wiltse muscle splitting approach, or tube system, the pedicle screws are placed (see FIG. 12). The pedicle screw inserter may have loop attachments that hold the side guidance elements of the pedicle screw during placement. Alternatively, the insertion tool or device that positions the pedicle screw may have protrusions (or slots/grooves) that mate with corresponding slots/grooves (or protrusions) on the upwardly directed extended guidance elements (similar to how the cap is guided in FIG. 4). Once the pedicle screw is placed the insertion tool or device needs to be removed to make room for placement of the rod and optionally, a separate locking assembly.

[00119] After each pedicle screw is placed, the side guidance elements are pushed to the side of the incision to make room so that the other screws can be placed without entanglement. After all screws are placed, a screw head, turner is inserted and guided down to the screw heads along each pair of guidance elements to align the heads of the screws in preparation for receiving the rods (see aligned screw heads in FIG. 13).

[00120] With the screw heads aligned, the side guidance elements are split between the medial and lateral sides. Then a rod is slid in between the medial and lateral guidance elements into the screw heads. Preferably, the rod should be bent before insertion. Markers on the guidance elements at predefined distances from the tip of the guidance elements can help guide the surgeon in bending the rod to the correct curvature. Guidance elements coming out of a single incision are similar to light rays that have been focused by a convex lens. These light rays converge at a point and then create a mirror virtual, image on the other side of the focal point. This same concept can be used to create a mirror image of the curvature of the rod to guide the bending of the rod to accurately fit into the screw heads. (See FIG. 14 and 25). After each end of the rod is properly positioned within a screw head, locking nuts or caps are screwed on the screw heads to secure it in place. Alternatively, a compressor thai is guided by the guidance elements is used, to compress pedicle screws on adjacent levels and then final tightening can be done during compression. The screw head guidance elements are then removed by any means including cutting, twisting, wagging, burning, radiating, dissolving, unscrewing, etc. (see FIG. 15 and FIG. 16, left side). Once the screws and rods in all vertebrae to-be-fused along one side of the vertebral column are stabilized, their mirror-image counterparts should be placed along the opposite side of the same vertebrae using similar fluoroscopic localization or other imaging means (see FIG. 15 with one rod, preparing for the second, and FIG. 16 with two rods placed).

[00121 ] The present invention can be used to dynamically stabilize or fuse vertebrae while at the same time removing a defective intervertebral disc and inserting a spacer in its place. The spacer may include bone graft material or bone inducing material incorporated therein to encourage healing. Exemplary bone inducing materials include bone morphogenetic protein, tricalcium phosphate, hydroxyapatite, and collagen.

[00 122] The various elements (guidance elements, screws, screw heads, rods, retention threads, locking assemblies, etc.) of the present invention may be provided in a range of sizes, shapes, strengths, flexibilities, and other physical characteristics to best accommodate individual patients and particular applications.

[00123] FIG. 23 shows how for a three level stabilization, the rod can be guided down by the guidance elements on a first screw head while the guidance elements on a second and third screw head are splayed outward or bent to open the encatchment area for the rod to easily enter. In the conventional case of pedicle screw towers, the rod had to be precisely inserted through the small opening within each rigid tower. The present invention overcomes this difficulty.

[00124] As shown in FIG. 24 a refined T-shape tool 108 / 109 may be used to separate the guidance elements 103. This gesture prevents them from becoming tangled (or disentangles them) and opens the space in between them such that a rod can be passed through it to enter the screw head. The horizontal arms 109 of the "T" extend outward perpendicular to the longitudinal insertion axis 108. These arms 109 may be aligned parallel against the main longitudinal body during insertion and removal. They may also be inside the main body and deployed from within via telescopic extension, or a spring-like mechanism. The end of each horizontal arm 109 may be U- shaped, V-shaped, or circular such that a guidance element 103 can be retained within it. If the ends are U-shaped or V-shaped the T-shaped tool 108 / 109 can be disconnected from the guidance element 103 easily after spacing by collapsing the arms to realign against the longitudinal insertion axis 108 or to collapse into the main body. If the ends are a closed loop shape such that the guidance elements 103 are fed through them and trapped within them, the loops should be configured to open to release them (like a jewelry clasp) after the tool 108 / 109 has performed its function.

[00125] The present invention is not limited to the embodiments described above. Various changes and modifications can, of course, be made, without departing from the scope and spirit of the present invention.

[ 00126] Additional advantages and modifications will readily occur to those skilled in the art.

Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

Claims

What is claimed is: 1. An apparatus especially adapted for fusing together or stabilizing at least two vertebrae, comprising:

at least two screws, each screw having, a head with a seat and a downwardly directed shaft;

at least one rod;

at least two locking assemblies to lock the rod into each screw head; and

one or more upwardly directed extended guidance element(s) for each screw;

wherein the upwardly directed extended guidance element(s) are connected to the screw head or downwardly directed screw shaft when the screw is inserted into a vertebrae, and are also disconnectable from the screw head or downwardly directed screw shaft, including after the screw has been inserted and the rod has been locked in place in the screw head; and

wherein the upwardly directed extended guidance element(s) are configured to guide one or more of (i) the rod, (ii) the locking assemblies, and (iii) tools to the screw heads.

2. The apparatus of claim 1, further comprising a tab connected to each screw head, that serves to direct placement of the rod and locking assembly, wherein the upwardly directed extended guidance element is an extension of the tab.

3. The apparatus of claim 1. wherein the upwardly directed extended guidance element is a blade having a width and a length greater than its thickness.

4. The apparatus of claim 3, wherein the blade is directly connected to the screw head.

5. The apparatus of claim 3, further comprising a tab connected to each screw head, that serves to direct placement of the rod and locking assembly, wherein the blade is directly connected to the tab and. connected to the screw head through the tab.

6. The apparatus of claim 1 , wherein at least one upwardly directed extended guidance element is bendable.

7. The apparatus of claim 1, wherein upwardly directed extended guidance element(s) associated with each of two or more screws extend upward from their respective screw heads through one or more skin incision sites to form, as idealized lines or cylinders in space, a configuration selected from the group consisting of:

(i) parallel configuration of the guidance elements associated with different screws; (ii) skew configuration, wherein the guidance elements are neither parallel or intersecting;

(iii) converging but not intersecting configuration;

(iv) intersecting at a '^''-configuration,, wherein distal ends intersect outside a surface of skin and at an angle between 0 and 180 degrees;

(v) intersecting at a "T" configuration, wherein a distal end of the extended guidance element(s) from one screw intersects the guidance elements ) from another screw(s) at a point other than at an end of the guidance element(s) and at an angle between 0 and 180 degrees;

(vi) intersecting at an "X"-configuration or a criss-cross configuration, wherein extended guidance element(s) of two or more screws intersect at points not at the ends of the guidance elements and at an angle between 0 and 180 degrees; and

(vii) diverging configuration where the distal ends outside the skin are farther apart than the proximal ends at the screw head.

8. The apparatus of claim 7, wherein two or more upwardly directed extended guidance elements extend upward from their respective screw heads to form the "X"- configuration, the "X"-configuration comprising guidance elements that intersect or criss-cross above or below a surface of skin at one or more incision sites.

9. The apparatus of claim 7, with more than two screws, wherein the extended guidance elements associated with any pair of screws can have a configuration, as specified in claim 7, that is different from that associated with other pairs of screws, as long as the combination of different configurations are allowed geometrically in 3 dimensional space. 10. The apparatus of claim 1, wherein the upwardly directed extended guidance elements for two or more screw heads are offset such, that if they cross or intersect there is no interference. 11. The apparatus of claim 10, wherein a potential lumen bounded by the upwardly directed extended guidance element(s) for each screw passes through and intersects with other potential lumens associated with guidance elements for other screws such that each lumen participating in the intersection continues to be freely accessible by tools, rods, and locking assemblies without interference down to the screw head. 12. The apparatus of claim 10, wherein the upwardly directed extended guidance elements are bent. 13. The apparatus of claim 10, wherein the upwardly directed extended guidance elements for at least one screw head are connected to an inside perimeter of the screw head and the upwardly directed extended guidance elements for at least one screw head are connected to an outside perimeter of the screw head.

14. The apparatus of claim 1, wherein the upwardly directed extended guidance elements for two or more screw heads are configured to pass through a common incision, wherein the common incision is smaller than the sum of the maximal widths of two largest elements inserted through the incision, yet larger than the maximum width of a single largest element inserted through the incision, wherein an element includes one or more of a guidance element, a screw, a screw head, a rod, a locking assembly, and associated tools.

15. The apparatus of claim 2 or 3, wherein the tab or blade has creases or perforations that permit it to be folded into panels.

16. The apparatus of claim 2 or 3, wherein the upwardly directed extended guidance element changes sliape from a flattened tab or blade at its distal end near a skin incision to a tube at its proximal end just above the screw head. 17. The apparatus of claim 1, further comprising a hinge positioned between the screw head and the upwardly directed extended, guidance element, wherein the hinge is configured to open as needed to receive the rod, the locking assembly, or another component and the hinge is also configured to close as needed to stabilize the rod, to accept the locking assembly, or to stabilize another component. 18. The apparatus of claim 17, wherein the upwardly directed extended guidance element is disconnected from the screw head through detachment of the hinge.

19. The apparatus of claim 17, wherein the hinge remains on the screw head after the upwardly directed extended guidance element is disconnected from the screw head and removed.

20. The apparatus of claim 17, wherein the hinge is a part of the locking assem bly.

21. The apparatus of claim 1, further comprising one or more hinge(s) along a middle region of one or more upwardly directed extended guidance elements that allow(s) the guidance elements to bend sufficiently to open to receive a rod or other component.

22. The apparatus of claim 1 , further comprising at least one retention thread for each rod, arranged in one or more loop(s) along one or more side(s) of the rod to serve as a guide rail as the upwardly directed extended guidance element(s) extending from the screw head pass through it;

wherein the retention thread is attached to the rod at an end face of the rod or along a side of the rod a short distance away from the end face, so as to ensure that the end of the rod fits completely through the screw head.

23. The apparatus of claim 22, wherein the retention thread is biodegradable and naturally disintegrates with time after the rod has been placed in the screw head, and securely tightened therein.

24. The apparatus of claim 1. wherein each locking assembly is configured to be guided by the upwardly directed extended guidance eiement(s) until the locking assembly is attached to the screw head and tightened to lock the rod into position.

25. The apparatus of claim 1. wherein each locking assembly is part of the screw head that can be manipulated to trap the rod.

26. The apparatus of claim 25, wherein each locking assembly that is part of the screw head snaps into place to trap the rod.

27. The apparatus of claim 25, wherein each locking assembly that is part of the screw head rotates to trap the rod.

28. The apparatus of claim 25, wherein each locking assembly that is part of the screw head slides to trap the rod.

29. The apparatus of claim 1, wherein at least a portion of the upwardly directed extended guidance element has screw threads or another means for retaining an element guided by it.

30. The apparatus of claim 1, further comprising:

one or more instrument s) for manipulating the rod and the screw(s) with respect to one another; and

one or more retractor(s), for holding muscle and tissue apart during insertion of the rod and locking assemblies, or for accessing other structures of a spine, as in a laminectomy, discectomy, interbody fusion, or posterior-lateral fusion; wherein the instruments) are guided by the upwardly directed extended guidance element(s) until the rod is securely locked into the screw head(s) by the locking assemblies; and

wherein the retractor(s) are also guided by the upwardly directed extended guidance element(s) and optionally, held in place by them.

31. The apparatus of claim 30, further comprising:

one or more instrument(s) for inserting the rod into the screw heads;

one or more instrument(s) for inserting the locking assemblies into the screw heads above the rod;

one or more instruments ) for adjusting an angle and an orientation of the screw heads; one or more instrument(s) for confirming that the rod is within the screw heads;

one or more instrument(s) for capturing the screw heads in order to advance, withdraw, or remove the screw;

one or more instrument(s) for compressing or distracting the vertebrae using the screws or screw heads;

one or more instrument(s) for reducing a dislocation or spondylolisthesis between vertebrae using the screws or screw heads;

one or more instruments) for realigning malaligned. misangled vertebrae using the screws or screw heads; or

one or more instrument(s) for tightening or locking the locking assemblies to secure the rod within the screw heads;

wherein any above instrument can perform more than one of the above functions and wherein the instruments) is guided by the upwardly directed extended guidance element(s).

32. The apparatus of claim 1, wherein each screw head has upper edges and further comprising flanged arms, attached to or formed from the upper edges of the screw head, the flanged arms being configured to receive an incoming rod at a wide range of angles.

33. The apparatus of claim 1, wherein the seat of each screw head is in a center of the screw head, in which the rod is inserted, and on each of two opposite sides of the seat is a wall and each wall or an extension thereof is highest in a center of it and lowest on edges of it, thereby configured to allow a malaligned or rotated rod or screw head, to align together and slowly conform to one another as the rod is inserted into the seat of the screw head.

34. The apparatus of claim 33, wherein the walls or extensions thereof are downwardly tapered and symmetrically convex.

35. The apparatus of claim 1, wherein the seat of each screw head is in a center of the screw head, in which the rod is inserted, and on each of two opposite sides of the seat or on extended tabs above the seat is a slanted wall or a slanted flange attached to a wall such that a distance between the two walls or flanges is greater as a distance away from the seat increases and lowest within the seat, and the walls or flanges converge to form a V-shape, such that the screw head is thereby configured to allow a malaligned or rotated rod or screw head to come together and slowly conform to one another as the rod is inserted into the seat of the screw head.

36. The apparatus of claim 1, wherein each pair of upwardly directed extended guidance elements is connected to a pair of flexible strands that attach to a top of the downwardly directed screw shaft or the seat at a base or a side of the screw head under or beside where the rod is to sit, such that as the rod is lowered into the screw head, guided by the upwardly directed extended guidance elements, the flexible strands are configured to wrap around the rod, each strand being just long enough (approximately half of a circumference of the rod) to wrap around the rod so that distal ends of the upwardly directed extended guidance elements meet together above the rod and can be placed together and inserted within a cannulated locking assembly and/or other cannulated tools.

37. The apparatus of claim 1 , wherein the upwardly directed extended guidance element is attached to the screw or screw head with a very thin material that is both flexible and can be tensed by pulling or tightening.

38. The apparatus of claim 37, wherein the material is in the form of a sheet that when tightened, guides the rod into the seat of the screw head.

39. The apparatus of claim 1, wherein the upwardly directed extended guidance element is attached to the screw or screw head through a mechanical clamp or device that securely holds the screw head, and the clamp/device is removed along with the extended guidance element after the rod is guided into place in the screw head and locked in place.

40. The apparatus of claim 1, wherein the upwardly directed extended guidance element is attached to the screw or screw head by a ring or loop that the downwardly directed screw shaft fits through but that the screw head cannot fit through.

The apparatus of claim 1 , wherein the upwardly directed extended guidance element is attached, to one or a multitude of wires, threads, strands, or extensor tabs that are then attached to the screw or screw head.

The apparatus of claim 1, further comprising a shortened tower such as one that is conventionally used for placing screws, rods, and locking assemblies in minimally invasive systems;

wherein the shortened tower is attached to the screw or screw head at its base and attached to the upwardly directed extended guidance element at its top; and

wherein the shortened tower is configured to function, at its base, as do standard towers conventionally used for minimally invasive pedicle screw systems, while also permitting insertion of multiple hybrid extended guidance element/tower constructs through a single small incision due to only a small extended guidance element portion, at its top, extending though the incision at skin level to prevent overcrowding of towers at that level.

43. The apparatus of claim 1, wherein at least one upwardly directed extended guidance element is coded to distinguish it from at least one other upwardly directed extended guidance element.

44. The apparatus of claim 1, wherein at least one upwardly directed extended guidance element is coded to group it with at least one other upwardly directed extended guidance element.

45. The apparatus of claim 1, wherein the upwardly directed extended guidance element(s) have markers thereon to denote their depth of insertion beneath skin of a patient's body such that these depth markers can be used to reflect a virtual image of a contour of the screw heads so that the rod can be pre-bent accurately outside the body, and in this manner the extended guidance element(s) act similarly to light rays that are focused into a single point by a convex lens which then creates a virtual mirror image at an equal distance from a focal point, the focal point in this case being a point at which the wires come closest together.

46. The apparatus of claim 1, wherein the rod is flexible to allow dynamic stabilization without fusion of the vertebrae.

47. The apparatus of claim 1, wherein the rod is made of a polymer material comprising polyetheretherketone (PEEK).

48. The apparatus of claim 1, wherein the upwardly directed extended guidance element comprises a slot or a groove therein, for receiving a correspondingly shaped protrusion or extension on an insertion tool or device.

49. The apparatus of claim 48, wherein the insertion tool or device is configured to guide the screw into position in a pedicle of a vertebra, by engaging with one or more slots or grooves in one or more upwardly directed extended guidance elements.

50. The apparatus of claim 48, wherein the insertion tool or device is configured to guide the rod down to the screw head, by engaging with one or more slots or grooves in one or more upwardly directed extended guidance elements.

51. The apparatus of claim 48, wherein the insertion tool or device is configured to guide the locking assembly, to secure the rod in place, to the screw head, by engaging with one or more slots or grooves in one or more upwardly directed extended guidance elements.

52. The apparatus of claim 51, wherein the locking assembly is a screw cap.

53. The apparatus of claim 1, wherein the locking assembly comprises an outer annulus and an inner screw, the outer annulus being threaded on its outside for engaging with corresponding threads on an inside of one or more upwardly directed extended guidance elements, and also being threaded on its inside for engaging with corresponding threads on an outside of the inner screw, thereby allowing the inner screw to be screwed downward into the pedicle screw head over the rod, to trap the rod in position.

54. The apparatus of claim 1, wherein the upwardly directed extended guidance element comprises a combination of two or more components and at least one component can be added or removed as necessary to lengthen or shorten a guidance trajectory from skin level to a pedicle screw head.

55. The apparatus of claim 54, wherein the components are selected from a group consisting of: wires, tabs, blades, and arms, and the components can be added or removed in situ while the apparatus is in a patient's body.

56. A method of using the apparatus of claim 1. comprising:

inserting the rod through a first incision; and

tunneling the rod through tissue to fit between upwardly directed extended guidance elements attached to screws that were inserted through additional incisions separate from an incision through which the rod was inserted.

57. The method of claim 56, further comprising:

spreading apart two or more upwardly directed extended guidance elements on a screw or screw head to widen a gap between them to allow easier capture of the rod, including when the rod does not have retention threads.

58. The method of claim 57, wherein the step of spreading apart two or more upwardly directed extended guidance elements is accomplished by opening one or more hinges along a middle region of one or more guidance elements.

59. A method of fusing together or dynamically stabilizing at least two vertebrae using the apparatus of claim 1, comprising:

(i) inserting a first screw into a first vertebra, wherein the first screw has a first screw head attached to a first group of one or more upwardly directed extended guidance element(s);

(ii) inserting a second screw into a second vertebra, wherein the second screw has a second screw head;

(iii) inserting a rod;

(iv) guiding the rod along the first group of upwardly directed extended guidance element(s) to the first screw head of the first screw in the first vertebra:

(v) guiding the rod to the second screw head of the second screw in the second vertebra; and

(vi) disconnecting one or more upwardly directed extended guidance element(s) Irom one or more screw head(s). The method of claim 59, wherein the second screw head is attached to a second group of one or more upwardly directed extended guidance element(s) and the rod is guided to the second screw head of the second screw through the second group of upwardly directed extended guidance element(s).

The method of claim 59, wherein the second screw is inserted through a conventional tower and the rod is also inserted through the tower and guided down to the second screw head of the second screw through the tower.

The method of claim 59, after the steps of guiding the rod and before the step of disconnecting the upwardly directed extended guidance element(s), further comprising steps of:

guiding the locking assembly along the upwardly directed extended guidance element(s) down to the screw head over the rod; and

tightening the locking assembly upon each screw head to secure a position of the rod. The method of claim 59, further comprising steps of:

(i) removing a defective disk from an intervertebral body space via an opening at a lamina, facet, foramina, and/ or an annulus; and

(ii) inserting a spacer therein.

The method of claim 63, further comprising a step of: inserting bone graft material around the spacer, the rod(s), and the screws.

A method of guiding a rod, specially adapted to fuse or stabilize adjacent vertebrae, into a screw head using the apparatus of claim 1 , comprising a step in which one or more upwardly directed extended, guidance element(s) attached to the screw head open up to receive and direct the rod into the screw head.

The method of claim 65, wherein a T-shaped tool is inserted to open up the upwardly directed extended guidance element(s) to receive the rod.

67. The method of claim 66, wherein the T-shaped tool has a hinge such that it forms a straight shape during insertion and removal, with sides of the T-shape parallel to a longitudinal axis and configured to turn perpendicular about the hinge after insertion and before removal to open up the upwardly directed, extended guidance element(s).

68. The method of claim 66, wherein the T-shaped tool has two radially extending arms that expand radially outward in a direction perpendicular to a longitudinal insertion axis when a housing covering them is retracted.

69. A method of guiding a rod adapted to fuse or stabilize adjacent vertebrae into a screw head using the apparatus as in claim 1, wherein the rod has a thread attached to its end face; comprising:

(i) pulling the thread to move the rod through the upwardly directed extended

guidance e!ement(s) attached to the screw head; and

(ii) pulling the thread to move the rod into the screw head.