Postoperative changes in sacropelvic junction in short-segment angular kyphosis versus Scheuermann kyphosis.

PURPOSE: To comparatively evaluate the biomechanical alterations those occur in the sagittal plane of sacropelvic junction in angular kyphosis (AK) and Scheuermann kyphosis (SK) patients after surgery. METHODS: The spine radiographs of 52 patients operated for short-segment AK (n = 20) or SK (n = 32) were studied. Main outcome measures were sacral slope, pelvic incidence, pelvic tilt, lumbar lordosis, and thoracic kyphosis angles. RESULTS: In AK group, local and thoracic kyphosis angles, as well as lumbar lordosis angle, showed statistically significant reduction with surgery. Thoracic kyphosis and lumbar lordosis angles were reduced significantly in SK group. Postoperatively, there were significant differences between groups in lumbar lordosis, pelvic tilt angle, and sacral slope (p = 0.021, p = 0.001, and p = 0.027, respectively). Thoracic kyphosis angle and sacral slope were increased, and there was a remarkable correlation between thoracic kyphosis and lumbar lordosis values in the AK group. CONCLUSIONS: The results of this study suggest that a significant sacropelvic improvement can be achieved by balanced sagittal vertical axis and T1 spinopelvic leading to a good sagittal alignment of spine in patients with AK and SK. Changes seen in morphological parameters after surgery may be closely related with baseline biomechanics and structure of the spine and pelvis. Therefore, further clinical and scientific trials are necessary both to elucidate the biomechanics, their clinical implications, and to develop new techniques and models for spine and pelvis surgery.