Methods and instrumentation for vertebral interbody fusion

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of U.S. patent application Ser. No. 09/498,426, filed on Feb. 4, 2000, which claims the benefit of the filing date of Provisional Application Serial No. 60/118,793, filed Feb. 4, 1999, each of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to surgical procedures for spinal stabilization and more specifically to instrumentation adapted for inserting a spinal implant within the intervertebral disc space between adjacent vertebra. More particularly, while aspects of the invention may have other applications, the present invention is especially suited for disc space preparation and implant insertion into a disc space from an anterior surgical approach to the spine.

[0003] Various surgical methods have been devised for the implantation of fusion devices into the disc space. Both anterior and posterior surgical approaches have been used for interbody fusions. In 1956, Ralph Cloward developed a method and instrumentation for anterior spinal interbody fusion of the cervical spine. Cloward surgically removed the disc material and placed a tubular drill guide with a large foot plate and prongs over an alignment rod and then embedded the prongs into adjacent vertebrae. The drill guide served to maintain the alignment of the vertebrae and facilitated the reaming out of bone material adjacent the disc space. The reaming process created a bore to accommodate a bone dowel implant. The drill guide was thereafter removed following the reaming process to allow for the passage of the bone dowel which had an outer diameter significantly larger than the reamed bore and the inner diameter of the drill guide. The removal of the drill guide left the dowel insertion phase completely unprotected.

[0004] More recent techniques have advanced this concept and have provided further protection for sensitive tissue during disc space preparation and dowel insertion. Such techniques have been applied to an anterior approach to the lumbar spine.

[0005] An initial opening or openings are made in the disc space and the height of the disc space is distracted to approximate normal height. Typically, a first distractor is inserted with a height estimated by radiological examination. If additional distraction is required, the first distractor is removed and a second, larger distractor is inserted. However, since the positioning of the distractors is performed without the benefit of protective guide sleeves, the switching of distractors increases the potential for damage to neurovascular structures and may correspondingly increase the time of the procedure.

[0006] For bilateral procedures, a double barrel sleeve may be inserted over the distractors, with a central extension extending into the disc space to maintain distraction. One limitation on guide sleeve placement is the amount of neurovascular retraction that must be achieved to place the guide sleeves against the disc space. For some patients, a double barrel sleeve may not be used because there is insufficient space adjacent the disc space to accept the sleeve assembly. Thus, there remains a need for guide sleeves requiring less neurovascular retraction for proper placement and providing greater protection to adjacent tissue.

[0007] While the above-described techniques are advances, improvement is still needed to reduce the procedure time by utilization of improved instruments and techniques, to reduce the potential for damage to sensitive tissue adjacent the disc space, and to limit the amount of vessel retraction necessary to utilize the protective instrumentation. The present invention is directed to this need and provides more effective methods and instrumentation for achieving the same.

SUMMARY OF THE INVENTION

[0008] The present invention relates to methods and instrumentation for vertebral interbody fusion. In one aspect of the invention, the instruments define a reduced width configuration that allows bilateral insertion of implants into the disc space.

[0009] In one aspect of the invention, a distractor is provided that includes a distractor shaft with a length. A distractor tip extends from on end of the shaft. The distractor tip has opposite first and second surfaces that define a distraction height between the surfaces. The distractor tip has a recessed area, preferably a concave surface, that extends between the first and second surfaces. Optionally, the distractor shaft may include a recessed area along its length that is an extension of the recessed area of the distractor tip. The recessed area of the distractor and/or shaft may permit the passage of and rotation of surgical devices adjacent thereto.

[0010] In another aspect of the present invention, a guide sleeve has a wall that defines a protected passageway to a distracted disc space. The guide sleeve includes a proximal end and a distal end. A pair of overlapping working channels extends between the ends. The sleeve has a first width at the proximal end and a second width at the distal end. The first width is greater than the second width. The reduced second width is provided by reducing the exterior wall thickness of the sleeve at the distal end. Preferably, a first flange and a second flange extend from the distal end at the reduced wall thickness portions. Preferably, the flanges have a thickness that corresponds to the reduced wall thickness. Still more preferably, the first and second lateral extensions have a height less than the height of the distracted disc space, and inhibit encroachment of adjacent tissue into the distracted disc space. In another form, the guide sleeve may include spikes projecting from the sleeve distal end between the flanges to engage the adjacent vertebral bodies. In a further form, the overlapping working channels are substantially cylindrical.

[0011] In another aspect, there is provided a guide sleeve assembly. The assembly includes a sleeve defining a working channel. A first distractor has a first distractor tip with a recessed area along a portion of its length, and a second distractor has a second distractor tip. With the first distractor disposed in the working channel of the sleeve in side-by-side relation with the second distractor, the recessed surface of the first distractor tip receives at least a portion of the second distractor tip. In one form, the recessed area of the first distractor tip is defined by a concave surface and the second distractor tip has opposite convex surfaces, one of which is positioned adjacent the concave surface of the first distractor tip. In another form, the first and second distractors define an overlap region in the guide sleeve working channel.

[0012] In a method according to the present invention, access is gained to a disc space. A first distractor having first distractor tip with a recessed area and a second concave distractor having a second distractor tip are disposed in side-by-side relation with the distractor tips inserted adjacent the disc space. Preferably, the distractors are also engaged within the working channel of an outer sleeve. The distractors distract and maintain the disc space at the desired height during the procedure. Once the desired distraction of the disc space has been achieved, the outer sleeve is advanced toward the disc space until disposed adjacent the disc space. If necessary, a driving cap may be positioned over the proximal end of the outer sleeve to apply a driving force thereto.

[0013] The outer sleeve is then driven into position so that opposing side flanges are positioned in the disc space and spikes on the outer sleeve enter the vertebral bodies. Preferably, the side flanges do not perform any distraction of the disc space. Once the outer sleeve is positioned, the second distractor may be removed and a substantially cylindrical working space is provided through the sleeve to the disc space adjacent the first distractor. Preferably, the working space defines an area that is greater than one half of the area of the working channel of the guide sleeve.

[0014] Various surgical procedures are performed through the working space, such as reaming, tapping and inserting a threaded implant into the disc space. Once the first implant is inserted, the second distractor is removed, and the first implant maintains the disc space distraction and defines a working space adjacent the inserted implant. Preferably, the first implant has a concave side wall to define a portion of a substantially cylindrical working space. The surgical procedures are then repeated to insert a second implant adjacent the first implant. In one embodiment, the second implant has a circular cross-section. In another embodiment, the implant has a cross-section that mirrors that of the first implant after insertion.

[0015] Although various sleeves are known in the art, in a preferred embodiment, outer sleeves according to the present invention have a reduced width portion adjacent the bone engaging distal end to limit the amount of retraction of the surrounding vasculature and neural tissue required for the procedure. The reduced width portion, preferably in combination with the previously described overlapping working channels, combine to greatly reduce the overall width of the sleeve. In a preferred form, a sleeve assembly includes a pair of opposite side flanges or lateral extensions having a first height. The lateral extensions provide protection from encroachment of tissue into the working area of the disc space. Preferably, the side flanges of the outer sleeve are not used to maintain distraction of the disc space and thus do not experience the forces of disc space distraction. As a result, the flanges and adjacent side walls may be formed with a reduced wall thickness.

[0016] A further aspect includes the provision of a visualization window along the centerline of the outer sleeve for visual access to the interior working channel while instruments are in the working channel. Even without the use of an imaging system, the present invention contemplates the use of manually adjustable depth stop that is to control the steps of trephining, reaming, tapping, and implant insertion. The term implant is used in a broad sense throughout the disclosure and is intended to encompass bone dowels, metallic cages and spacers, and other implants used for interbody fusion regardless of shape or material of construction.

[0017] Related objects, advantages, aspects, forms, and features of the present invention will be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1<i>a </i>is a perspective view of a distractor according to the present invention.

[0019]FIG. 1<i>b </i>is an enlarged front view of the tip of the distractor of FIG. 1<i>a. </i>

[0020]FIG. 1<i>c </i>is an enlarged side view of the tip of the distractor of FIG. 1<i>a. </i>

[0021]FIG. 2<i>a </i>is a perspective view of a distractor according to another aspect of the present invention.

[0022]FIG. 2<i>b </i>is an enlarged front view of the tip of the distractor of FIG. 2<i>a. </i>

[0023]FIG. 2<i>c </i>is an enlarged side view of the tip of the distractor of FIG. 2<i>a. </i>

[0024]FIG. 2<i>d </i>is an elevation view of a distractor clip.

[0025]FIG. 3 is a perspective view of a guide sleeve according to another aspect of the present invention.

[0026]FIG. 4 is a front view of the guide sleeve of FIG. 3.

[0027]FIG. 5 is a side view of the guide sleeve of FIG. 3.

[0028]FIG. 6 is a perspective view of a guide sleeve assembly according to another aspect of the present invention.

[0029]FIG. 7 is an enlarged end view of the distal end of the guide sleeve assembly of FIG. 6.

[0030]FIG. 8 is an enlarged end view of the proximal end of the guide sleeve assembly of FIG. 6.

[0031]FIG. 9 is an anterior to posterior view of a guide sleeve assembly according to FIG. 3, the guide sleeve assembly is positioned in relation to a pair of adjacent vertebral bodies and blood vessels.

[0032]FIG. 10 is a partial cross-sectional view of the disc space through line <b>10</b>-<b>10</b> of FIG. 9.

[0033]FIG. 11 is a perspective view of the guide sleeve assembly during insertion of the distractors into the disc space.

[0034]FIGS. 11<i>a </i>and <b>11</b><i>b </i>are front and rear elevation views, respectively, of a distractor driver cap for driving the distractors into the disc space.

[0035]FIGS. 12<i>a</i>-<b>12</b><i>b </i>are perspective views of the guide sleeve assembly <b>150</b> with an impactor cap disposed thereon prior to seating the guide sleeve.

[0036] FIGS. <b>13</b> is a perspective view of the guide sleeve assembly with an impactor cap disposed thereon.

[0037]FIG. 14 is a perspective view of the guide sleeve assembly with a slap hammer disposed on one of the distractors.

[0038]FIGS. 15<i>a</i>-<b>15</b><i>b </i>are a perspective view and an end view, respectively, of the guide sleeve assembly with a distractor removed.

[0039]FIGS. 16<i>a</i>-<b>16</b><i>b </i>are a perspective view and an end view, respectively, of the guide sleeve assembly with a reamer disposed adjacent a distractor.

[0040]FIGS. 17<i>a</i>-<b>17</b><i>c </i>are a perspective view, detail view and end view, respectively, of the guide sleeve assembly with a tap disposed adjacent a distractor.

[0041]FIGS. 18<i>a</i>-<b>18</b><i>c </i>are a perspective view, detail view and end view, respectively, of the guide sleeve assembly with an implant disposed adjacent a distractor.

[0042]FIGS. 19<i>a</i>-<b>19</b><i>c </i>are perspective views and an end view, respectively, of the guide sleeve assembly showing withdrawal of the other distractor.

[0043]FIGS. 20<i>a</i>-<b>20</b><i>b </i>are a perspective view and an end view, respectively, of the guide sleeve assembly with a reamer disposed adjacent an implant.

[0044]FIGS. 21<i>a</i>-<b>21</b><i>c </i>are a perspective view, detail view and end view, respectively, of the guide sleeve assembly with a tap disposed adjacent an implant.

[0045]FIGS. 22<i>a</i>-<b>22</b><i>c </i>are a perspective view, detail view and end view, respectively, of the guide sleeve assembly with an implant disposed adjacent an implant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

[0047] The present invention relates to methods and instrumentation for performing vertebral interbody fusion. Specifically, although aspects of the present invention may have other uses either alone or in combination, the instruments and methods disclosed herein are particularly useful for anterior lumbar interbody fusion. However, the surgical instruments and methods according to the present invention are not limited to such an approach, and may find application in, but without limitation, lateral and anterior-lateral approaches to the spine as well. Also, the surgical instruments and methods of the present invention may find application at all vertebral segments of the spine, and in areas other than spinal surgery.

[0048] Referring now to FIGS. 1<i>a</i>-<i>c, </i>there is shown a convex or first disc space distractor <b>50</b> according to one aspect of the present invention. Distractor <b>50</b> includes a proximal end <b>53</b> configured for engagement with conventional tools and handles (not shown) used in operative procedures on the spine. A shaft <b>54</b> is joined with a distractor tip <b>56</b>. In the illustrated embodiment, shaft <b>54</b> has a hollow interior and a clip hole <b>55</b> communicating with the hollow interior; however, the present invention also contemplates a solid shaft <b>54</b>. Also, while an integral shaft and head are shown, head <b>56</b> may be removably attached to shaft <b>54</b>. One such removable attachment is more fully disclosed in U.S. patent application entitled METHOD AND INSTRUMENTATION FOR VERTEBRAL INTERBODY FUSION, Ser. No. 09/287,917, filed Apr. 7, 1999, which is incorporated herein by reference in its entirety (hereinafter referred to as the '917 patent application.) Distractor tip <b>56</b> is designed such that it can be inserted in a disc space to establish a first working distraction height <b>72</b> (see FIG. 1<i>b</i>). More specifically, distractor tip <b>56</b> has a rounded leading edge <b>62</b> that extends to opposing inclined surfaces <b>58</b> and <b>59</b>, which in turn extend more proximally and blend into substantially planar opposing surfaces <b>60</b> and <b>61</b>, respectively. Extending between planar surfaces <b>60</b> and <b>61</b> and proximal the rounded tip <b>62</b> are opposite convex surfaces <b>64</b> and <b>66</b>.

[0049] Planar surfaces <b>60</b> and <b>61</b> extend in a substantially parallel alignment along a longitudinal axis A of distractor <b>50</b> and define height <b>72</b> therebetween. It should be understood that the inclined surfaces <b>58</b> and <b>59</b> cooperate to aid insertion of the distractor tip <b>56</b> into the disc space and to initially distract the disc space to at least a height <b>72</b>. If first distraction height <b>72</b> is sufficient, further procedures as known in the art may then be carried out to accomplish implant insertion. While a specific distractor has been described in detail, it is contemplated that other known distractor configurations may be substituted for the same without deviating from the scope of this invention.

[0050] Referring now to FIGS. 2<i>a</i>-<i>c, </i>there is shown a second disc space distractor <b>80</b> according to one aspect of the present invention. Distractor <b>80</b> includes a proximal end <b>83</b> configured for engagement with conventional tools and handles (not shown). A shaft <b>84</b> is joined with a distractor tip <b>86</b>. In the illustrated embodiment, shaft <b>84</b> has a hollow interior and a hole <b>85</b> communicating therewith. While an integral shaft and head are shown, head <b>86</b> may be removably attached to shaft <b>84</b>, as similarly described with respect to the removable attachments disclosed in the '917 patent application. Similar to distractor tip <b>56</b> of distractor <b>50</b>, distractor tip <b>86</b> is designed such that it can be inserted in a disc space to establish a first working distraction height <b>72</b>′ (see FIG. 2<i>b</i>) that is preferably the substantially the same as working height <b>72</b>. More specifically, distractor tip <b>86</b> has a rounded leading edge <b>92</b> that extends to opposing inclined surfaces <b>88</b> and <b>89</b> which, in turn, extend more proximally and blend into substantially planar opposing surfaces <b>90</b> and <b>91</b>, respectively.

[0051] Planar surfaces <b>90</b> and <b>91</b> extend substantially parallel to longitudinal axis B of distractor <b>80</b> to define height <b>72</b>′ therebetween. Extending between planar surfaces <b>90</b> and <b>91</b> are convex surface <b>94</b> and a recessed area defined by opposite concave surface <b>96</b>. Along the distractor shaft <b>84</b>, there is defined a concave surface <b>98</b> that is adjacent to and coplanar with concave surface <b>96</b> of distal tip <b>86</b> to define a concave surface extending along the length of distractor <b>80</b>. In the illustrated embodiment, surface <b>98</b> has a slot <b>87</b> formed therein communicating with the hollow interior of shaft <b>84</b>; however, it the present invention also contemplates a solid shaft <b>84</b> and a shaft <b>84</b> without slot <b>87</b>. As explained more fully below, concave surfaces <b>96</b>, <b>98</b> are configured to receive convex surface <b>64</b> or <b>66</b> of distractor <b>50</b> to reside therein when distractors <b>50</b> and <b>80</b> are disposed in side-by-side relation. Concave surfaces <b>96</b>, <b>98</b> also partially define a working space that allows operative procedures to be performed therethrough.

[0052] It should be understood that the inclined surfaces <b>88</b> and <b>89</b> cooperate to aid insertion of distractor tip <b>86</b> into the disc space, and to distract the disc space and maintain disc space distraction to at least a height <b>72</b>, <b>72</b>′. To further aid in distractor insertion, in FIG. 2<i>d </i>there is shown a distractor clip <b>75</b> having a cross member <b>76</b> with first clip member <b>77</b> and second clip member <b>78</b> extending therefrom. Clip members <b>77</b> and <b>78</b> are each received in a corresponding one of holes <b>55</b> and <b>85</b> to couple distractor <b>50</b> to distractor <b>80</b>. Clip <b>75</b> prevents splaying and maintains the relative positioning of distractors <b>50</b>, <b>80</b> during insertion into the disc space. If first distraction height <b>72</b> is sufficient, further procedures as known in the art may then be carried out to accomplish implant insertion. It should be further understood that second distractor <b>80</b> has a second width <b>74</b> that is less than a first width <b>70</b> of first distractor <b>50</b>.

[0053] Specifically, but without limitation, the distractor heads <b>56</b>, <b>86</b> may be formed with heights <b>72</b> ranging from 6 mm to 24 mm. Preferably, height <b>72</b> of the next sized distractor increases or decreases in 2 mm increments. Other variations and may be provided as long as the working distractor height provided approximates the disc height in a normal spine and accommodates insertion of an implant into the disc space as more fully described below.

[0054] Referring now to FIG. 3, there is shown a guide sleeve <b>100</b> that is useful with the distractors <b>50</b> and <b>80</b> described above. Guide sleeve <b>100</b> has a wall <b>110</b> defining a working channel <b>130</b> having a figure eight shaped cross-section (FIG. 9) extending in a substantially unobstructed manner from a proximal end <b>102</b> to a distal end <b>104</b>. Sleeve <b>100</b> includes upper windows <b>106</b> and <b>108</b> formed in wall <b>110</b> on at least one side of sleeve <b>100</b> for engagement by a removal tool to remove sleeve <b>100</b>. The sleeve <b>100</b> also includes lower elongated visualization window <b>112</b> centered about the longitudinal axis L with an elongated slot <b>111</b> extending proximally window <b>112</b>. Window <b>112</b> provides the surgeon with the ability to visualize the instruments inserted in guide sleeve <b>100</b> as well as the openings in the disc space and vertebral bodies, without entirely removing instrumentation from guide sleeve <b>100</b>. The reduce width of sleeve <b>100</b> allows the use of one window <b>112</b> for visualization of implant insertion into its respective bilateral location in the disc space, and separate windows along each insertion path are not necessary. However, it should be understood that any number of visualization windows and configurations thereof are contemplated herein, such as those described in the '917 patent application. The present invention also contemplates that covers may be used for visualization windows, as described in greater detail in the '917 patent application.

[0055] At proximal end <b>102</b> is provided a flange ring <b>155</b>. Flange ring <b>155</b> strengthens sleeve <b>100</b> and provides a load transfer member to facilitate transfer of a driving force to sleeve <b>100</b>, as described more fully below. Adjacent distal end <b>104</b>, the material thickness along the exterior outer edge of wall <b>110</b> is reduced in order to provide a reduced thickness wall portion <b>114</b> and an opposite reduced thickness wall portion (not shown). The reduced thickness wall portions define a smaller cross-sectional area for the sleeve <b>100</b> as well as a reduced width extending transverse to the longitudinal axis L. The reduced cross-sectional area and smaller width of guide sleeve <b>100</b> reduces the amount of vasculature and neural tissue retraction adjacent the disc space that would otherwise be required to place a similarly sized guide sleeve without the width reduction.

[0056] Distal end <b>104</b> includes a pair of flanges <b>118</b> and <b>120</b> extending from wall <b>110</b> on opposite sides of working channel <b>130</b>. Flanges <b>118</b> and <b>120</b> are configured to extend partially into the disc space. Flanges <b>118</b>, <b>120</b> are each formed by and are an extension of the corresponding reduced thickness wall portions <b>114</b> described above. In a preferred embodiment, flanges <b>118</b> and <b>120</b> do not provide distraction of the disc space but are primarily provided to protect surrounding vessels and neurological structures from damage during the procedures. Since the lateral flanges do not provide structural support for distraction, the material thickness of the flanges and adjacent side walls may be reduced. Additionally, distal end <b>104</b> includes spikes <b>122</b>, <b>124</b>, positioned between flanges <b>118</b>, <b>120</b> and a third spike <b>126</b> and a fourth spike <b>128</b> positioned opposite spikes <b>122</b>, <b>124</b> between flanges <b>118</b>, <b>120</b> as shown in FIG. 7. These spikes may be urged into the bone of the adjacent vertebral bodies to hold guide sleeve <b>100</b> in a fixed position relative to the vertebral bodies.

[0057] Referring to FIGS. 4 and 5, guide sleeve <b>100</b> is shown in front and side views, respectively, to further illustrate an additional aspect of the invention. A proximal end <b>102</b> the guide sleeve <b>100</b> has a maximum width W1. At distal end <b>104</b> of sleeve <b>100</b>, wall <b>110</b> has a reduced wall thickness at side walls <b>114</b> and <b>113</b> defining a width W2 that is less than width W1. The side walls <b>113</b>, <b>114</b> are preferably not entirely flat and have a slight curvature. Side walls <b>113</b>, <b>114</b> provide a reduction in wall thickness of wall <b>110</b> and taper to the full wall thickness of wall <b>110</b> at the termination of side walls <b>113</b> and <b>114</b>. The reduction in width of wall <b>110</b> decreases the amount of vasculature and neural tissue retraction in the area adjacent the disc space. The desirable reduction in width is accomplished with little reduction in the required strength of the device since distractors <b>50</b>, <b>80</b> are used to distract and maintain the distraction of the vertebral bodies instead of the extensions or side flanges <b>118</b>, <b>120</b> of guide sleeve <b>100</b>.

[0058] There are also shown in FIGS. 4 and 9 a first working channel portion <b>107</b>, defined about axis L1, and a second working channel portion <b>109</b>, defined about axis L2. These working channel portions <b>107</b>, <b>109</b> are positioned on either side of longitudinal axis L of sleeve <b>100</b>. There is no wall or other structure separating working channel portions <b>107</b> and <b>109</b>. Working channel portion <b>107</b> is that portion of working channel <b>130</b> about axis L1 between longitudinal axis L and inside surface of <b>116</b> of guide sleeve <b>100</b>. Similarly, working channel portion <b>109</b> is that portion of working channel <b>130</b> about axis L2 between longitudinal axis L and inside surface <b>116</b>. Thus, working channel portions <b>107</b> and <b>109</b> are substantially equal in area, and each has a truncated circular shape, with the truncated portions of each working channel <b>107</b> and <b>109</b> positioned adjacent one another.

[0059] Referring now to FIG. 6, there is illustrated a distractor/guide sleeve assembly <b>150</b> that includes distractors <b>50</b> and <b>80</b> disposed within working channel <b>130</b> of guide sleeve <b>100</b> in side-by-side relation. Distractors <b>50</b>, <b>80</b> reside within sleeve <b>100</b> with each distractor substantially occupying all or a portion of a corresponding one of working channel portions <b>107</b> and <b>109</b> of working channel <b>130</b>. Each distractor <b>50</b>, <b>80</b> extends from proximal end <b>102</b> to distal end <b>104</b> of the guide sleeve <b>100</b>. Flange ring <b>155</b> is in the form of a flange extending about the proximal end <b>102</b> of guide sleeve <b>100</b> and contacts a driving cap positioned on distractors <b>50</b>, <b>80</b> in order to maintain the relative positioning between sleeve <b>100</b> and distractors <b>50</b>, <b>80</b> during insertion of assembly <b>150</b>.

[0060] Referring now to FIG. 7, there is illustrated an end view at distal end <b>104</b> of the assembly <b>150</b> showing distractors <b>50</b> and <b>80</b> in side-by-side relation. More particularly, shaft <b>54</b> of distractor <b>50</b> is received within concave portion <b>98</b> of distractor shaft <b>84</b>. As also illustrated in this view, concave portion <b>96</b> of distractor tip <b>86</b> is coextensive with concave surface <b>98</b> to form a concave surface that extends the length of the distractor <b>80</b>. The concave surface of distractor <b>80</b> has a radius of curvature R that is preferably about one half the diameter of the cage or implant to be inserted into the disc space. For example, an 18 mm diameter implant requires use of a distractor <b>80</b> having a radius of curvature R of about 9 mm.

[0061] When distractor <b>50</b> is removed from guide sleeve <b>100</b>, there is defined a cylindrical working space through the working channel <b>130</b> adjacent and along the recessed areas of distractor <b>80</b>. The cylindrical working space includes that portion of the working channel <b>130</b> between concave surfaces <b>96</b>, <b>98</b> and inside wall <b>116</b> of the guide sleeve <b>100</b>. Thus, the working space occupies substantially all of working channel portion <b>107</b>, (FIG. 4) and a portion of working channel portion <b>109</b>. The area of the portion of the working channel portion <b>109</b> occupied by the cylindrical working space is indicated in FIG. 7 by the hatched area A, and is hereinafter referred to as the overlap region. This overlap region A allows operative procedures to be performed in the working space adjacent the distractor <b>80</b> using conventionally sized tools and implements while providing a guide sleeve <b>100</b> of reduced overall width. The amount of width reduction achieved is approximately the maximum width of overlap region A. It should be understood that shaft <b>84</b> need not have a recessed area to provide a cylindrical working space in the disc space, but rather can be provided with a reduced diameter or size that maintains access to the overlap region A in the disc space.

[0062] In FIG. 8 there is shown a top view of the guide sleeve assembly <b>150</b>, looking down on proximal ends <b>53</b>, <b>83</b> of the distractors <b>50</b>, <b>80</b> and the proximal end <b>102</b> of guide sleeve <b>100</b>. In one embodiment, there is provided adjacent proximal end <b>53</b> of distractor <b>50</b> a locking segment <b>140</b> formed with and extending from the distractor shaft <b>54</b>. Locking segment <b>140</b> has a first projection <b>142</b> and a second projection <b>144</b>. First and second projections <b>142</b>, <b>144</b> are received within corresponding notches <b>146</b>, <b>148</b> defined in concave surface <b>98</b> of shaft <b>84</b> of distractor <b>80</b> to prevent rotation of distractors <b>50</b> and <b>80</b> with respect to one another. The present invention also contemplates other mechanisms for engaging distractors <b>50</b> and <b>80</b> to prevent rotation relative to one another as would occur to those of ordinary skill in the art. For example, the above described distractor clip <b>75</b> can be used to couple the distractors <b>50</b>, <b>80</b> together. Moreover, it is contemplated that the distractors <b>50</b>, <b>80</b> may be inserted without any locking mechanism.

[0063] The present invention contemplates that access to the disc space has heretofore been provided by known surgical techniques and therefore will not be further described herein. The use of intraoperative templates for providing access to the disc space is known in the art. One example of a procedure for gaining access to the disc space is disclosed in the '917 patent application. Another reference including techniques for template positioning and disc space distraction using a starter distractor to initially distract the disc space is the surgical technique brochure entitled <i>Reduced Profile Instrumentation </i>published in 1999 by Sofamor Danek, said brochure being incorporated by reference herein in its entirety (hereinafter the Danek brochure.) The present invention also contemplates the use and application of other procedures for gaining access to the disc space in conjunction with the procedures and instruments discussed below as would occur to those skilled in the art. The templates contemplated herein define the area necessary for placement of implants and instruments having a specific configuration and size. While in a preferred embodiment, templates are provided for cylindrical implants having diameters ranging from 16 mm to 24 mm, it is contemplated that other diameters of implant and templates for use therewith may be used and other shapes, such as, but without limitation, squares and rectangles.

[0064] Access to an anterior portion of the spinal column is achieved by known methods. Blood vessels, particularly the aorta, vena cava, and branches thereof are mobilized to provide space for bilateral implant placement. The template is inserted into the body and advanced until the pins are disposed adjacent a disc space. The circumference of the template is selected to correspond to the circumference needed for bilateral placement of a pair of implants. More specifically, the area of the template closely approximates the area needed for placement of the guide sleeve disclosed herein, such as that shown in FIG. 7. It is contemplated that a guide sleeve <b>100</b> need not necessarily be used, and tissue to the surgical site is retracted by other means while the disc space is distracted by distractors <b>50</b> and <b>80</b>. The surgical procedures are then performed in the working space defined by the distractors <b>50</b>, <b>80</b> as discussed below without use of a guide sleeve.

[0065] Referring to FIG. 9, a cross section through guide sleeve <b>100</b>, with distractors <b>50</b>, <b>80</b> removed for clarity, is provided. Sleeve <b>100</b> is inserted into a disc space D between two adjacent vertebra V1 and V2. Disposed adjacent guide sleeve <b>100</b> are vessels <b>560</b> and <b>562</b> graphically representing portions of the aorta or vena cava. Referring to FIG. 10, a cross-section through line <b>10</b>-<b>10</b> of FIG. 9, sleeve <b>100</b>, flanges <b>118</b>, <b>120</b> on guide sleeve <b>100</b> extend into the disc space where the surgical procedures are being performed. Flanges <b>118</b>, <b>120</b> and sleeve <b>100</b> inhibit contact between vessels and tissue surrounding the disc space and the tools used during the surgical procedure. Spikes <b>122</b>, <b>124</b>, <b>126</b>, and <b>128</b> may be inserted into the bone of the corresponding vertebral body V1, V2.

[0066] Various tools and implements are usable with guide sleeve <b>100</b> including distractors <b>50</b>, <b>80</b> disclosed herein and more specifically within the working spaces defined by the working channel <b>130</b> of guide sleeve <b>100</b>. Several of these tools are disclosed in the Danek brochure and in the '917 patent application, while other tools are known to those skilled in the art to which the present invention relates.

[0067] In accordance with a preferred method of using the apparatus of the present invention, reference will now be made to FIGS. 11 through 22. In FIG. 11, the sleeve assembly is assembled and prepared for insertion through the skin and to the disc space. Distractor driver cap <b>250</b> of FIGS. 1<i>a </i>and <b>1</b><i>b </i>is positioned on proximal end <b>53</b>, <b>83</b> of distractors <b>50</b>, <b>80</b>. Driver cap <b>250</b> includes a body <b>252</b> having T-shaped slots <b>253</b> and <b>254</b> configured to receive flanged posts <b>53</b><i>a </i>and <b>83</b><i>a </i>of distractors <b>50</b> and <b>80</b>, respectively. Opposite slots <b>253</b>, <b>254</b> are windows <b>256</b> and <b>257</b>. Preferably, the flanged portion of posts <b>53</b><i>a </i>and <b>83</b><i>a </i>extend into a corresponding one of the windows <b>256</b> and <b>257</b> and also into a corresponding one of the upper portions <b>253</b><i>a </i>and <b>254</b><i>a </i>of slots <b>253</b> and <b>254</b> to secure driver cap <b>250</b> to distractors <b>50</b>, <b>80</b>.

[0068] In use, distractor cap <b>250</b> contacts flange ring <b>155</b> with distractors <b>50</b>, <b>80</b> in sleeve <b>100</b> such that distractor tips <b>56</b>, <b>86</b> can be driven into the disc space while flanges <b>118</b>, <b>120</b> remain positioned outside the disc space. The driving force applied to distractor cap <b>250</b> is transmitted to flange ring <b>155</b>, and drives sleeve <b>100</b> towards the disc space along with distractors <b>50</b>, <b>80</b>. Alternatively, if distractors <b>50</b>, <b>80</b> are not positioned in guide sleeve <b>100</b>, distractor cap <b>250</b> is secured to proximal ends <b>53</b>, <b>83</b> and distractor tips <b>56</b>, <b>86</b> are driven into the disc space. Distractor cap <b>250</b> is then removed and sleeve <b>100</b> placed over the inserted distractors <b>50</b>, <b>80</b> and the procedure continues as discussed below. In this alternate technique, clip <b>75</b> may be used to couple distractors <b>50</b>, <b>80</b> together during insertion. In a further variation, alternating insertion of distractors <b>50</b>, <b>80</b> is not precluded by the present invention. However, insertion of distractors <b>50</b>, <b>80</b> into the disc space simultaneously enables the surgeon maintain the positioning of distractors <b>50</b>, <b>80</b> and control the depth of insertion of distractor tips <b>56</b>, <b>86</b> with respect to one another.

[0069] In FIG. 12<i>a, </i>an impactor cap <b>160</b> is disposed about proximal end <b>102</b> of sleeve <b>100</b> over flange ring <b>155</b>. Sleeve <b>100</b> is now relatively free to move with respect to distractors <b>50</b>, <b>80</b>. A driving force is applied to impactor cap <b>160</b> to drive sleeve <b>100</b> towards the disc space and position flanges <b>118</b> and <b>120</b> therein adjacent the distractor tips <b>56</b>, <b>86</b> already positioned into the disc space as shown in FIG. 12<i>b. </i>Preferably, flanges <b>118</b> and <b>120</b> do not distract the disc space and prevent migration of tissue into the working space when distractor <b>50</b>, <b>80</b> is removed from sleeve <b>100</b>.

[0070] As shown in greater detail and enlarged FIG. 13, impactor cap <b>160</b> is positioned around and contacts the flange ring <b>155</b>. Flange ring <b>155</b> is preferably of uniform size and shape for various sized guide sleeves <b>100</b>, thus providing a modular attachment to each of the various sized guide sleeves for a single impactor cap <b>160</b>. Impactor cap <b>160</b> has a hollow interior <b>161</b> for receiving proximal ends <b>53</b>, <b>83</b>. Hollow interior <b>161</b> has a depth d sufficient to allow movement of guide sleeve <b>100</b> into the disc space while the position of distractors <b>50</b>, <b>80</b> is maintained.

[0071] In FIG. 14, a slap hammer <b>165</b> is engaged to distractor <b>50</b> in order to withdrawal distractor <b>50</b> from the disc space. In FIG. 15<i>a </i>the distractor <b>50</b> is removed from the working channel <b>130</b> of sleeve <b>110</b> using the slap hammer <b>165</b>. The distractor tip <b>86</b> of concave distractor <b>80</b> remains disposed in the disc space to maintain the disc space distraction height during subsequent operative steps. In an alternate embodiment, it is contemplated that shaft <b>84</b> of distractor <b>80</b> is removably connected to tip <b>86</b>, in which case the shaft may be withdrawn while leaving tip <b>86</b> in place. In a further embodiment, shaft <b>84</b> has a reduced size to accommodate insertion and rotation of devices into overlap region A of the disc space. With a removable or smaller diameter shaft, only tip <b>86</b> requires a recessed area.

[0072] In FIG. 15<i>b, </i>the withdrawn distractor <b>50</b> leaves a working space comprised of working channel portion <b>109</b> and an overlap portion, indicated by hatched area A. Thus, the concave surfaces <b>96</b>, <b>98</b> of distractor <b>80</b> and inside surface <b>116</b> of sleeve <b>110</b> define a substantially cylindrical working space for completion of further operative procedures as described further below. The working space defines a substantially circular cross section along guide sleeve <b>100</b> that is adapted for receiving surgical tools therethrough to prepare the disc space for insertion of an implant. The overlapping configuration of distractors <b>50</b>, <b>80</b> provides a reduced overall width for guide sleeve <b>100</b>.

[0073] In FIGS. 16<i>a</i>-<b>16</b><i>b, </i>there is shown a reamer <b>170</b> disposed through guide sleeve <b>110</b>. A cutting head <b>171</b> has threads as known in the art to ream the disc space. As shown in FIG. 16<i>b, </i>reamer <b>170</b> is positioned within the working space adjacent distractor <b>80</b>, while distractor tip <b>86</b> maintains the disc space distraction. Concave surface <b>98</b> of shaft <b>84</b> of distractor <b>80</b> and the inside surface <b>116</b> of sleeve <b>110</b> acts as a guide for insertion and/or withdrawal of reamer <b>170</b>. The depth of reaming can be controlled with a depth stop <b>172</b> and verified via fluoroscopy

[0074] In FIGS. 17<i>a</i>-<b>17</b><i>c, </i>the reamer <b>170</b> is withdrawn and replaced by a tapping tool <b>175</b> with a head <b>176</b> to prepare the space for a threaded implant. As shown in FIGS. 17<i>b </i>and <b>17</b><i>c, </i>tapping tool <b>175</b> is positioned within the working space adjacent the concave distractor <b>80</b>, while distractor tip <b>86</b> maintains the disc space distraction. The concave surface <b>98</b> of shaft <b>84</b> of distractor <b>80</b> and inside surface <b>116</b> of sleeve <b>110</b> acts as a guide for insertion of tapping tool <b>175</b>. Tapping tool <b>175</b> has a depth stop <b>178</b> to control the tapping depth in the disc space. Depth and sagittal alignment can also be verified via fluoroscopy during tapping.

[0075] In FIGS. 18<i>a</i>-<b>18</b><i>c, </i>the tapping tool <b>175</b> is withdrawn and replaced by an implant insertion device <b>190</b> with a threaded implant <b>200</b> engaged on a distal end thereof. Threaded implant <b>200</b> and insertion device <b>190</b> may be any one of the types and configuration disclosed in a first pending PCT Application No. PCT/US00/00590 filed on Jan. 11, 2000 and a second PCT Application No. PCT[US00/00604, also filed Jan. 11, 2000; each claiming priority to U.S. Provisional Application No. 60/115, 388, filed Jan. 11, 1999, each of said above referenced PCT applications being incorporated by reference herein in its entirety. Further, the implants of the present invention may be any other known implant and insertion device, so long as at least one implant has at least one recessed side wall. The implants may be formed of any biocompatible material. Concave surface <b>98</b> of shaft <b>84</b> of distractor <b>80</b> and inside surface <b>116</b> of sleeve <b>110</b> acts as a guide for insertion of the implant into the disc space.

[0076] Inserter <b>190</b> includes a thumbscrew <b>191</b> having a threaded shaft (not shown) extending through inserter <b>190</b> to couples implant <b>200</b> thereto via an internally threaded opening in a slotted end <b>201</b> (FIG. 19) of implant <b>200</b>. T-handle <b>192</b> is used to rotate implant <b>200</b> and thread it into the disc space, as shown in the enlarged view of FIG. 18<i>b. </i>As shown more clearly in the enlarged view of FIG. 18<i>c, </i>implant <b>200</b> is inserted so that a concave face <b>202</b> is disposed toward concave surface <b>96</b> of distractor <b>80</b>. This positioning of concave face <b>202</b> can be confirmed by providing alignment markings on insertion device <b>190</b> and sleeve <b>100</b>. Further, insertion device <b>190</b> includes countersink marking <b>193</b> to provide an indication of the countersink of implant <b>200</b> into the disc space. To facilitate implant rotation, inserter <b>190</b> can be provided with a movable slide at its distal end that occupies the recessed area of concave surface <b>202</b> providing a round construct for threading. While implant <b>200</b> is threaded into place, distractor tip <b>86</b> maintains the disc space distraction.

[0077] In FIGS. 19<i>a</i>-<b>19</b><i>b, </i>when implant <b>200</b> is placed in the desired position, and implant inserter <b>190</b> is removed from guide sleeve <b>100</b>, distractor tip <b>86</b> is withdrawn from the disc space. Preferably, a slap hammer <b>165</b> is engaged to distractor <b>80</b> in order to withdraw distractor tip <b>86</b> from the disc space and distractor <b>80</b> from guide sleeve <b>100</b>. As shown in FIGS. 19<i>b</i>-<b>19</b><i>c, </i>distractor <b>80</b> is removed from working channel <b>130</b> of sleeve <b>110</b>. Implant <b>200</b> remains disposed in the disc space to maintain the disc space distraction height during subsequent operative steps. The withdrawn distractor <b>80</b> leaves a working space comprised of working channel portion <b>107</b> and an overlap region A. Thus, concave surface <b>202</b> of implant <b>200</b> and inside surface <b>116</b> of sleeve <b>110</b> define a cylindrical working space in the disc space for further procedures as described below. The working space defines a circular cross section that is adapted for receiving conventionally sized surgical tools to prepare the disc space for insertion of a second implant adjacent implant <b>200</b>, while providing a reduced overall width.

[0078] In FIGS. 20<i>a</i>-<b>20</b><i>b, </i>the above described reamer <b>170</b> is disposed through guide sleeve <b>110</b>. Cutting head <b>171</b> has threads as known in the art to ream the disc space. As shown in FIG. 20<i>b, </i>reamer <b>170</b> is positioned within the working space adjacent the concave surface <b>201</b> of implant <b>200</b>, while implant <b>200</b> maintains the disc space distraction. The concave surface <b>201</b> of implant <b>200</b> and inside surface <b>116</b> of sleeve <b>110</b> acts as a guide for insertion and operation of reamer <b>170</b>.

[0079] In FIGS. 21<i>a</i>-<b>21</b><i>c, </i>reamer <b>170</b> is withdrawn and replaced by the above-described tapping tool <b>175</b> with head <b>176</b> to prepare the space for a second threaded implant. As shown in FIGS. 21<i>b </i>and <b>21</b><i>c, </i>head <b>176</b> of tapping tool <b>175</b> is positioned within the working space adjacent concave surface <b>201</b> of implant <b>200</b>, while implant <b>200</b> maintains the disc space distraction. The concave surface <b>201</b> and inside surface <b>116</b> of sleeve <b>110</b> acts as a guide for insertion of tapping tool <b>175</b>.

[0080] In FIGS. 22<i>a</i>-<b>22</b><i>c, </i>the tapping tool is withdrawn and replaced by the above described implant insertion device <b>190</b>, with a threaded implant <b>210</b> engaged on a distal end thereof. Threaded implant <b>210</b> may either have a circular cross-section, such as that shown in solid lines in enlarged FIGS. 22<i>b </i>and <b>22</b><i>c, </i>or have a cross-section identical to implant <b>200</b> with a concave surface <b>202</b> as shown in hidden lines. In either event, concave surface <b>201</b> of implant <b>200</b> acts as a guide for threading of implant <b>210</b> into the disc space.

[0081] If an implant like that of implant <b>200</b> is used, it is preferred to position implant <b>210</b> so that its concave surface <b>212</b>′ is disposed towards concave surface <b>202</b> of implant <b>200</b>, forming a cavity <b>215</b>′ therebetween as indicated in dashed lines in FIG. 22<i>c. </i>The cavity may then be packed with bone growth promoting material. T-handle <b>192</b> is used to rotate implant <b>210</b> and thread it into the disc space, as shown in FIG. 22<i>b, </i>adjacent to implant <b>200</b>. If a circular implant similar to that shown in FIG. 22<i>c </i>is used, implant <b>210</b> is nested within concave surface <b>201</b> of implant <b>200</b>. Bone growth material can be placed in cavity <b>204</b> of implant <b>200</b> and in cavity <b>213</b> of implant <b>210</b>.

[0082] While the use of threaded implants has been primarily discussed, the present invention likewise contemplates using push-in type implants and/or expandable implants in the disc space. Also, while it is preferred that the present invention be utilized for insertion of two implants at bilateral locations within the disc space, insertion of a single implant into the disc space is also contemplated herein.

[0083] Of course, the present invention makes use of depth stops and other devices for measuring and controlling the depth of the various procedures performed in the disc space. These devices and procedures are more fully explained in the Danek brochure and in the '917 patent application. Additionally, the present invention is not limited to use with the tools and instruments described above, and guide sleeve <b>100</b> and distractors <b>50</b>, <b>80</b> may be used with other such devices as would normally occur to those skilled in the art to which the invention relates.

[0084] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.