Key-vertebral Screws Strategy for Main Thoracic Curve Correction in Patients with Adolescent Idiopathic Scoliosis

Abstract

STUDY DESIGN:: The following study was a prospective radiographic and retrospective clinical data assessment of adolescent idiopathic scoliosis (AIS) patients who underwent a key-vertebral screws strategy (KVSS) at a single institution with a minimum of two years follow-up. OBJECTIVES:: To introduce the KVSS for the operative treatment of AIS of the main thoracic curve and to address the role of the fulcrum bending radiograph in predicting the outcome of surgical management by this method. SUMMARY OF BACKGROUND DATA:: The application of multilevel pedicle screws for the main thoracic curve in AIS patients is popular in an effort to provide spinal stability, enhance fusion outcome, and provide optimal curve correction. However, with the application of pedicle screw also comes a potential risk for soft tissue and neural injury and increased health-care costs. It remains unknown whether limited screw placement can provide proper curve correction without compromising patient outcome. METHODS:: Seventeen consecutive patients with AIS extending to the main thoracic spine, who underwent posterior fusion and fixation via the KVSS, which is that screws are placed at important strategic points in the spine (i.e. bilaterally at the upper and lower end segments of the fusion block, apical vertebra on convex side, adjacent cephalad and caudal screw placement on concave side), at a single institution with a minimum of two years follow-up were included. The assessment of preoperative standing posteroanterior (PA) and sagittal, fulcrum bending radiograph, and postoperative standing PA and sagittal plain radiographs were assessed in all patients. The flexibility of the curve as well as the fulcrum-bending correction index (FBCI) were calculated for all patients. Postoperatively, radiographs were assessed at immediate (i.e. one week) and last follow-up. Clinical assessment entailed evaluation of patient demographics and the presence of any intra- or postoperative complications. RESULTS:: The mean age at the time of surgery was 15.6 years. The mean follow-up was 39.8 months. The average fulcrum bending radiograph flexibility was 62.2%. The mean immediate curve correction was 71.2%, which did not differ in comparison to last follow-up assessment (P>0.05). The mean immediate and last follow-up FBCIs were 119.3% and 112.5%, respectively (P=0.079). A significant negative correlation was found between immediate FBCI to that of the fulcrum bending radiograph curve flexibility (r=-0.706; P=0.002), which remained similar on last follow-up (r=-0.681; P=0.003). Sagittal alignment did not significantly change from immediate to last follow-up (P=0.163) Fusion was achieved in all patients. No instrumentation-related complications were noted. CONCLUSIONS:: Key-vertebral-screws strategy is a safe and cost-effective method for the surgical treatment of the main thoracic curve in AIS patients. Moreover, in the context of this strategy, the fulcrum bending radiograph may have some predictive utility in the correction of the main thoracic curve in AIS patients.