Long segment fusion for adult degenerative scoliosis: long-term outcomes and sagittal complications

Abstract

Objective To investigate the long-term outcomes of posterior long segment instrumentation and fusion in adult degenerative scoliosis (ADS), and to explore the correlative factors of sagittal imbalance after long segment instrumentation and fusion, and to summarize the impacts of different lowest instrumented vertebra (LIV) on sagittal complication rates. Methods ADS patients who underwent long segment instrumentation and fusion between January 2008 and January 2014 were retrospectively reviewed and divided into two groups depended on LIV (L 5 group and S1 group). The follow-up time was at least five years. Radiographic parameters, Visual Analogue Score (VAS), Oswestry Disability Indexscore(ODI), the 12-item Short Form Health Survey-Physical Component Summary (SF-12 PCS)and sagittal complications were analyzed. And the correlation between sagittal imbalance and sagittal complications were calculated. Patients were divided into two groups(sagittal imbalance group and sagittal balance group) to explore the correlative factors of sagittal imbalance. Results All of 56 patients were included and evaluated in this study, and 35 cases stopped at L 5, 21 cases at S1. The mean follow-up time was 6.6±1.6 years. No significant difference were found in age, gender, follow-up time and surgery method (P>0.05) between two groups. No significant differences were found in Cobb angle(11.8°±7.3° vs 12.6°±6.4°), coronal balance distance(CBD) (0.7±0.6 cm vs 1.0±0.5 cm), sagittal vertebral axis(SVA)(3.0±3.1 cm vs 2.6±5.6 cm), thoracic kyphosis(TK) (21.4°±9.6° vs 22.5°±6.9°), lumbar lordosis(LL) (-32.7°±7.3° vs-34.8°±9.1°), pelvic tilt (PT) (23.4°±9.8° vs 23.3°±8.1°), VAS score(2.0±1.2 vs. 2.2±0.9), ODI score(18.5%±6.4% vs 19.3%±5.2%) and SF-12 PCSscore(45.5±5.2 vs 42.4±7.0) between two groups at final follow-up time(P>0.05). Radiographic parameters including Cobb angle, CBD, SVA and health related quality of life scores including VAS score, ODI score and SF-12 PCS scores were improved significantly at two weeks postoperatively, two-year follow-up time andfinal follow-up time in two groupscompared with those preoperatively (P 0.05). The incidence of adjacent segment degeneration in L 5 group was higher than that in S1 group (P<0.05) at final follow-up time, and the incidence of pseudojoint in S1 group was higher than that in L 5 group (P=0.002) at final follow-up time. Conclusion Posterior long segment instrumentation and fusion for adult degenerative spinal deformity can obtain satisfying long-term clinical outcomes, and postoperative sagittal imbalance was related to preoperative sagittal/coronal imbalance, postoperativeinternal fixation failure, PJK, pseudoarticulation formation and adjacent segment degeneration. Distal fusion at L 5 or S1 may lead to high risk of adjacent segment degeneration or pseudoarticulation formation respectively. Key words: Adult; Lumbar vertebrae; Intervertebral disc degeneration; Scoliosis; Postoperative complications