Predictors of Deterioration in Sagittal Balance Following Long Fusion Arthrodesis to L5 in Patients with Adult Scoliosis

BACKGROUND The aim of this study was to identify the predictors of deterioration in sagittal balance in patients with adult scoliosis following long fusion arthrodesis to L5. MATERIAL AND METHODS A retrospective clinical study included 63 patients with adult scoliosis who underwent long fusion arthrodesis to L5, between February 2005 and May 2015. Radiological imaging values included the angle of lumbar lordosis (LL), and the angle of pelvic incidence (PI). The patients were divided into two cohorts, according to the threshold of average loss of sagittal vertical axis (SVA): a cohort with stable sagittal balance (SSB) and a cohort with deteriorated sagittal balance (DSB). Multivariate logistic regression analysis and the receiver operating characteristic (ROC) curve were used to identify the predictors of clinical outcome. RESULTS There were significant differences between the SSB and DSB cohorts in age (p<0.001), preoperative SVA (p<0.001), last follow-up SVA (p<0.001), preoperative LL (p=0.001), last follow-up LL (p<0.001), subsequent L5-S1 disc degeneration (p<0.001) and PI (p=0.028). Patient age >61.5 years (OR=1.251, 95% CI, 1.055-1.484) (P=0.010), preoperative SVA >3.54 cm (OR=1.844, 95% CI, 1.249-2.732) (P=0.002) and preoperative LL <19.0 degrees (OR=0.922, 95% CI, 0.869-0.979) (P=0.008) were identified as predictors of deterioration in sagittal balance. CONCLUSIONS Deterioration in sagittal balance following long fusion arthrodesis to L5 in patients with adult scoliosis was associated with subsequent L5-S1 disc degeneration and loss of LL, age >61.5 years, preoperative SVA >3.54 cm, and preoperative LL <19.0 degrees.