Hybrid dynamic stabilization with posterior spinal fusion in the lumbar spine

BACKGROUND Instrumented lumbar arthrodesis has been established as the gold standard in the care of patients with degenerative disc disease. However, spinal fusion results in the elimination of motion of the functional spinal unit and has been implicated in the development of adjacent-level degeneration. Motion-preserving devices such as the dynamic rod allow for stabilization of a pathologic motion segment above a fused segment and create a transitional zone (index level) that decreases the loads applied to the supra-adjacent normal segment. METHODS After institutional review board approval, 28 patients were included in this prospective, consecutive, nonrandomized clinical trial. Each subject was consented for dynamic stabilization. There was no attempt at fusion at the dynamic level. The cohort underwent a posterior lateral spinal fusion with single- or 2-level transforaminal lumbar interbody fusion by use of a cage, with superior-level posterior dynamic instrumentation. Functional clinical outcomes were measured with a 100-point visual analog scale, Oswestry Disability Index, and Short Form 36 questionnaire. Radiographic measurements, fusion evaluation, complications, and screw loosening were recorded. RESULTS A minimum of 24 months' follow-up data included 22 patients. No device failure or screw breakage was identified. Postoperative range of motion averaged 2.5° at the index level, and the superior adjacent-level range of motion remained unchanged (P > .05). Disc height was preserved at all levels (P > .05). Of 180 screws, 6 (3%) showed radiographic loosening. Functional outcomes showed significant improvement in mean postoperative visual analog scale score by 24.7 points (P < .01) and Oswestry Disability Index by 27.6 points (P < .01), as well as the Short Form 36 physical (P < .01) and mental (P < .05) components from baseline to 2-year follow-up. CONCLUSIONS Our preliminary results at 2 years are satisfactory. CLINICAL RELEVANCE Ultimately, further follow-up will assess the potential for this treatment to delay adjacent-level changes in the long term.