Poster Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

Introduction: Although adjacent segment degeneration (ASD) after lumbar fusion operation is inevitable, an early revision operation signifies a short symptom-free period and increases the risk of successive surgeries. We aimed to elucidate the risk factors associated with revision surgery for ASD after lumbar fusion operation and demonstrate factors associated with early revision due to ASD.

Methods: This case-control study included 86 patients who had revision operations for ASD after lumbar fusion operation in the revision group, while 166 patients who did not warrant revision for ASD for at least 5 years post follow-up were in the no-revision group. Sagittal parameters, Pfirrmann grading, facet degeneration grading, and disc space height (DSH) of adjacent segments were measured. Revision operations within 5 years post-surgery were defined as early revision. A comparison between revision and no-revision, and early revision and late revision groups was performed.

Results: The revision group demonstrated a significantly greater preoperative C7-S1 sagittal vertical axis (SVA) (p=0.001), postoperative C7-S1 SVA (p<0.001), and postoperative pelvic incidence (PI)-lumbar lordosis (LL) (p<0.001) than that of the no-revision group. Preoperative DSH of the proximal adjunct segment (p=0.001), postoperative PI-LL (p=0.014), and postoperative C7-S1 SVA (p=0.037) showed significant association with ASD in logistic regression analysis. The early revision group had a significantly greater age (p=0.001) and number of levels fused (p=0.030) than that of the late revision group. Multivariate Cox regression analysis showed that older age (p=0.045), a greater number of levels fused (p=0.047), and a narrower preoperative DSH of the proximal adjacent level (p=0.011) were risk factors for early revision.

Discussion:  Postoperative sagittal imbalance including greater PI-LL and C7-S1 SVA were risk factors for revision operation for ASD but not for early revision, and are more likely to affect long-term risk. Narrow DSH of the proximal adjacent level increased the risks of revision and early revision surgeries. Moreover, increased age and a greater number of levels fused further increased the risk for early revision for ASD (Figure: Summary of risk factors for revision operation for ASD and early revision). Our study offers crucial insights for surgical planning, patient counseling, and ongoing research, highlighting the multifaceted nature of lumbar fusion surgeries. Further investigations are warranted to refine the practical implications of these findings in clinical practice.