How Sublaminar Bands Affect Postoperative Sagittal Alignment in AIS Patients with Preoperative Hypokyphosis? Results of a Series of 34 Patients with 2-Year Follow-Up

Hypokyphosis is currently observed in thoracic idiopathic scoliosis. The use of sublaminar bands allows a good restoration of sagittal balance of the spine. The aim of the study was to provide a middle-term radiographic analysis of patients with adolescent idiopathic scoliosis with preoperative hypokyphosis treated by posterior arthrodesis with sublaminar bands. This retrospective study included 34 patients with Lenke 1 scoliosis associated with hypokyphosis (TK < 20°). A radiographic evaluation was performed with a 2-year follow-up. Cobb angle, cervical lordosis, thoracic kyphosis, lumbar lordosis, and pelvic parameters were measured preoperatively, postoperatively, and at 6-month and 2-year follow-up. The mean preoperative thoracic kyphosis was 10.5° versus 24.1° postoperatively (p < 0.001), representing a mean gain of 13°. Cobb angle ranged from 59.3° to 17.9° postoperatively (mean correction 69%, p < 0.001). Cobb angle increased between the immediate postoperative measurement and the 6-month follow-up (17.9 versus 19.9, p = 0.03). Cervical curvature changed from a 5.6° kyphosis to a 3.5° lordosis (p = 0.001). Concerning lumbar lordosis, preoperative measurement was 39.7° versus 41.3° postoperatively (p = 0.27). At 6-month follow-up, lumbar lordosis significantly increased to 43.6° (p = 0.03). All parameters were stable at final follow-up. Correction performed by sublaminar bands is efficient for both fontal and sagittal planes. Moreover, the restoration of normal thoracic kyphosis is followed by an adaptation of the adjacent curvatures with improved cervical lordosis and lumbar lordosis.