[Clinical study of the Cobb+1 to Cobb fusion strategy for Lenke 5C adolescent idiopathic scoliosis patients with the lower lumbar apex].

To investigate the indications and surgical outcome of Cobb+1 to Cobb fusion strategy in Lenke 5C adolescent idiopathic scoliosis (AIS) patients with the lower lumbar apex. The clinical data of Lenke 5C AIS patients treated in Nanjing Drum Tower Hospital from August 2015 to December 2018 were retrospectively analyzed. The patients were followed-up for at least 2 years after surgery and treated with selective Cobb+1 to Cobb fusion strategy. The patients were divided into the normal lumbar apex group (apex location of the main curve was between T and L) and the lower lumbar apex group (apex location of the main curve was below the disc of L/L). The occurrence of proximal decompensation in the two groups was compared. In addition, according to whether the patients had proximal decompensation at the last follow-up, the patients in the lower lumbar apex group were further divided into proximal decompensation group and non-decompensation group. The radiographic parameters and Scoliosis Research Society-22 (SRS-22) scores of the two groups were compared. A total of 52 patients (19 cases in the normal lumbar apex group and 33 cases in the lower lumbar apex group), aged (15.3±1.6) years, were followed up for 2-5 (3.2±1.2) years. Six patients (6/19) in the normal lumbar apex group and 5 cases (15.2%) in the lower lumbar apex group showed proximal decompensation during follow-up, and the incidence was significantly higher in the normal lumbar apex group (=0.034). Within the lower lumbar apex group, the patients with proximal decompensation (=5) showed similar Risser grade, baseline thoracic Cobb angle, and main Cobb angle as those without proximal decompensation(=28), and the differences were all not statistically significant (all >0.05). However, the baseline thoracic/lumbar apical vertebra translation (AVT) ratio was significantly larger in patients with proximal decompensation (0.6±0.2 vs 0.4±0.2, =0.042), but the postoperative upper instrumented vertebra (UIV) tilt angle was similar (4.5°±2.3° vs 6.2°±3.4°, =0.312). Cobb+1 to Cobb fusion strategy, selecting UIV at 1 level above upper end vertebra (UEV), could be performed in Lenke 5C patients with the lower lumbar apex location. In addition, UIV could be selected at UEV+1 in patients with small baseline thoracic curve.