CA2264672C

CA2264672C - Method and apparatus for spinal fixation

Info

Publication number: CA2264672C
Application number: CA2264672A
Authority: CA
Inventors: Erik J. Wagner; Vincent J. Jannetty
Original assignee: Zimmer Spine Inc
Current assignee: Zimmer Spine Inc
Priority date: 1996-10-24
Filing date: 1997-10-16
Publication date: 2010-11-30
Anticipated expiration: 2017-10-16
Also published as: WO1998017188A1; CA2264672A1; US5989250A; AU723776B2; JP2007307394A; EP0934026B1; US6613050B1; AU4891797A; JP2002514100A; JP4146500B2; EP0934026A1

Abstract

A spinal fixation implant system for correction and fixation of the human spine to facilitate an anatomically correct fusion. The spinal fixation system may include a connector, a spinal rod, a spinal fixation component, a sleeve, and a fastener. The spinal fixation component preferably includes a fixation device such as a hook or screw for securing the spinal rod to vertebrae of the thoracic or lumbar spine. The spinal fixation component preferably includes a threaded end on its top that is adapted to receive the fastener. The fixation component may include a body having a tapered cavity for engaging the receiving end of the connector. Tightening of the fastener preferably downwardly translates the sleeve over the fixation component body to force the connector through the tapered cavity, which compresses the receiving end about the spinal rod to fixation connect the spinal rod and the spinal fixation component. In an alternate embodiment, assembly pliers may be used to move the connector into the tapered cavity. The fixation component may also include a rotatable fixation member.

Description

ï»¿l0l52025303540CA 02264672 1999-02-26W0 98/ 17188 PCT/US97/16971METHOD AND APPARATUS FOR SPINAL FIXATIONBACKGROUND OF THE INVENTION1. Field of the Invention The present invention generally relates to spinal ï¬xation systems and the like. More particularly. anembodiment of the invention relates to a spinal implant system for correction. ï¬xation. and stabilization of thehuman spine to allow the development of a solid spinal fusion.2. Description of the Related ArtSpinal ï¬xation, such as lumbar sacral fusion and the correction of spinal deformities such as scolioticcurves, is a well known and frequently used medical procedure. Pedicle. lateral. and oblique mounting devicesmay be used to secure corrective spinal instrumentation to a portion of the spine that has been selected to befused by arthrodesis.A spinal ï¬xation system typically includes corrective spinal instrumentation that is attached toselected vertebrae of the spine by screws, hooks. and clamps. The corrective spinal instrumentation includesspinal rods or plates that are generally parallel to the patientâs back. The corrective spinal instrumentationmay also include transverse connecting rods that extend between neighboring spinal rods. Spinal ï¬xationsystems are used to correct problems in the lumbar and thoracic portions of the spine, and are often installedposterior to the spine on opposite sides of the spinous process and adjacent to the transverse process.Various types of screws, hooks. and clamps have been used for attaching corrective spinalinstrumentation to selected portions of the patientâs spine. Examples of pedicle screws and other types ofattachments are illustrated in US. Patent Nos. 4,763,644; 4,805,602; 4,887,596; 4,950.269: and 5,129,388.Each of these patents is incorporated by reference as if fully set forth herein.An eyebolt assembly of the TSRHÂ® spinal system sold by Danek Medical Inc. is illustrated in Figurel. The eyebolt assembly 2 encircles spinal rod 4 such that assembly mass completely surrounds the spinal rod.The spinal rod must be inserted through the eyebolt, which rests within the yoke of spinal hook 8. The spinalhook attaches the spinal rod to a bony element of the spine. A nut 6 is threaded onto a post of the eyeboltassembly to ï¬xably secure the rod within the yoke. The nut is tightened so that the assembly resists axial.torsional, and shear forces to inhibit motion of the spinal rod relative to the assembly in the directions ,,.eindicated by the arrows in Figure 1. Further details of the TSRHÂ® spinal system are provided in the TSRI-lgSpinal Implant System Surgical Technique Manual and the TSRHÂ® Crosslink Surgical Technique Manual.Both of these publications are available from Danek Medical Inc. and are incorporated by reference as if fullyset forth herein.Manual insertion of a spinal rod through the bores of a number of spacedâapart eyebolts within asurgical wound tends to be difficult. The bore axis of each eyebolt must be properly aligned along a commonaxis, which is difficult since the corrective procedure requires that the spinal rod initially be placed under1ï»¿ll)1520253035CA 02264672 1999-02-26W0 98/17188stress to resist deforming forces of the spine. Therefore. the use of systems such as the TSRl-lÂ® spinal systemmay require that a predetermined number of screws or books be pre-loaded onto the spinal rod in a particularorder and spacing prior to the insertion of the spinal rod into the surgical wound. After insertion of the spinalsystem into the surgical wound. however, it is often necessary to add. delete. or reposition one or more hooksor screws. Before such modiï¬cations can be made. the spinal system typically must be removed from thesurgical wound and at least partially disassembled.To overcome such problems, some spinal ï¬xation systems include âopen backâ hooks or screws toallow a spinal rod to be dropped into the open back of the hook or screw and secured within the open back by aseparate component and a set screw. Such a system is illustrated in U.S. Patent No. 5,102,412 to Rogozinski,which is incorporated by reference as if fully set forth herein. Such systems tend to be susceptible to fatiguestress failure and require assembly within the surgical wound. In addition, adding a hook or screw to theconstruct tends to require that the spinal rod first be repositioned. A further disadvantage of this approach isthat component mass completely surrounds the spinal rod, resulting in an increase in the profile width of thedevice and greater impingement of the device upon the fusion mass. A low proï¬le width is generally desiredto minimize sinus formation and soft tissue irritation from hardware prominence.U.S. Patent No. 5.242.445 to Ashman relates to a âsplit eyebolt" assembly for adding eyebolts to anassembled spinal ï¬xation construction. Attaching the split eyebolt to a spinal rod requires a special crimpingtool to crimp the split eyebolt over the rod. The crimping tool tends to be difficult to operate within thesurgical wound. Furthermore, the threads of the opposing sides of the split eyebolt are often misaligned aftercrimping. making it difï¬cult or impossible to thread a nut onto the split eyebolt. The split eyebolt alsocompletely encircles the spinal rod thereby increasing the impingement of the construct upon the fusion mass.It is therefore desirable that an improved spinal ï¬xation system be derived that facilitates assemblyand surgical implantation by allowing the spinal rod to be positioned within the surgical wound (a) after theï¬xation components (e.g., screws, hooks) have been implanted, (b) without modifying the fixation components.and (c) whereby ï¬xation components may be subsequently added, deleted, and/or repositioned withoutdisassembling the system.SUMMARY OF THI_E INVENTIONIn accordance with the present invention, a spinal ï¬xation system is provided that largely eliminatesor reduces the aforementioned disadvantages of conventional spinal ï¬xation constructions. An embodiment ofthe invention relates to an implant system for ï¬xation of the human spine that includes a spinal rod, a ï¬xationcomponent, a connector, and a fastener.The connector may be used to connect the spinal rod to the ï¬xation component and preferablyincludes a receiving end and a fastening end. The receiving end may contain a first arm and a second arm thattogether form a substantially U-shaped borehole into which the spinal rod may be axially positioned. Thereceiving end preferably surrounds only part of the spinal rod such that the unsurrounded portion of the spinalrod is exposed from the borehole. The exposed portion of the spinal rod may extend out of an open end of theU-shaped borehole. The spinal rod may be circular and preferably includes a cross-section having a2PCT/US97/16971ï»¿l01520253035CA 02264672 1999-02-26W0 93/17133 PCT/US97/16971circumferential portion. The receiving end of the connector preferably surrounds and engages greater thanabout âIt radians and less than about 2 1! radians of the circumferential portion.The receiving end of the connector preferably acts as a âpinch clampâ by exerting a clamping force onopposing sides of the spinal rod to secure the spinal rod within the borehole. The connector preferablycontains a slot between the receiving end and the fastening end that enables the first arm and the second arm tobe deï¬ected relative to one another. The deï¬ection of the arms allows the distance between a tip of the ï¬rstarm and a tip of the second arm to be changed so that the spinal rod may be inserted through an open end ofthe Uâsliaped borehole that is deï¬ned between the tips of the amis.The ï¬xation component preferably includes a ï¬xation device such as a bone screw or hook forengaging vertebrae of the thoracic or lumbar spine. The ï¬xation component also preferably includes a bodycontaining a cavity with an inner surface. The cavity is preferably sized to receive a portion of the connector.The connector is preferably partially disposed within the cavity such that at least a portion of the fastening endextends from the cavity, whereby the inner surface of the cavity engages an outer surface of the receiving end.The cavity of the body is preferably a tapered cavity that narrows in a direction from a ï¬rst end of the cavity toa second end of the cavity. The tapered cavity preferably surrounds a portion of the receiving end and impartsa compressive force against the receiving end to secure the spinal rod within the borehole.The fastener preferably engages both the body and the portion of the fastening end that extends fromthe cavity. The fastener may secure the connector and the ï¬xation component together. The fastener ispreferably a nut adapted to be threaded upon the fastening end. The fastener may be selectively tightened toallow an engagement between the connector and the spinal rod that may be overcome by the application of adistraction force to the connector. Rotation of the nut in a tightening direction about the fastening endpreferably draws a portion of the receiving end through the tapered cavity, causing the inner surface of thecavity to compress the arms of the receiving end. In turn, the arms may exert a compressive force against thespinal rod to clamp it within the borehole. The magnitude of the compressive force against the spinal rodpreferably varies as a function of the degree to which the nut is tightened. The open end of the U-shapedborehole preferably has a width that can be adjusted by tightening the fastener.The ï¬xation component may include a spacer located between the fastener and the spinal rod forlaterally offsetting the ï¬xation device a selected lateral distance from the spinal rod. The spacer may include asurface having a plurality of radially-spaced teeth. The ï¬xation component may comprise a plurality ofradially-spaced protrusions adapted to ï¬t adjacent to the teeth on the surface of the spacer. The tightening ofthe nut preferably causes the spacer and the ï¬xation component to become pressed together such that acomplementary engagement between the teeth of the spacer and the protrusions of the ï¬xation device is formedto inhibit rotation of the ï¬xation device about the spacer.The body may include a U-shaped yoke formed between a top section and a bottom section that eachhave an edge adjacent to the yoke. The tapered cavity preferably is formed between the top section and thebottom section and extends in a perpendicular direction relative to the U-shaped yoke. The ï¬xation componentis preferably adapted to pivot about the spinal rod in a substantially vertical plane. The edges of the top andbottom sections preferably contact the spinal rod during the pivoting of the ï¬xation component to deï¬ne theï»¿101520253035CA 02264672 1999-02-26W0 98/ 17188 PCT/US97/16971range of pivotal motion of the ï¬xation component about the spinal rod. The edges are preferably curved in adirection away from the spinal rod to increase the range of pivotal motion of the ï¬xation component.The ï¬xation component may include a transverse connector to maintain a ï¬xed distance between thespinal rod and a neighboring spinal rod. The transverse connector may include a reduced section that has awidth less than that of the body, allowing the reduced section to be more easily bent. The reduced section maybe bent to shorten the lateral distance between the spinal rod and an adjacent spinal rod. The transverseconnector may contain a beveled section between the body and the reduced section.In an embodiment. the connector includes a receiving end forming a substantially Uâshaped boreholeand a capped end opposite the receiving end. The connector may be forced into the cavity of a ï¬xationcomponent body with an instrument such as a pair of assembly pliers. The instrument preferably includes afirst elongated member and a second elongated member. The elongated members may be moved relative toone another to exert a compressive force against the connector and the ï¬xation component to move theconnector within the cavity of the fixation component body. The first elongated member preferably includes acurvate indention for engaging the spinal rod. The second elongated member preferably includes a boreholefor receiving an end of the connector.In an embodiment, the ï¬xation component includes a fastening end. The fastening end preferably isadapted to receive a fastener (e. g., threaded nut). Downward translation of the fastener preferably moves asleeve downwardly over the body of the ï¬xation component. The sleeve preferably contains a substantially U-shaped opening having a angled locking surface for engaging the spinal rod. During assembly. the fastener ispreferably tightened to move the sleeve downwardly, thereby imparting a force on the spinal rod that causes theconnector to move through the tapered cavity.In an embodiment, the ï¬xation component may include a pivotable ï¬xation device. The ï¬xationdevice is preferably adapted to pivot about the body of the ï¬xation component along the longitudinal axis ofthe body. The body of the ï¬xation component may be adapted to inhibit the lateral motion of the ï¬xationdevice. The body of the ï¬xation component may be adapted to engage a portion of the connector.In an embodiment the connector may include an opening adapted to completely surround thecircumferential portion of the spinal rod. The connector may include a slot running through the center of theconnector. communicating with the opening. The slot may be adapted to allow the circumference of theopening to vary. Insertion of a spinal rod preferably causes the slot to widen such that the circumference of theopening increases. The connector may be placed within the ï¬xation component such that the slot is narrowedto secure a spinal rod to the connector.An advantage of the present invention relates to a ï¬xation component that may be added to or deletedfrom a spinal ï¬xation construct in a surgical wound without disassembling the construct.Another advantage of the present invention relates to a spinal ï¬xation system requiring minimalassembly within the surgical wound.Yet another advantage of the present invention relates to a spinal ï¬xation system having a relativelynarrow proï¬le width to reduce impingement upon the fusion mass.ï»¿l01520253035CA 02264672 1999-02-26W0 98/ 17188 PCTIUS97/16971BRIEF DESCRIPTION OF THE DRAWINGSFurther advantages of the present invention will become apparent to those skilled in the art with t11ebeneï¬t of the following detailed description of the preferred embodiments and upon reference to theaccompanying drawings in which:Figure 1 depicts a TSRHÂ® spinal system eyebolt assembly;Figure 2 depicts a side view of an embodiment of a spinal ï¬xation system connected to a vertebra;Figure 3 depicts a top view of the spinal ï¬xation system of Figure 1;Figure 4 depicts a side view of a tapered connector constructed in accordance with the presentinvention;Figure 5 depicts a side view of a tapered connector prior to assembly with a ï¬xation component bodyand a spinal rod;Figure 6 depicts a side view of a tapered connector assembled with a spinal ï¬xation component and aspinal rodâ.Figure 7 depicts a side view of a transverse connector disposed between a pair of spinal rods inaccordance with the present invention;Figure 8 depicts a front view and side View partially in section of a bone screw constructed accordingto teachings of the present invention;Figure 9 depicts a front view and side view partially in section of a bone screw having radially-spacedprotrusions in accordance with the present invention;Figure 10 depicts a front View and a side view partially in section of a reversible ï¬xation componentconstructed according to teachings or the present invention; ,4:Figure 11 depicts a side view partially in section of a spacer disposed between a spinal rod and afastener in accordance with the present invention;Figure 12 depicts a side view partially in section of a spinal fixation system prior to assembly;ï»¿1020253035 CA 02264672 1999-02-26wo 98/17188 PCT/US97/16971Figure 13 depicts a side view partially in section of a spinal ï¬xation system assembled with aninstrument;Figure 14 depicts a side view partially in section of a spinal ï¬xation system that includes a set screwengaging a connector;Figure 15 depicts a spinal ï¬xation system that includes a locking sleeve:Figure 16 depicts a side view of the spinal ï¬xation system of Figure 15 after assembly:Figure 17 depicts a side view partially in section of the system of Figure 15 after assembly;Figure 18 depicts a side view of a spinal ï¬xation system that includes a rotatable ï¬xation device;Figure 19 depicts a top view of a ï¬xation component that includes a rotatable ï¬xation device;Figure 20 depicts a cross sectional view of the side of a spinal ï¬xation system that includes a rotatableï¬xation device;Figure 2] depicts a side view of a tapered connector adapted to completely surround a portion of aspinal rod;Figure 22 depicts a cross sectional view of the side of a spinal ï¬xation system that includes a rotatableï¬xation device and a connector adapted to completely surround a portion of a spinal rod;Figure 23 depicts a rear view of a spinal ï¬xation system adapted to completely surround a portion of aspinal rod; andFigure 24 depicts a cross sectional view of the side of a spinal ï¬xation system adapted to completelysurround a portion of a spinal rod.While the invention is susceptible to various modiï¬cations and alternative forms, speciï¬c .1embodiments thereof are shown by way of example in the drawings and will herein be described in detail. Itshould be understood, however, that the drawings and detailed description thereto are not intended to limit theinvention to the particular form disclosed, but on the contrary, the intention is to cover all modiï¬cations,equivalents and alternatives falling within the spirit and scope of the present invention as deï¬ned by theappended claims.ï»¿101520253035CA 02264672 1999-02-26W0 98/ 17188 PCT/US97/16971DETAILED DESCRIPTION OF THE PREFJEAKRED EMBODIMENTSFigure 2 depicts a spinal ï¬xation system 10 constructed according to teachings of the presentinvention. In an embodiment of the invention, spinal ï¬xation system 10 includes a spinal rod 12 generallyaligned parallel with a portion of the spine. Connector 16 secures spinal fixation components to the spinal rodvia fastener 18. The ï¬xation components may include various ï¬xation devices including bone screw 14,transverse connector 20. and spinal hooks 22 and 24.Spinal rod 12 is preferably constructed of stainless steel or another relatively rigid material. Thespinal rod preferably has a substantially circular cross-section (although other crossâsectional geometries maybe employed) and a diameter between about 1/8 of an inch and about 1/4 of an inch. The spinal rod may havea shot-peened surface to increase its resistance to fatigue failure. The spinal rod may impart forces against thespine to maintain a portion of the spine in a ï¬xed position to correct a spinal deformity or injury. The spinalrod may be contoured to a selected shape prior to or after surgical implantation.Bone screw 14 is preferably inserted within the main body of a vertebra 26 and may contain threads28 to create a ï¬xable engagement with the vertebra. Alternatively, the bone screw may have a substantiallysmooth shank containing no threading. The stress imparted to spinal ï¬xation systems resulting from a spinaldefomiity may cause fatigue failure of a threaded bone screw if a solid spinal fusion does not develop after aperiod of time. Threaded screws having relatively long shanks tend to fail at a location adjacent to the screwhead. A substantially smooth, unthreaded shank tends to remove the stress concentration on the screw shankfrom a location adjacent to the screw head where failure of the screw often occurs. The bone screw may alsoinclude a tap relief 30 to facilitate its insertion into vertebra 26. The angle of the bone screw relative to thespinal rod is preferably adjustable. The bone screw may be angled to correct the angle 32 of a vertebra relativeto other vertebrae in the spine. The angle between the bone screw and spinal rod is preferably ï¬xable bytightening fastener 18. Furthermore, the height of the vertebra 26 may be adjusted by applying a distractionforce in the directions indicated by arrow 34 between a pair of fixation devices such as bone screw 14 andspinal hook 24 prior to tightening fasteners 18. The distraction force may be applied with the use of a tool in amanner well known to those skilled in the art.The spinal hooks 22 and 24 may be any of a number of types of hooks well known to those skilled inthe art including large laminar, small laminar, thoracic laminar. and pedicle hooks. Each spinal hook may bepositioned in the caudal direction (illustrated by hook 24 in Figure 2) or in the cranial direction (illustrated byhook 22 in Figure 2). Spinal hooks may be positioned on opposing sides of the spinal rod as shown in Figure2. _,Figure 3 depicts a top view of an embodiment of spinal ï¬xation system 10 that includes a pair ofspinal rods 12 in spaced relation on each side of the vertical axis 40 of the spine. Spinal hooks 22 and 24 arepreferably positioned for attachment to bony elements of the posterior human spine. One or more transverseconnectors 20 may be used to rigidly link the rods to improve the strength of the assembly. Each of theï¬xation components may be attached to the spinal rod using a fastener 18 that engages connector 16 and theï¬xation component.ï»¿101520253035CA 02264672 1999-02-26W0 98/ 17188 PCT/U S97/ 16971Transverse connector 20 may connect neighboring rods to increase the rigidity of the construct and toprevent the movement of the rods relative to one another. The transverse connector may be attached to thespinal rod using crosslinking plates that are well known to those skilled in the art and described in the TSRHÂ®Crosslink Surgical Technique Manual. which is incorporated by reference herein. It is preferred thatneighboring rods be connected by two transverse connectors that may be aligned parallel and in spaced relationfrom one another. If the spinal rod is bent, transverse connector 20 is preferably attached to the spinal rod at alocation other than the âpeakâ of the curved section of the rod so that additional stress is not placed at thatlocation.An embodiment of connector 16 is illustrated in Figure 4. The connector preferably includes afastening end 50 and a receiving end 54 opposite the fastening end. The fastening end may be a threaded endcontaining male machine threads 52 that are adapted to engage a fastener. The fastener is preferably a nut.The receiving end preferably includes a first arm 56 and a second arm 58 that together form a U-shapedborehole 62. The first arm has a tip 72 and the second arm has a tip 74 (each labeled in Figure 5), and anopening 60 or open end is preferably deï¬ned by the tips of the first and second arm. A slot 64 preferablyextends between the receiving end and the fastening end. The slot may extend from borehole 62 proximate thereceiving end to a location proximate the fastening end. The slot may terminate in an enlarged opening 66within the receiving end. The borehole is preferably adapted to receive a spinal rod 12 such that the first andsecond arms of the receiving end surround more than about half of a circumferential portion of the spinal rod.The connector preferably does not completely surround the perimeter of the spinal rod. Theunsurrounded portion of the spinal rod is preferably exposed frotn the open end 60 of the U-shaped boreholeand may extend from the borehole through the open end. It is preferred that component mass be placed aroundonly slightly greater than one-half of the circumference of the spinal rod to miiiimize the profile width of theconstruct. In this manner, the impingement of the construct upon the fusion mass is lessened, thereby reducingirritation of the surrounding tissue and facilitating the development of a correct spinal fusion in a minimalamount of time. Conventional assemblies tend to completely surround the spinal rod with component mass,causing a relatively greater impingement upon the fusion mass, which may interfere with fusion development.The angle 68 in Figure 4 is deï¬ned by the circumferential portion of a spinal rod that is surrounded bythe first arm, second arm. and the end of slot 64. The angle 68 is preferably less than about 2 7: radians (e. g.,360Â° around the cross-section of the spinal rod) and greater than about âIt radians (e.g., 1800 around the cross-section of the spinal rod). It is preferred that more than about half of the circumferential portion the spinal rodbe surrounded by a portion of the receiving end (e.g., ï¬rst arm, second arm. end of slot 64) to allow the spinalrod to be adequately secured within the borehole. If less than half of the circumferential portion of the spinal:rod were surrounded by the receiving end, forces resulting from spinal deformations might tend to pull thespinal rod from within borehole 62. First arm 58 and second arm 68 preferably engage the surface of greaterthan about half of the circumferential portion of the spinal rod.The first arm and the second arm preferably each have an outside surface that is slightly tapered suchthat the distance between the outside surfaces of the arms narrows in a direction from tips 72 and 74 to thefastening end 50. The taper of the outside surfaces of the arms preferably deï¬nes a locking angle 70. Lockingangle 70 is preferably a conical angle, although it may be formed within a substantially ï¬at wedge instead.8ï»¿10l520253035CA 02264672 1999-02-26wo 93/17133 PCT/US97/16971Locking angle 70 is preferably less than about 30â. more preferably less than about 25Â°, and more preferablystill between about 1â and about 20".Figures 5 and 6 illustrate the insertion of spinal rod 12 within borehole 62 in an embodiment of theinvention. The spinal rod is preferably axially positioned within the borehole by passing the spinal rodthrough opening 60. Slot 64 preferably enables deï¬ection of the ï¬rst arm and the second arm relative to oneanother to allow the width of opening 60 to be altered. In the absence of an external force of a selectedmagnitude against the first or second arms. the width of opening 60 is preferably less than the outside diameter76 of the spinal rod. Receiving end 54 is preferably adapted to form a "snapâf1t" engagement with the spinalrod that may be realized by forcing the spinal rod into the inner surfaces of tips 72 and 74 of the first andsecond arms, respectively. The force against the inner surfaces of the tips 72 and 74 preferably causes the armsto slightly deï¬ect in opposite directions. resulting in a slight widening of at least a portion of the slot. In thismanner, the width of opening 60 may be increased by an amount sufficient to allow the insertion of the spinalrod through opening 60 and into the borehole. Once the spinal rod is fully inserted within the borehole (asshown in Figure 6), the arms preferably move back toward one another, causing the slot to narrow to its initial.unstressed width. If the diameter of the spinal rod is slightly greater than that of the borehole, the arms mayremain slightly deï¬ected and the slot may remain slightly widened after the spinal rod is snapped into theborehole. It is generally preferred that the diameter of the spinal rod and the diameter of the borehole be equal.In an embodiment of the invention. connector 16 connects the spinal rod to a ï¬xation component thatengages a portion of the spine. The fixation component preferably includes a ï¬xation device such as a bonescrew, hook, transverse connector, or similar device. The ï¬xation component preferably includes a body 8()having a tapered cavity into which connector 16 may be inserted. The tapered cavity preferably tapers in adirection that is substantially perpendicular to the longitudinal axis of the ï¬xation component. The taperedcavity preferably has a ï¬rst end 84, a second end 86. and an inside surface 82. The inside surface 82 ispreferably tapered at an angle that corresponds to locking angle 70. The tapered cavity preferably narrows in adirection from first end 84 to second end 86. The tapered cavity is preferably sized so that fastening end 50and a portion of receiving end 54 may be inserted within the tapered cavity through an aperture proximate theï¬rst end. The outer width of the receiving end proximate tips 72 and 74 is preferably slightly greater than thewidth of the aperture proximate the ï¬rst end, thereby inhibiting the complete insertion of the receiving endinto the tapered cavity.Fastener 18 may be a hex nut and preferably contains female threading 19. which is sized to fit themale machine threads of the fastening end 50. The nut preferably engages fastening end 50 and body 80whereby rotating the fastener in a tightening direction creates a tensile force in the connector in direction 88.Â».Tightening of the fastener preferably moves the connector within the tapered cavity in a direction from ï¬rstend 84 to second end 86, thereby creating an interference fit between the arms of the receiving end and insidesurface 82. As the fastener is tightened, the arms are preferably deï¬ected toward one another such that the slotis narrowed and the arms of the receiving end exert a compressive force against the spinal rod disposed withinthe borehole.The magnitude of the compressive force exerted by the receiving end on the spinal rod is preferablyvariable as a function of the degree to which the fastener is tightened. The fastener may be selectively9ï»¿101520253035CA 02264672 1999-02-26W0 98/ 17188 PCTIUS97/16971tightened so that the connector is âlooselyâ engaged to the spinal rod. The âlooseâ engagement preferably ï¬xesthe position of the connector on the rod in the absence of a selected force against the connector, while allowingthe connector to slide over the surface of the rod upon receiving a distraction force. For instance, the fastenermay be partially tightened to loosely attach a connector and ï¬xation device onto the rod at a selected location.A distraction force may be applied to the connector to move the connector to a selected location on the rod, andthe fastener may then be fully tightened to maintain the connector at the selected location.The arms 56 and 58 preferably exert a clamping force onto âopposite sidesâ of the rod (i.e.. sections ofthe outer surface of the spinal rod that are separated by about 180â). The engagement between the arms 56 and58 and the âopposite sidesâ of the spinal rod preferably âcentersâ the rod within the borehole as shown inFigure 6 so that substantially no gaps exist between the inner surface of the arms and the spinal rod. The rodmay be constrained on opposing sides in this manner to provide further resistance to forces that mightotherwise result in axial movement of the rod. When the arms 56 and 58 are deï¬ected to engage the spinalrod, the receiving end preferably forms a âlocking taper" engagement with the spinal rod. A âlocking taper"engagement is taken to mean a largely irreversible deï¬ection of the receiving end. That is. if the fastenerbecomes loose after the receiving end has been compressed about the spinal rod. the clamping force exerted bythe receiving end will be maintained to ï¬xably hold the spinal rod within the borehole.In an embodiment of the invention depicted in Figure 7. a transverse connector 20 is disposed betweena pair of spinal rods in spaced relation to secure the rods at a ï¬xed distance 90. The spinal rods are ï¬xedwithin the borehole of a connector in the manner depicted in Figures 5 and 6 and described above. Thetransverse connector may include a beveled surface between body 80 and a reduced section 92. Reducedsection 92 preferably has a smaller width or diameter than body 80 to allow the reduced section to be bent moreeasily. Slight variations in distance 39 may be achieved by bending transverse connector 20 proximate reducedsection 92. The bending of the transverse connector may be accomplished using a rod bender and a methodwell known to those skilled in the art. Alternately, the transverse connector may have a substantially constantwidth or diameter such that the width of section 92 and the width of body 80 are approximately equal.The ï¬xation component may include a bone screw that is used to correct the angle 32 betweenvertebrae. It is preferred that the bone screw be adapted to pivot about the spinal rod to form an oblique anglebetween the longitudinal axis of the spinal rod and the shank of the bone screw. The bone screw preferablycan be pivoted in either direction 96 or direction 98 such that an oblique angle between about 90Â° and about 60"is formed between the shank and the longitudinal axis of the spinal rod. Other ï¬xation devices (e. g., hooks)may be pivoted with respect the spinal rod in the same manner. As illustrated in Figure 8, the tapered cavitymay contain an engaging side 100 adapted to contact ï¬at 102 of connector 16 to limit the pivoting of a ï¬xationdevice (e.g., bone screw) about the spinal rod within a selected range, thereby preventing a gross misalignmentthat might complicate the assembly of the construct during a surgical procedure.Body 80 preferably includes a top section 104 and a bottom section 106 that together form a U-shapedyoke 112 that is substantially perpendicular to inside surface 82 of the tapered cavity. The ï¬xation componentmay pivot about the spinal rod. The edges of top section 104 and/or bottom section 106 may contact the spinalrod to prevent the pivoting of the ï¬xation component about the spinal rod beyond a selected degree. Topsection 104 preferably contains a curved edge 108, and bottom section 106 preferably contains a curved edge10 ï»¿101520253035CA 02264672 1999-02-26WO 98/17188 PCTIUS97/16971110. Curved edges 108 and 110 preferably increase the degree that the ï¬xation component can pivot and allowa ï¬xation device (e.g.. bone screw 14) to form an angle within a selected range that is perpendicular with oroblique to the spinal rod.In an embodiment of the invention, body 80 is laterally offset from the spinal rod. Body 80 maycontain a spacer 114 that extends laterally to offset a ï¬xation component from the spinal rod. Offsetting aï¬xation component from the spinal rod may reduce the degree that the spinal rod must be contoured for properpositioning of bone screws (e. g., pedicle screws) in regions of the spine such as the lower lumbar region. Theoffset between the ï¬xation component and the spinal rod may be equal to the width of the spacer. The offset ispreferably less than about 15 mm, more preferably less than about 10 mm. and more preferably still betweenabout 3 mm and about 9 rmn.The spacer may contain a tapered cavity for receiving connector 16 as illustrated in Figure 9. In anembodiment. the spacer contains a first plurality of protrusions or teeth that are adapted to form anengagement with a second plurality of protrusions or teeth 120 disposed on a surface of a ï¬xation device. Theteeth of the spacer and the teeth of the ï¬xation device preferably are radially spaced at a ï¬xed spacing 118.The teeth of the spacer and the protrusions of the ï¬xation device preferably form a complementary ï¬t such thatadjacent, opposing teeth contact one another over interface length 116 when fastener 18 is tightened. Thecomplementary engagement of the teeth preferably inhibits and/or prevents the ï¬xation device from rotatingabout spacer 114, thereby ï¬xing the angle formed between the ï¬xation device and the spinal rod.An embodiment including a reversible ï¬xation device is illustrated in Figure 10. The body 80 of thehook preferably includes a ï¬rst Uâshaped yoke 137 disposed on a ï¬rst side 134 of the body and a second U-shaped yoke 138 disposed on a second side 136 of the body. A cavity 132 preferably extends through the bodyfrom the ï¬rst side 134 to the second side 136. The cavity preferably contains a pair of tapered inner surfaces133 and 135 that taper in opposite directions such that the cavity narrows in a direction from the ï¬rst side 134to the middle of the cavity and narrows in a direction from the second side 136 to the middle of the cavity. Thetapered inner surfaces preferably each terminate in an engaging portion 130 disposed in the middle of thecavity. Connector 16 may be positioned within the cavity so that the receiving end extends from either ï¬rstside 134 as shown in Figure 10B or from second side 136 as shown in Figure 10C. Thus, the reversible hookmay be mounted so that either ï¬rst side 134 or second side 136 is proximate the spinal rod, with the hookdirected toward either the caudal or cranial direction in each case. The ï¬xation component may contain a slot109 through which the fastening end of the connector may be inserted during assembly of the construct. Theengaging portion 130 preferably engages the outer surface of the receiving end to limit the extent to which thereceiving end may be inserted into cavity 132. Fastener 18 preferably engages body 80 proximate the engagingportion.An alternate embodiment including a spacer 114 is illustrated in Figure 1 1. The spacer preferablysurrounds a portion of connector 16 and contains a tapered surface 140 corresponding to the outside surface ofthe arms of the receiving end. As fastener 18 is tightened, the connector is preferably drawn within the spacerwhereby surface 140 engages and exerts a clamping force against the outer surface of the receiving end. Atensile force created by the tightening of fastener 18 preferably maintains the spacer in a ï¬xed position betweenbody 80 and the spinal rod. The tapered surface 140 may terminate in an engaging surface 142 that engagesllï»¿ll)1520253035CA 02264672 1999-02-26wo 93/17133 PCT/US97/16971the receiving end, thereby limiting the extent to which the receiving end may be drawn within the spacer. Thereceiving end preferably forms a âpinch clampâ about the spinal rod, wherein the tips 72 and 74 of the armsterminate slightly beyond a vertical axis 144, which extends through the center of the spinal rod. The fastenermay be fully tightened to create a selected offset length 145 that is preferably between about 2 mm and about10 mm.To surgically install spinal ï¬xation system 10. the threaded end of connector 16 is preferably insertedthrough the tapered cavity of a spinal ï¬xation component and fastener 18 is loosely threaded onto the threadedend. The spinal ï¬xation component is then attached to the spine via a hook or screw in a selected location. Aplurality of spinal ï¬xation components may be attached to the spine in like manner. Spinal rod ll may becontoured to match the desired curvature of the spine and placed into the surgical opening. The spinal rod ispreferably snapped within the borehole of the connector of each spinal ï¬xation component. The spine ispreferably manipulated such that each of the vertebra is at a selected angle and height relative to neighboringvertebrae and then each fastener 18 is fully tightened to ï¬xably secure the spinal rod into the borehole of eachconnector and to secure each of the spinal ï¬xation devices at a selected angle relative to the spinal rod. It isgenerally preferred that the only assembly of system components that occurs within the surgical wound is (a)the snapping of the spinal rod within one or more connectors and (b) the ï¬nal tightening of one or morefasteners that have already been engaged with the fastening end. Each of the fasteners is preferably tightenedwith a torque of at least 150 lb-in. One or more transverse connectors may be added across neighboring spinalrods for support to increase the strength of the overall construct and maintain the spinal rods at a ï¬xeddistance from one another.In an alternate embodiment, each connector and spinal ï¬xation component can be pre-assembled onthe spinal rod prior to the implantation of the rod i11to the surgical wound. A connector may first be snappedonto the spinal rod. A ï¬xation component may be added onto the connector such that the fastening end of theconnector extends through the tapered cavity and the arms of the receiving end contact the inner surface of thetapered cavity. The fastener is preferably positioned on the fastening end and partially tightened to maintainthe connector and ï¬xation component engaged with the spinal rod. The fastener is preferably loosely securedon the fastening end to allow the connector and ï¬xation component to slide along the length of the rod when aselected force is applied to the connector. The spinal rod may be contoured as necessary, and the pre-assembled system may be inserted within the surgical wound. The location of the spinal fixation componentsmay be adjusted along the length of the rod as necessary, and the construct may be connected to the spine viaï¬xation devices. Once a ï¬xation component is placed at a selected location, its corresponding fastener may befully tightened to ï¬x its location. Fixation components may be added to or deleted from the construct as ,4Â»necessary without altering the position of the spinal rod or other ï¬xation components.In an alternate embodiment, the system may be partially pre-assembled such that a number ofconnectors are initially snapped onto the spinal rod. Fixation components may be inserted within the surgicalwound and connected to the spine at selected locations via ï¬xation devices. The rod may be selectivelycontoured and inserted within the surgical wound and aligned proximate the spine. A connector is preferablyslid along the rod to a selected location proximate a ï¬xation component on the spine, and the fastening end ofthe connector is inserted through the tapered cavity of the ï¬xation component. A fastener may be placed on12ï»¿101520253035CA 02264672 1999-02-26wo 98/17188 PCT/US97/16971the fastening end to clamp the connector onto the spinal rod and to secure the ï¬xation componenttherebetween. Additional connectors and ï¬xation components may be secured to the spinal rod in like manner.After the rod is implanted into the surgical wound. it may be necessary to add or delete a ï¬xationcomponent. Conventional systems tend to require that the spinal rod be removed from the surgical wound toallow a ï¬xation component to be threaded onto or removed from the rod. ln addition, ï¬xation components ofconventional systems may have to be removed from the construct to slide the added ï¬xation component to aselected position. Connector 16 is preferably snapped onto the spinal rod at a selected location. Thus, aconnector and any ï¬xation device (e. g., screw. hook. transverse connector) may be added to the spinal rodwithout removing ï¬xation components from the spinal rod or removing the spinal rod from the surgicalwound. In the same manner, a connector and ï¬xation device may be removed from the spinal rod withoutaltering the position of the spinal rod or adjacent connectors. The fastener 18 may be loosened and a tool maybe used to unclamp the receiving end of the connector from the spinal rod, thereby eliminating the need toslide the component off the end of the spinal rod as in some conventional systems.FURTHj_1â.__l_1 IMPROVEMENTSThe following embodiments may be used in combination with any of the features of the above-described embodiments.An embodiment of a spinal ï¬xation system that is assembled with a threadless wedge is depicted inFigure 12 and Figure 13. Figure 12 depicts the spinal ï¬xation system prior to assembly. The spinal ï¬xationsystem preferably includes connector 216 for attaching spinal rod 12 to ï¬xation component body 80.Connector 216 preferably includes a receiving end that includes a pair of deï¬ectable arms forming asubstantially U-shaped borehole for receiving the spinal rod as in the above described embodiments. The outersurface of the receiving end may be tapered to complement the tapered inner surface of the cavity disposedwithin the ï¬xation component. The outer surface of the receiving end and the tapered inner surface may besubstantially ï¬at. It is to be understood that the outer surface of the connector may be untapered while theinner surface of the cavity is tapered, or alternatively. the outer surface of the connector may be tapered whilethe inner surface of the cavity is untapered. The end of the connector opposite the receiving end may becapped as shown in Figure 12.An instrument 200 is preferably used to move the connector through the cavity to cause the arms ofthe connector to clamp against the spinal rod to secure it within the borehole. The instrument is preferably apair of assembly pliers that includes a ï¬rst member 202 and a second member 204. Members 202 and 204 arepreferably substantially elongated and capable of moving relative to one another to apply a compressive forceonto components of the spinal ï¬xation system to assemble the components. The members are preferablyconnected together via hinge 206. The hinge may include a pivotal connector (e.g., bolt) about which themembers can pivot relative to one another.One of the members preferably includes an indention 210 for engaging the spinal rod. The indentionpreferably has a curvate shape that conforms to the shape of the spinal rod. The other memberpreferablyincludes a bore 208 that is sized to receive the end of the connector. Bore 208 preferably has a width that is13ï»¿101520253035CA 02264672 1999-02-26wo 98/17188 PCT/US97/16971greater than that of the end of the connector such that the end is capable of passing into or through the bore.Member 204 preferably includes contacting sections 214 that surround bore 208 for engaging the ï¬xationcomponent. Figure 13 depicts the spinal ï¬xation system after assembly. Member 202 preferably engages thespinal rod at indention 210, while member 204 engages the ï¬xation component with contacting sections 214.The handles of instrument 200 are preferably squeezed together to decrease the distance between members 202and 204, thereby forcing the connector to move within the cavity of the ï¬xation component. The end of theconnector preferably moves through the cavity and into bore 208 whereby second member 204 does not inhibitthe movement of the connector through the cavity. A locking taper engagement between the connector and thespinal rod is preferably formed. and then instrument 200 may be removed from the assembly. In an alternateembodiment, member 202 engages the tips of the arms of the connector rather than the spinal rod.In an embodiment depicted in Figure 14, the ï¬xation component includes a bore 222 through its topsurface that communicates with the ï¬xation component cavity. A locking element 220 is preferably insertedinto bore 222 to inhibit movement of the connector within the ï¬xation component cavity after the connectorhas been secured therein. Locking element 220 is preferably a set screw. Bore 222 is preferably threaded forengaging threads on the set screw. The locking element may engage the connector proximate indention 218disposed on the outer surface of the connector.In an embodiment depicted in Figure 15. ï¬xation component 230 preferably includes a tapered cavityfor receiving connector 216 as in the above described embodiments. The ï¬xation system preferably includes asleeve 234 that is adapted to ï¬t about the body of the ï¬xation component. The sleeve is preferablysubstantially cylindrical and may substantially surround the ï¬xation component body. The sleeve preferablyincludes a substantially U-shaped opening 236 sized to permit spinal rod 12 to pass therethrough. The U-shaped opening is preferably substantially offset from the center of the sleeve as shown in Figure 15. Opening236 may include an angled interior locking surface 237 for engaging the spinal rod. Fixation component 230preferably includes a fastening end 232 on its top. Fastening end 232 preferably includes threading. Afastener 238 is preferably securable to the fastening end. Fastener 238 is preferably a nut that includesthreading that complements the threading on the fastening end.Figure 16 depicts a side view of the spinal ï¬xation system after assembly, and Figure 17 depicts across sectional view of the assembled spinal ï¬xation system. To assemble the system, the spinal rod ispreferably snapped into the borehole of connector 216. A circurriferential portion of the spinal rod preferablyextends from the opening in the connector. The connector having the spinal rod disposed therein is thenpreferably positioned within the cavity of the ï¬xation component. Sleeve 234 is preferably slid over fasteningend 232 and around the body of the ï¬xation component until locking surface 237 contacts the spinal rod. .9Fastener 238 may be threaded onto the fastening end such that the bottom surface of the fastener contacts thetop of sleeve 234. Rotation of the fastener preferably downwardly translates the fastener along the fasteningend and forces sleeve 234 down along the body of the ï¬xation component. The angle 239 of locking surface237 from a vertical axis allows the downward motion of the sleeve to impart a force on the spinal rod in adirection axially through the tapered cavity. Angle 239 preferably ranges from about 10 to 30 degrees. Thedistance that connector 216 moves within the tapered cavity is preferably a function of the degree to which14ï»¿101520253035CA 02264672 1999-02-26wo 98/17188 PCT/US97/16971fastener 238 is tightened. It is preferred that a locking taper engagement is formed between the connector andthe ï¬xation body cavity after fastener 238 is tightened.In an embodiment. depicted in Figure 18, ï¬xation component 300 preferably includes a body 302 anda ï¬xation device 304. The body 302 preferably includes a cavity 318 (shown in Figure 19) adapted to receive aconnector 216. The body 302 may include a substantially Uâsl1aped indentation 306 adapted to permit aportion of spinal rod 12 to rest within the indentation. The indentation 306 preferably runs along the bottom312 of the body 302 in a direction substantially perpendicular to the longitudinal axis of the ï¬xation device304. The body 302 may include a bore (not shown) that communicates with the cavity 318. A locking elementis preferably inserted into the bore to inhibit movement of the connector 216 within the body cavity 318 afterthe connector has been secured therein.The body 302 is preferably adapted to hold a ï¬xation device 304. The ï¬xation device 304 preferablyincludes a head 310. The head 310 may be semi-spherical in shape. An opening (not shown) may extendthrough the central portion of the head 310, at a position equidistant from any position along the semi-spherical portion of the outside surface of the head. The ï¬xation device may a bone screw (as shown), hook,traverse connector, or similar device. The body 302 may include a cavity 318 (shown in Figure 19) adapted tocontain a portion of the head 310. A substantially cylindrical pm 308 is preferably positionable within thehead 310 and the body 302 such that the ï¬xation device 304 may be rotated about the pin 308 along thelongitudinal axis of the body. The pin 308 may inhibit movement of the ï¬xation device 304 in a directionperpendicular to the longitudinal axis of the body 302. The pin 308 may be a rivet or a screw. The pin 308may be substantially hollow.Figure 19 depicts a top view of the ï¬xation component 300. The cavity 318 may be substantially U-shaped and include a front section 306 and a rear section 308. The front section 306 is preferably adapted toreceive the ï¬xation device 304. The front section 306 preferably includes at least two substantially ï¬at arms320 which extend out from the rear section 308. The arms 320 are preferably oriented on opposing sides of thebody 302. The distance 322 between the two arms 320 may be substantially great.er than the width of the head310 of the ï¬xation device 304. It is generally preferred that the distance 322 between the two arms 320 andthe width of the head 310 be equal.In another embodiment, the head 310 of the ï¬xation device 304 may have at least two substantiallyï¬at edges 324. The distance 322 between the two arms 320 is preferably substantially the same as the width ofthe head 310 between the edges 324. The edges 324 are preferably oriented on opposing sides of the head 310.The ï¬xation device 304 may be mounted within the cavity 318 such that the edges 324 are contained by thearms 320 of the body 302. The arms 320 may interact with the edges 324 such that movement in a direction ,.perpendicular to the longitudinal axis of the body 302 is inhibited,The rear section 308 of the cavity 318 is substantially rounded and adapted to receive a connector 216.Figure 20 depicts a cross sectional view of the ï¬xation component 300; secured to a spinal rod 12, with aconnector 216 oriented within the rear section of the cavity. Connector 216 preferably includes a receiving endthat includes a pair of deï¬ectable arms forming a substantially U-shaped borehole for receiving the spinal rod,as described in previous embodiments. The width of the body 302 between the rear side 328 and the interiorsurface 326 of the cavity 318 is preferably variable. The distance between the rear side 328 and the interior15ï»¿101520253035CA 02264672 1999-02-26W0 98/17188 PCT/US97/16971surface 326 of the body 302 preferably becomes narrower in a direction from the top 314 toward the bottom312. The interior surface 326 of the body 302 may be substantially ï¬at.The head 310 of the ï¬xation device 304 is preferably located within the body 302 in a position such aportion of the connector 216 may be inserted between the head and the interior surface 326. Movement of theconnector 216 through the bottom 312 of the body 302. in a direction toward the top 314, may allow the outeredges 330 of the coimector to engage the interior surface 326 of the body and the head 310 of the fixationdevice 304. As the connector 216 is moved further toward the top 314 of the body 302, a compressive forcemay be exerted by the interior surface 326 and the head 341 upon the connector. The magnitude of thecompressive force may be varied as the position of the connector 216 is varied within the cavity. Thecompressive force preferably secures spinal rod 12 within the U-shaped borehole of the connector 216. Thecompressive force may inhibit rotation of the fixation device 304. Instrument 200 (not shown) may be used toposition the connector 216 within the body 302 in a position which preferably secures the spinal rod to theconnector. The connector 216 may be positioned within the body 302 such that the spinal rod 12 is securedwithin the connector, and the rotation of the ï¬xation device 304 is inhibited.Figure 18 depicts a view of an assembled spinal ï¬xation assembly. To assemble the system the spinalrod 12 is snapped into the borehole of connector 216. A circumferential portion of the spinal rod 12 preferablyextends from the borehole in the connector 216. The connector 216 having the spinal rod 12 disposed thereinis then preferably positioned within the body 302. The fixation device 304 may be rotated about the pin 308until the desired angle between the body 302 and the ï¬xation device is achieved. The angle may be varied in adirection toward the top 314 through an arc of at least 90 degrees or toward the bottom 312 through an arc ofat least 90 degrees. The connector 216 may then be moved further within the body 302. As the connector 216is moved. the head 310 and the interior surface 326 of the body 302 may impart a force upon the connector (asshown in Figure 20) causing the amis of the borehole to compress. In this manner the connector 216 may besecured onto the spinal rod 12. The force may also inhibit further rotation of the ï¬xation device 304. Themagnitude of the force is preferably a function of the distance that the connector 216 is placed within the body302. Instrument 200 may be used to position the connector 216 within the body 302.An embodiment of a connector 350 is depicted in Figure 21. The connector 350 is adapted to secureï¬xation components to a spinal rod. The substantially conical connector 350 includes a receiving section 352and an upper section 354. The receiving section 352 preferably includes a substantially circular opening 356.The opening 356 is preferably adapted to receive a spinal rod (not shown) such that the receiving section 352of the connector 350 substantially surrounds the circumferential portion of the spinal rod. The upper section354 preferably includes a slot 358 extending longitudinally through the center of the upper section. The slot at358 may extend from the top of the connector to the opening 356. the slot communicating with the opening.A spinal rod is preferably axially positioned within the opening 356 bypassing the spinal rod throughopening. Slot 358 preferably enables the circumference of opening 356 to be altered. Insertion of the spinalrod into opening 356 results in a slight widening of at least a portion of the slot 358. In this manner, thecircumference of opening 356 may be increased by an amount sufficient to allow the insertion of the spinal rodthrough opening 356. If the diameter of the spinal rod is slightly greater than that of the opening 356, the slot16ï»¿101520253035CA 02264672 1999-02-26wo 98117188 PCT/US97/16971358 may remain slightly widened after the spinal rod is inserted into the opening. It is generally preferred thatthe diameter of the spinal rod and the diameter of the opening 356 be equal.Figure 22 depicts a cross sectional view of an assembled spinal ï¬xation assembly including aconnector 350 and a ï¬xation component 300. Movement of the connector 350 through the bottom 312 of thebody 302, in a direction toward the top 314. may allow the outer edges 360 of the connector to engage theinterior surface 326 of the body and the head 310 of the ï¬xation device 304. As the connector 350 is movedfurther toward the top 314 of the body 302. a compressive force may be exerted by the interior surface 326 andthe head 310 upon the connector. The magnitude of the compressive force may be varied as the position of theconnector 350 is varied within the cavity. The compressive force preferably forces slot 358 to narrow, therebysecuring spinal rod 12 within the opening 356 of the connector 350. The compressive force may inhibitrotation of the ï¬xation device 304. Instrument 200 (not shown) may be used to position the connector 350within the body 302 in a position which preferably secures the spinal rod 12 within the connector. Theconnector 350 may be positioned within the body 302 such that the spinal rod 12 is secured within theconnector, and the rotation of the ï¬xation device 304 is inhibited.To assemble the system depicted in Figure 22 the spinal rod 12 is inserted into the opening 356 ofconnector 350. A circumferential portion of the spinal rod 12 preferably is completely surrounded by theconnector 350. The connector 350 having the spinal rod 12 disposed therein is then preferably positionedwithin the body 302. The ï¬xation device 304 may be rotated about the pin 308 until the desired angle betweenthe body 302 and the ï¬xation device is achieved. The connector 350 may then be moved ï¬irther within thebody 302. As the connector 350 is moved. the head 310 and the interior surface 326 of the body 302 mayimpart a force upon the connector causing the slot 358 of the connector to narrow. In this manner theconnector 350 may be secured onto the spinal rod 12. The force may also inhibit further rotation of theï¬xation device 304. The magnitude of the force is preferably a function of the distance that the connector 350is placed within the body 302. Instrument 200 may be used to position the connector 350 within the body 302.In an embodiment depicted in Figure 23, ï¬xation component 230 may be adapted to receive connector350. Connector 350 preferably includes an opening 356 for receiving the spinal rod 12 and a slot 358 (shownin Figure 24) as in the above described embodiments. The ï¬xation component 230 preferably can be pivotedin either direction 362 or direction 364 such that an oblique angle between 90Â° and about 60Â° is formedbetween the ï¬xation component and the longitudinal axis of the spinal rod 12 as in the above describedembodiments. The ï¬xation component 230 preferably comprises a bone screw (as shown), hook, traverseconnector, or similar device.To assemble the system, depicted in a cross section view in Figure 24, the spinal rod 12 is preferably:inserted into the opening 356 of connector 350. The connector 350 having the spinal rod 12 disposed thereinis then preferably positioned within the cavity of the ï¬xation component 230. The ï¬xation component 230may be rotated until the desired angle between the ï¬xation component and the longitudinal axis of the spinalrod is achieved. The connector 350 may then be moved further within the fixation component 230. As theconnector 350 is moved, the interior surfaces 366 of the ï¬xation component may impart a force upon theconnector causing the slot 358 of the connector to narrow. In this manner the connector 350 may be securedonto the spinal rod 12. The force may also inhibit further rotation of the ï¬xation component 230. The17ï»¿10CA 02264672 1999-02-26wo 93/17133 PCT/US97/16971magnitude of the force is preferably a function of the distance that the connector 350 is placed within the body302. Instrument 200 (not shown) may be used to position the connector 350 within the body 302.Further modifications and alternative embodiments of various aspects of the invention will beapparent to those skilled in the art in view of this description. Accordingly. this description is to be construedas illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying outthe invention. It is to be understood that the forms of the invention shown and described herein are to be takenas the presently preferred embodiments. Elements and materials may be substituted for those illustrated anddescribed herein, pans and processes may be reversed. and certain features of the invention may be utilizedindependently, all as would be apparent to one skilled in the art after having the benefit of this description ofthe invention. Changes may be made in the elements described herein without departing from the spirit andscope of the invention as described in the following claims.18

Claims

What is claimed is:

1. An implant system for fixation of the human spine, comprising:

a connector comprising a threaded end, a receiving end opposite the threaded end, the receiving end terminating in a first arm and a second arm that together form a substantially U-shaped borehole, the first arm comprising a first tip and the second arm comprising a second tip, and wherein an opening is formed between the first tip and the second tip;

a spinal rod axially positionable within the borehole;

a fixation component comprising a body, the body comprising a tapered cavity having an inner surface, the tapered cavity being adapted to receive the connector such that the inner surface engages the first arm and the second arm; and a nut adapted to engage the threaded end of the connector and the body of the fixation component, and wherein the nut is adapted to being tightened to cause movement of the receiving end within the tapered cavity and deflection of the first and second arms such that the first and second arms exert a compressive force against the spinal rod to maintain the spinal rod within the borehole.

2. The implant system of claim 1 wherein the spinal rod comprises a diameter, and wherein the opening has a width defined by the first tip and the second tip, and wherein the width is adjustable by rotating the nut about the threaded end.

3. The implant system of claim 1 wherein the first and second arms are deflectable in a direction toward one another and in a direction away from one another.

4. The implant system of claim 1 wherein the spinal rod is positioned within the borehole and wherein a portion of the spinal rod is exposed from the receiving end of the connector in a direction away from the threaded end.

5. The implant system of claim 1 wherein the connector further comprises a slot between the receiving end and the fastening end, and wherein the nut is adapted to be tightened to move the connector within the tapered cavity in a direction from a first end of the tapered cavity to a second end of the tapered cavity, the tapered cavity being narrower at a location proximate the second end than at a location proximate the first end, and wherein contact between the tapered cavity and the receiving end causes deflection of the first arm and the second arm such that a portion of the slot narrows and the arms exert a compressive force against the spinal rod to clamp the spinal rod within the borehole.

6. The implant system of claim 1 wherein the spinal rod comprises a cross-section having a circumferential portion, and wherein between about pi. radians and about 2.pi. radians of the circumferential portion is surrounded by the receiving end.

7. The implant system of claim 1 wherein the fixation component further comprises a bone screw having a shank with a threaded portion and a tap relief.

8. The implant system of claim 1 wherein the fixation component further comprises a bone screw having a substantially smooth, unthreaded shank.

9. The implant system of claim 1 wherein the fixation component further comprises a transverse connector for connecting the spinal rod to a neighboring spinal rod at a fixed distance.

10. The implant system of claim 1 wherein the body comprises a substantially U-shaped yoke having an axial length, the yoke being formed between a top section and a bottom section, the top section comprising a first edge, the bottom section comprising a second edge, the first and second edges defining a width of the yoke, and wherein the first and second edges are curved such that the width of the yoke varies across the axial length of the yoke.

11. The implant system of claim 1 wherein the fixation component further comprises a fixation device and a spacer adapted to fit between the nut and the spinal rod to laterally offset the fixation device from the spinal rod.

12. The implant system of claim 1 wherein the fixation component further comprises a fixation device and a spacer, the spacer being adapted to fit between the nut and the spinal rod, the fixation device comprising protrusions, the spacer being adapted to offset the fixation device from the spinal rod and comprising teeth adapted to form a complementary engagement with the protrusions to inhibit rotation of the fixation device about the spacer.

13. The implant system of claim 1 wherein the body further comprises a top section and a bottom section, the tapered cavity being formed in between the top section and the bottom section, the top section and the bottom section each comprising edges that are curved in a direction away from the spinal rod.

14. The implant system of claim 1 wherein the fixation component further comprises a fixation device and a spacer, the fixation device extending from the body, the spacer having a width between about 1 mm and about 10 mm and being adapted to fit between the nut and the spinal rod to laterally offset the fixation device from the spinal rod.

15. The implant system of claim 1 wherein the compressive force exerted against the spinal rod is selectively variable and is a function of a position of the nut on the threaded end.

16. The implant system of claim 1 wherein the fixation component further comprises a transverse connector connecting the spinal rod to a neighboring spinal rod, the transverse connector comprising a reduced section and a beveled section, the reduced section having a width less than a width of the body, the beveled section connecting the reduced section to the body.

17. The implant system of claim 1 wherein the fixation component further comprises a transverse connector connecting the spinal rod to a neighboring spinal rod, the transverse connector comprising a reduced section and a beveled section, the reduced section having a width less than a width of the body, the beveled section extending between the body and the reduced section, and wherein the reduced section comprises a bend to shorten a lateral distance between the spinal rod and the neighboring spinal rod.

18. The implant system of claim 1 wherein the first arm and the second arm each further comprise a tapered outer surface that is angled toward the threaded end.

19. The implant system of claim 1 wherein the spinal rod is positioned within the borehole, and wherein a portion of the spinal rod is exposed from the borehole, and wherein the exposed portion extends from the borehole through the opening.

20. The implant system of claim 1 wherein the body comprises a substantially U-shaped yoke having an axial length defined between a pair of outer edges, the yoke being formed between a top section and a bottom section, the top section comprising a first edge, the bottom section comprising a second edge, the first and second edges defining a width of the yoke, and wherein the first and second edges are curved such that the width of the yoke varies across the axial length of the yoke, and wherein the width of the yoke is greater at one of the outer edges of the yoke than at a location between the outer edges of the yoke.

21. The implant system of claim 1 wherein the first and second arms are deflectable to form a locking taper engagement with the spinal rod.

22. The implant system of claim 1, further comprising a slot in the connector between the receiving end and the fastening end, the slot enabling the first arm and the second arm to be deflected relative to one another.

23. The implant system of claim 1 wherein the fixation component further comprises a hook adapted to connect the fixation component to a spine element.

24. An implant system for fixation of the human spine, comprising:

a connector comprising a receiving end and a fastening end located substantially opposite the receiving end, the receiving end forming a borehole;

a spinal rod axially positionable within the borehole such that a portion of the spinal rod is exposed from the borehole, the spinal rod being fixable within the borehole by a clamping force exerted by the connector;

a fixation component comprising a body, the body comprising a cavity having an inner surface, and wherein the connector is adapted to be at least partially disposed within the cavity such that the inner surface of the cavity engages an outer surface of the receiving end; and a fastener adapted to engage the fastening end to secure the connector and the fixation component together during use, the fastener being adjustable to cause movement of the receiving end to substantially secure the spinal rod within the borehole during use.

25. The implant system of claim 24 wherein the receiving end comprises a first arm having a first tip and a second arm having a second tip, the first arm and the second arm together forming a substantially U-shaped borehole, and wherein an opening is defined between the first tip and the second tip.

26. The implant system of claim 25 wherein the spinal rod comprises a diameter, and wherein the opening has a width defined by the first tip and the second tip, and wherein the width is adjustable by changing a position of the fastener on the fastening end.

27. The implant system of claim 24 wherein the receiving end comprises a first arm having a first tip and a second arm having a second tip, the first arm and the second arm together forming a substantially U-shaped borehole, and wherein an opening is defined between the first tip and the second tip, and wherein the opening has a width that is adjustable by tightening the fastener.

28. The implant system of claim 24 wherein the cavity of the body is a tapered cavity having a first end and a second end, and wherein the tapered cavity narrows in a direction from the first end to the second end.

29. The implant system of claim 24 wherein the cavity of the body is a tapered cavity having a first end and a second end, and wherein the tapered cavity narrows in a direction from the first end to the second end, and wherein the tapered cavity is adapted to substantially surround a portion of the receiving end and impart a compressive force against the receiving end to fixably secure the spinal rod within the borehole.

30. The implant system of claim 24 wherein the receiving end further comprises a first arm having a first tip and a second arm having a second tip, the first arm and the second arm together forming a substantially U-shaped borehole, and further comprising a slot in the connector between the receiving end and the fastening end, the slot enabling the first arm and the second arm to be deflected relative to one another, the deflection of the arms causing a change in a distance between the first tip and the second tip.

31. The implant system of claim 24 wherein the fastener is a threaded nut, and wherein the fastening end comprises threading adapted to engage the nut.

32. The implant system of claim 24 wherein the fastener is a threaded nut and the fastening end comprises threading adapted to engage the nut, and wherein tightening of the nut along the fastening end causes movement of the receiving end within the cavity whereby the inner surface of the cavity exerts a compressive force against an outer surface of the receiving end as a function of the tightening of the nut, the compressive force clamping the spinal rod within the borehole.

33. The implant system of claim 24 wherein the fixation component further comprises a fixation device for attaching the spinal rod to a vertebra.

34. The implant system of claim 24 wherein the spinal rod comprises a circumferential portion, and wherein greater than about pi. radians and less than about 2.pi.
radians of the circumferential portion is engaged by the receiving end.

35. The implant system of claim 24 wherein the body comprises a substantially U-shaped yoke having an axial length, the yoke being formed between a top section and a bottom section, the top section comprising a first edge, the bottom section comprising a second edge, the first and second edges defining a width of the yoke, and wherein the first and second edges are curved such that the width of the yoke varies across the axial length of the yoke.

36. The implant system of claim 24 wherein the fixation component further comprises a fixation device and a spacer adapted to fit between the fastener and the spinal rod, the spacer being adapted to laterally offset the fixation device from the spinal rod.

37. The implant system of claim 24 wherein the fixation component further comprises a fixation device and a spacer adapted to fit between the fastener and the spinal rod, the fixation device comprising protrusions, the spacer offsetting the fixation device from the spinal rod and comprising teeth adapted to form a complementary engagement with the protrusions to inhibit rotation of the fixation device about the spacer.

38. The implant system of claim 24 wherein the body further comprises a top section and a bottom section, the cavity being formed in between the top section and the bottom section, the top section and the bottom section each comprising edges that are curved, and wherein the fixation component is adapted to pivot about the spinal rod in a substantially vertical plane, and wherein the curved edges are adapted to contact the spinal rod during the pivoting of the fixation component, thereby defining a range of pivotal motion of the fixation component.

39. The implant system of claim 24 wherein the fixation component further comprises a fixation device and a spacer, the fixation device extending from the body, the spacer having a width between about 1 mm and about 10 mm and disposed between the fastener and the spinal rod to laterally offset the fixation device from the spinal rod.

40. The implant system of claim 24 wherein the fixation component further comprises a transverse connector for connecting the spinal rod to a neighboring spinal rod, the transverse connector comprising a reduced section and a beveled section, the reduced section having a width less than a width of the body, the beveled section being located between the body and the reduced section.

41. The implant system of claim 24 wherein the fixation component further comprises a transverse connector for connecting the spinal rod to a neighboring spinal rod, the transverse connector comprising a reduced section and a beveled section, the reduced section having a width less than a width of the body, the beveled section being located between the body and the reduced section, and wherein the reduced section comprises a bend to shorten a lateral distance between the spinal rod and the neighboring spinal rod.

42. The implant system of claim 24 wherein the connector is adapted to be at least partially disposed within the cavity such that at least a portion of the fastening end extends from the cavity.

43. The implant system of claim 24 wherein the spinal rod is positionable within the borehole such that a side portion of the spinal rod is exposed from the borehole.

44. An implant system for fixation of the human spine, comprising:

a connector comprising a threaded end, a receiving end opposite the threaded end, the receiving end terminating in a first arm and a second arm that together form a substantially U-shaped borehole, the first arm comprising a first tip and the second arm comprising a second tip, and wherein an opening is formed between the first tip and the second tip;

a spinal rod axially positionable within the borehole;
a fixation component comprising:

a body, the body comprising a tapered cavity having an inner surface, the tapered cavity being adapted to receive the connector such that the inner surface engages the first arm and the second arm;

a fixation device; and a spacer, wherein the spacer is adapted to fit between a nut and the spinal rod to laterally offset the fixation device from the spinal rod; and a nut adapted to engage the threaded end of the connector and the body of the fixation component, and wherein the nut is adapted to being tightened to cause movement of the receiving end within the tapered cavity and deflection of the first and second arms such that the first and second arms exert a compressive force against the spinal rod to maintain the spinal rod within the borehole.

45. The implant system of claim 44, wherein the fixation device further comprises protrusions and the spacer further comprises teeth adapted to form a complementary engagement with the protrusions to inhibit rotation of the fixation device about the spacer.

46. The implant system of claim 44, wherein the fixation device extends from the body and the spacer has a width between about 1 millimeter (mm) and about 10 mm.

47. The implant system of claim 44, wherein the fixation component further comprises a hook adapted to connect the fixation component to a spine element.

48. The implant system of claim 44, wherein the fixation component further comprises a transverse connector connecting the spinal rod to a neighboring spinal rod, the transverse connector comprising a reduced section and a beveled section, the reduced section having a width less than a width of the body, the beveled section extending between the body and the reduced section, and wherein the reduced section comprises a bend to shorten a lateral distance between the spinal rod and the neighboring spinal rod.

49. An implant system for fixation of the human spine, comprising:

a connector comprising a threaded end, a receiving end opposite the threaded end, the receiving end terminating in a first arm and a second arm that together form a substantially U-shaped borehole, the first arm comprising a first tip and the second arm comprising a second tip, and wherein an opening is formed between the first tip and the second tip;

a spinal rod axially positionable within the borehole;
a fixation component comprising:

a body, the body comprising a tapered cavity having an inner surface, the tapered cavity being adapted to receive the connector such that the inner surface engages the first arm and the second arm;

a fixation device, wherein the fixation device comprises protrusions; and a spacer, wherein the spacer is adapted to fit between a nut and the spinal rod to laterally offset the fixation device from the spinal rod and further comprising teeth adapted to form a complimentary engagement with the protrusions to inhibit rotation of the fixation device about the spacer; and a nut adapted to engage the threaded end of the connector and the body of the fixation component, and wherein the nut is adapted to being tightened to cause movement of the receiving end within the tapered cavity and deflection of the first and second arms such that the first and second arms exert a compressive force against the spinal rod to maintain the spinal rod within the borehole.

50. The implant system of claim 49, wherein the fixation device extends from the body and the spacer has a width between about 1 millimeter (mm) and about 10 mm.

51. The implant system of claim 49, wherein the fixation component further comprises a hook adapted to connect the fixation component to a spine element.

52. The implant system of claim 49, wherein the fixation component further comprises a transverse connector connecting the spinal rod to a neighboring spinal rod, the transverse connector comprising a reduced section and a beveled section, the reduced section having a width less than a width of the body, the beveled section extending between the body and the reduced section, and wherein the reduced section comprises a bend to shorten a lateral distance between the spinal rod and the neighboring spinal rod.

53. The implant system of claim 49, wherein the body comprises a substantially U-shaped yoke having an axial length, the yoke being formed between a top section and a bottom section, the top section comprising a first edge, the bottom section comprising a second edge, the first and second edges defining a width of the yoke, and wherein the first and second edges are curved such that the width of the yoke varies across the axial length of the yoke.

54. An implant system for fixation of the human spine, comprising:

a connector comprising a threaded end, a receiving end opposite the threaded end, the receiving end terminating in a first arm and a second arm that together form a substantially U-shaped borehole, the first arm comprising a first tip and the second arm comprising a second tip, and wherein an opening is formed between the first tip and the second tip;

a spinal rod axially positionable within the borehole;
a fixation component comprising:

a body, the body comprising a tapered cavity having an inner surface, the tapered cavity being adapted to receive the connector such that the inner surface engages the first arm and the second arm;

a fixation device, wherein the fixation device extends from the body; and a spacer, wherein the spacer has a width greater than about 1 mm, wherein the spacer has a width less than about 10 mm, and wherein the spacer is adapted to fit between a nut and the spinal rod to laterally offset the fixation device from the spinal rod;
and a nut adapted to engage the threaded end of the connector and the body of the fixation component, and wherein the nut is adapted to being tightened to cause movement of the receiving end within the tapered cavity and deflection of the first and second arms such that the first and second arms exert a compressive force against the spinal rod to maintain the spinal rod within the borehole.

55. The implant system of claim 54, wherein the fixation device further comprises protrusions, and the spacer further comprises teeth adapted to form a complementary engagement with the protrusions to inhibit rotation of the fixation device about the spacer.

56. The implant system of claim 54, wherein the fixation component further comprises a hook adapted to connect the fixation component to a spine element.

57. The implant system of claim 54, wherein the fixation component further comprises a transverse connector connecting the spinal rod to a neighboring spinal rod, the transverse connector comprising a reduced section and a beveled section, the reduced section having a width less than a width of the body, the beveled section extending between the body and the reduced section, and wherein the reduced section comprises a bend to shorten a lateral distance between the spinal rod and the neighboring spinal rod.

58. The implant system of claim 54, wherein the body comprises a substantially U-shaped yoke having an axial length defined between a pair of outer edges, the yoke being formed between a top section and a bottom section, the top section comprising a first edge, the bottom section comprising a second edge, the first and second edges defining a width of the yoke, and wherein the first and second edges are curved such that the width of the yoke varies across the axial length of the yoke, and wherein the width of the yoke is greater at one of the outer edges of the yoke than at a location between the outer edges of the yoke.

59. An implant system for fixation of the human spine, comprising:

a connector comprising a threaded end, a receiving end opposite the threaded end, the receiving end terminating in a first arm and a second arm that together form a substantially U-shaped borehole, the first arm comprising a first tip and the second arm comprising a second tip, and wherein an opening is formed between the first tip and the second tip;

a spinal rod axially positionable within the borehole;
a fixation component comprising:

a body, the body comprising a tapered cavity having an inner surface, the tapered cavity being adapted to receive the connector such that the inner surface engages the first arm and the second arm; and a hook adapted to connect the fixation component to a spine element; and a nut adapted to engage the threaded end of the connector and the body of the fixation component, and wherein the nut is adapted to being tightened to cause movement of the receiving end within the tapered cavity and deflection of the first and second arms such that the first and second arms exert a compressive force against the spinal rod to maintain the spinal rod within the borehole.

60. The implant system of claim 59, wherein the fixation component further comprises a fixation device and a spacer adapted to fit between the nut and the spinal rod to laterally offset the fixation device from the spinal rod.

61. The implant system of claim 59, wherein the fixation component further comprises a fixation device and a spacer, the spacer being adapted to fit between the nut and the spinal rod, the fixation device comprising protrusions, the spacer being adapted to offset the fixation device from the spinal rod and comprising teeth adapted to form a complementary engagement with the protrusions to inhibit rotation of the fixation device about the spacer.

62. The implant system of claim 59, wherein the fixation component further comprises a fixation device and a spacer, the fixation device extending from the body, the spacer having a width between about 1 millimeter (mm) and about 10 mm and being adapted to fit between the nut and the spinal rod to laterally offset the fixation device from the spinal rod.

63. The implant system of claim 59, wherein the fixation component further comprises a transverse connector connecting the spinal rod to a neighboring spinal rod, the transverse connector comprising a reduced section and a beveled section, the reduced section having a width less than a width of the body, the beveled section extending between the body and the reduced section, and wherein the reduced section comprises a bend to shorten a lateral distance between the spinal rod and the neighboring spinal rod.