WO2010065545A1 - Outils et procédés de dimensionnement d’espace de disque intervertébral - Google Patents

Outils et procédés de dimensionnement d’espace de disque intervertébral Download PDF

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Publication number
WO2010065545A1
WO2010065545A1 PCT/US2009/066264 US2009066264W WO2010065545A1 WO 2010065545 A1 WO2010065545 A1 WO 2010065545A1 US 2009066264 W US2009066264 W US 2009066264W WO 2010065545 A1 WO2010065545 A1 WO 2010065545A1
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WO
WIPO (PCT)
Prior art keywords
instrument
expandable device
force
intervertebral space
pad members
Prior art date
Application number
PCT/US2009/066264
Other languages
English (en)
Inventor
Jeffrey L. Trudeau
Thomas S. Kilpela
Qi-Bin Bao
Weston Pernsteiner
Original Assignee
Pioneer Surgical Technology, Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US12/368,964 external-priority patent/US9216098B2/en
Application filed by Pioneer Surgical Technology, Inc filed Critical Pioneer Surgical Technology, Inc
Publication of WO2010065545A1 publication Critical patent/WO2010065545A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
    • A61F2/4657—Measuring instruments used for implanting artificial joints
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/02—Surgical instruments, devices or methods, e.g. tourniquets for holding wounds open; Tractors
    • A61B17/025—Joint distractors
    • A61B2017/0256—Joint distractors for the spine
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
    • A61F2/4657—Measuring instruments used for implanting artificial joints
    • A61F2002/4658—Measuring instruments used for implanting artificial joints for measuring dimensions, e.g. length
    • A61F2002/4661—Measuring instruments used for implanting artificial joints for measuring dimensions, e.g. length for measuring thickness
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
    • A61F2/4657—Measuring instruments used for implanting artificial joints
    • A61F2002/4668—Measuring instruments used for implanting artificial joints for measuring angles

Definitions

  • the present invention relates to sizing tools used to measure the space between vertebrae for placement of artificial implants therebetween, and in particular, to sizing tools that can expand within an intervertebral space and methods for their use.
  • Damage to or degeneration of a spinal disc can result from a number of factors such as abuse or age.
  • the disc itself is composed primarily of an annulus and a nucleus contained therein.
  • the annulus is a fibrous annular piece that connects to the adjacent vertebrae and contains the nucleus, which is in turn a gel-like viscous material capable of shock absorption and flowable to permit poly-axial rotation and resilient compression of the vertebrae and spine.
  • disc degeneration results from damage occurring to the annulus such that the flowable nucleus material may leak or seep out of the annulus.
  • Disc degeneration also can occur in other ways, such as by being deprived of nutrient flow leading to a dried disc susceptible to damage. Because the nuclear material is flowable, extensive damage to the annulus is not necessary for leakage to occur.
  • Discectomy is effective for relieving sciatic pain by removing the damaged or herniated disc tissue compressing the spinal nerves.
  • current discectomy often may lead to a reduction of the disc space between adjacent vertebrae, as well as instability in the affected portion of the spine.
  • Such long-term effects with current discectomy often result in further surgery several years after the initial discectomy surgery.
  • a disc arthroplasty restores or reconstructs the disc using a prosthesis to replace a portion or entirety of the damaged disc.
  • the primary objective of disc arthroplasty is to restore or maintain the normal disc anatomy and functions, while addressing and treating the causes of the pain.
  • prosthetic disc implants have problems due to the complexity of the natural disc structure and biomechanical properties of a natural spinal disc.
  • the term natural refers to normal tissue including portions of the spine and the disc.
  • TDP total disc prosthesis
  • the other type is a disc nucleus prosthesis, or DNP, that is used to replace only the nucleus of a spinal disc after a nucleotomy while retaining the annulus of the disc and, possibly, the endplates intact.
  • DNP disc nucleus prosthesis
  • failure of the natural disc does not require extensive damage to the annulus.
  • An undamaged annulus would often be capable of retaining a non-flowing prosthetic nucleus.
  • Implantation of a DNP involves making a small incision in the annulus, clearing of the natural nucleus from the annulus through the procedure known as nucleotomy, and inserting the DNP through, and then within, the annulus. Accordingly, DNPs are typically smaller and require less extensive surgery than TDPs while still mimicking some of the biomechanical properties of a natural intervertebral disc.
  • Implantation of most DNPs with pre-formed dimensions requires a 5-6 mm, or larger, incision in the annulus for implantation and uses minimal disc tissue resection. Moreover, recovery and post-surgical pain are minimal due to the minimal invasiveness of the procedure, and interbody fusion remains a viable revision surgery. In addition, the incision in the annulus is kept as small as possible to minimize the potential for the implant to back out through the incision. The annulus itself is used to at least aid in maintaining the implant within the nuclear space. This permits the DNP to sit in the intervertebral space without anchors that violate the endplates of the vertebrae.
  • the ability of the annulus to retain the implant is diminished if not eliminated.
  • the risk of enlarging the incision on the annulus in the DNP procedure is increased because sizing tools are typically also placed through the incision.
  • the size of the implant should match the size of the natural disc and/ or nuclear cavity (i.e. the height of the space between adjacent vertebrae and the width and length dimensions or the footprint of the space within the annulus). If the implant is too large or too small, the implant may cause damage to the spine or pain to the patient.
  • DNP requires less extensive surgery than for a TDP since it replaces only part of the disc.
  • Implantation of most known DNPs with preformed dimensions generally requires a 5-6 mm, or larger, incision in the annulus for implantation.
  • the incision should be kept as small as possible to hold the DNP within the annulus without using anchors on the DNP that extend into the endplates of the vertebrae for securing the DNP.
  • the minimal invasiveness of the procedure results in minimal recovery and post-surgical pain, and interbody fusion remains a viable revision surgery.
  • maintaining a small incision and keeping damage to the annulus to a minimum is a high priority. Therefore, it would be desirable to provide a DNP and trial spacer that does not require an enlarged incision and does not significantly damage the annulus or other tissue during insertion and placement of the DNP.
  • a natural nuclear space within the annulus has a length in the lateral direction (orthogonal to the anterior-posterior direction) that is longer than the width of the space in the anterior-posterior direction. Since it would be desirable to have the sizing tool as well as the implant match the shape of the nuclear space, some conventional sizing tools or implants are generally rectangular, oval or obround with a length greater than its width in order to more closely fit the nuclear space. In this case, the short or narrow side of the sizing tool or implant is presented as the leading edge for insertion (i.e. it faces the incision) in order to maintain a reduced incision on the annulus. This frequently requires an anterior-lateral approach to the surgical site which requires a general surgeon's service, typically in conjunction with an orthopedic surgeon or neurosurgeon, or both, which then raises the costs of the procedure.
  • a posterior or posterior-lateral approach while less costly, does not typically permit the access required for inserting sizing tools, removal of the natural disc and implantation of the prosthetic device because the geometry and structure of the spine blocks or fills the path to the nuclear space that is needed for the approach. This is especially true for a sizing tool as described where the sizing tool's long side would need to be presented first for insertion and extraction from a posterior approach. Therefore, a need exists for a sizing tool that is not limited to particular surgical approaches.
  • Some implants utilize an inflatable bladder or balloon-like structure as disclosed by U.S. Patent Publication No. 2004/0133280. These inflated structures, however, are not configured to be deflated in any controlled manner. Uncontrolled collapse of an inflated body within an annulus may result in a deflated structure that is too large or irregularly shaped to be retracted through the incision without enlarging the incision or damaging the annulus or other tissue.
  • Another problem occurs when the top or bottom end of a sizing tool does not match the geometry of the endplates on the opposing vertebrae which may be slanted to align with the lordotic or kyphotic curve of the spine.
  • a mismatch occurs, such as when the top plate of a sizing tool remains horizontal while the endplate of a vertebrae it faces is slanted, measurement readings of the height of the nuclear space may be inaccurate.
  • an intervertebral space sizing method and apparatus for measuring within the intervertebral space comprises placing an expandable and contractible device into the intervertebral space and measuring a characteristic of the space using an expandable device in an expanded size and then contracting the device to a contracted size and removing it from the intervertebral space.
  • the expandable, contractible device is shifted to an expanded size or position, e.g., in the superior-inferior direction relative to the intervertebral space, so that the device abuts adjacent vertebrae in order to determine the distance from one vertebra to the other.
  • the expandable device is configured to measure the width or footprint of the intervertebral space or an angle of the endplate of a vertebra.
  • the device is contracted after the measuring operation to a smaller size to be removed to lessen any damage during the withdrawal operation.
  • a holder or support for the device is held by the surgeon to insert and remove the device.
  • the intervertebral space being measured may be with or without an annulus forming a nuclear space within the annulus, the device is particularly useful for being inserted and removed through a small incision in the annulus used to remove the disc.
  • the implantable space in a preferred form is an intervertebral space.
  • a measuring instrument is implemented in the form of an expandable intervertebral sizing instrument.
  • Many features of the expandable intervertebral sizing instrument are applicable to surgical instruments in general, but in a preferred form, the intervertebral sizing instrument according to the present invention is particularly suited for determining the size and lordotic angle at a set distraction force of an intervertebral space to appropriately size spinal implants such as spinal cages, VBR/IBFs, and motion preservation implants such as TDPs, or DNPs.
  • the expandable sizing instrument has a mechanism in the form of a measuring head configured to expand within an intervertebral space, i.e.
  • the measuring head includes a spacer mechanism which preferably includes a pair of pads that can toggle or pivot to effectively conform to the configuration of the vertebral surfaces including the lordotic angles thereof to facilitate accurate measurement of the space between the vertebrae.
  • the pads may be radio-opaque, which allows the exact angle of the vertebral surfaces to be determined via fluoroscopy or x-ray imaging while the pads are positioned within the intervertebral space in an expanded configuration.
  • the expandable sizing instrument has a thin curved outer shaft to reach within the narrow confines of the intervertebral space from a variety of surgical approaches, i.e. angles of entry.
  • the outer shaft could also be straight for conventional surgical approaches.
  • the outer shaft also preferably includes an indicator mechanism that displays a visual indication of the amount of space or height within the intervertebral space, which corresponds to the distance between the outer surfaces of the pads, which abut the inner surfaces of the adjacent vertebrae when the measuring head is in an expanded configuration.
  • the expandable sizing instrument has a handle mechanism which has an adjustable force-setting mechanism including a compressible spring that creates the amount of force used to distract the vertebrae, i.e. the distraction force.
  • the amount of force is controlled by the force adjustment mechanism in the form of a knob which can set the desired amount of distraction force via rotation thereof.
  • a certain amount of distraction force is required to slightly distract the adjacent vertebrae so that when the implant is inserted, there is sufficient compressive force exerted on the implant by the vertebrae to keep the implant from slipping out of place.
  • Using an inadequate amount of distraction force while sizing the intervertebral space can result in undersizing the implant, because the implant will not fit snugly between the vertebrae.
  • Using an excessive amount of force can result in excessive distraction of the vertebrae, which may cause the selection of an implant that is too large for the space, and can damage the vertebral surfaces, endplates, or connective tissues in and around the spinal joint.
  • a user may reliably set the distraction force of the sizing instrument and thereby avoid excessive risk of inaccurately sizing the implant or causing injury to the patient.
  • the expandable sizing instrument is operated by adjusting the force adjustment mechanism, and positioning or placing the tip of the inserter within the intervertebral space.
  • An actuator mechanism such as a trigger or lever operably connected to the spacer mechanism, is operable to cause the spacer mechanism to expand or contract.
  • the actuator mechanism When the actuator mechanism is moved to a first position, the spacer mechanism expands and the indicator mechanism indicates the size of the intervertebral space corresponding with the expanded size of the spacer mechanism.
  • the spacer mechanism may be contracted by moving the actuator mechanism to a second position, which corresponds to an insertion or removal configuration of the measuring head.
  • One advantage of the expandable sizing instrument is the ability to eliminate multiple insertions of different sized trial spacers to determine the correct size implant.
  • the elimination of multiple insertions into the narrow confines of the intervertebral space reduces the time required for the surgery and amount of time the patient is under anesthetic.
  • the reduction of time under anesthetic correspondingly reduces the health risk and the recovery time of patients due to the surgery and anesthetic.
  • Another advantage of the expandable sizing instrument is the ability to reduce the potential of tissue damage to the remaining annulus fibrosus or disc during the implantation of a disc nucleus prosthesis, or DNP.
  • the repeated insertion and removal of static trial spacers can cause damage to the annulus, because the remaining annulus is generally stretched each time a spacer is inserted or removed.
  • the expandable sizing instrument has the advantage of minimizing tissue damage to the annulus.
  • an additional advantage of the expandable sizing instrument is the ability to improve consistency and reliability of the insertion of spinal implants such as spinal cages, VBR/IBFs, TDPs, or DNPs.
  • the expandable sizing instrument allows the accurate and consistent sizing of intervertebral implants in an objective measurable way.
  • the precise measurement of the intervertebral space reduces reliance upon the subjective manner in which surgeons determine the correct implant size based on the subjective "feel" of the fit of a trial spacer and hence reduces human error.
  • the objective measurement provided by an expandable sizing instrument according to the present invention allows for more consistency and reliability in the implantation of correctly sized spinal implants.
  • the expandable sizing instrument saves labor because there is less training required to size implants and a lessened likelihood of subsequent revision surgeries.
  • FIG. 1 is a perspective view of an expandable sizing instrument in accordance with the present invention showing a pair of pad members of a measuring head in an open configuration thereof.
  • FIG. 2 is an exploded perspective view of the expandable sizing instrument of FIG. 1.
  • FIG. 3 is a side elevational view of the expandable sizing instrument showing the pad members in a closed configuration thereof, with the actuator in the forward orientation, which corresponds with an insertion and removal configuration of the sizing instrument.
  • FIG. 4 is a side elevational view of the expandable sizing instrument showing the pad members in an opened configuration thereof, with the actuator in an intermediate rearward orientation, which corresponds with an opened configuration of the sizing instrument.
  • FIG. 5 is a cross-sectional view of the expandable sizing instrument of
  • FIG. 4 showing the biasing member in the form of a coil spring and a force adjustment mechanism disposed in the handle portion of the instrument.
  • FIG. 6 is an enlarged, fragmentary cross-sectional view of the expandable sizing instrument measuring head in the opened configuration, showing upper and lower link members connecting the upper and lower pad members to the distal drive member via pin connections.
  • FIG. 7 is an enlarged, fragmentary cross-sectional view of a drive mechanism of the expandable sizing instrument, showing the connection of the inner shaft to the distal drive member via a linkage member.
  • FIG. 8 is an enlarged, fragmentary cross-sectional view of the indicator and force applicator mechanism of the expandable sizing instrument, with the actuator in a forward position corresponding with a closed configuration of the measuring head.
  • FIG. 9 is an enlarged, fragmentary cross-sectional view of the force applicator mechanism of the expandable sizing instrument, and particularly the force adjustment mechanism thereof, which is operable to adjust the amount of distraction force transmitted to the vertebrae via the pad members.
  • FIGS. 10 and 11 are elevational views of the measuring head of the expandable sizing instrument in the respective closed and opened configurations.
  • FIG. 12 is an enlarged, fragmentary cross-sectional view of the pads in the opened configuration, showing the pivotable bearing system with pins disposed in the throughbores of the upper and lower linkages having central narrow portions and outer portions having expanded configurations, which allow the pad members to pivot in a plurality of directions.
  • FIG. 13 is a plan view of the expandable sizing instrument showing the distraction force indicator disposed on the handle thereof.
  • FIG. 14 is a plan view of the expandable sizing instrument measuring head in the open configuration.
  • FIG. 15 is a top sectional view of the expandable sizing instrument measuring head in the opened configuration as shown in FIG. 13.
  • FIG. 16 is an enlarged, fragmentary cross-sectional view of the expandable sizing instrument measuring head in the opened configuration.
  • FIG. 17 is an enlarged, fragmentary cross-sectional view of the expandable sizing instrument in the opened configuration.
  • FIG. 18 is an enlarged, fragmentary cross-sectional view of the expandable sizing instrument showing the indicator mechanism and actuator mechanism.
  • FIG. 19 is an enlarged, fragmentary cross-sectional view of the force adjustment mechanism.
  • FIGS. 20 and 21 are rear views of the expandable sizing instrument in respective closed and opened configurations thereof showing the adjustment knob disposed on the handle.
  • FIG. 22 is a rear cross-sectional view of the force adjustment member, the orientation plug, and the biasing member disposed within the handle.
  • FIG. 23 is a perspective view of the expandable sizing instrument operating in the intervertebral space from a generally anterior insertion orientation, with the measuring head in the measuring configuration.
  • FIG. 24 is an enlarged, fragmentary perspective view of the sizing indicator for the expandable sizing instrument.
  • FIG. 25 is an enlarged, fragmentary side view of the sizing indicator for the expandable sizing instrument showing a measurement of 11 mm, corresponding with an opened position of the measuring head.
  • FIGS. 26 and 27 are respective side elevational and enlarged, fragmentary cross-sectional views of the expandable sizing instrument in the locked open configuration.
  • a system for replacing a spinal disc from an intervertebral space between adjacent, superior and inferior vertebrae includes a number of alternative sizing tools described herein and used for determining the size of the intervertebral space. After the size is determined using the sizing tools described herein, an artificial disc implant with an appropriate size that fits the measured space can be implanted so that the relatively complicated procedure for implanting the disc does not need to be repeated.
  • the sizing tools may be used for implantation of either a disc nucleus prosthesis (DNP) or a total disc prosthesis (TDP).
  • the sizing tool described herein has a holder with a distal end connected to an expandable device that is placed within the intervertebral or nuclear space.
  • the illustrated expandable device has a superior portion that can be shifted closer to or farther from an inferior portion by an expansion mechanism connected to the expandable device.
  • the expansion mechanism is provided on the sizing tool for expanding the expandable device in a superior-inferior direction and within the intervertebral space so that the expandable device abuts both vertebrae forming the space to determine the distance or height from one vertebra to the other.
  • intervertebral space includes the space with or without an annulus forming a nuclear space.
  • proximal refers to a direction of the instrument away from the patient and towards the user while the term “distal” refers to a direction of the instrument towards the patient and away from the user.
  • distal refers to a direction of the instrument towards the patient and away from the user.
  • proximal end of the expandable sizing instrument 1001 is shown on the top right of the figure shown as direction A.
  • proximal direction is referring to any motion toward the user and in FIG. 1 is toward the top right in direction A.
  • distal end of the inserter 1001 is shown on the bottom left of FIG. 1.
  • distal direction is referring to any motion toward the patient and in FIG. 1 is toward the bottom left shown as direction B in FIG. 1.
  • the expandable sizing instrument 1001 allows a precise amount of distraction force to be set by the force adjustment mechanism 1801 and the amount of intervertebral space 2101 can be measured by the spacer mechanism 1101, as shown in FIG. 1.
  • the pads 1103 of measuring head 1100 of the inserter 1001 allow for measurement of varying angulations of endplates 2401 due anatomical differences of patients as shown in Fig. 12 and Fig. 23. All external surfaces of the inserter 1001 preferably are electropolished to improve the efficiency of cleaning and sterilization.
  • the spacer mechanism 1101 is operable to measure the height of the intervertebral space 2101. The spacer mechanism 1101 expands from a closed position shown in FIG. 3 to an expanded open configuration shown in FIG. 4.
  • the spacer mechanism 1101 has a height of 7 mm in a closed configuration and a maximum height of 11.5 mm in a fully open configuration. As shown in FIG. 6, the pads 1103 are connected to the inside linkage 1105 and outside linkage 1107 by the pad pins 1109.
  • the pads 1103 are able to pivot on the inside linkage 1105 and outside linkage 1107 utilizing a pivotable bearing system 1114.
  • the pivotable bearing system 1114 allow the pads 1103 to conform to the varying angulations of the inner endplate surfaces of adjacent vertebrae, which facilitates precise measurement of the intervertebral space. Further, because the pads 1103 can conform more closely to the inner endplate surfaces, the pads 1103 distribute distraction forces more evenly on the endplate surfaces. Consequently, the endplates are less likely to be damaged by the pads 1103 during distraction of the vertebrae and measurement of the intervertebral space.
  • the pivotable bearing system 1114 allows the pads 1103 to tilt about a plurality of different axes such that the pads have two degrees of freedom.
  • the pads 1103 may tilt forwards and backwards about the longitudinal axis of pad pins 1109, as well as laterally from side to side as shown in FIG. 12.
  • the pads 1103 may tilt forwards or backwards and simultaneously to one side or the other such that pads 1103 may tilt in any direction.
  • This poly axial articulation of the pads 1103 allows the pads to conform with the configuration of the endplates, regardless of surgical approach made with the tool. For example, the configuration of the endplates along an anterior approach will likely vary from the configuration of the endplates along a lateral approach.
  • a sizing tool according to the present invention thus allows the surgeon to accurately measure the invertebral space from a plurality of different surgical approaches.
  • the poly axial articulation of the pads 1103 is made possible through the configuration of the throughbores through which the pad pins 1109 are disposed and the bearing surfaces 1107a, 1107b, 1105a, 1105b of the upper and lower linkages 1107 and 1105.
  • the pads 1103 rest on the inside bearing surfaces 1105a and the outside bearing surfaces 1107a when in a non-tilted orientation.
  • the pad bearing surfaces 1103a can tilt at the lordotic angle ⁇ so that the pads 1103 can conform closely to the contour of the endplates.
  • the inner bearing surfaces of the pads 1103c and the pad pins 1109 engage with the inside and outside bearing surfaces 1105b and 1107b, which are angled with respect to the non-tilted orientation of the pads 1103.
  • the lordotic angle ⁇ can vary depending on the anatomy of the patient's vertebrae 2201.
  • the pads 1103 are configured to toggle independently to tilt at a minimum angle of 11 degrees in any direction when the pads 1103 are in an open configuration corresponding with a measurement of 8 mm.
  • the pads 1103 may be tilted a greater amount when the pads 1103 are opened further than 8 mm, because the pad members 1103 do not interfere with one another when distracted further apart.
  • the pads 1103 preferably do not toggle when positioned in a closed configuration.
  • the top pad 1102a and the bottom pad 1102b also pivot independently so that the top pad 1102a can have a lordotic angle which is different from the bottom pad 1102b.
  • the spacer mechanism 1101 may be used to determine the lordotic angle because the pads 1103 tilt or pivot to conform to the lordotic angle of the endplates 2401 and an x-ray or fluoroscopy will clearly indicate the lordotic angle since the radio-opaque pads 1103 will be readily visible on the x-ray or fluoroscopy films.
  • the pads 1103 may pivot in any direction to conform to the lordotic angle of the vertebrae no matter what insertion approach is taken by the user.
  • the pads 1103 may be pivotable to the same angle ⁇ in each direction, or the angle may vary in some directions.
  • the distal ends of pads 1103 may be pivoted towards one another at a greater angle than ⁇ so that the proximal ends of the pads are distracted far enough apart to allow access to the components of spacer mechanism 1101 for easier cleaning.
  • the spacer mechanism 1101 is shiftably connected to the distal drive member 1303 by the inside linkage 1105, and the outside linkage 1107.
  • the opener pin 1111 connected to the outer shaft 1201 causes the inside linkage 1105, and the outside linkage 1107 to distract apart from each other when the distal drive member 1303 moves in the distal direction B because the inside linkage opening cam surface 1111a and the outside linkage opening cam surface 1111b slide along the stationary opener pin 1111.
  • the opener pin 1111 effectively allows the spacer mechanism 1101 to be expandable within the intervertebral space 2101.
  • the closer pin 1113 connected to the outer shaft 1201 closes the inside linkage 1105, and the outside linkage 1107.
  • Closing cam surfaces 1113a, 1113b in the linkages 1105, 1107 provide a guide path that allows the linkages to slide along the closer pin 1113.
  • the stationary closer pin 1113 acts on the sloped closing cam surfaces 1113a, 1113b, providing the linkages 1105 with a closing force which causes the pads 1103 to retract and come together.
  • the closer pin 1113 effectively allows the spacer mechanism 1101 to be collapsible within the intervertebral space 2101 as well as for allowing adjustments of position and removal of the inserter 1001.
  • the pads 1113 and linkages 1105, 1107 is to maintain a substantially constant force distribution on the pads 1103.
  • the pads are operable to provide the set distraction force to the adjacent vertebral bodies with which they are engaged.
  • several factors are considered including spring choice, cam geometry, and pad size. Given a known surface area of the pads, the necessary distraction force for a given cam surface geometry may be calculated using known methods, such as three dimensional modeling software.
  • the force vectors which are perpendicular to the closing cam surface 1111a, 1111b at the contact point between the opener pin 1111 and the closing cam surface 1111a, 1111b, are calculated.
  • the necessary input force is calculated for the initial closed configuration of the pads 1103. Once the input force for the initial closed configuration is determined, additional calculations for the input force at the halfway open configuration and fully open configuration of the pads 1103 are calculated. Based on the input forces at the three points, the spring constant needed at each point can be calculated based on the known displacement of the linkages 1105, 1007 in the proximal-distal direction.
  • the geometry of the closing cam surface 1111a and 1111b may be modified to obtain substantially identical spring constants for each of the three points.
  • the closing cam surfaces 1111a, 1111b have a generally sinusoidal contour along the portion thereof that the opener pin 1111 travels.
  • the appropriate spring is then chosen based on the calculated spring constant.
  • the spring 1703 has a diameter of 0.975 inches and a length of 4 inches.
  • the return spring 1511 preferably has a diameter of 0.281 inches and a length of 0.75 inches, with a spring constant of 9.2. Different springs may be used depending on the desired range of distraction force or pressure and the size of the pads 1103.
  • the amount of distraction force is adjustable to a set level through rotation of the knob 1805 of the force adjustment mechanism 1801, which is operable to selectively compress or allow expansion of spring 1703.
  • the adjustable distraction force ranges from 20 PSI to 70 PSI and the pads 1103 have a surface area between 0.133 to 0.307 square inches.
  • Different sized and shaped pad members may be used, depending on user preference, vertebral size, implant size or shape, insertion approach, and other factors.
  • racetrack-shaped pad members may be used for sizing the intervertebral space for a similarly-shaped nuclear implant.
  • pads 1103 with a round configuration may preferable for use over pads with an elongate configuration, depending on the surgical approach used. For instance, pads with an elongate configuration may be better suited for lateral approaches, because a smaller incision may be made in the annulus to fit the narrow profile of the pads.
  • the spacer mechanism 1101 is preferably made of stainless steel.
  • the inside linkage 1105 and the outside linkage 1107 are 440 stainless steel and provided with a low friction coating to allow smooth cam action by the opener pin 1111 and closer pin 1113 on the linkages 1105 and 1107.
  • the linkages 1105, 1107 are coated with chrome.
  • the outer shaft 1201 provides structural support for both the mechanical operation of the spacer mechanism 1101 previously described and for the drive mechanism 1301 as shown in FIG. 5.
  • the outer shaft 1201 has a small diameter tubular configuration so that it has a narrow circular profile as shown in FIGS. 10 and 11.
  • the narrow profile is desirable to fit within the narrow confines of the intervertebral space 2101 as shown in FIG. 23.
  • the outer shaft 1201 has a curve at angle ⁇ which is shown at approximately 10 degrees in the preferred embodiment.
  • the curve at angle ⁇ of the outer shaft 1201 is configured to allow the inserter 1001 to reach the center of the vertebral body 2201 when the inserter 1001 is used from a posterior approach.
  • the outer shaft 1201 could have a curve at angle ⁇ of zero or be straight for a conventional surgical approach.
  • the outer shaft 1201 also provides structural support to mechanically guide the drive mechanism 1301 as shown in FIGS. 5 and 15.
  • the outer shaft 1201 constrains the distal drive member 1303 and linkage 1305 to move in the proximal and distal directions A and B upon actuation of the actuator mechanism 1501.
  • the outer shaft 1201 also provides the structural connection by joining the spacer mechanism 1101 to the rest of the inserter 1001.
  • the outer shaft 1201 is made of stainless steel in its preferred embodiment
  • the drive mechanism 1301 provides mechanical linkage for the inserter
  • the drive mechanism 1301 is mounted within the outer shaft 1201 to drive the spacer mechanism 1101.
  • the drive mechanism 1301 is composed of three shiftable shafts: distal drive member 1303, linkage 1305 and inner shaft 1307.
  • the distal drive member 1303, linkage 1305 and inner shaft 1307 are mechanically connected by pins 1309 (shown in FIGS. 7 and 17) in order to provide force in the proximal and distal directions A and B at angle ⁇ (shown in FIGS. 13 and 14).
  • the drive mechanism 1301 is made of stainless steel in its preferred embodiment.
  • the indicator mechanism 1401 provides an objective, accurate measurement of the height of the intervertebral space 2101 because the indicator mechanism 1401 is calibrated to the amount of displacement of the drive mechanism 1301 which, in turn, causes a specific known amount of expansion or compression of the spacer mechanism 1101. As shown in FIGS. 5, 8, 15 and 18, the indicator mechanism 1401 is mounted within the outer shaft 1201 and through the inner shaft 1307.
  • the gauge 1403 has a spherical gauge surface 1405 engaged by a compressed gauge spring 1407 biasing the gauge 1403 into position.
  • the spring force is resisted by the gauge pin bearing surfaces 1411 within the inner shaft 1307.
  • the gauge 1403 will pivot or rotate about the spherical gauge surface 1405 to cause the gauge tip 1413 to shift to provide an indication of the size of the intervertebral space 2101.
  • the gauge tip 1413 is free to tilt about the spherical gauge surface 1405 through the outer shaft cutout 1205.
  • the gauge tip 1413 is visible to the operator, typically the surgeon.
  • the indicator mechanism 1401 indicates with the gauge tip 1413 the amount of intervertebral space 2401 available for the implant, which corresponds to the vertical distance between the vertebrae 2501.
  • the indicator mechanism 1401 is made of stainless steel in its preferred embodiment.
  • the actuator mechanism 1501 allows the operator to deploy the spacer mechanism 1101 from the compressed configuration shown in FIG. 3 to the expanded configuration shown in FIG. 4.
  • the operator expands the spacer mechanism 1101 by moving the lever 1503 generally upwardly away from shaft 1201 in direction C to measure the height of the intervertebral space 2101.
  • the operator compresses the spacer mechanism 1101 by moving the lever 1503 generally downwardly toward the shaft 1201 in direction D opposite to direction C in preparation for removing the inserter 1001 from an intervertebral space 2101.
  • the lever 1503 is typically down, i.e.
  • the lever 1503 is mounted to the outer shaft 1201 by the shaft pin 1510. [0075] As shown in FIGS. 5, 8 and 18, the actuator in the form of lever 1503 is connected to the drive mechanism 1301 and force mechanism 1701 by a linkage 1507 with a lever pin 1509 and shaft pin 1510. The force on the drive mechanism 1301 created by the pressure of the patient's tissue on the spacer mechanism 1101 and the return spring 1511 is counterbalanced by the force created by the force mechanism 1701 as shown FIGS. 8 and 18. However, the lever 1503 can alter this balance as desired by the user. Finally, as shown in FIGS.
  • the lever 1503 can be locked open by depressing the lever 1503 until it reaches its locked position, which is caused by interference between the lever body 1503 and the linkage 1507, generally shown in FIG. 27.
  • the spacer mechanism 1101 will be in the most expanded position.
  • the actuator mechanism 1501 is made of stainless steel in its preferred embodiment.
  • the handle mechanism 1601 provides a handle grip 1609 for the operator and provides structural support when the inserter 1001 is grasped by the human hand.
  • the handle mechanism 1601 provides increased distance for the operator especially while conducting x-rays or fluoroscopy. Direct radiation exposure can be minimized by the surgeon grasping the proximal end of the handle mechanism 1601.
  • the handle mechanism 1601 is connected to the outer shaft 1201 by the front handle cap 1605 and set screws 1607.
  • the position of the outer shaft 1201 in relation to the force mechanism 1701 can be adjusted by the set screws 1607 to account for manufacturing error, i.e. stack up error, which occurs during the machining of the various parts.
  • the front handle cap 1605, grip 1609, and end cap 1611 contains the force mechanism 1701 whose main component is a compression spring 1703.
  • the end cap 1611 also provides a bushing for the adjustment shaft 1803.
  • the handle mechanism 1601 is made of stainless steel in its preferred embodiment.
  • the handle mechanism 1601 can be made of Lexan or other clear strong plastics to allow visual feedback of the force mechanism 1701 which is contained within the handle mechanism 1601.
  • the force mechanism 1701 provides a generally constant distraction force through all phases of motion of the spacer mechanism 1101 during a sizing operation of the intervertebral space 2101 and does not require the operator to manually adjust the amount of force used.
  • the force applicator mechanism 1701 automatically sets the distraction force without constant user intervention to maintain the distraction force at a set level.
  • the main component of the force mechanism 1701 is the large compression spring 1703 mounted within the handle mechanism 1601 and shown in FIGS. 5 and 15. As shown in FIGS. 8 and 18, the spring 1703 fits within and exerts a force on the adjustable fitting 1705.
  • the adjustable fitting 1705 is threadably connected to the mechanical adaptor 1707 which in turn transmits a force (that varies with the compression of the spring 1703) to the connection pin 1709.
  • the connection pin 1709 is then connected to the linkage 1507 of the actuator mechanism 1501 and the force exerted by the spring 1703 is transmitted all the way to the spacer mechanism 1101. Should the force exerted on the spacer mechanism 1101 by the vertebrae 2501 increase beyond the force of the spring 1703, then the pads 1103 and spring 1703 will collapse until an equilibrium is reached.
  • the compression spring 1703 is proximally fixed by the orientation plug 1711.
  • the orientation plug 1711 fits within the proximal coils 1703a of spring 1703 and the end cap 1611.
  • the orientation plug 1711 has radial flanges 1711a which fit within slots of the end cap 1611 to prevent the plug 1711 from rotating.
  • the plug 1711 is threadably connected to the adjustment shaft 1803. Rotation of the adjustment shaft 1803 adjusts the force level of the compression spring 1703 by advancing or retracting orientation plug 1711 to respectively increase or reduce compression of the spring 1703.
  • the rotation of the shaft 1803 is carried by the bearing 1713 which is preferably made of Teflon PFE to reduce the friction during rotation and adjustment of the shaft 1803.
  • the variable force of the spring 1703 is adjustable via the knob 1805 of the force adjustment mechanism 1801.
  • the components of the force mechanism 1701 are made of stainless steel in its preferred embodiment.
  • the force adjustment mechanism 1801 provides the element for controlling the amount of distraction force exerted by the inserter 1001 and to allow adjustment of the distraction force to a range of set levels for the user, preferably between 20 and 70 psi.
  • the ability to control the amount of distraction is beneficial because different amounts of force may be needed to achieve the desired amount of distraction, which may depend on the portion of the spine 2001 in which the implant is to be inserted due to anatomical differences, i.e. the cervical region of the spine versus the lumbar portion of the spine. For example, the cervical region may require less distraction force than the larger lumbar region. Similarly, the amount of distraction force required depends on the degree of disc 2301 removal required for the implant.
  • the force adjustment mechanism includes large knob 1805 mounted to the handle mechanism 1601 via the adjustment shaft 1803 shown in FIGS. 5 and 15.
  • the knob 1805 is mounted on the most proximal end of the inserter 1001 as shown in FIGS. 20 and 21.
  • the force adjustment knob 1805 utilizes handle markings 1807 to indicate the amount of distraction force.
  • the knob 1805 is rotated until the plug marking 1809 reaches the desired handle marking 1807 which corresponds to a precise amount of distraction force.
  • the plug marking 1809 is preferably a laser etching on the orientation plug 1711 shown in FIGS. 9 and 19. The plug marking is visible through an aperture 1811 in the handle grip 1609 as shown in FIGS. 13 and 14.
  • the rotation of the knob 1805 causes the adjustment shaft 1803 to rotate and compress the spring 1703 and thus causes adjustment of the amount of force generated by the force mechanism 1701, as described above.
  • the force adjustment mechanism 1801 is made of stainless steel in its preferred embodiment. Alternatively, an internal scale within the handle mechanism 1601 could be used.
  • the inserter 1001 can be manufactured by standard turning, milling, and Electro Discharge Machining (EDM). Alternatively, the inserter 1001 can be made from any suitable, structurally strong materials.
  • the inserter 1001 can be constructed of suitable materials which are compatible with the uses and environments into which the device will be utilized. Preferably, the inserter 1001 is constructed of metallic materials such as stainless steel or titanium. The best mode of sterilizing the expandable space inserter 1001 is by sterilization through autoclave, i.e. steam.
  • the surgical procedure begins with sterilizing the surgical field and inserter 1001. Once the patient is anesthetized, a surgical incision is made in the patient from one of three basic approaches based on the surgeon's preference: 1) an anterior approach, i.e. from the front of the patient, 2) laterally, i.e. from the side of the patient, or 3) posteriorly, i.e. from the back of the patient. Once the incision is made the surrounding tissue is distracted or moved out of the way using standard instruments and methodology.
  • the installation site of the implant is prepared by removing the damaged tissue of the intervertebral disc 2301, i.e. a discectomy.
  • the discectomy can be either a complete discectomy in which the entire disc is removed or a partial discectomy where the nucleus pulposus is removed and the annulus fibrosus is punctured.
  • a full discectomy is more typical for the implantation of a spinal cage, Vertebral Body Replacement (VBR), or Interbody Fusion Device (IDF).
  • VBR Vertebral Body Replacement
  • IDF Interbody Fusion Device
  • a partial discectomy is more typical for the implantation of a DNP. In either procedure, the disc material is removed with a ring curette which cuts out the disc.
  • the annulus fibrosus is punctured and the nucleus pulposus is removed.
  • the endplates of the vertebra are typically roughened with the use of a rasp because of the need to remove all disc material and to encourage blood flow and healing in the intervertebral space 2101.
  • the roughening of the endplates 2401 flattens the surface of the vertebrae 2401 to conform to the surface of the implant thus reducing the risk that the implant will shift out of position.
  • the expandable sizing instrument 1001 surgical instrument is then deployed to determine the height and angles of the endplates 2401 in the intervertebral space 2101.
  • the first step comprises adjusting the force adjustment mechanism 1801 by rotating the knob 1805 and setting the desired amount of distraction force as shown in FIG. 23.
  • the distal end of the spacer mechanism 1101 is then inserted and positioned within the intervertebral space 2101.
  • the actuator mechanism 1501 is deployed by moving the lever 1503 to cause the spacer mechanism 1101 to expand in the intervertebral space 2101.
  • the operator of the inserter 1001 typically the surgeon, will then read the amount of intervertebral space, i.e. the distance between the vertebrae 2501, by viewing the indicator mechanism 1401.
  • the force adjustment mechanism 1801 can be adjusted by rotating the knob 1805 while the spacer mechanism 1101 is within an intervertebral space 2101. Fluoroscopy can then be performed by taking and developing an x-ray or fluoroscopy image while the inserter 1001 is in a fixed position to determine the lordotic angle of the vertebrae 2501. After the invertebral space has been measured, the pads 1103 are retracted by pushing the actuator 1501 distally and the measuring head 1100 is removed from the intervertebral space. A properly sized implant is then selected and inserted as known in the art.

Abstract

La présente invention concerne un procédé et un appareil pour effectuer une mesure de taille dans un espace intervertébral en plaçant un dispositif expansible et contractable dans l’espace intervertébral, l’expansion du dispositif, la mesure d’une taille caractéristique de l’espace, la contraction du dispositif et ensuite son retrait. La mesure peut être effectuée par un dispositif de radiographie externe ou un autre dispositif d’imagerie du dispositif expansé in situ ou par des dispositifs actionnés mécaniquement. La présente invention concerne un appareil et un procédé pour la mesure de l’espace intervertébral à une force de distraction contrôlée. L’appareil comprend un dispositif expansible pour effectuer une mesure dans l’espace intervertébral et faciliter la mesure des angulations de la courbe lordotique de l’espace intervertébral.
PCT/US2009/066264 2008-12-01 2009-12-01 Outils et procédés de dimensionnement d’espace de disque intervertébral WO2010065545A1 (fr)

Applications Claiming Priority (4)

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US11890408P 2008-12-01 2008-12-01
US61/118,904 2008-12-01
US12/368,964 US9216098B2 (en) 2006-08-10 2009-02-10 Intervertebral disc space sizing tools and methods
US12/368,964 2009-02-10

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EP3772350A1 (fr) * 2019-08-05 2021-02-10 Zimmer Biomet Spine, Inc. Système pour déterminer la taille d'un implant cervical

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EP3772350A1 (fr) * 2019-08-05 2021-02-10 Zimmer Biomet Spine, Inc. Système pour déterminer la taille d'un implant cervical

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