Does sagittal imbalance impact the surgical outcomes of short-segment fusion for lumbar spinal stenosis associated with degenerative lumbar scoliosis?

BACKGROUND: The degenerative lumbar scoliosis (DLS) patients who mainly complained about neurogenic claudication due to spinal canal stenosis are well-indicated for short segment fusion (SSF) at the affecting levels. However, it is unclear whether we should consider global sagittal balance or not. The aim of this study was to evaluate the impact of sagittal balance on the surgical outcomes of degenerative lumbar scoliosis (DLS) patients who underwent SSF.

METHODS: We retrospectively reviewed 70 DLS patients who underwent SSF (less than 3 levels) and could be followed for at least 2 years. The PI-LL, PT, SVA, and T1 pelvic angle (TPA) were measured using standing whole spine X-rays preoperatively (PreO) and at final follow-up (FFU). Surgical outcomes were assessed with the improvement in Japanese Orthopaedic Association score (JOAs) for low back pain (LBP), and the level of LBP was measured using the visual analogue scale (LBP-VAS). We analysed the relationships between the radiographic parameters and the surgical outcomes.

RESULTS: We divided the patients into the three groups (poor/fair/good) based on the JOAs. The analysis with the Jonckheere-Terpstra trend test indicated that the following radiographic parameters had a significant trend with surgical outcomes in each group: (poor/fair/good; p value); PreO PI-LL (26/20/17°; P = 0.04), SVA (46/75/35.5 mm; P = 0.02), TPA (28/27/23°; p = 0.04), FFU PI-LL (33/25/8.5°; P = 0.004), SVA (93/90.5/32.5 mm; P = 0.001), and TPA (33/29/25°; P = 0.007). Additionally, LBP-VAS had a significant correlation between the three groups at final follow-up (P = 0.004). There were significant correlations between improvement in JOAs and PI-LL, SVA, and TPA both PreO and at FFU (P < 0.05).

CONCLUSIONS: Sagittal spinal imbalance and spinopelvic malalignment significantly impact the surgical outcomes of SSF for DLS. Preoperative evaluation of spinopelvic alignment and sagittal balance is of critical importance when SSF are performed for DLS patients.