Predictable correction of the unfused lumbar lordosis after thoracic correction and fusion in Scheuermann kyphosis

Study Design. A retrospective examination of preoperative and postoperative radiographs of the sagittal spine of 30 patients with Scheuermann kyphosis. Objectives. To determine significant correlations between kyphosis and lordosis in Scheuermann kyphosis, determine predictability of spontaneous sagittal lordosis correction after thoracic correction and fusion, and understand better the biomechanics of the spine. Summary of Background Data. Previous studies described relations between kyphosis and lordosis in healthy people. To our knowledge, no relationships, have been described between kyphosis and lordosis in Scheuermann kyphosis. Methods. On radiographs, maximum kyphosis, maximum lordosis, sacral slope and L5-S1 angle were measured in the preoperative and postoperative standing lateral radiographs of the spine, and correlations were calculated. Results. Preoperative significant correlations were present between kyphosis and lordosis ( R = 0.421; P = 0.021), and between lordosis and sacral slope ( R = 0.824; P < 0001). Postoperative correlations were stronger ( R < 0.591; P = 0.001 and R = 0.844; P = 0.001). The percentage of correction of kyphosis was correlated with the percentage of spontaneous decrease of lordosis ( R = 0.593; P < 0.001). A negative correlation between L5-S1 angle and upper lumbar segment of lordosis was found before and after surgery. Conclusions. This study shows a significant correlation between kyphosis and lordosis before and after surgery. Surgical correction of thoracic hyperkyphosis gives a predictable spontaneous decrease of lumbar lordosis. Correction of lordosis occurs mainly in the upper segment of lumbar lordosis.