Abstract:
An instrument for inserting a spinal implant into an intervertebral space is disclosed. The instrument includes an elongated body having inner and outer shafts configured to longitudinally translate with respect to each other, a holding tip which is configured to articulate with respect to the elongated body in response to the longitudinal translation of the inner and outer shafts, and a driveshaft assembly configured to cooperate with the articulation of the holding tip and secure a spinal implant to the instrument. A spinal implant and a system for inserting a spinal implant into an intervertebral space including an insertion instrument and a spinal implant are also disclosed.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to apparatus and systems for orthopedic spine surgery and, in particular, to an apparatus for inserting a spinal implant into an intervertebral space. 
     2. Description of Related Art 
     The human spine is comprised of thirty-three vertebrae and twenty-four as an adult. An infant contains 7 cervical vertebrae, 12 dorsal or thoracic vertebrae, 5 lumbar vertebrae, 5 sacral vertebrae, and 4 coccygeal or caudal vertebrae. In an adult, the 5 sacral vertebrae fuse together to form the sacrum and the 4 coccygeal vertebrae fuse to form the coccyx. Intervertebral discs lie between each pair of adjacent vertebrae. Every intervertebral disc maintains a space between adjacent vertebrae and acts as cushion under compressive, bending, and rotational loads and motions. Each intervertebral disc has a fibrocartilaginous central portion called the nucleus pulposus. The nucleus pulposus of a healthy intervertebral disc contains significant amount of water. This water content provides spongy quality and allows it to absorb spinal stress. 
     Each intervertebral disc has an annulus fibrosus, which condition might be affected by the water content of the nucleus pulposus. The annulus fibrosus consist of a ring of fibrocartilage and fibrous tissue forming the circumference of the intervertebral disc. Excessive pressure or injuries to the intervertebral discs may adversely affect the annulus fibrosus. Usually, the annulus fibrosus is the first portion of the intervertebral discs that is injured. The annulus fibrosus may be injured in several ways. Typically, the annulus fibrosus tears due to an injury. When these tears heal, scar tissue forms in the annulus fibrosus. Given that scar tissue is not as strong as normal ligament tissue, the annulus becomes weaker as more scar tissue forms. An annulus fibrosus with scar tissue is usually weaker than a normal annulus fibrosus. The formation of scar tissue may eventually lead to damage to the nucleus pulposus. As a result of this damage, the nucleus fibrosus may, for instance, lose water content, hindering the intervertebral disc&#39;s ability to act as a cushion. The reduced cushioning capability might increase stresses on the annulus fibrosus and, consequently, cause still more tears. Hence, the annulus fibrosus may undergo a degenerative cycle consisting of exponential reduction of water content. Eventually, the nucleus pulposus may lose all its water. As the nucleus pulposus loses its water content, it collapses and thus allows the vertebrae above and below the disc space to move closer to each other. In other words, the intervertebral disc space narrows as the nucleus pulposus loses water. When the nucleus pulposus collapses, the facet joints, which are located on the back of the spine, shift, altering the way these joints work together. 
     When a disc or vertebra is damaged due to disease or injury, performing a spinal fusion is one of the techniques used for treating the patient. During spinal fusion, a surgeon removes part or all of the intervertebral disc, inserts a natural or artificial disc spacer, and constructs an artificial structure to hold the affected vertebrae in place. While the spinal fusion may address the diseased or injured anatomy, the natural biomechanics of the spine are affected in a unique and unpredictable way. 
     There remains a need for an instrument for inserting spinal implants which provides greater control of the spinal implant during insertion. 
     SUMMARY 
     The present disclosure relates to an insertion instrument for placing a spinal implant into an intervertebral space, a spinal implant, and a system for inserting the spinal implant in an intervertebral space using the insertion instrument. 
     The insertion instrument includes an elongated body having an inner and outer shaft; a tip assembly having an inner shaft tip, an outer shaft tip, and a holding tip; a handle assembly; an articulation assembly; and a driveshaft assembly. The articulation assembly is configured to translate the inner shaft in relation to the outer shaft. The relative translation of the inner shaft and the outer shaft induces translation of the inner shaft tip and the outer shaft tip with respect to each other. The translation of the inner shaft tip and the outer shaft tip induces articulation of the holding tip in relation to the elongated body defining an angle of articulation. The driveshaft assembly extends through a bore within the elongated body, the tip assembly, and the holding tip. The driveshaft assembly is configured to secure a spinal implant to the distal end of the holding tip. 
     In an embodiment of the insertion instrument, the driveshaft assembly includes a coupling knob, a coupling shaft, a torque limiter, and a universal joint. The universal joint cooperates with the articulation of the holding tip with respect to the elongated body. The distal end of the universal joint is threaded to secure the implant to the insertion instrument. 
     In another embodiment of the insertion instrument, the handle assembly is rotatable about elongated body. The handle assembly is configured to lock in a selected radial position with respect to the elongated body. 
     In one embodiment of the spinal implant, the spinal implant is generally convex between the leading and trailing ends. The leading end of the implant is generally bullet shaped and has a blunt tip. The sidewalls of the implant may share a radii of curvature. The top and the bottom of the implant may have two sets of teeth. The first set of teeth is located near the leading end of the implant. The first set of teeth has ridges substantially parallel to the sidewalls sharing the radii of curvature. The second set of teeth is located near the trailing end of the body. The second set of teeth has ridges substantially perpendicular to the sidewalls with a vertical face open to the trailing end. The trailing end of the spinal implant has a threaded opening. At least one sidewall has a groove. 
     In an embodiment for the system for inserting a spinal implant into an intervertebral space with an insertion instrument, the system includes the insertion instrument and the spinal implant discussed above. The trailing end of the spinal implant configured to cooperate with the distal end of the holding tip and the distal end of the driveshaft assembly. The spinal implant is secured to the holding tip by the rotation of the driveshaft assembly. The torque limiter in the driveshaft assembly is configured to limit the rotation of the driveshaft assembly when the spinal implant is secured to the holding tip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view showing the system for inserting a spinal implant into an intervertebral space with an insertion instrument with the spinal implant secured to the insertion instrument; 
         FIG. 2  is a perspective view showing the system for inserting a spinal implant into an intervertebral space with an insertion instrument with the coupling shaft removed and the spinal implant free; 
         FIG. 3  is an exploded view, with parts separated, of the insertion instrument of  FIG. 1 ; 
         FIG. 4  is an enlarged view of the detail area  4  of  FIG. 3 ; 
         FIG. 5  is a top view of the insertion instrument in the straight configuration; 
         FIG. 5A  is a side cross-section view of the insertion instrument of  FIG. 5  taken along section line  5 A- 5 A; 
         FIG. 6  is a top view of the insertion instrument in an articulated configuration; 
         FIG. 7  is a side view of the insertion instrument in the straight configuration; 
         FIG. 8  is a bottom cross-section view taken along section line  8 - 8  of the distal portion of the instrument of  FIG. 7 ; 
         FIG. 8A  is an articulated configuration of the distal portion shown in  FIG. 8 ; 
         FIG. 9  is a perspective view of the insertion instrument showing the handle assembly configured to rotate about the elongated body; 
         FIG. 10  shows the system being used to insert the spinal implant, which is secured to the insertion instrument by the driveshaft assembly, into an intervertebral space, the insertion instrument in the straight configuration; 
         FIG. 11  shows the system being used to insert the spinal implant, which is secured to the insertion instrument by the driveshaft assembly, into an intervertebral space, the insertion instrument in an articulated configuration; 
         FIG. 12  shows the system being used to insert the spinal implant into an intervertebral space, the spinal implant free from insertion instrument and the insertion instrument in an articulated configuration; 
         FIG. 13  is a perspective view of the spinal implant; 
         FIG. 14  is a top view of the spinal implant; 
         FIG. 15  is a side view of the spinal implant; 
         FIG. 16  is a front view of the spinal implant from the leading end; and 
         FIG. 17  is a back view of the spinal implant from the trailing end. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Particular embodiments of the present disclosure will be described herein with reference to the accompanying drawings. As shown in the drawings and as described throughout the following description, and as is traditional when referring to relative positioning on an object, the term “proximal” or “trailing” refers to the end of the apparatus that is closer to the user and the term “distal” or “leading” refers to the end of the apparatus that is farther from the user. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. 
     Referring now to the drawings, in which like reference numerals identify identical or substantially similar parts throughout the several views,  FIGS. 1 and 2  illustrate an embodiment of system  10  for inserting a spinal implant into an intervertebral space with an insertion instrument. 
     The embodiment of insertion instrument  20  shown in  FIG. 3  includes elongated body  30 , tip assembly  40 , handle assembly  50 , articulation assembly  60 , and driveshaft assembly  70 . Elongated body  30  defines longitudinal axis A-A ( FIG. 1 ). Elongated body  30  includes inner shaft  310  and outer shaft  320 . Inner shaft  310  has open distal and proximal ends  311 ,  312  which define first passage  318  therethrough. Outer shaft  320  has open distal and proximal ends  321 ,  322  which define first lumen  329  therethrough ( FIG. 5A ). Inner shaft  310  is at least partially disposed within first lumen  329 . 
     Now referring to  FIG. 4 , tip assembly  40  includes inner shaft tip  410 , outer shaft tip  420 , and holding tip  430 . Outer shaft tip  420  has open distal and proximal ends  421 ,  422  which define second lumen  429  therethrough. Outer shaft tip  420  includes distally extending arm  425 . Inner shaft tip has second passage  418  therethrough and recessed area  415 . Inner shaft tip  410  is at least partially disposed within second lumen  429 . Distally extending arm  425  is slidably received in recessed area  415 . Proximal end of the inner shaft tip  412  is positioned at distal end of the inner shaft  311 . Proximal end of the outer shaft tip  422  is positioned at distal end of the outer shaft  321 . 
     Holding tip  430  has third passage  438  therethrough ( FIG. 5A ). Referring back to  FIG. 4 , proximal end of the holding tip  432  is coupled to distal end of the inner shaft tip  411  by articulating connection  436 . Distal end of the distally extending arm  429  is coupled to the proximal end of the holding tip to offset hole  439  at the distal end of the holding tip  431 . Holding tip  430  may include distally extending finger  435  offset from the center of holding tip  430 . 
     Referring now to  FIGS. 3 and 9 , handle assembly  50  includes handle  510  and body portion  520 . Body portion  520  is coaxially aligned with elongated body  30 . Body portion  520  is coupled to the proximal end of the outer shaft  322 . Handle  510  is substantially orthogonal to longitudinal axis A-A. Handle  510  may be rotatable a full 360° about longitudinal axis A-A. 
     In a particular embodiment, handle assembly  50  includes locking mechanism  530  to lock handle assembly  50  in a radial position in relation to longitudinal axis A-A. Locking mechanism  530  may be collar  531  located on handle  510 . Locking mechanism  530  may be selectively engagable. Handle  510  may have predefined radial positions and a means for engaging the locking mechanism  530  at each of the predefined radial positions. 
     Referring back to  FIGS. 2 and 3 , articulation assembly  60  includes articulation knob  610 . Articulation knob  610  is coupled to inner shaft  310 . Rotational movement of articulation knob  610  about longitudinal axis A-A induces longitudinal translation of outer shaft  320  in relation to inner shaft  310 . Outer shaft tip  420  and inner shaft tip  410  cooperate with the translation of outer shaft  320  and inner shaft  310 , respectively, as shown in  FIGS. 8 and 8A . The translation of outer shaft tip  320  with respect to inner shaft tip  310  results in the articulation of holding tip  430  with respect to elongated body  30 . The articulation of holding tip  430  defines angle of articulation θ as shown in  FIGS. 6 and 8A . 
     In an embodiment of insertion instrument  20 , angle of articulation θ has a minimum angle of articulation and a maximum angle of articulation. The minimum angle of articulation is about 0°, defining a substantially straight configuration as shown in  FIG. 5 . The maximum angle of articulation is about 60°. Any angle of articulation other than 0° defines an articulated configuration as is illustrated in  FIG. 6 . 
     In another embodiment of insertion instrument  20 , when articulation knob  610  is rotated in a first direction, holding tip  430  transitions from a minimum angle of articulation to a maximum angle of articulation. Once the maximum angle of articulation is reached, articulation knob  610  cannot rotate any further in the first direction. 
     In an embodiment of articulation assembly  60 , articulation knob  610  has marked angles of articulation  620 . The outer surface of articulation knob  610  has indicia for each of the marked angles of articulation  620  of the holding tip. 
     Now referring to  FIG. 5A , first, second, and third passages  318 ,  418 ,  438  are capable of axial alignment. When three passages  318 ,  418 ,  438  are in axial alignment, bore  28  through insertion instrument  20  is defined. 
     Referring to  FIG. 3 , driveshaft assembly  70  includes coupling knob  710  on proximal end of the driveshaft assembly and a shaft extending distally from coupling knob  710 . The distally extending shaft is configured to extend through bore  28 . Distal end of the driveshaft assembly  701  extends or protrudes from distal end of the holding tip  431  as shown in  FIGS. 8 and 8A . Driveshaft assembly  70  may be flexible to cooperate with the articulation of holding tip  430  with respect to elongated body  30 . Driveshaft assembly  70  cooperates with the rotation of coupling knob  710 . 
     In an embodiment shown in  FIGS. 3 and 4 , driveshaft assembly  70  further includes universal joint  750  and coupling shaft  730 . Universal joint  750  includes threaded distal end  760 , articulating member  780 , and proximal end  770 . Threaded distal end  760  is at least partially disposed within third passage  438  with the threaded distal tip  701  extending or protruding from distal end of the holding tip  430  as shown in  FIG. 8 . Articulating member  780  is disposed within at least second and third passages  418 ,  438  cooperating with angle of articulation θ as shown in  FIG. 8A . Proximal end of the universal joint  770  is at least partially disposed within second passage  418  and is configured to couple with coupling shaft  730 . Coupling shaft  730  extends distally from coupling knob  710 . Coupling shaft  730  configured to traverse at least first passage  318  and couple to the proximal end of the proximal end of the universal joint  772 . 
     In another embodiment shown in  FIGS. 3 and 4 , coupling shaft  730  includes hexagonal distal end  731 . Proximal end of the universal joint  770  includes hexagonal opening  776 . The hexagonal distal end of the coupling shaft  731  is configured to cooperate with the hexagonal opening  776 . Further, coupling shaft  730  is made of a rigid material. The cooperation of coupling shaft  730  and universal joint  750  allows coupling shaft  730  to be selectively removable from first passage  318 . Coupling shaft  730  cooperates with the rotation of coupling knob  710 . In this embodiment, when coupling shaft  730  traverses first passage  318  hexagonal distal end of the coupling shaft  731  contacts the proximal end universal joint  770 , rotation of coupling knob  710  causes coupling shaft  730  to couple to universal joint  750 . Continued rotation of coupling knob  710  induces rotation of universal joint  750 , causing threaded distal end of the universal joint  760  to rotate. Coupling knob  710  may include a torque limiter such that at a preset torque continued rotation of coupling knob  710  no longer induces rotation of coupling shaft  730 . Universal joint  750  is configured to rotate at any angle of articulation θ. 
       FIGS. 13-17  show an embodiment of spinal implant  80 . Spinal implant  80  includes body  800  with substantially contoured first end surface  810  at leading end  801  and second end surface  820  opposite thereto at trailing end  802 . Body  800  extends between first and second end surfaces  810 ,  820  to define top and bottom engaging surfaces  803 ,  804 . Top and bottom engaging surfaces  803 ,  804  are opposite one another. Body further defines sidewalls  805 . Sidewalls  805  are substantially parallel to one another and have a common radius of curvature. 
     Body  800  is configured such that top and bottom engaging surfaces  803 ,  804  intersect with sidewalls  805  forming a substantially trapezoidal cross-section with rounded corners as shown in  FIGS. 16 and 17 . Top and bottom engaging surfaces  803 ,  804  converge towards the radii of curvature. Body  800  is configured such that top and bottom engaging surfaces  803 ,  804  have a substantially streamlined convex profile. Further, body  800  is configured such that at least one of the top and bottom engaging surfaces  803 ,  804  has at least first and second surface regions  806 ,  807  having distinct surface characteristics as shown in  FIG. 15 . 
     Still referring to  FIG. 15 , top and bottom engaging surfaces  803 ,  804  and sidewalls  805  converge at leading end  801  to define blunt nose  810 , shown in  FIG. 16 . Blunt nose  810  has a tip with substantially planar surfaces  860  on top and bottom engaging surfaces  803 ,  804  and a rounded shape defined by sidewalls  805 . Substantially planar surfaces  860  define first surface region  806  while second surface region  807  is proximal to first surface region  806  on each of top and bottom engaging surfaces  803 ,  804 . 
     In an embodiment, the surface characteristic of first surface region  806  includes a plurality of protrusions having a first configuration. The surface characteristic of second surface region  807  includes a plurality of protrusions having a second configuration distinct from that of first surface region  806 . 
     Referring now to  FIG. 14 , the configuration of the plurality of protrusions of first surface region  806  may define first set of ridges  861 . Each ridge of first set of ridges  861  has a position along at least one of top and bottom engaging surfaces  803 ,  804 . Each ridge of first set of ridges  861  includes first ridge face  862  substantially orthogonal to at least one of top and bottom engaging surfaces  803 ,  804  and substantially parallel to sidewalls  805 . Each ridge of first set of ridges  861  includes second opposing ridge face  863  defining channel  864  between first ridge face  862  and second opposing ridge face  863 . Channel  864  may be flat or grooved. 
     Referring now to  FIG. 15 , the plurality of protrusions of second surface region  807  defines a set of saw tooth protrusions  871 . Each of saw tooth protrusions  871  has a position along at least one of top and bottom engaging surfaces  803 ,  804 . Each of saw tooth protrusions  871  has first tooth face  872  substantially orthogonal to top and bottom engaging surfaces  803 ,  804  and substantially parallel to trailing surface  820 . Each of saw tooth protrusions  871  defines second opposing tooth face  873 . First tooth face  872  and second tooth face  873  define bone engagement region  874  between the tooth faces  872 ,  873 . 
     Now referring back to  FIG. 14 , in a particular embodiment, spinal implant  80  includes body  800  with at least one opening  880  extending through body  800 . Opening  880  may extend through top and bottom engaging surfaces  803 ,  804 . Further, inner sidewalls  885  of opening  880  may share the radii of curvature with sidewalls  805 . 
     In a preferred embodiment shown in  FIG. 17 , spinal implant  80  has threaded opening  825  in trailing surface  820 . Further, spinal implant  80  grooved depression  850  on at least one of sidewalls  805  near trailing end  802 . 
     In an embodiment of system  10  for inserting a spinal implant in an intervertebral space with an insertion instrument, system  10  includes spinal implant  80  and insertion instrument  20  configured to cooperate as discussed in detail below and shown in  FIGS. 10-12 . 
     System  10  includes spinal implant  80  having threaded opening  825  configured to receive distal end of the driveshaft assembly  701 . Threaded opening  825  and distal end of the driveshaft assembly  701  each threaded in a manner such that the threads cooperate to threadably couple driveshaft assembly  70  to spinal implant  80 . When spinal implant  80  is secured to distal end of the holding tip  431  by driveshaft assembly  70  a coupling torque is defined. The coupling torque may be used to limit continued rotation of driveshaft assembly  70  when spinal implant  80  is secured to distal end of the holding tip  431 . 
     In an embodiment, insertion instrument  20  includes distally extending finger  435  configured to engage grooved depression  850  in at least one sidewalls  805 . Thus securing spinal implant  80  in position with respect to holding tip  430 . 
     System  10  may include insertion instrument  20  where holding tip  430  is configured to articulate with respect to elongated body  30  defining an angle of articulation θ. Further, insertion instrument  20  may be configured to selectively receive or release spinal implant  80  without regard to angle of articulation θ. 
     While several embodiments of the disclosure have been shown in the drawings and/or discussed herein, 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. Different embodiments of the disclosure may be combined with one another based on the particular needs of the patients to achieve optimal results of the surgical procedures. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.