Does Dynesys Dynamic System Actually Prevent the Adjacent Segment Degeneration? Results of a Comparative Study with Average 6-Year Follow-Up.

Abstract

The Dynesys dynamic system (DDS) has demonstrated comparable clinical and radiological outcomes to spinal fusion in treating degenerative lumbar disorders. Short-term follow-up showed that DDS prevents adjacent segment degeneration (ASD). However, the long-term outcomes, especially regarding clinical ASD, remain unclear. This study aims to investigate the long-term clinical and radiological outcomes of the DDS, focusing on the efficacy in preventing clinical ASD beyond 5 years postoperatively. Eligible subjects treated from 2013 to 2017 were categorized into transforaminal lumbar interbody fusion (TLIF) or DDS group. Clinical outcomes were evaluated using visual analog scale, Japan Orthopedic Association score and Oswestry disability index. Radiographic evaluations included assessments of segmental instability, disc degeneration, endplate degeneration, facet joint degeneration, and radiographic ASD. Complications and patient satisfaction were analyzed. Forty subjects in TLIF group and 35 subjects in DDS group were enrolled. The mean follow-up duration was 80.5 months. The 2 groups demonstrated comparable results in visual analog scale scores, Japan Orthopedic Association scores and Oswestry disability index. DDS group exhibited lower incidence of disc degeneration (17.14% vs. 42.5%) and radiological ASD (42.85% vs. 70%) than TLIF group. Besides, DDS group showed a lower incidence of clinical ASD (0% vs. 2.5%) than TLIF group. Screw loosening occurred in 4 and 5 subjects in DDS group and TLIF group, respectively. No subject required revision surgery. DDS appears to decrease disc degeneration of the cranial adjacent segment and reduce the incidence of radiological ASD. Its effect on preventing clinical ASD remains to be further clarified.