Method for Improving Accuracy of Lumbar Pedicle Screw Placement in Scoliosis Surgery

This study aims to retrospectively analyze a new operative technique, the so-called“window procedure”, for pedicle screw insertion in patients with scoliosis. Postoperative computer tomography (CT) was used to assess the accuracy of pedicle screw placement. We retrospectively studied 11 patients with scoliosis, including nine cases of idiopathic patients, one case of cerebral palsy, and one case of poliomyelitis scoliosis, who received adequate levels of posterior fusion with pedicle screws in thoraco-lumbar and lumbar and hooks system in the thoracic spine. The lumbar pedicle screws were inserted using the“window procedure”technique-creating a small window by partially removing interlaminal ligamentum flavum. Postoperative CT, including coronal and axial plans, were positioned for assessing the position of the lumbar pedicle screws. The parameters used to identify the position of the pedicle screws consisted of post-op CT evaluation in all patients, supported by a grant from Chang Gung Memorial Hospital Research Program (CMRP), in which screw position was graded as screw medialization or lateralization (＞ 4mm, 2-4 mm, ＜2 mm) and neutral. Postoperative CT evaluated a total of 50 pedicle screws. Levels of pedicle screw placement were T11 to L5. Moreover, 46 of 50 screws were found to be seated neutrally within the pedicles (92%). Pedicle screw perforations were found, including two medial and two lateral perforations (＜2 mm). There were no neurological complications. The window procedure used in this study for patients with scoliosis is simple, safe and effective. This method can enhance the accuracy of lumbar pedicle screw placement in scoliosis surgery.