K-rod Posterior Dynamic Stabilization Could Reduce Adjacent Segment Degeneration: A Mi nimum 5-Year Follow-up

Objective To evaluate the efficacy of posterior dynamic stabilization (PDS) in treating single-level lumbar degenerative disease and to examine its effect on first cephalad adjacent segment (FCAS) degeneration. Methods This retrospective study included 97 patients who underwent single-level lumbar fusion or PDS between April 2010 and April 2012. Clinical outcomes were assessed using the Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) preoperatively and postoperatively. Radiographic analysis quantified the range of motion (ROM) at the surgical segment, FCAS, and entire lumbar spine. Magnetic resonance imaging (MRI) was used to evaluate degenerative changes in the FCAS. Results Eighty-six patients completed a minimum 5-year follow-up and were categorized into two groups: the PDS group (n = 42) and the fusion group (n = 44). Baseline demographic and clinical characteristics were comparable between groups (all P > 0.05). Both groups showed significant postoperative improvements in VAS and ODI scores (P < 0.05), with no significant intergroup differences at any time point. The PDS group had significantly shorter operative times and less intraoperative blood loss than the fusion group (P < 0.05). Radiographic evaluation demonstrated that the K-rod dynamic system partially preserved ROM at the surgical level over 5 years and limited the increase in FCAS ROM compared to the fusion group (P < 0.05). Postoperative lumbosacral alignment parameters were similar between groups. During follow-up, one case of radiographic adjacent segment degeneration (ASDeg) occurred in the PDS group, while the fusion group showed five cases of ASDeg and one case of symptomatic adjacent segment degeneration (ASDis) requiring revision surgery. Conclusion PDS effectively preserves motion at the surgical segment and has a smaller impact on FCAS mobility. Over long-term follow-up, the incidence of ASDeg and ASDis was lower in the PDS group compared to fusion surgery.