Clinical predictive model of lumbar curve Cobb angle below selective fusion for thoracic adolescent idiopathic scoliosis: a longitudinal multicenter descriptive study.

PURPOSE: To implement a clinically applicable, predictive model for the lumbar Cobb angle below a selective thoracic fusion in adolescent idiopathic scoliosis. METHODS: A series of 146 adolescents with Lenke 1 or 2 idiopathic scoliosis, surgically treated with posterior selective fusion, and minimum follow-up of 5 years (average 7) was analyzed. The cohort was divided in 2 groups: if lumbar Cobb angle at last follow-up was, respectively, ≥ or < 10°. A logistic regression-based prediction model (PredictMed) was implemented to identify variables associated with the group ≥ 10°. The guidelines of the TRIPOD statement were followed. RESULTS: Mean Cobb angle of thoracic main curve was 56° preoperatively and 25° at last follow-up. Mean lumbar Cobb angle was 33° (20; 59) preoperatively and 11° (0; 35) at last follow-up. 53 patients were in group ≥ 10°. The 2 groups had similar demographics, flexibility of both main and lumbar curves, and magnitude of the preoperative main curve, p > 0.1. From univariate analysis, mean magnitude of preoperative lumbar curves (35° vs. 30°), mean correction of main curve (65% vs. 58%), mean ratio of main curve/distal curve (1.9 vs. 1.6) and distribution of lumbar modifiers were statistically different between groups (p < 0.05). PredictMed identified the following variables significantly associated with the group ≥ 10°: main curve % correction at last follow-up (p = 0.01) and distal curve angle (p = 0.04) with a prediction accuracy of 71%. CONCLUSION: The main modifiable factor influencing uninstrumented lumbar curve was the correction of main curve. The clinical model PredictMed showed an accuracy of 71% in prediction of lumbar Cobb angle ≥ 10° at last follow-up. LEVEL OF EVIDENCE IV: Longitudinal comparative study.

Lumbar hyperlordosis of neuromuscular origin: pathophysiology and surgical strategy for correction.

Lumbar hyperlordosis of neuromuscular origin is rare and requires surgical treatment in order to preserve a good sitting posture. We report twenty-seven cases of a preponderantly sagittal hyperlordosis deformity of the lumbar spine in patients with neuromuscular disorders and identify the indications and results of treatment. Seventeen males and ten females, aged 13 to 27 years, underwent operations for a lumbar hyperlordosis of neuromuscular origin responsible for major difficulties in sitting. In all patients, the sacrum was horizontal and associated in twenty-six cases with marked pelvic anteversion. Eleven patients were treated surgically by a posterior approach. The sixteen remaining patients had a preliminary discectomy, followed by posterior correction and fusion. Lumbar hyperlordosis was reduced from 8 degrees to 77 degrees between L1 and S1. The horizontal sacrum was partially reduced with an improvement from 8 degrees to 50 degrees . Consequently, patients recovered a comfortable sitting position. One patient died of respiratory complications six weeks after surgery. Surgical correction is a demanding procedure which can be performed by a posterior approach. It is mandatory to analyse the spino-pelvic balance to avoid iliac retroversion and the loss of the role of the ischia in the sitting position.