WO2012162571A1

WO2012162571A1 - Tendon-sparing implants for arthroscopic replacement of hip cartilage

Info

Publication number: WO2012162571A1
Application number: PCT/US2012/039481
Authority: WO
Inventors: Kevin A. Mansmann
Original assignee: Mansmann Kevin A
Priority date: 2011-05-24
Filing date: 2012-05-24
Publication date: 2012-11-29

Abstract

Surgical implant devices are disclosed which will allow completely arthroscopic resurfacing of the acetabular socket, and the femoral head, in hip joints, in both humans, and in animals such as dogs. Such devices, made of flexible polymers with smooth articulating surfaces and porous anchoring surfaces, can be provided with centered openings, to allow a surgeon to spare the major ligament (the ligamentum teres) which connects the femoral head to the pelvis. Various anchoring means are also disclosed.

Description

TENDON-SPARING IMPLANTS FOR

ARTHROSCOPIC REPLACEMENT OF HIP CARTILAGE

BACKGROUND

This invention is in the field of orthopedic surgery, and relates to surgical implant devices designed for use in the arthroscopic (minimally invasive) replacement of damaged cartilage in hip joints, in animals or humans.

Extensive background information on the tools, devices, and methods that are used for repairing injured, degenerated, or otherwise damaged cartilage in hip joints is contained in numerous medical school textbooks, review articles, vendor catalogs and training materials, and other reference works that are well-known to surgeons. Well-known medical school texts which describe and illustrate this type of surgery include Campbell 's Operative Orthopaedics (a multi-volume set which was last issued in paper as the 11th edition in 2007, with online updating since then) and Wheeless ' Textbook of Orthopaedics (which is available in a "dynamic online" form which is extensively illustrated, at www.wheelessonline.com/ortho).

In addition, numerous orthopedic supply companies (including Stryker, Zimmer, Smith & Nephew, and various others) sell surgical implants used for so-called "hip replacement" surgery, which is one of the most common and well-known types of orthopedic surgery. All such manufacturing companies and vendors have published detailed information, for surgeons, on how to surgically implant their products. Furthermore, detailed information on such implants also is available to the public via a website run by the U.S. Food and Drug Administration (FDA), which uses panels of impartial experts to review any applications that are submitted by companies to test or use any new type of surgical implant in human patients.

Additional background information on new types of cartilage-replacing implants which are flexible, and which are specifically designed for arthroscopic implantation, is available in various issued patents and published applications that were invented or

Mansmann (i.e., the same applicant herein), an orthopedic surgeon whc

Such prior published applications include:

Serial number 12/067654, published as 2009/132047, "Anchoring systems and interfaces for flexible surgical implants for replacing cartilage";

Serial number 11/471090, published as 2007/293947, "Multi-part implants for combined repair of hyaline and meniscal cartilage in joints";

Serial number 11/390539, published as 2007/224238, "Implants for replacing hyaline cartilage, with hydrogel reinforced by three-dimensional fiber arrays";

Serial number 11/105677, published as 2005/287187, "Hydrogel implants for replacing hyaline cartilage, with charged surfaces and improved anchoring";

Serial number 10/677444, published as 2004/133275, "Implants for replacing cartilage, with negatively-charged hydrogel surfaces and flexible matrix reinforcement";

Serial number 10/011933, published as 2002/183845, "Multi-perforated non-planar device for anchoring cartilage implants and high-gradient interfaces";

Serial number 10/071930, published as 2002/173855, "Cartilage repair implant with soft bearing surface and flexible anchoring device"; and,

Serial number 09/818811, published as 2002/022884, "Meniscus-type implant with hydrogel surface reinforced by three-dimensional mesh".

Because of the different anatomic structures of the knees and hips, in humans, the cartilage segments in knee joints are much closer to the skin surfaces, and are much more easily accessible to surgeons without having to cut deep into soft tissues, compared to cartilage segments in hip joints. In addition, by alternately bending and extending a knee joint while it is being surgically repaired, various parts and surfaces of the cartilage segments in a knee can be made even more accessible, to the surgeon repairing that joint. Accordingly, the research to date by Mansmann (including the development of implant devices that are fully suited for testing in large animals, such as sheep and goats) has focused primarily on implant devices that are sized, shaped, and designed for implantation in knee joints.

Now that that work is firmly on a pathway which includes testing in large animals, Dr. Mansmann has turned his attention to the challenges of implants designed for hip repairs, as described below. Based on a detailed understanding of the "technology

developing over the past 10 years, for creating implant devices contain

polymers that are designed and suited for arthroscopic repair of knee joints, the Applicant herein has determined that the time has arrived to begin doing focused and targeted work to modify and redesign those types of implant devices, so that they will be suited for replacing injured, diseased, or otherwise damaged cartilage in hip joints, in humans.

In addition, the Applicant has recognized that there is a potentially very large and unmet need for hip repairs that are minimally invasive, and completely arthroscopic, in dogs. Due to historical patterns of dog breeding which generally can be encompassed by the term

"in-breeding", many breeds of dogs are prone to severe congenital hip problems. Accordingly, the Applicant has recently recognized that the technology and designs he has been developing and refining over the past decade, for flexible cartilage-replacing implants, have reached a point where they can be adapted and optimized for insertion and emplacement in four-legged animals such as dogs, using arthroscopic methods and tools. By adapting this technology to provide arthroscopic hip repairs in dogs (which can be directly adapted for other types of four-legged animals), this approach can minimize the pain and discomfort that will be suffered by an animal, both immediately after surgery, and during a longer recovery period. For animals that cannot talk, and that cannot understand why they must suffer at the hands of humans, this can greatly improve the nature, quality, and caliber of hip repair surgery.

It should be noted that this work, to create flexible implants that can be used to arthroscopically replace hip cartilage, does not merely involve reshaping and resizing the implant devices that are disclosed herein. Instead, these new designs arise after careful study and analysis of: (i) the natural patterns of lubrication of a healthy hip joint, by native synovial fluid; and, (ii) the major and even drastic alteration in the pattern of lubrication which occurs, when a "conventional" hip replacement is performed.

Most "conventional" hip replacements that are performed in human patients, at the current time, use two "loading" surfaces which are both made of hard and rigid materials. At least one surface, in essentially all implants used in humans today, is made of an extremely hard and rigid material, such as a titanium or cobalt steel alloy, or a ceramic. In most implants used today, the surface which covers the convex "head" or "ball" at the upper end of the femur bone (i.e., the long bone that passes from the hip to the knee), is made of tha

The other cartilage-replacing implant surface, in a hip replacem

surface known as the "acetabular socket", which is part of the pelvic bone. In a human pelvis, the two acetabular sockets face generally forward, somewhat downward, and in a somewhat "lateral" or "outward" direction (the term "lateral" indicates the direction away from an imaginary vertical "center plane" of a human or animal; by contrast, the term "medial" indicates an orientation or movement toward the center plane). In most hip implants being used in humans today, the implant component which replaces the acetabular socket is made of a very hard and effectively rigid polymer, most commonly a material called "ultra-high molecular- weight polyethylene", abbreviated as UHMWPE. Some implants in the past used "metal-on-metal" interfaces; however, those tended to suffer from problems of degradation and leaching, over time, leading to unhealthy levels of cobalt or other unusual minerals in a patient's blood and tissues.

Because the very hard and rigid materials used in conventional hip replacements are machined and finished in ways which make them extremely smooth, and because the sizes, shapes, and nature of those types of hip-replacing implants effectively requires that the native femur-pelvic interface must be completely removed and replaced, conventional hip replacements are designed to not require constant lubrication. Therefore, they severely disrupt the flow and distribution of "synovial fluid" (i.e., the natural fluid which lubricates mammalian joints), in a hip joint, after hip replacement surgery. Instead of being designed to sustain and promote the normal presence (and the distribution and flow patterns) of synovial fluid, as a liquid which will coat and lubricate the "articulating surfaces" of the cartilage-replacing materials in hip implants, conventional hip implants are designed to function without such lubrication.

It also should be noted that conventional hip implants completely remove and eliminate a major physiological structure which is present in healthy hip joints, called the ligamentum teres. The medical term "ligament" refers to specialized bands, sheets, or segments of connective tissues which connect two different structures to each other (the term "tendon" is similar, but it is limited to the specialized connective tissues that connect muscles, to other types of tissues). The specific ligament which is called the ligamentum teres directly couples the acetabular socket (i.e., part of the pelvic bone) to the femur bone (i.e., the thigh bone, where the ligamentum teres occupies and is attached to a dimple, or depression, which generally is in the very center of the "femoral ball", also called the "femoral head". In a conventional hip re]

ligamentum teres is simply cut out and removed, in its entirety.

Conventional cartilage replacement surgery, in hip joints, requires "open joint" surgery. In this type of surgery, the term "minimally invasive" is often used; however, instead of referring to arthroscopic surgery, it refers to methods for limiting the longest skin incision to only about 3 inches long (about 8 cm), in humans, and that does not qualify as "arthroscopic" surgery.

In addition, numerous articles can be found which describe arthroscopic surgery, on hips; two moderately recent reviews include Katz et al, "Advances in arthroscopic surgery," Curr Opin Rheumatol. 19(2): 106-10 (2007) and Larson et al, "Advanced techniques in hip

arthroscopy," Instr Course Lect. 58: 423-36 (2009). However, those types of arthroscopic surgery do not involve or include what is commonly known as a "hip replacement" or "hip resurfacing", in which the cartilage surfaces on both a femoral head, and an acetabular socket, are completely replaced.

Accordingly, the Applicant herein has focused on the development of flexible implants which will: (i) enable complete replacement of both the acetabular and femoral cartilage, in hip joints, using entirely arthroscopic methods and tools; and, (ii) much more closely emulate, mimic, and function in the same ways as the natural cartilage surfaces they are replacing.

As a final matter of Background information, it should be noted that the cartilage segment of an acetabular socket includes more than just a thin layer of hyaline cartilage which is directly bonded to a hard surface of pelvic bone. Instead, the cartilage in an acetabular socket also includes a component called a "labrum" (the adjective is "labral"). That term comes from the same root word as "lip", and it refers to a somewhat thicker and enlarged ring (or rim) of cartilage, which generally surrounds the acetabular socket.

The cartilage which forms the labral segment does not have the same internal fibrous structure as hyaline cartilage. The internal structure of hyaline cartilage is optimized to form a relatively thin layer, which clings directly and tightly to an underlying and supporting bone. The structure and strength of hyaline cartilage is provided by relatively short fibers of collagen, which is the main type of fibrous connective protein in the soft tissues of animals.

By contrast, the larger and thicker cartilage segment which forms the labral portion of a hip socket uses a more complex type of anchoring system and internal structure. Even though it is bonded mainly to the rim of the acetabular socket, its substantially gi

(compared to a thin layer of hyaline cartilage) requires its internal struc

collagen fibers that are much longer than the short collagen fibers found in thin layers of hyaline cartilage. Accordingly, the labral segments in hip joints are made of a specialized type of cartilage called "fibrocartilage".

Since labral segments are substantially thicker than the thin-layered hyaline cartilage which covers most of an acetabular socket, and since they have a different type of anchoring system than hyaline cartilage, the labral cartilage in a hip joint poses an additional set of challenges and complications, to anyone who seeks to replace injured or diseased cartilage in a hip, with anything other than "classic" hip implants made of hard alloys and hard plastics.

Nevertheless, due to an innovative anchoring system described herein, which has been developed only recently by the Applicant herein, the new types of implants disclosed herein are able to meet and satisfy that challenge.

Accordingly, one object of this invention is to disclose the design and structure of surgical implants that: (i) are sized, shaped, and suited for replacing damaged cartilage in hip joints; and, (ii) are made of flexible materials that will enable the surgical emplacement of such implants, into hip joints, using entirely arthroscopic methods and tools, to minimize damage to surrounding tissues.

Another object of this invention is to disclose the design and structure of surgical implants for replacing injured or diseased cartilage in hips joints, in a manner which:

(i) spares, retains, and protects the so-called ligamentum teres, i.e., the large and important ligament which, in a normal and healthy joint, directly connects the femoral head to the acetabular socket; and,

(ii) preserves and sustains the normal and natural patterns of synovial fluid distribution and wetting, in a hip joint.

To the best of the Applicant's knowledge and belief, the implants disclosed herein are the first feasible and practical implants ever disclosed, for completely replacing the injured or diseased cartilage in a hip joint that requires resurfacing, which can indeed spare and protect the ligamentum teres, and which can also preserve the normal and natural patterns of synovial fluid distribution, in a hip joint. Another object of this invention is to disclose the design and stt

implants that are especially well-suited for minimally-invasive hip rep£

animals, notably including dogs, which suffer from frequent and severe hip problems. These implants can enable better forms of surgical hip repair for dogs (and for other four-legged companion animals, and for livestock as well), since the minimally-invasive nature of these implants will substantially reduce the pain and discomfort suffered by the animal, and will also reduce the convalescent and recovery period, following surgery.

These and other objects of the invention will become more apparent through the following summary, drawings, and detailed description.

SUMMARY OF THE INVENTION

Structures and designs are disclosed for surgical implants that are sized, shaped, and suited for replacing damaged cartilage in hip joints. In general, they will be sold and implanted in sets, and/or as matched pairs; one implant will be used to resurface the acetabular socket in a pelvic bone, while the other implant will be used to resurface the ball (head) of a femoral bone. In a preferred embodiment, these implants will contain flexible polymeric materials to enable entirely arthroscopic implanttaion. One side of each implant will provide a smooth but durable "articulating surface", which will be kept wet and lubricated by natural synovial fluid, after implantation. The opposing side of each implant device will be covered by a layer of porous material which will encourage tissue ingrowth into the implant, to provide greater long-term strength and stability.

These are believed to be the first types of hip repair implants which can entirely replace the ball-and-socket cartilage segments in a hip, while using a central vacancy and an access channel to allow a surgeon to spare and preserve a major ligament, called the ligamentum teres, which directly connects a femoral head to a pelvic socket. They also are believed to be the first hip repair implants which will preserve and sustain the normal flow and distribution of synovial fluid, which will lubricate a repaired hip joint. In addition, these implants include enlarged labral rim structures, which closely resemble and emulate the enlarged labral cartilage rims that occur in the acetabular sockets of natural hip joints.

These implants can be manufactured in a range and assortment

of which will be designed and suited for humans, while others are designed and suited for various types of four-legged animals, such as dogs. Their design, and the anchoring means that will be used to secure them to the bones in a hip joint, will enable surgical emplacement using entirely arthroscopic methods and tools, to minimize pain, damage to surrounding tissues, and the time required for recovery and convalescence.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a perspective view which depicts the anchoring surface and the outer rim of a flexible C-shaped implant, which will replace both the hyaline surface and the labral rim of a damaged cartilage segment in the acetabular socket of a hip joint. The central opening in the "C" shaped structure of this implant leaves room for the "ligamentum teres" (which couples the acetabular socket to the femur bone) to remain intact and in its normal position, in a repaired joint.

FIGURE 2 is a perspective view which depicts the same C-shaped flexible implant shown in FIGURE 1. This drawing also depicts, in a partial cutaway segment, a portion of a flexible cable, with a loop of suture material wrapped around it; these components will provide part of the anchoring means that will be used to anchor the implant to a pelvic bone.

FIGURE 3 is a perspective view which depicts the same C-shaped flexible implant shown in FIGURE 1 , and which generally shows the anchoring surface that will be pressed directly against a prepared pelvic bone surface from which the cartilage has been removed. The anchoring surface will be made of a porous material, to promote tissue ingrowth into the anchoring surface, to provide a strong and permanent anchoring attachment. This drawing also depicts two protrusions (which can also be called prominences, extensions, fingers, pegs, or similar terms) which will fit into accommodating holes that will be drilled into the pelvic bone, to help anchor and stabilize the implant.

FIGURE 4 is a perspective view which depicts the same sides and components of the C-shaped flexible implant shown in FIGURE 3, from a different angle.

FIGURE 5 is a perspective view of a generally hemispherical ir

the "ball" condyle at the upper end of a femur bone, in a hip joint. This implant has a continuous ring which surrounds a central opening; accordingly, it is designed for repairing a hip in which the ligamentum teres has been severed, or damaged to a point where it does not need to be spared, during insertion of the implant.

FIGURE 6 is a perspective view of the "underside" of the femoral ball implant shown in FIG. 5. This view depicts a porous anchoring surface, which will be pressed directly against the femoral bone, and which will promote tissue ingrowth into the anchoring surface, to create a stronger anchoring attachment.

FIGURE 7 is a perspective view of a "split" implant for resurfacing a femoral cartilage surface. This "split" implant has a seam or juncture which will allow the implant to be "opened", while it is being emplaced on the surface of a femoral ball, so that the surgeon will not need to sever and subsequently reconstruct an intact and functioning ligamentum teres.

FIGURE 8 is a flow chart which summarizes the major steps that will be performed, during a hip resurfacing operation which uses the implant components shown in FIGS. 1-7.

DETAILED DESCRIPTION

As briefly summarized above, structures and designs are disclosed for surgical implants that are designed and suited for replacing injured, diseased, or otherwise damaged or defective cartilage, in hip joints. These implants will be offered and made available: (i) to surgeons, in a first range of sizes that are designed, sized, and suited for use in human patients; and, (ii) to veterinarians, in second and additional size and shape ranges that are designed, sized, and suited for use in specific types of animals, notably including dogs, which suffer from frequent and widespread hip problems, and which have hip joints that are relatively close to the surface, and which are easily accessible.

In a first embodiment, which is strongly preferred at least for use in humans, these types of implants will be made of materials which have sufficiently flexibility to allow them to be rolled into generally cylindrical configurations, so that they can be inserted into hip joints via arthroscopic insertion tubes. Accordingly, these including:

(1) flexible polymer components, which will provide smooth ar

wettable, and actually lubricated when in use) articulating surfaces, which will replace the articulating surfaces previously provided by hyaline cartilage segments that require replacement due to injury, disease, congenital defects, or other problems;

(2) flexible anchoring components, such as flexible multi-stranded cables, or rings or segments made of super-elastic and/or shape-memory materials (such as nitinol, a metal alloy that becomes softer and more pliable when chilled, as just one example), embedded within or otherwise coupled to the flexible polymer component. In a preferred embodiment, an anchoring cable or ring can be embedded within an enlarged molded component which surrounds the periphery (outer rim) of an implant. That enlarged molded component can be designed and sized to settle and "seat", in a snug and conforming manner, into a groove or trench that can be machined into the bone surface, immediately before the implant device is inserted into the joint. A plurality of anchoring screws or pegs, and/or suture strands or cerclage wires, can be wrapped around an anchoring cable, ring or segment, and the "free ends" of the strands or wires, which emerge from the molded polymer, can provide a surgeon with means to anchor the implant to a bone surface; and,

(3) a flexible layer of porous mesh or similar material, which will be affixed to the "anchoring" surface of the implant, and which will be designed to promote tissue ingrowth into the porous anchoring surface of the implant, to promote stronger and more durable anchoring of an implant to a bone surface.

Damage to either cartilage surface in a hip joint almost always leads, fairly rapidly, to abrasion of and damage to the other cartilage surface, since the two cartilage surfaces must press, rub, and slide against each other. As a result, in essentially all cases of interest, a pelvic implant and a femoral implant will be implanted as a "matched pair", in which the two implant devices will be inserted into a single joint, during a single operation. One implant will replace the concave cartilage surface (including both the hyaline cartilage, and the labral rim) of an acetabular socket, in a pelvic bone. The other implant will replace the convex cartilage surface on a femoral ball. However, since these two types of implant devices will manufactured and packaged separately, they can be handled, sold, and shipped separately, if desired. Because of their design, and because the largest components of

made of flexible materials, these implants will enable a "complete" hip

entire hyaline and labral cartilage segment of an acetabular socket will removed and replaced, and the entire cartilage surface on a femoral ball also will be removed and replaced), in a manner which can be done arthroscopically (i.e., using minimally-invasive tools and methods, to minimize disruption of, and damage to, surrounding tissues and blood vessels).

However, even though these implants will enable arthroscopic emplacement, they will not require arthroscopic implantation. For example, if an orthopedic surgeon determines that a non-arthroscopic approach would be preferable for a specific repair procedure (such as on a patient who was injured in an accident, fall, etc., and who will require reconstructive surgery to repair one or more broken bones), the surgeon will be able to emplace and anchor these implants, using non-arthroscopic methods and tools.

Each such implant will have both an articulating surface, and an anchoring surface. In an acetabular implant 100 as illustrated in FIGS. 1-4 (which will replace the cartilage in an acetabular socket in a pelvic bone), the articulating surface 110 will have a generally concave shape. By contrast, in a femoral implant 200 as illustrated in FIGS. 5 and 6 (which will replace the cartilage layer that coats the ball or head of a femur), the articulating surface 210 will have a generally convex shape.

As described in various prior patents and published patent applications by the same inventor here, which are listed in the Background section, the articulating surface of either type of implant will be made of a flexible polymer which is hydrophilic, and which will provide a very smooth but durable and lubricious articulating surface. In vertebrate animals, the smooth and wet "articulating" surface of a hyaline cartilage segment in any articulating joint (this excludes spinal joints, and certain other types of joints which do not involve sliding and running of cartilage surfaces across and against each other) will press, rub, and slide against the corresponding surface of a different hyaline cartilage segment, which covers the surface of a different bone in that joint. Accordingly, each cartilage-replacing implant described herein will have a smooth and wettable surface on the "articulating" side or surface of that implant.

These types of smooth and wettable articulating surfaces can be manufactured, in flexible form, by using certain well-known types of polymers. An extended description of polymer technology is not required herein to adequately disclose or enable this i

skilled in the art, since these types of options and features are well witt

specialize in making these types of polymers. Briefly, such polymers contain long polymeric chains (often called "backbone" chains), which have certain selected types of hydrophilic pendant groups bonded to those backbone chains, at a desirable density (or spacing, or similar terms). The "backbone" chains typically are manufactured, in desired lengths which will impart a suitable balance of hardness and flexibility to a polymer, by selecting precursor compounds (usually called monomers) that will react with each other in a controllable manner, to form large numbers of selected types of bonds which can repeat an endless number of times, in a backbone chain. To control the lengths of the backbone chains, a small quantity (usually 1% or less) of one or more "terminating" agents (which will effectively create a non-reactive "cap" or "terminus" at the end of a long chain) can be incorporated into the reaction mixture, during the polymerization reaction. In addition, the spacing and density of the hydrophilic side chains (or pendant groups, moieties, or similar terms) can be controlled, by selecting and incorporating one or more types of monomers which will provide those types of side chains (also called side groups, pendant groups, moeties, etc.) at a desired density and spacing. As mentioned above, these aspects of polymer technology are well known to those skilled in this particular art, and can be used to create any of numerous types of well-known polymers, which usually are named based on the types of molecular bonds in the backbone chains (such as polyacrylics, polyvinyls,

polyacrylonitriles, polyurethanes, etc.).

If desired, known methods can be used to create polymers that will contain and hold a quantity of water, within the molecular matrix of the polymer. If this approach is used, the final polymer, once it has been fully hydrated (i.e., saturated with water), can be classified and labeled as a "hydrogel", if it is flexible (since the terms "gel" and "gelatinous" imply nonrigid behavior). Hydrogel polymers are of particular interest, and are generally preferred for use herein, for two reasons:

(1) since natural cartilage is a polymeric hydrogel (where collagen, the fibrous protein in animal tissue, provides the molecular strands that hold the cartilage polymer together and give it structure and strength), synthetic polymers manufactured in hydrogel form can more closely emulate the structural, mechanical, and behavioral traits of natural cartilage, compared to other types of polymers that are not hydrogels;

(2) in addition, since the process of hydration (i.e., adding wate

cause a volumetric swelling of the polymer, it may be possible to insert, into a joint, an implant containing a polymer component that is not yet hydrated, or which is only partially hydrated. This approach may be able to reduce the volume of an implant, while it is being inserted into a joint via an arthroscopic insertion tube.

PELVIC IMPLANT, FOR ACETABULAR SOCKET

Referring to the drawings, FIGS. 1-4 depict a "pelvic implant" 100 which is designed, sized, and suited for replacing both the hyaline and labral cartilage in an acetabular socket, on the left or right side of a pelvic bone.

The implant has a central component 110, which provides: (i) an unoccupied "access channel" 112, which leads to a "central vacancy" 114. The term "access channel" 112 (either with or without the adjective, "unoccupied") indicates that a segment of twine or rope (or, in practical terms, an undamaged ligamentum teres which remains fully attached, at both ends, to large bones) can be moved into the central vacancy 114, via the access channel 113, without having to be "threaded into the hole" from either above or below the device, and without having to breach or violate the material that flanks and brackets the access channel.

Accordingly, this implant device has a shape that can be called a "horseshoe"

configuration, or which resembles the letter "C", or the letter "U". This shape generally emulates the shape of the hyaline cartilage surface in a normal and healthy acetabular socket, in which the ligamentum teres directly passes from a centered location in the acetabular socket, into a small depression in the center of the femoral ball. Accordingly, the access channel 112 of implant 100 will allow the implant to be physically inserted into the acetabular socket, even if that ligament is present, in a manner which causes the ligament to pass through the access channel. Once the implant reaches the desired "depth", in the gap between the pelvic bone and the femoral head, it will be rotated, around the ligament, until the access channel reaches a desired orientation, which generally will be pointed slightly away from a vertically downward direction (at least, in a human patient), in a manner which will emulate the orientation of an acetabular cartilage segment (which also has a "horseshoe" shape) in a healthy hip joint. The implant will then be anchored to the pelvic bone, in that position.

As mentioned above, central component 110 will have a smootl

surface 118, on one side of the component 110. The side with the articulating surface 118 can be called the "front" of the implant, if desired, especially for implants designed for humans, since it will face in the anterior direction, after implantation in a human pelvis. In implants designed for four-legged animals, the side with the articulating surface 118 can be called the "lateral" side (a term which indicates that something points outwardly, either left or right, away from the vertical center plane of the animal, as distinct from the "medial" direction, which indicates an inward direction or orientation, toward the animal's center plane).

This implant design is believed by the Applicant to be the first such implant design, for hip replacement implants, which will closely emulate the physiology and behavioral

performance of native cartilage in an acetabular socket. In specific, the geometry and shape of this type of implant will both: (i) enable a surgeon to spare and preserve an intact ligamentum teres, so that the joint will contionue to function in a more normal and natural manner, after the surgery; and, (ii) permit and promote the same types and patterns of synovial fluid secretion, flow, and distribution, within a hip joint, that occur in a normal and healthy hip joint. For an implant in a weight-bearing hip joint which provides a relatively soft and flexible bearing surface, similar to cartilage (and different from the types of super-hard alloy implants used in conventional hip resurfacing), sustained lubrication by synovial fluid will be critical to enabling the implant to last for multiple years or even decades.

As indicated in FIGS. 2-4, a porous anchoring surface 150 is located on the opposite side of the implant (which can be called the back or posterior side, in a human hip implant, and which can be called a medial (as opposed to lateral) surface, in most types of four-legged animals). After implantation, the porous anchoring surface will be pressed directly against a bone surface from which any native cartilage has been removed. After a surgeon has removed the native cartilage, he or she usually will perform a scraping, abrading, or similar procedure, on the bone surface; this is frequently referred to as a "freshening" step, by orthopedic surgeons, since it primes and activates various natural repair mechanisms which will help accelerate tissue regrowth and repair, after surgery has been completed. The anchoring layer 150 may be made of a flexible mesh (made of thin strands of titanium steel or other biocompatible metal, or made of a stranded polymer or similar material, if desired) which will actively pn

the anchoring surface, after the device has been implanted into an anim

If desired, the porous anchoring surface 150 can be coated, embedded, or otherwise treated so that it will carry or contain one or more types of cells and/or bioactive compounds, either before or during implantation. For examples, various types and mixtures of

growth-stimulating hormones (including bone-stimulating hormones, often referred to as osteogenic hormones) stromal precursor cells (i.e., partially-mature cells which are capable of differentiating into various types of connective tissue cells), and platelet cells (i.e., specialized white blood cells which play key roles in the repair and regeneration of injured tissues) have begun to play important roles in orthopedic surgery, and in various types of medical

interventions which involve little or no cutting (commonly referred to, among practitioners and specialists, as "sports medicine" and/or "regenerative medicine"). These and various other known bioactive agents can be used to create liquefied mixtures which can be coated onto (and/or embedded within, with the help of centrifugation or similar force-generating procedures) a porous anchoring surface of an implant as described herein.

Each of FIGS. 1-4 also depicts an enlarged and generally curving cylindrical component 120 positioned around the outer rim of implant 100. That enlarged rim structure will replace the "labral rim" component of a damaged acetabular socket, described in the Background section.

The enlarged rim component 120 also provides a useful and convenient anchoring means. As depicted in the partial cutaway segment shown in FIG. 2, the smooth-surfaced polymeric material which will provide the wettable articulating surface of the implant has been molded around an anchoring cable 122, which may be made of thin and flexible twisted or braided strands of a biocompatible metal (such as a stainless steel alloy) or polymer (such as nylon, ultra-high molecular- weight polyethylene, etc.). A strand of suture material 124 also is shown; it has been wrapped around cable anchoring 122, using several "turns" to reduce any risk of sliding or other displacement. Each of the two protruding (or free) ends of suture strand 124 can be affixed by the surgeon to a nearby location on the pelvic bone, to provide additional anchoring for the implant.

Any desired number of these types of anchoring strands can be affixed to the embedded anchoring cable, around the periphery of the implant; the preferred number will depend on factors such as: (i) the size of the implant; and, (ii) the type, size, and w

human that the device will be implanted in. If desired, the two "free en<

coupled to "racheting" anchors (i.e., anchoring devices that will allow a strand to be pulled in one direction, so that the anchoring strand can be conveniently tightened at an appropriate time, during the surgery, and which will prevent any travel of the strand in the opposite direction), or to any of various types of "lockable" anchoring mechanisms. The two ends of an anchoring strand can be positioned and anchored separately, or they can be kept together as a coupled pair.

As indicated in FIGS. 2-4, the enlarged rim component 120 truncates, at each end, in anchoring components 132 and 134. The two anchoring components 132 and 134 will provide suitable means for securely attaching the implant, at those two locations, to prepared surfaces in the pelvic bone. For example, these devices can provide "snap cap" attachments, with a metallic or other stiff-but-yielding "split ring" component that can be pressed down onto the rounded head of an anchoring screw. That is one preferred mode of attachment, since it will allow each of the two anchoring screws to be emplaced in the pelvic bone, at appropriate locations, after the damaged native cartilage has been removed from the bone surface, but before the implant device is inserted into the joint, while the available working space is relatively open and uncluttered. Alternately, the two anchoring attachments can be in the forms of eyelets or similar devices, which will allow an anchoring screw to be driven through each eyelet and then covered by a protective covering layer or device; this can avoid any risk of misalignment of the implant with the anchoring screws.

Alternately, the two anchoring components 132 and 134 can be designed and used as protrusions (which can also be called pegs, fingers, extensions, prominences, or similar terms) which will fit into accommodating holes which can be drilled or otherwise prepared in the receiving bone, before the implant is inserted into the hip joint that is being repaired. If this approach is used, the two protrusions 132 and 134, rather than containing a "snap cap" or similar device which will be coupled to the head of an anchoring screw, will simply have paired or multiple anchoring sutures emerging from each of the two protrusions 132 and 134. This design is likely to be preferred, for example, for implants designed for medium-sized or small dogs, where: (i) the amount of weight and compressive forces that will be loaded onto the implant will not be great; and (ii) there may not be sufficient thickness, in the pelvic bone at the anchoring site, to accommodate the shaft of an anchoring screw.

FEMORAL IMPLANT

FIGS. 5 and 6 depict a femoral implant 200, which is designed, sized, and shaped to replace damaged cartilage on the convex surface of the ball (also called the head) of a femur (i.e., the long bone inside the thigh). As with the pelvic implants, these femoral implants will have a smooth and wettable articulating surface 210 on one side. That side can be called the outside (or outer surface, or similar terms) of a femoral implant, since its generally hemispherical shape clearly gives it an outer (external) surface.

The other side (which can be called the inside, interior, or similar terms) of femoral implant 200 will provide a porous anchoring surface 220. As with the pelvic implants, this anchoring layer will directly contact a "freshened" bone surface after the surgery, it will be designed to promote tissue ingrowth into the anchoring layer, and it can be coated or embedded with growth factors, platelet cells, stromal precursor cells, or other biologically active

compounds.

For simplicity of illustration, the femoral implant 200 in FIGS. 5 and 6 is depicted with a continuous outer ring 202, surrounding a somewhat off-center opening (or orifice, vacancy, or similar terms) 204. Vacancy 204 is designed to allow passage of a ligamentum teres (mentioned above) through vacancy 204, following surgery, as described in more detail below. In addition, vacancy 204 enables and facilitates the flow and distribution of synovial fluid across the articulating surfaces of the acetabular and femoral implants, as they press, rub, and slide against each other. To the best of the Applicant's knowledge and belief, no prior hip replacement implants provide for sparing of the ligamentum teres, and no prior hip replacement implants enable or promote the normal and natural flow and distribution of synovial fluid, to lubricate a completely resurfaced joint.

If desired, an "elevated ring" of material 230 can be provided, around the anchoring surface of femoral implant 200. This "elevated ring" can be designed to settle into a groove which has been machined, by the surgeon, into the entire circumference (or any desired and controlled portion) of the femoral head, to provide a "snap-on" type of emplacement fitting, which can give additional strength and stability to the implant. Although not shown in the drawings, a femoral implant can

molded within the polymeric component, in a manner which surrounds

the device, and a plurality of suture strands can be wrapped around the cable. These components will be directly comparable to the anchoring cable 122 and anchoring suture strands 124, which are shown in FIG. 2 for a pelvic implant, and the same teachings and comments above, for anchoring cables strands in pelvic implants, also apply to femoral implants.

If a continuous outer ring 202 surrounds the center vacancy 204, the implant 200 cannot be moved into position over a ligamentum teres which is intact. Therefore, these types of implants are designed for use in animals or patients in which the ligamentum teres has already been severed, or has become damaged or degraded so badly that a surgical reconstruction is advisable. That is the condition which exists in most dogs that have been suffering from hip problems for sustained periods of time; accordingly, this class of implants will generally be advisable for use, in dogs (and human patients) with severed or badly damaged center ligaments.

By contrast, FIG. 7 depicts a "split" femoral implant 300, which has a seam or juncture 310, which can be opened temporarily. This seam or juncture 310 provides an access channel to an somewhat off-centered vacancy 312, and it will allow implant 300 to be opened somewhat, while it is being placed and positioned on the surface of a femoral ball, so that the surgeon will not need to sever and subsequently reconnect an intact and functioning ligamentum teres.

If desired, seam 310 (which can also be referred to as access channel 310, since the seam can indeed be opened, when needed, to convert it into an access channel) can be provided with a "tongue and groove" or "chevron" design which does not require any flexure, when being closed. This would be comparable to various types of planks or sheets, made of wood or similar non-rubbery materials, that are used in cabinet-making, flooring, and other types of carpentry.

Alternately, since the polymers that will be used to make these devices will be made of elastomeric materials, the "tongue" component can have an enlarged "head" on a slightly smaller "neck", in a manner comparable to the types of rounded protrusions that are present on conventional jigsaw puzzle pieces. This would require an assembly step that would require the use of a moderate compressive force, to "snap" the tongue component into the corresponding groove, which in turn will impart a somewhat higher level of strength and stability to the juncture that will result from that type of closure step. Accordingly, a design which requires some level of compressive force, so that closure of the seam or juncture

reinforced, is regarded as generally preferable to a non-snapping tongu

used for materials such as wood.

Alternate and/or additionally, other designs and mechanisms can be incorporated into a "split" implant, to help ensure a tight, reliable, and secure closure. For example, a securing mechanism can be provided, on a component such as a peripheral anchoring cable, which will allow a surgeon to adjust the level of tensile force on that component, in an adjustable manner, such as by rotating a threaded component, or by pulling a suture strand through a gripping or anchoring device which contains a ratchet mechanism.

Thus, there has been shown and described a new and useful class of flexible implants, designed for surgical replacement of damaged cartilage in hip joints. Although this invention has been exemplified for purposes of illustration and description by reference to certain specific embodiments, it will be apparent to those skilled in the art that various modifications, alterations, and equivalents of the illustrated examples are possible. Any such changes which derive directly from the teachings herein, and which do not depart from the spirit and scope of the invention, are deemed to be covered by this invention.

Claims

1. An implant device for replacing cartilage in an acetabular socket in a mammalian hip joint, comprising at least one component having a smooth articulating surface which emulates the size and shape of a native cartilage segment which covers an acetabular socket in said mammalian hip joint,

wherein said implant device contains both a central vacancy, and an access channel which provides access to said central vacancy, wherein said central vacancy and said access channel are sized and suited to enable:

a. surgical implantation of said implant device, into an acetabular socket from which native cartilage has been removed, in a manner which does not require alteration of a ligamentum teres which is connected to said acetabular socket; and,

b. natural patterns of distribution of synovial fluid across articulating surfaces within said hip joint.

2. The implant device of Claim 1, wherein said implant has sufficient flexibility to enable said implant to be rolled into a cylindrical configuration having a diameter which will allow insertion of said implant device, into a joint that requires surgical repair, through an arthroscopic insertion tube.

3. The implant device of Claim 1, which also comprises at least one anchoring component selected from the group consisting of:

a. a flexible multi-stranded cable which is embedded, within a molded polymer component, around at least a portion of an outer peripheral rim of said implant device;

b. a flexible reinforcing component which is embedded, within a molded polymer component, around at least a portion of an outer peripheral rim of said implant device, and which is made of a shape-memory material and/or a super-elastic material;

c. at least one coupling attachment, embedded within or connected to said implant, which will enable said implant device to be securely attached to at least one a

been driven into a pelvic bone; and,

d. a plurality of flexible strands or wires which emerge from said implant device, and which have free ends which can be attached to anchors that can be embedded within a bone.

4. The implant device of Claim 1, wherein said articulating surface contains an enlarged rim component which is sized and shaped to emulate labral cartilage in a hip joint.

5. The implant device of Claim 1, wherein said implant device is designed, sized, and suited for implantation in a dog hip.

6. The implant device of Claim 1, wherein said implant device is designed, sized, and suited for implantation in a human hip.

7. An implant device for replacing hyaline cartilage in a mammalian hip joint, comprising:

a. at least one polymeric component having a smooth articulating surface which emulates the size and shape of a natural hyaline cartilage segment in a hip joint of a patient or animal suited to receive such implant;

b. at least one anchoring surface comprising a layer of material which is porous, and which is designed and suited to promote tissue ingrowth after surgical implantation; and,

c. a plurality of anchoring components which, acting together, enable surgical anchoring of said implant to a hip bone from which native cartilage has been removed;

wherein said implant device has sufficient flexibility to enable said implant to be rolled into a cylindrical configuration which will allow insertion of said implant device into a joint that requires surgical repair, through an arthroscopic insertion tube,

and where said implant is sized, designed, and suited to replace a hyaline cartilage surface in a mammalian hip joint.

8. The implant device of Claim 7, wherein said anchoring components are selected from the group consisting of:

a. a flexible multi-stranded cable which is embedded, within a r

component, around at least a portion of an outer peripheral rim of said implant device;

c. at least one coupling attachment, embedded within or connected to said implant, which will enable said implant device to be securely attached to at least one anchoring screw which has been driven into a pelvic bone; and,

9. The implant device of Claim 7, wherein said articulating surface contains a central vacancy and an access channel which are sized and shaped to enable a surgeon to insert and emplace said implant device around an intact ligamentum teres without altering said ligamentum teres.

10. An implant device for replacing hyaline cartilage on an femoral head in a mammalian hip joint, comprising at least one component having a smooth convex articulating surface with a size and shape which emulates femoral hyaline cartilage in a hip joint of patient or animal suited to receive such implant,

and wherein said implant device contains a central vacancy which is sized, positioned, and suited to coexist, after implantation, with an intact ligamentum teres which is connected to said femoral head.

11. The implant device of Claim 10, wherein said implant device is provided with an access channel which leads to said central vacancy, wherein said access channel can be temporarily opened, during surgical implantation, to allow said implant device to be emplaced upon a femoral head which is being resurfaced, around a ligamentum teres which remains connected to said femoral head, without requiring any alteration of saic

12. The implant device of Claim 10, which also cocmprises anchoring components selected from the group consisting of: