Multicenter comparison of the factors important in restoring thoracic kyphosis during posterior instrumentation for adolescent idiopathic scoliosis

Study Design: Multicenter review, prospectively collected data. Objectives: To determine factors predictive of postoperative correction of hypokyphosis when segmental posterior pedicle screw implants were used in treating thoracic adolescent idiopathic scoliosis (AIS). Summary of Background Data: Correcting hypokyphosis, which is common in patients with thoracic AIS, may be important in preventing junctional kyphosis, maintaining lumbar lordosis, and improving pulmonary function. Methods: A multicenter, prospective database was reviewed for Lenke type 1-4 AIS patients with preoperative kyphosis of 5° to 20°, treated with posterior pedicle screws and 5.5-mm rods. Surgeons with a minimum of 20 patients identified were included. Patients were divided into 2 groups postoperatively based on first erect X-rays: those remaining hypokyphotic (HK) (T5-T12 less than 20° or an increase less than 5° in T5-T12 kyphosis) and those restored to normal kyphosis (NK) (T5-T12 greater than 20° with 5° or more increase). Regression analysis was done on 5 preoperative factors thought to influence the postoperative kyphosis: preoperative kyphosis, surgeon, rod material (standard, high-strength, and ultra-high-strength steel; titanium; and cobalt chromium), implant density, and use or no use of a posterior release (Ponte osteotomies). Results: Of 280 patients included, 222 remained hypokyphotic and 53 achieved normal kyphosis. There were no differences in preoperative kyphosis (13.4° ± 5°, HK group vs. 14.5° ± 4°, NK group) and age (14.7, HK group vs. 14.6, NK group) between patients brought to greater than 20 (NK) and those who remained less than 20 (HK). Of the factors evaluated, the surgeon who performed the operation was the only significant predictor of restoration of normal kyphosis. Comparison of surgeons showed that the rate of normalizing kyphosis ranged from 6% to 42% (p =.001). There was no difference in the degree of preoperative kyphosis among surgeons. Conclusions: Restoration of thoracic kyphosis remains a challenge in posteriorly treated thoracic AIS patients. The surgeon was the only significant predictor of restoring normal kyphosis, which emphasizes the importance of intraoperative techniques. © 2013 Scoliosis Research Society.