Insertion tool for use with trial intervertebral distraction spacers

#This invention relates generally to a treatment for scoliosis and more specifically to the instruments, implants, distracting trial spacers, and surgical methodology used in the treatment and correction of scoliosis.

#The bones and connective tissue of an adult human spinal column consists of more than 20 discrete bones. These more than 20 bones are anatomically categorized as being members of one of four classifications: cervical, thoracic, lumbar, or sacral. They are coupled sequentially to one another by tri-joint complexes that consist of an anterior intervertebral disc and the two posterior facet joints. The anterior intervertebral discs of adjacent bones are cushioning cartilage spacers.

#The spinal column of bones is highly complex in that it includes these 20 bones coupled to one another (and others), and it houses and protects critical elements of the nervous system having innumerable peripheral nerves and circulatory bodies in close proximity. In spite of these complications, the spine is a highly flexible structure, capable of a high degree of curvature and twist in nearly every direction.

#FIGS. 1a-c illustrates a first embodiment of an intervertebral trial spacer of the invention is illustrated in side, top and side cutaway views, respectively.

#FIG. 1d illustrates a first set of intervertebral spacers of the invention in a side view.

#FIGS. 2a-c illustrate a second embodiment of an intervertebral spacer of the invention in side, top and side cutaway views, respectively.

#While the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which particular embodiments and methods of implantation are shown, it is to be understood at the outset that persons skilled in the art may modify the invention herein described while achieving the functions and results of this invention. Accordingly, the descriptions which follow are to be understood as illustrative and exemplary of specific structures, aspects and features within the broad scope of the present invention and not as limiting of such broad scope. Like numbers refer to similar features of like elements throughout.

#First, the patient spine is exposed through an anterior approach (i.e. the surgeon creates an access hole which permits direct interaction with the anterior and/or anterio-lateral portion of the intervertebral bodies). In the case of scoliosis, as well as in other disorders in which the intervertebral space requires distraction and/or repositioning, the surgeon removes the intervertebral disc material, usually leaving some portion of the annulus (the cylindrical weave of fibrous tissue which normally surrounds and constrains the softer cartilage cushion of the disc material). The surgeon then, in succession, inserts a series of intervertebral trial spacers of defined width. Each of the series of spacers is of a progressively wider thickness, resulting in the continual widening of the space until restoration of the proper disc height has been achieved. Proper disc height restoration is determined by surgical experience, and by observation of the annulus. (Often, the tightening of the annulus indicates that the proper disc height has been reached, inasmuch as the annulus is much less likely to be distorted by the same disruption that caused the intervertebral disc to collapse in the first place.)

#More particularly, with respect to the specific instruments disclosed herein, a series of solid trial spacer elements and an instrument for their insertion and removal is now provided. Each trial spacer is a generally cylindrical disc having a deep annular groove at its midpoint, which forms a central trunk and radial flanges at each end of the trunk. Stated alternatively, two cylindrical upper and lower halves of the disc are held in a closely coaxial spaced apart association by the central trunk, which forms a coaxial bridge between the upper and lower halves. The annular groove is particularly useful for holding the spacer using the spacer insertion instrument of the invention, described below, in that the holding end of the insertion instrument fits within the groove.