Instrumentation for surgical implant insertion

Abstract: A surgical retractor including a sleeve member having two opposed retractor arms (20) at its distal end portion. By inserting the retractor arms of the retractor within a space defined between adjacent bony structures, first and second supporting surfaces (20a, 20b) of each retractor arm respectively engage the opposed structures thereby distracting the structures, for performing a surgical procedure. A method for inserting a spinal implant is also disclosed. Instrumentation for performing the procedure is also disclosed.

Description: 1. Technical Field The present disclosure generally relates to instrumentation for implant insertion and, in particular, to instrumentation for insertion of spinal implants to facilitate fusion of adjacent vertebral bodies. 2. Background of the Related Art A large number of orthopaedic procedures involve the insertion of either natural or prosthetic implants into bone or associated tissues. These procedures include, for example, ligament repair, joint repair or replacement, non-union fractures, facial reconstruction, spinal stabilization and spinal fusion. In a typical procedure, an insert, dowel or screw is inserted into a prepared bore formed in the bone or tissues to facilitate repair and healing. See, for example, U.S. Patent Nos.: 5,470,334 to Ross et al.; 5,454,811 to Huebner; 5,480,403 to Lee et al.; 5,400,805 to Warren; 5,358,511 to Gatturna et al.; and 4,877,020 to Vich. Some implants are particularly configured with cavities and bores to facilitate bony in growth and enhance anchoring of the implant at the insertion site. See, for example, U.S. Patent Nos.: 4,328,593 to Sutter et al.; 4,936,851 to Fox et al.; and 4,878,915 to Brantigan. Implants in the form of fusion cages having internal cavities to receive bone growth stimulation materials such as bone chips and fragments are disclosed, for example, in U. S. Patent Nos.: 4,501,269 to Bagby; 4,961,740 to Ray et al.; 5,015,247 to Michaelson; and 5,489,307 to Kuslich et al. These types of implants are particularly well suited for inter-vertebral spinal fusion procedures necessitated by injury, disease or some degenerative disorder of the spinal disc. Subsequently, there may be progressive degeneration leading to mechanical instability between adjacent vertebrae necessitating direct fusion of the vertebrae while maintaining a pre-defined inter-vertebral space. This fusion may be accomplished by the insertion of one or more of the specialized implants as discussed above and also discussed in commonly assigned U.S. Patent No. 5,026,373, to the contents of which the skilled reader is referred for details. Both anterior (trans-abdominal) and posterior surgical approaches are used for inter-body fusions of the lumbar spine. Fusions in the cervical area of the spine are primarily performed using a posterior approach. Typically, an implant such as a plug, dowel, prosthesis or cage is inserted into a preformed cavity inside the inter-body, inter-discal space. Since it is desirable in these procedures to promote a "bone to bone" bridge, connective tissue and at least a portion of the distal tissue is removed. Preferably, relatively deep cuts are made in the adjacent bones in order to penetrate into the softer, more vascularised cancellous region to facilitate bone growth across the implant. One of the more critical tasks performed in the insertion of a surgical fusion implant, particularly, in inter-vertebral spinal fusion, is the formation of the implant receiving cavity or bore between/within the adjacent vertebrae. More particularly, the drilled bore must be equally centred within the inter-vertebral space and preferably parallel to the vertebral end plates to ensure removal of equal portions of bone from the adjacent vertebrae throughout the length of the cut and subsequent appropriate seating of the implant relative to the vertebral bodies. Surgical instruments for spinal fusion implant insertion are known. For example, U. S. Patent No. 5,484,437 to Michaelson discloses a method and apparatus incorporating an outer and an inner sleeve arrangement. The outer sleeve is positioned over the spinal distractor and has teeth at one end which are driven directly into the posterior surface of the adjacent vertebrae. The inner sleeve is positioned within the outer sleeve and serves to guide instruments such as a drill used to form the implant receiving bore. U.S. Patent Nos.: 5,487,307 to Kuslich et al.; 5,015,247 to Michaelson; and 4,878,915 to Brantigan also disclose outer sleeves with teeth mounted to the vertebrae. Other arrangements include the use of guide rods which are placed in pilot holes formed in the vertebral bodies. The guide rods guide a bore forming hollow drill into the inter-vertebral space. Although some current instrumentation and methods associated therewith for enhancing the placement of spinal fusion implants have been generally effective for their intended purposes, there exist certain limitations with the design of this instrumentation which detract from their usefulness. For example, the arrangement disclosed in the Michaelson '437 patent and similar arrangements do not provide for automatic alignment of the outer sleeve to ensure that the bore formed by a drill introduced into the outer sleeve is in optimal alignment for a tapping procedure (if required) and reception of the spinal implant. Rather, such orientation is dependent directly upon the skill of the surgeon. Moreover, the outer sleeve, which is mounted via teeth only at its extreme distal end to the posterior surface of the adjacent vertebrae, is subject to disorientation or dislodgment during insertion and/or removal of the drill and/or tapping instrument. The use of guide rods increases the number of steps required to implant the fusion cage. DE 43 28 690 A1 discloses a device for locking vertebrae with respect to each other wherein spacers are inserted into an inter-vertebral space after the space has been generated by distracting adjacent vertebrae with separate means, for example a distracting forceps. Accordingly, a plurality of structural elements and separate steps are necessary to distract two opposed vertebrae. Accordingly, the present disclosure is directed to instrumentation to facilitate the introduction of a fusion implant, which ensures optimal alignment of the drilled bore for reception of the fusion implant and, if appropriate, for bore tapping procedures. The instrumentation of the present disclosure also reduces the number of steps required for implantation of the fusion cage. SUMMARY The present disclosure is directed to instrumentation utilized to perform spinal fusion implant surgery. In particular, a surgical retractor is provided according to claim 1 including an elongated member having proximal and distal end portions and defining a longitudinal passageway for reception of surgical instrumentation. The distal end portion of the member includes first and second retractor arms extending in a general longitudinal direction. Each retractor arm has first and second supporting surfaces for engaging opposed adjacent tissue portions, e.g. opposed vertebral bodies. Each retractor arm defines a dimension between the first and second supporting surfaces sufficient to distract the opposed tissue portions, e.g. vertebral bodies, upon entry thereof. The retractor arms each possess distal tapered portions for facilitating entry into the inter-vertebral space. The first and second supporting surfaces of each retractor arm are preferably in general parallel relation to each other and the longitudinal axis of the sleeve member. The first and second supporting surfaces of each retractor arm. BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the disclosure are described herein below with reference to the drawings wherein: FIG. 1 illustrates a surgical retractor constructed in accordance with the principles of the present disclosure and utilized in distracting adjacent bony structures; FIG. 2 is a cross-sectional view of the retractor taken along the lines 2-2 of FIG. 1; FIG. 3 is a side plan view illustrating positioning of the retractor of FIG. 1 within an inter-vertebral space between adjacent vertebrae in accordance with a preferred method for inserting the implant; FIG. 4 is a side plan view illustrating insertion of a drilling instrument into the retractor to drill a bore within the adjacent vertebrae; FIG. 5 is a side plan view illustrating insertion of a tapping instrument into the retractor to tap an internal thread in the bore; FIG. 6 is a side plan view illustrating insertion of the insertion instrument with mounted implant through the retractor and placement of the implant within the tapped bore; FIG. 7 is a side plan view of a syringe containing bone inducing substances; FIG. 8 is a side plan view illustrating loading of the bone-inducing substances into the implant with the use of forceps; FIG. 9 is a side plan view of a cap mounting instrument utilized in mounting the implant end cap onto the body of the implant; FIG. 10 is an axial plan view of the mounting head of the mounting instrument of FIG. 17; FIG. 11 is a perspective view of the mounting head and the end cap; FIG. 12 is a view illustrating insertion of the mounting instrument and end cap within the surgical site to mount the end cap to the body of the implant; and FIG. 13 is an enlarged top view in partial cross-section of a pair of implants positioned into the inter-vertebral space of a lumbar spinal section. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiments of the method and instrumentation disclosed herein are discussed in terms of orthopaedic spinal fusion procedures and instrumentation. It is also envisioned, however, that the disclosure is applicable to a wide variety of procedures including, but, not limited to ligament repair, joint repair or replacement, non-union fractures, facial reconstruction and spinal stabilization. In addition, it is believed that the present method and instrumentation finds application in both open and minimally invasive procedures including endoscopic and arthroscopic procedures wherein access to the surgical site is achieved through a cannula or small incision. The following discussion includes a description of each instrument according to the present invention utilized in performing a spinal fusion followed by a description of the preferred method for spinal fusion utilizing the instrumentation. In the discussion which follows, the term "proximal", as is traditional, will refer to the portion of the structure which is closer to the operator, while the term "distal" will refer to the portion which is further from the operator. Referring now to the drawings in which like reference numerals identify similar or identical elements throughout the several views, FIG. 1 illustrates in perspective view a surgical retractor of the present disclosure. Retractor 10 is particularly contemplated for distracting adjacent bony structures, e.g., adjacent opposed vertebral bodies, to facilitate the insertion and application of an implant, for providing a cannula for insertion of the instruments, and for ensuring proper alignment of the instrumentation and accurate insertion of the implant. Although described for spinal procedures, it is envisioned that retractor 10 may also be utilized to distract other structures as well including joints, ligaments, etc... Referring now to FIGS. 1-2, retractor 10 includes sleeve 12 defining longitudinal axis "a" and having enlarged head 14 disposed at a proximal end thereof. Sleeve 12 defines a longitudinal opening extending therethrough to receive surgical instrumentation described below. Sleeve 12 and enlarged head 14 are preferably monolithically formed of a suitable rigid material including stainless steel, aluminium alloy or the like. Sleeve 12 may be formed of a suitable polymeric material as well. Sleeve 12 may be a variety of sizes including, for example, 12 mm, 14 mm, 16 mm and 18mm in diameter. The retractor size utilized will generally correspond to the diameter of the instrumentation and/or implant to be applied. Sleeve 12 may include first and second longitudinally extending openings 16 formed in its outer wall. Openings 16 are diametrically arranged with relation to each other and terminate at their distal ends in collar 18. Each opening 16 extends radially for about between 10%-50% the circumference or perimeter of sleeve 12 and longitudinally for greater than 50% the length of sleeve 12. Openings 16 are contemplated to permit the lateral introduction of surgical instrumentation required to carry out the fusion procedure as an alternative to introducing the instrumentation through the open proximal end of sleeve 12. These openings 16 also enhance illumination at the surgical site. Sleeve 12 further includes first and second diametrically opposed retractor arms or tangs 20. Retractor arms 20 extend distally from collar 18 in a general longitudinal direction parallel to one another and define longitudinal slotted portion 22. Each arm 20 has an arcuate outer surface (i.e., defining a radius of curvature substantially equivalent to the radius of curvature of the remaining portion of the sleeve). Each retractor arm 20 has first and second vertebrae supporting surfaces 20a, 20b in general parallel relation to each other and preferably parallel to the longitudinal axis of sleeve 12. In the illustrated embodiment, supporting surfaces 20a, 20b are substantially planar. The height "h" of each arm 20 (i.e., the distance between supporting surfaces 20a, 20b) corresponds to the height of the intended distraction distance between adjacent tissue portions, i.e. adjacent vertebrae. For example, in spinal fusion application, the height "h" of each arm 20 ranges from about 0.3 to 0.4 inches and more preferably from about 0.28 to about 0.35 inches. One skilled in the art will readily appreciate that this dimension can be varied as needed depending upon the procedure. Each arm 20 further includes tapered end portions 23 defining a generally V-shaped configuration. End portions 23 facilitate insertion of retractor arms 20 within the surgical site, e.g., within the inter-vertebral space. Referring still to FIGS. 1-2, an impact end cap 26 is positionable over enlarged head 14 and preferably has an inner diameter approximating the outer diameter of the head 14 to form a releasable frictional fit between the two components. Impact cap 26 is intended to receive the impact of a driving instrument used to insert retractor 10 within the bony tissue as will be discussed. Such impaction, drives the arms 20 of sleeve 12 into the disc space (with the height h spanning the space) and distracts the opposing vertebrae bodies as surfaces 20a engage the upper (or lower) vertebral body and surfaces 20b engage the opposing vertebral body, thereby firmly mounting the retractor 20 to maintain its alignment and orientation and ensure that an equal amount of material is cut on both vertebral end plates when a drill is inserted therethrough (described below). Application of Instrumentation The use of the instrumentation kit in conjunction with the insertion of a fusion cage 200 into an inter-vertebral space defined between adjacent lumbar vertebrae will be described. The subsequent description will be particularly focused on an open posterior spinal fusion procedure, however, it is to be appreciated that an anterior approach is contemplated as well. The inter-vertebral space is accessed utilizing appropriate retractors, e.g., laminar retractors, dural extractors to expose the posterior vertebral surface. Thereafter, retractor 10 of FIG. 1 with impactor cap 26 mounted thereon is positioned adjacent the inter-vertebral space. With reference to FIG. 3, retractor arms 20 are inserted within the inter-vertebral space and the retractor 10 is gently impacted into the space with a mallet. The preferred orientation of retractor arms 20 within the inter-vertebral space is shown in FIG. 3. As shown, retractor arms 20 are arranged such that first and second supporting surfaces 20a, 20b of each retractor arm respectively engage the opposed vertebral bodies V 1 , V 2 . Upon insertion of retractor arms 20, the vertebral bodies V 1 , V 2 are distracted whereby the retractor arms 20 become firmly lodged within the inter-vertebral space. The arrangement of retractor arms 20 provides a double point contact with each vertebral body (curved end plate), i.e., the first supporting surfaces 20a of retractor arms 20 engage vertebral body V 1 at two different locations and in spaced relation. The second supporting surface 20b engage vertebral body V 2 in the same manner. Thus, the load exerted by vertebral bodies V 1 , V 2 is distributed at two different locations on retractor 10 and along the entire lengths of the supporting surfaces 20a, 20b thereby firmly and uniformly loading the retractor 10 in the inter-vertebral space. It is also to be noted that as discussed above, the particular arrangement of the retractor arms 20 within the inter-vertebral space automatically appropriately aligns retractor 10 with relation to the vertebral bodies V 1 , V 2 , i.e., in parallel relation with the vertebral end plates for the subsequent drilling process. Tapered surfaces 24 of retractor arms 20 facilitate entry of the retractor arms 20 into the inter-vertebral space. The depth of penetration of retractor arms 20 is limited by collar 18 as described above. Referring now to FIG. 4, a drilling instrument 40 is now used to prepare the disc space and vertebral end plates for insertion of the fusion implant. The cutting depth of drilling instrument 40 is adjusted as desired (i.e., to correspond to the length of the fusion cage) by adjusting the positional collar 56 and securing the collar 56 at the desired position with locking collar 58 as described above. With a T-handle mounted to drilling instrument 40 (not shown in the Figs.), the instrument is introduced into retractor 10 and advanced to contact the posterior surface of the vertebral bodies V 1 , V 2 . Drill bit 48 communicates with vertebral bodies V 1 , V 2 through slotted opening 22 defined between retractor arms 20 (FIG. 1). Drilling instrument 40 is advanced into the inter-vertebral space by rotating T-handle in the direction indicated by the directional arrow of FIG. 4 until positional collar 56 engages the proximal end of enlarged head 18 of the retractor 10. This shears the soft tissue and cuts the bone. Depth markings are also monitored to further assist the surgeon. Thereafter, drilling instrument 40 is removed by rotating T-handle in the opposite direction and the instrument 40 is removed from the retractor 10. When juxtaposed sides of the adjacent vertebral disc have been adequately prepared by drilling the holes and completely removing any remaining soft tissue, tapping instrument 70 is selected and attached to the T-handle. The purpose of the tapping instrument 70 is to cut the threads into the opposing vertebral endplates. This ensures that the implant will be positioned correctly and will have the correct purchase into the endplates for immediate bone graft material to endplate contact. With reference now to FIG. 5, tapping instrument 70 is inserted into retractor 10 and positioned adjacent the drilled bone. With retractor 10 as a direct guide, T-handle is rotated in the direction of the directional arrow of FIG. 5 while simultaneously applying sufficient downward (distal) pressure on the T-handle to advance the tapping instrument 70 and promote even purchase into the endplates. Upon advancement of the tapping instrument 70, the de-burred bone chips collect within a conveyance channel of tapping head 74, and are conveyed proximally during rotational movement of the tapping head away from the tapping site. Tapping instrument 70 is advanced into the bone until the desired depth has been achieved, which occurs when the distal end of tapping head 74 "bottoms out" on the bone. To further ensure that the tapping instrument 70 reaches the proper depth, the depth markings on tapping instrument 70 are also monitored. Tapping head 74 communicates with vertebral bodies V 1 , V 2 through slotted openings 22 defined between the retractor arms 20. When tapping instrument 70 reaches the appropriate depth, the tapping instrument 70 is rotated via T-handle in an opposite direction to back the instrument out of the bone and the instrument 70 is removed from the retractor 10. With reference now to FIG. 6, attention is focused on the insertion of the selected fusion implant 200. Cage body 202 is mounted onto insertion instrument. With T-handle attached in the manner described above, insertion instrument 100 with mounted cage body 202 is inserted into retractor 10 and the cage body 202 is positioned within the tapped bore by rotating insertion instrument in the direction depicted in FIG. 6. Cage body 202 is advanced until it is completely seated with the bore. The indicator lines on insertion instrument 100 assist the surgeon in determining when the cage is in proper position. Alignment bars indicate to the user the orientation of the cage to assist in ensuring that the perforations are in communication with the vertebral end plates when the cage is finally positioned. Insertion instrument 100 is then removed from retractor 10. With reference now to FIG. 7, bone growth inducing substances are harvested from, e.g., the illiac crest, and can be packed into a syringe body or tube "s" (as shown in FIG. 7) or other holding device. As depicted in FIG. 8, with the use of forceps "f", the bone growth inducing substances are removed from the syringe "s" and introduced into the cage body 202 until the cage body 202 is completely filled with bone growth inducing substances. The bone growth inducing substances can be lightly impacted to pack the cage. With reference to FIGS. 9-11, after filling cage body 202, the end cap 212 is mounted to the cage body 202. A preferred instrument 300 for applying end cap 212 includes handle 302 and elongated portion 304 connected to the handle and extending distally therefrom. At the distal end of elongated portion 304 is mounting head or section 306. Mounting head 306 includes distal annular portion 308 with annular nub 310 projecting therefrom and four equidistantly spaced flanges 312. Flanges 312 extend in a radial direction and are preferably spaced about 90° apart as best depicted in FIG. 9. Flanges 312 engage the end cap 312 to limit proximal flexure of the end cap 312 as it is mounted to the cage body 202. In the mounted condition of end cap 212 onto instrument 300, annular nub 310 of the instrument 300 is received within annular opening 216 of end cap 212. Preferably, annular nub 310 and opening 216 are correspondingly dimensioned such that a friction fit between the two components is established. With reference now to FIG. 12, instrument 300 with mounted end cap 212 is introduced into the operative site and advanced to cage body 202. Thereafter, end cap 212 is mounted to cage body 202 by inserting the end cap 212 within the interior cavity whereby the end cap 212 snaps into a correspondingly dimensioned groove defmed in the cage body 202. During insertion, the peripheral area of end cap 212 is permitted to deform due in part to the flexible characteristics of its material of fabrication and to notches 216, thus enabling the end cap 212 to pass within the cage body 202. It is to be noted that during insertion, flanges 312 of instrument 300 (FIG. 11) prevent any tendency of end cap 212 to rotate relative to the instrument. With end cap 212 mounted within cage body 202, instrument 300 is removed. FIG. 13 illustrates two lateral fusion implants 200 inserted within the lumbar inter-vertebral space. The second fusion cage 200 is inserted in accordance with the method and instruments previously discussed. While the above description contains many specifics, these specifics should not be construed as limitations on the scope of the disclosure, but merely as exemplifications of preferred embodiments thereof. For example, the forceps and/or end cap insertion tool can be inserted through the retractor 10 prior to removal of the retractor 10. Those skilled in the art will envision many other possible variations that are within the scope of the claims appended hereto. The claims identify embodiments of the invention additional to those described in detail above.

Claims: A surgical retractor instrument (10) comprising an elongated member (12) having proximal and distal end portions (14, 18) and defining a longitudinal passageway (16) for reception of surgical instrumentation, the distal end portion (18) having first and second retractor arms (20) extending in a general longitudinal direction, each retractor arm having first and second supporting surfaces (20a, 20b) for engaging opposed adjacent tissue portions, the first and second supporting surfaces (20a, 20b) of each retractor arm (20) being substantially planar characterized in that each retractor arm defines a dimension between the first and second supporting surfaces (20a, 20b) sufficient to distract the opposed tissue portions upon entry thereof, with both surfaces of each retractor arm engaging respectively the opposed adjacent tissue portions, and each retractor arm (20) has a tapered end portion (23) for facilitating entry into the space between opposed adjacent tissue portions. A surgical retractor according to claim 1 for use in distracting adjacent vertebrae, wherein the first and second retractor arms (20) extend longitudinally from the distal end portion (18) of the elongate member (12) the first and second supporting surfaces (20a, 20b) defining a first vertebra supporting surface and a second vertebra supporting surface respectively, the first and second vertebra supporting surfaces (20a, 20b) of each retractor arm being spaced on each retractor arm at a predetermined distraction distance (h). The surgical retractor according to claim 2 wherein the retractor arms (20) each possess distal tapered portions (23) for facilitating insertion into the intervertebral space. The surgical retractor according to claim 2 or 3 wherein the first and second supporting surfaces (20a, 20b) of each retractor arm (20) are in general parallel relation. The surgical retractor according to claim 4 wherein the first and second supporting surfaces (20a, 20b) of each retractor arm (20) are in general parallel relation to a longitudinal axis (a) of the elongate body. The surgical retractor according to any one of the preceding claims wherein the elongate member (12) includes at least one longitudinal opening (16) defined in an intermediate wall portion. The surgical retractor according to any of the preceding claims, wherein each retractor arm (20) includes tapered end portions (23) for facilitating insertion of the retractor arms (20).

Inventors: JAYNE KIRK, MITCHELL STEVEN T, WINSLOW CHARLES J, JAYNE, KIRK, MITCHELL, STEVEN T., WINSLOW, CHARLES J.
Applicants: HOWMEDICA OSTEONICS CORP, HOWMEDICA OSTEONICS CORP.
Application year: 1997
Main classification: A61B17
IPC codes: A61B19, A61F2, A61B17