Patent Publication Number: US-9839449-B2

Title: Translational plate and compressor instrument

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 14/334,991, filed Jul. 18, 2014, which claims the benefit of, and priority to, U.S. Provisional Application Ser. No. 61/856,265, filed Jul. 19, 2013. The entire contents of each of the above applications are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a device and instrument for use in orthopedic surgeries and, more specifically, to a plate that is attachable to the vertebrae that is configured to compress during the procedure and an instrument configured to engage the plate to compress the plate. 
     2. Discussion of Related Art 
     The human spinal column is a highly complex structure. It includes twenty-four discrete bones, known as vertebrae, coupled sequentially to one another to house and protect critical elements of the nervous system. The cervical portion of the spine, which includes the neck of the spine up to the base of the skull, includes the first seven vertebrae. 
     For many reasons, such as aging and trauma, the intervertebral discs can begin to deteriorate and weaken. This may result in chronic pain, degenerative disc disease, or even tearing of the disc. Ultimately, the disc may deteriorate or weaken to the point of tearing and herniation, in which the inner portions of the disc protrude through the tear. A herniated disc may press against or pinch the spinal nerves, thereby causing radiating pain, numbness, and/or diminished strength or range of motion. 
     Many treatments are available to remedy these conditions, including surgical procedures in which one or more damaged intervertebral discs are removed and replaced with a prosthetic. However, should the prosthetic protrude from between the adjacent vertebrae and contact the surrounding nerves or tissues, the patient may experience additional discomfort. In procedures for remedying this problem, a spinal plate is affixed to the vertebrae and oriented to minimize such protrusion. In addition, the plate provides fixation and support to maintain spinal stability while the fusion occurs. 
     Spinal plates and cervical plates in particular, are known in the art. Fixed cervical plates generally exhibit unalterable, static dimensions. During the natural subsidence of the spinal column after surgery, the overall length of the spinal column gradually decreases. Fixed cervical plates resist this change due to their fixed axial length, which may eventually stress the spine and cause pain or discomfort. Adjustable cervical plates attend to this predicament by providing a mechanism through which the plate is shortened to accommodate for a measure of subsidence. However, some adjustable plates require subsequent surgical procedures to adjust the axial dimensions of the plate. In addition to accommodating subsidence, it is critical for the plate to provide means to apply constant loading of an implant placed between adjacent vertebrae in order to promote fusion. 
     SUMMARY 
     In an aspect of the present disclosure, a bone plate that is operatively attachable to bone includes a first segment, a second segment, and a locking mechanism. The first segment includes a compression notch. The first and second segments are positioned along a longitudinal axis and are movable relative to one another. The locking mechanism inhibits relative axial movement of the first and second segments away from one another along the longitudinal axis. The locking mechanism includes first and second grooves disposed on the second segment. The first and second grooves and the compression slot are configured to receive an instrument to move the first segment towards the second segment along the longitudinal axis. The locking mechanism can be releasable to permit axial movement of the first and second segments apart from one another. The locking mechanism can include a tongue that extends from the first segment. The tongue operatively engages the first and second grooves to sequentially and releasably lock the first and second segments to inhibit axial movement of the first and second segments apart from one another while enabling axial movement of the first and second segments towards one another. The first and second segments are attachable to vertebral bodies such that the first and second segments move toward one another in response to the subsidence of the vertebral bodies. The first and second segments can include screw holes that receive screws. The locking mechanism can include a third and fourth groove disposed on the second segment. Each of the grooves can be spaced apart at a length along the longitudinal axis from another groove. The compression notch may be placed at a lateral mid-point of the first segment. 
     According to another aspect of the present disclosure, a surgical system includes a bone plate and a compression instrument. The bone plate includes a first segment having a compression notch, a second segment, and a locking mechanism that includes first and second grooves disposed on the second segment. The compression instrument includes a handle, a first tip, and a second tip. The first tip is sized and configured to engage one of the first and second grooves of the locking mechanism. The second tip is sized and configured to engage the compression notch. The first and second tips are movable relative to one another. The first and second tips are configured to move the first segment towards the second segment along the longitudinal axis when engaged with one of the first and second grooves and the compression slot. A tongue of the locking mechanism can include a tab that is configured to operatively engage the first and second grooves to sequentially and releasably lock the first and second segments. The first tip of the compression instrument can be configured to disengage the tab of the locking mechanism from the first and second grooves. The locking mechanism can be releasable to permit axial movement of the first and second segments apart from one another. The system can further include a spacer positioned between the first and second segment of the bone plate. The spacer can be configured to maintain a predefined space between the first and second segments. 
     According to yet another aspect of the present disclosure, a method of attaching a bone plate to vertebrae includes providing a bone plate, securing a first segment of the bone plate to a first vertebra with a first bone screw inserted through a first screw hole, securing a second segment of the bone plate to a second vertebra with a second bone screw inserted through a second screw hole, and compressing the first segment towards the second segment of the bone plate. Compressing the first segment of the bone plate towards the second segment of the bone plate includes compressing a handle of a compression instrument while a first tip of the compression instrument engages one of first and second grooves and a second tip of the compression instrument engages a compression notch. The method can include removing a spacer from between the first and second segments before compressing the first segment of the bone plate towards the second segment of the bone plate. 
     Further, to the extent consistent, any of the aspects described herein may be used in conjunction with any or all of the other aspects described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of the present disclosure are described hereinbelow with reference to the drawings, wherein: 
         FIG. 1  is a perspective view of an exemplary embodiment of a translational plate in accordance with the present disclosure including three segments; 
         FIG. 1A  is a perspective view of another exemplary embodiment of a translational plate in accordance with the present disclosure including two segments with bone screws inserted through the screw holes and spacers positioned between the segments; 
         FIG. 2  is an exploded view illustrating the components of the plate shown in  FIG. 1 ; 
         FIG. 3  is a top view of the plate shown in  FIG. 1  with the segments in a spaced-apart position; 
         FIG. 4  is a side cross-sectional view taken along the longitudinal axis “A-A” shown in  FIG. 3 ; 
         FIG. 5  is an enlargement of the detail area  5  shown in  FIG. 4 ; 
         FIG. 6  is a top view of the plate shown in  FIG. 1  with the segments in a compressed position; 
         FIG. 7  is a cross-sectional view taken along the line “ 7 - 7 ” shown in  FIG. 6 ; 
         FIG. 8  is an enlargement of the detail area  8  shown in  FIG. 7 ; 
         FIG. 9  is a side view of an exemplary embodiment of a compressor instrument in accordance with the present disclosure; 
         FIG. 10  is an enlargement of the detail area  10  shown in  FIG. 9 ; 
         FIG. 10A  is a enlarged side view of another exemplary embodiment of the tips of a compressor instrument in accordance with the present disclosure; 
         FIG. 11  is a cross-sectional view taken along the longitudinal axis of the plate shown in  FIG. 1  engaged with the compressor instrument of  FIG. 9 ; 
         FIG. 12  is an enlargement of the detail area  12  shown in  FIG. 11 ; 
         FIG. 13  is a cross-sectional view taken along the longitudinal axis of the plate shown in  FIG. 1  engaged with a compressor instrument including the tips shown in  FIG. 10A ; 
         FIG. 14  is an enlargement of the detail area  14  shown in  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are now described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. As used herein, the term “clinician” refers to a doctor, a nurse, or any other care provider and may include support personnel. Throughout this description, the term “proximal” will refer to the portion of the device or component thereof that is closer to the clinician and the term “distal” will refer to the portion of the device or component thereof that is farther from the clinician. In addition, the term “cephalad” is used in this application to indicate a direction toward a patient&#39;s head, whereas the term “caudad” indicates a direction toward the patient&#39;s feet. Further still, for the purposes of this application, the term “medial” indicates a direction toward a side of the body of the patient, i.e., away from the middle of the body of the patient. The term “posterior” indicates a direction toward the patient&#39;s back, and the term “anterior” indicates a direction toward the patient&#39;s front. Additionally, in the drawings and in the description that follows, terms such as front, rear, upper, lower, top, bottom, and similar directional terms are used simply for convenience of description and are not intended to limit the disclosure. 
     A translational plate  10  that allows for adjustment over a specified range, while maintaining the strength and functionality of plate  10 , will now be described with reference to  FIGS. 1-8 . Plate  10  may generally be operatively coupled to a patient&#39;s spine, and in particular to the cervical vertebrae, i.e., the vertebrae in the patient&#39;s neck. Plate  10  includes a plurality of adjacent segments that are axially movable relative to one another. The number of segments that plate  10  includes corresponds to the number of vertebral levels plate  10  is to bridge. As shown in  FIGS. 1 and 2-8 , plate  10  includes three segments  12 ,  14 ,  16 . As shown in  FIG. 1A , a translational plate  10   a  includes two segments  12 ,  16 . It is also contemplated that the translational plate may include more than three segments. 
     With reference to  FIGS. 1 and 3 , segments  12 ,  14 ,  16  of plate  10  include mating or inter-locking surfaces that fit together in a dove-tail or tongue-and-groove mechanism, allowing segments  12 ,  14 ,  16  to move or slide relative to one another along longitudinal axis “A-A” facilitates lengthening or shortening of plate  10 . As will be described in detail below, a locking mechanism  18  ( FIG. 2 ) inhibits lengthening of plate  10 , but facilitates shortening of plate  10 , without an additional procedure. As shown in  FIG. 3 , segment  12  includes a groove  5  that is shaped to receive a portion  7  of adjacent segment  14 , which in turn includes a groove  9  that is shaped to receive a portion  11  of adjacent segment  16 . 
     With additional reference to  FIG. 2 , one or more rails  20  extend longitudinally from the segments  12 ,  14  and are receivable within slots  27  of the adjacent segments  14 ,  16 , respectively. One or more rails  21  extend longitudinally from segments  14 ,  16  and are receivable within slots  29  of the adjacent segments  12 ,  14 , respectively. The length of the rails  20 ,  21  (as well as the length of tongue  22  and number and positioning of grooves  24   a - d ) determines the range within which the segments  12 ,  14 ,  16  are slidable relative to one another. Rails  20  of segment  12  are slidably received within slots  27  of segment  14 ; rails  20  of segment  14  are slidably received within slots  27  of segment  16 ; rails  21  of segment  14  are slidably received within slots  29  of segment  12 ; and rails  21  of segment  16  are slidably received within slots  29  of segment  14 . Rails  20  have a substantially triangular cross-section and rails  21  have a circular cross-section; however, rails  20 ,  21  may define an alternative geometrical cross-sections, e.g., rails  20 ,  21  may alternatively define a square shape, an I-beam, a C-channel, or the like. Rails  20 ,  21  may have the same geometrical cross-section. Rails  20  may be operatively coupled to segments  12 ,  14  or may be an integral portion of the segments  12 ,  14 . Rails  21  may be operatively coupled to segments  14 ,  16  or may be an integral portion of segments  14 ,  16 . 
     Rails  20 ,  21  facilitate movement of segments  12 ,  14 ,  16  relative to one another along longitudinal axis “A” and stabilize plate  10  by inhibiting movement of segments  12 ,  14 ,  16  that is not along the longitudinal axis “A”, e.g., rotation and/or twisting. As rails  20 ,  21  are inserted into slots  27 ,  29 , as described above, locking mechanism  18  inhibits the backward movement of segments  12 ,  14 ,  16  away from one another. By inhibiting the backward movement of segments  12 ,  14 ,  16  away from one another, i.e., expansion of plate  10 , the integrity and position of plate  10  is maintained while allowing compression of the anatomy, constant loading of the bone graft, and subsidence of the anatomy, which may occur over time. 
     With reference to  FIGS. 4 and 5 , a locking mechanism  18  includes a tongue  22  and grooves  24   a - d . Once rails  20 ,  21  couple segments  12 ,  14 ,  16  to one another there is no additional manipulation required for locking mechanism  18  to be engaged, i.e., locking mechanism  18  releasably secures segments  12 ,  14 ,  16  to each other to prevent segments  12 ,  14 ,  16  from moving apart while permitting segments  12 ,  14 ,  16  to move together. Tongues  22  of segments  12 ,  14  are slidably received within segments  14 ,  16 , respectively. Rails  20 ,  21  facilitate sliding of tongue  22  of locking mechanism  18  to slide relatively effortlessly past the grooves  24   a - d  in a releasably locked engagement therewith, i.e., as tab  22   a  is engaged with one of grooves  24   a - c . Tongue  22  may also include a guide channel  25   b  to receive a guide pin  25   a  therein to facilitate aligning of tongue  22  and to minimize off-axis movement of segments  12 ,  14 ,  16  relative to one another. 
     Tongue  22  includes an undercut feature or tab  22   a  at a distal end thereof that is configured and adapted to engage grooves  24   a - d , thereby causing tongue  22  to releasably lock to one of grooves  24   a - d , which are spaced at intervals or levels. As shown in  FIG. 3 , segment  12  and segment  14  can be maximally spaced apart by a length x 1 , and segments  14 ,  16  can be maximally spaced apart by a length x 2 . The lengths x 1 , x 2  by which segments  12 ,  14  and segments  14 ,  16  are spaced, respectively, correspond to groove  24   a - d  to which the tab  22   a  of tongue  22  is releasably secured. After installation, plate  10  is able to shorten in response to subsidence without the need for a secondary operation, as segments  12 ,  14 ,  16  move together and tab  22   a  of tongue  22  moves into the next adjacent groove  24   b - d . Grooves  24   a - d  can be spaced-apart at lengths or levels each representing a 1 mm reduction in lengths x 1 , x 2 . However, it is contemplated that each groove  24   a - d  can be spaced-apart at a length greater or less than 1 mm. It has been shown that when grooves  24   a - d  are spaced-apart at a length of 1 mm, optimal compression is maintained on an implant positioned between adjacent vertebrae promoting fusion of the vertebrae and the implant. 
     The interaction of tab  22   a  with grooves  24  allows segments  12 ,  14 ,  16  to move closer together but not apart, i.e., once one of grooves  24  engages tab  22   a , movement of segments  12 ,  14 ,  16  apart is inhibited. The shape of tab  22   a  allows tab  22   a  to disengage groove  24  in a direction that will move segments  12 ,  14 ,  16  together, but not in a direction that would move or distract segments  12 ,  14 ,  16  apart without requiring an additional, secondary user operation. It is desirable to maintain loading on the vertebral bodies to help maintain a graft and/or implant in position until fusion is completed to facilitate the healing process. Inhibiting segments  12 ,  14 ,  16  of plate  10  from moving or distracting apart from each other aids in the healing process by maintaining loading on the vertebrae. 
     Referring to  FIGS. 1-1A , segments  12 ,  14 ,  16  of plate  10  can include a first compression notch  54  and a second compression notch  55 . Compression notches  54 ,  55  are configured to cooperate with locking mechanism  18  to compress lengths x 1 , x 2  after bone screws  40  attach plate  10  to vertebrae such that a compression force or preload is applied to the space between vertebrae engaged by segments  12 ,  14 ,  16  of plate  10 . First compression notch  54  is positioned adjacent to and spaced apart from the outer edges (top and bottom edges when plate  10  is attached to vertebrae) of segments  12  and  16  as shown in  FIGS. 1 and 3 . As shown, the compression notches  54  are placed at or near the lateral mid-point of the plate segment  12 ,  14 ,  16 , with the screw holes  28  disposed laterally outward of the axis between the notches  54  and  55 . 
     With reference to  FIGS. 1A and 2 , plate  10  includes screw holes  28  adapted for the reception of bone screws  40  therethrough. An insert  30  may be press-fitted into each screw hole  28 . In an embodiment, inserts  30  may be removable. Inserts  30  may be formed from a material that is softer than that forming the bone screws  40 . For example, the insert  30  may be formed from commercially pure implant grade titanium. An inward facing lip (not shown) is configured and adapted to engage threads  41  of bone screw  40 . The harder material, e.g., implant grade titanium alloy, of bone screw  40  deforms the softer material, e.g., commercially pure titanium, forming the lip of insert  30 . This engagement inhibits the screw from migrating out of plate  10 , as well as the bone, as is described in U.S. Pat. Nos. 8,449,585 and 6,322,562, both of which are incorporated herein by reference. Although plate  10  is shown as having screw holes  28 , it is contemplated that a plate may be used that lacks holes  28 . For example, a plate may be attached to a bone by using screws that are self-starting or self-tapping or drills may be used to prepare holes within a plate for screws. 
     Other structures for locking screws to plates are known and can be used. In addition, inserts  30 , although shown and described as being part of plate  10 , may be used with a static plate that does not include movable or adjustable segments. Inserts  30  when used with a bone plate, whether adjustable or static, would provide enhanced screw retention within the screw holes of such plates. 
     As described, screws  40  may be formed from a biocompatible material. By way of example, plate  10  may be formed from a PEEK or titanium alloy, inserts  30  formed from commercially pure implant grade titanium, and screws  40  formed from a titanium alloy. The use of materials having different characteristics, such as different hardness, facilitates screw-plate engagement, and inhibits screw back out. 
     Plate  10 , locking mechanism  18 , and rails  20 ,  21  can be made from a relatively hard material, e.g., implant grade titanium alloy, and inserts  30  are made from a relatively softer material, e.g., commercially pure implant grade titanium. In another embodiment, plate  10  and/or rails  20 ,  21  may be made of another implant grade material, such as, but not limited to, commercially pure titanium, titanium alloys, cobalt chrome alloys, PEEK, and the like. 
     Referring to  FIGS. 4-8 , segments  12 ,  14 ,  16  of plate  10  may be maximally spaced apart thereby facilitating the greatest degree of adjustment to fit the anatomy of the patient as shown in  FIGS. 4 and 5 . Tab  22   a  of tongue  22  may be received within the outward most groove  24   a  such that segments  12 ,  14 ,  16  are maximally spaced apart, but are inhibited from moving apart from one another without a secondary user operation to disengage tab  22   a  from groove  24   a . Plate  10  is placed onto the vertebral bodies such that screw holes  28  are located on the anterior portion of the most cranial vertebral body. Screws  40  ( FIG. 1A ) are placed into the two most cranial screw holes  28  to anchor plate  10  in place. The next adjacent segment is adjusted to align holes  28  with the next vertebral body so that screws  40  can be inserted through holes  28  and into the vertebral body. This process is repeated for each additional vertebral segment. As shown in  FIGS. 6-8 , segments  12 ,  14 ,  16  of plate  10  are in a minimally spaced apart or compressed position with tab  22   a  engaging groove  24   d.    
     A standard plate holder (not shown) can be used to facilitate placement of plate  10  and holding of plate  10  during insertion of the screw  40 . In addition, a compression instrument  60  ( FIG. 9 ) may be used to help expand or contract the adjacent segments  12 ,  14 ,  16  as described in detail below. Removable spacers or wedges  90  ( FIG. 1A ) may hold segments  12 ,  14 ,  16  in a predetermined spaced orientation during implantation by being positioned between segments  12 ,  14 ,  16  and impeding movement of segments  12 ,  14 ,  16  toward one another in a predetermined spaced orientation during the implantation of plate  10 . Removable wedges  90  can be positioned over and configured to engage rails  21  between segments  12 ,  14 ,  16 . After implantation of plate  10 , removable wedges  90  are removed from the plate  10 , thereby permitting segments  12 ,  14 ,  16  to move relative to one another. It will be appreciated that removable wedges  90  are removed before a compression instrument is used to compress or preload plate  10  as described in detail below. It is envisioned that wedges  90  are usable with all disclosed embodiments of the plate. 
     Referring to  FIGS. 9-10A , a compression instrument  60  is sized and configured to engage plate  10 . Compression instrument  60  includes a first tip  62 , a second tip  64 , and a handle  65 . First tip  62  is sized and configured to engage grooves  24   a - d  of plate  10  and second tip  64  is sized and configured to engage compression notches  54  of plate  10  of adjacent segments. In embodiments, first tip  62  can include more than one protrusion each configured to engage adjacent grooves  24   a - d . In some embodiments, first tip  62 ′ includes a protrusion configured to engage a suitable structure, e.g., notches  54 ,  55 , grooves  24   a - d , etc., on one segment  12 ,  14 ,  16  and second tip  64  is configured to engage a suitable structure, e.g., notches  54 ,  55 , grooves  24   a - d , etc., on an adjacent segment  12 ,  14 ,  16 . First and second tips  62 ,  64  are moveable relative to one another. Handle  65  is operatively associated with first and second tips  62 ,  64  to move tips  62 ,  64  relative to one another. Handle  65  can have a first arm  66  operatively associated with first tip  62  and a second arm  67  operatively associated with second tip  64 . First and second arms  66 ,  67  can pivot about a pivot pin  69  to move tips relative to one another. Handle  65  can include clamping members  68   a ,  68   b  positioned on first and second arms  66 ,  67  respectively. Clamping members  68   a ,  68   b  can each have ridges that engage ridges on the opposing clamping member  68   a ,  68   b  such that as first and second arms  66 ,  67  are moved towards each other, clamping members  68   a ,  68   b  provide tactile feedback of each level of compression. 
     With reference to  FIGS. 11 and 12 , compression instrument  60  engages locking mechanism  18  of segments  12  and  14 . First tip  62  of compression instrument  60  is inserted into grooves  22   a - d  of locking mechanism  18  of segment  14  and second tip  64  of compression instrument  60  is inserted into first compression notch  54  of segment  12 . In some embodiments, first tip  62  disengages tab  22   a  of tongue  22  from grooves  24   a - d  when inserted into grooves  24   a - d . Handle  65  is manipulated to move tips  62 ,  64  towards one another such that segments  12  and  14  are moved towards the compressed position such that a preload or compression force is applied to the vertebrae engaged by segments  12  and  14  of plate  10 . Tab  22   a  and/or clamping members  68   a ,  68   b  can provide tactile feedback for each level of compression applied to segments  12 ,  14 . It will be appreciated that compression can be applied to each set of adjacent segments  12 ,  14 ,  16  of plate  10 . For example, to compress adjacent segments  14  and  16 , first tip  62  can be inserted in grooves  24   a - 4  of segment  16  and second tip  64  is inserted in second compression notch  55  of segment  14 . 
     In embodiments where first tip  62  disengages tab  22   a  from grooves  24   a - d , compression instrument  60  can release locking mechanism  18  allowing the segments  12 ,  14 ,  16  to move apart from one another to allow for surgical adjustment. 
     With reference to  FIGS. 13 and 14 , compression instrument  60  engages locking mechanism  18  of segments  14  and  16 . First tip  62 ′ of compression instrument  60  is inserted in first compression notch  54  of segment  16  and second tip  64  of compression instrument  60  is inserted into second compression notch  55  of segment  14 . Handle  65  is manipulated to move tips  62 ′,  64  towards one another such that segments  14  and  16  are moved towards the compressed position such that a preload or compression force is applied to the vertebrae engaged by segments  14  and  16  of plate  10 . Tab  22   a  and/or clamping members  68   a ,  68   b  can provide tactile feedback for each level of compression applied to segments  14 ,  16 . It will be appreciated that compression can be applied to each set of adjacent segments  12 ,  14 ,  16  of plate  10 . In particular, compression will be applied to an adjacent pair of segments and the instrument will be repositioned to apply compression to a different pair of adjacent segments. 
     While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.