Chapter 34 Lateral Percutaneous Interspinous System for the Treatment of Lumbar Stenosis
One of the main problems of degenerative spine disease is a narrowed spinal canal [1]. The pathologic progression begins with degenerative changes within the disc, which eventually lead to a loss of disc height. Resultant instability may worsen the spondylosis by inducing facet joint hypertrophy [2]. Furthermore, hypertrophy and buckling of the ligamentum flavum, particularly during extension, contribute to a reduction in the size of the thecal sac. This reduction limits the space available for the cauda equina, so the patient experiences symptoms of neurogenic claudication. The patient experiences relief in flexion [3].
Traditionally, spinal fusion has been the mainstay of surgical approaches for the management of low back pain or lumbar instability. Furthermore, there is some evidence that fusion may increase the biomechanical stresses imposed on the adjacent segments that could lead to transitional disease, which may occur earlier in patients with instrumented fusion [4].
Dynamic stabilization is a system that favorably alters the movement and load transmission of a spinal motion segment, without fusing the segment [5,6]. In other words, such a system would restrict motion in the direction or plane that produces pain, or painful motion, but would otherwise allow a full range of motion [7–10,12].
An interspinous distraction device was first described by Dr. Fred L. Knowles more than 50 years ago. Dr. Jacques Senegas was one of the first innovators in this area, and since his work [12], many new interspinous devices have been developed for ideal performance and clinical results [13–15].
Currently a variety of interspinous process implants are available [16] with different characteristics in material (allograft, polyetheretherketone [PEEK], titanium, elastomeric compounds, etc), kinematic features (static and dynamic), and surgical technique (open and percutaneous techniques) but share the goal of achieving some distraction between two vertebral bodies in order to accomplish the following goals:
These devices help open the spinal canal diameter to relieve the patient’s neurogenic symptoms. However, upon insertion many interspinous devices require sacrifice of the integrity of the supraspinous ligament, paraspinous muscles, and fascia. These structures are important elements that maintain spinal stability, so their preservation inherently stabilizes the motion segment [7–11,17].
New technology now allows insertion of interspinous process implants via a minimally invasive lateral percutaneous approach that involves shortened surgery time, hospital stay, and rehabilitation and allows a faster return to daily activities. The RENEGADE interspinous implant (Globus Medical, Audubon, PA) is generally barbell shaped with a fluted conical insertion end to facilitate distraction and a central portion that rests on the spinous processes. The unique design allows for percutaneous insertion and simultaneous distraction of the interspinous space (Fig. 34-1).
Contraindications
Insertion of a lumbar interspinous implant is contraindicated by the following conditions:
Advantages
Advantages of percutaneous interspinous process implantation over open implantation are as follows:
