INTRODUCTION
Fusion and instrumentation are widely accepted treatment options for unstable degenerative spondylolisthesis. However, the reduction in the number of mobile segments alters the biomechanical behavior of adjacent motion segments. As a result, adjacent-segment disease (ASD) frequently develops following lumbar fusion, often requiring additional surgical interventions. To address this issue, dynamic stabilization using the segmental spinal correction system (SSCS)—a pedicle screw-based posterior dynamic stabilization procedure—has been proposed as a strategy to mitigate the risk of ASD, as it is expected to avoid creating fusion-related stresses on neighboring levels. This study aimed to evaluate the long-term clinical outcomes of SSCS stabilization in patients with degenerative spondylolisthesis.
METHODS
Nineteen consecutive patients who underwent posterior dynamic stabilization using the SSCS were reviewed with a minimum follow-up of six years. The cohort consisted of 9 males and 10 females with a mean age of 69 years (range, 62–81 years). The mean follow-up period was 121 months (range, 72–168 months). Clinical outcomes were evaluated using the visual analog scale (VAS) for low back pain, leg pain, and numbness, as well as the Japanese Orthopaedic Association (JOA) score and the prevalence of symptomatic ASD. Radiographic assessments included the range of motion at the stabilized segment, spontaneous facet arthrodesis, and slippage of adjacent vertebrae.
RESULTS
Preoperative VAS scores for low back pain, leg pain, and numbness were 45 ± 29, 58 ± 32, and 60 ± 29, respectively. These improved postoperatively to 13 ± 13, 4 ± 8, and 12 ± 21. The JOA score also improved from 15.6 ± 3.6 to 23.2 ± 3.3. Symptomatic ASD occurred in 3 patients (16%), although none required additional surgery. The range of motion of the stabilized segments was 11.3 ± 6.3 degrees preoperatively and decreased to 3.1 ± 2.3 degrees at the final follow-up. Spontaneous facet arthrodesis was observed at the stabilized levels in 11 patients (58%). Anterior slippage of adjacent vertebrae occurred in 4 patients (21%).
DISUCUSSION
The long-term clinical outcomes of SSCS stabilization in degenerative spondylolisthesis were favorable. At the final follow-up, the mobility of the stabilized segments had significantly decreased, with no instrumentation failure observed, and symptomatic ASD occurred in only 16% of patients. In contrast, the incidence of ASD following lumbar interbody fusion has been reported to range from 30% to 40% at 10-year follow-up. SSCS stabilization appears to have a lower impact on adjacent segments compared to lumbar interbody fusion, potentially reducing the need for reoperation due to ASD.