Geared cam expandable interbody implant and method of implanting same

A kit for inserting an expandable spinal implant into a patient's disc space between an upper vertebral body and a lower vertebral body, the kit comprising:

• the implant, the implant comprising:
• an upper endplate, the upper endplate including a proximal end, a distal end, an outer surface, at least one side surface, and an inner surface, a portion of the inner surface including an upper rack portion, the upper rack portion including at least one downwardly-projecting tooth intermediate the proximal end and the distal end of the upper endplate, and at least one distal-most downwardly-projecting tooth proximate the distal end of the upper endplate;
• a lower endplate, the lower endplate including a proximal end, a distal end, an outer surface, at least one side surface, and an inner surface, a portion of the inner surface including a lower rack portion, the lower rack portion including at least one upwardly-projecting tooth intermediate the proximal end and the distal end of the lower endplate, and at least one distal-most upwardly-projecting tooth proximate the distal end of the lower endplate, the proximal end of the lower endplate being pivotally connected to the proximal end of the upper endplate;
• a chassis portion mounted within the implant between the upper endplate and the lower endplate, the chassis portion having a proximal end and a distal end, the proximal end having an opening defined therein, at least one depression defined therein proximate the opening, a first set of inner threads defined in the opening, and a second set of inner threads defined intermediate the proximal end and the distal end of the chassis portion;
• a yoke movably mounted within the chassis portion, the yoke having a proximal end and a distal end, and being defined by first and second substantially parallel spaced apart walls, each of the first and second spaced apart walls having a proximal end and a distal end;
• a rotating portion rotatably mounted within the chassis portion, the rotating portion having an outer surface, a proximal end, and a distal end, the proximal end having an opening defined therein, the distal end being positioned proximate the distal end of the yoke, and threads defined on at least a portion of the outer surface, the threads being engageable with the second set of inner threads in the chassis portion;
• at least one first spur gear rotatably mounted to at least one of the distal ends of at least one of the first and second spaced apart walls of the yoke, the at least one first spur gear having at least one projecting first spur gear tooth configured to movably engage with the downwardly-depending teeth on the upper rack portion;
• at least one second spur gear rotatably mounted to at least one of the distal ends of at least one of the first and second spaced apart walls of the yoke, the at least one second spur gear having at least one projecting second spur gear tooth configured to engage with the upwardly-projecting teeth on the lower rack portion;
• and
• at least one spike pivotally attached to one of the first and second spaced apart walls of the yoke;
• wherein the rotating portion is further configured to translate rotational motion thereof to linear motion of the yoke, the yoke translating the linear motion to rotational motion of at least the at least one first spur gear, thereby rotating the at least one first spur gear with respect to the yoke;
• wherein the rotation of at least the at least one first spur gear with respect to the yoke defines a first linear walking motion of the at least one projecting first spur gear tooth along the downwardly-depending upper rack gear teeth toward the distal end of the implant, thereby pivoting the upper endplate to at least the partially-expanded position;
• and
• wherein the linear motion of the yoke translates to pivotal motion of the at least one spike, from a collapsed position to a fully-deployed position transverse to the mid-longitudinal axis;
• and
• an insertion tool attachable to the proximal end of the implant.

A method of implanting an expandable spinal implant into a patient's disc space between an upper vertebral body and a lower vertebral body, the method comprising:

• utilizing the expandable spinal implant, the implant having a proximal end and a distal end defining a mid-longitudinal axis therebetween, and being expandable between a collapsed position, a partially-expanded position, and a fully-expanded position, the implant comprising:
• an upper endplate, the upper endplate including a proximal end, a distal end, an outer surface, at least one side surface, and an inner surface, a portion of the inner surface including an upper rack portion, the upper rack portion including at least one downwardly-projecting tooth intermediate the proximal end and the distal end of the upper endplate, and at least one distal-most downwardly-projecting tooth proximate the distal end of the upper endplate;
• a lower endplate, the lower endplate including a proximal end, a distal end, an outer surface, at least one side surface, and an inner surface, a portion of the inner surface including a lower rack portion, the lower rack portion including at least one upwardly-projecting tooth intermediate the proximal end and the distal end of the lower endplate, and at least one distal-most upwardly-projecting tooth proximate the distal end of the lower endplate, the proximal end of the lower endplate being pivotally connected to the proximal end of the upper endplate;
• a chassis portion mounted within the implant between the upper endplate and the lower endplate, the chassis portion having a proximal end and a distal end, the proximal end having an opening defined therein, at least one depression defined therein proximate the opening, a first set of threads defined in the opening, and a second set of inner threads defined intermediate the proximal end and the distal end of the chassis portion;
• a yoke movably mounted within the chassis portion, the yoke having a proximal end and a distal end, and being defined by first and second substantially parallel spaced apart walls, each of the first and second spaced apart walls having a proximal end and a distal end;
• a rotating portion rotatably mounted within the yoke, the rotating portion having an outer surface, a proximal end and a distal end, the proximal end having an opening defined therein, the distal end being positioned proximate the distal end of the yoke, and threads defined on at least a portion of the outer surface, the threads being engageable with the second set of inner threads on the chassis portion;
• at least one first spur gear rotatably mounted to at least one of the distal ends of at least one of the first and second spaced apart walls of the yoke, the at least one first spur gear having at least one projecting first spur gear tooth configured to movably engage with the downwardly-projecting rack teeth on the upper rack portion;
• at least one second spur gear rotatably mounted to at least one of the distal ends of at least one of the first and second spaced apart walls of the yoke, the at least one second spur gear having at least one projecting second spur gear tooth configured to engage with the upwardly-projecting teeth on the lower rack portion;
• and
• at least one spike pivotally attached to at least one of the first and second spaced apart walls of the yoke;
• wherein the rotating portion is further configured to translate rotational motion thereof to linear motion of the yoke, the yoke translating the linear motion to rotational motion of at least the at least one first spur gear, thereby rotating the at least one first spur gear with respect to the yoke;
• wherein the rotation of the at least one first spur gear with respect to the yoke defines a first linear walking motion of the at least one projecting first spur gear tooth along the downwardly-projecting teeth of the upper rack portion toward the distal end of the implant, thereby pivoting the upper endplate to at least the partially-expanded position;
• and
• wherein the linear motion of the yoke is further translated to pivotal motion of the at least one spike from a collapsed position to a fully-deployed position transverse to the mid-longitudinal axis;
• inserting the implant, in the collapsed position, into the disc space between the upper vertebral body, and the lower vertebral body with an insertion tool;
• rotating the rotating portion, defining the rotational motion;
• translating the rotational motion of the rotating portion into the linear motion of the yoke toward the distal end of the implant;
• translating the linear motion of the yoke into rotational motion of at least the at least one first spur gear, and into pivotal motion of the at least one spike;
• rotating the at least one first spur gear with respect to the yoke;
• walking the at least one first spur gear along the downwardly-projecting teeth of the upper rack portion toward the distal end of the implant;
• translating the linear motion of the yoke into the rotational motion of at least the at least one second spur gear;
• walking the at least one second spur gear along the upwardly-projecting teeth of the lower rack portion toward the distal end of the implant;
• reaching the fully-expanded position when one of the at least one first spur gear contacts the at least one distal-most projecting tooth on the upper rack portion, and the at least one second spur gear contacts the at least one distal-most projecting tooth on the lower rack portion;
• and
• pivoting the at least one spike to the fully-deployed position transverse to the mid-longitudinal axis and into an engagement with at least one of the upper vertebral body and the lower vertebral body.