Spinal stenosis is a narrowing of the spinal canal, through which the spinal cord passes, that causes compression of the spinal cord. Such a narrowing can be caused by numerous factors including bone spurs, degeneration of the intervertebral disks and facet joints, and thickening of the ligaments. Among the symptoms spinal stenosis can produce are pain and/or numbness in the arms, clumsiness of the hands, and gait disturbances.
One such procedure for the repair of spinal stenosis is called a laminoplasty, in which the targeted vertebra is cut such that the vertebra can be spread apart to increase the diameter of the spinal canal. The cut produces two lamina ends, between which a laminoplasty plate is positioned to bridge the gap formed in the vertebra. Normally, a plate of an appropriate size is selected, bent to the desired shape and then fastened to the vertebra utilizing a plurality of screw holes positioned on the plate.
Two different laminoplasty procedures are in current use. The first is called the unilateral or “open door” laminoplasty in which one lamina (positioned to one side of the spinous process) is cut all the way through, while the other lamina (on the opposite side of the spinous process) is cut only partially through to create a hinge. The vertebral portion, including the spinous process, is then rotated about the hinge, and the plate is secured within the opening, maintaining the opening of the spinal canal.
The second procedure is called the bilateral or “French door” laminoplasty in which the midline of the spinous process is cut lengthwise all the way through, and each of the lamina are cut partially through to form two hinges. The bisected spinous process is then spread apart, and a plate is secured within the opening, again increasing the diameter of the spinal canal. Such laminoplasty procedures relieve pressure on the spinal cord while maintaining the stabilizing effects of the posterior elements of the vertebrae. By relieving pressure on the spinal cord it is the goal of laminoplasty to stop the progression of damage to the spinal cord and allow for a degree of recovery of function.
Commonly in “open door” laminoplasty procedures, the laminoplasty plate is of a solid construction having a rigid length to which the lamina ends must be positioned relative thereto. Alternatively the plate of an appropriate size is selected and bent to the desired shape and preferably has a plurality of screw holes, but again, such a plate has a rigid length. Adjustable length plates are also known in the art, though they are cumbersome and difficult to implant as they include multiple moving parts, all of which must be handled by a surgeon. Also, the accompanying instrumentation with such plates includes multiple handles which decrease the precision with which a surgeon can operate.