Predictability of the fulcrum bending radiograph in scoliosis correction with alternate-level pedicle screw fixation

Abstract

Background: The fulcrum bending radiograph accurately predicts scoliosis curve correction in patients with thoracic adolescent idiopathic scoliosis who are managed with hooks. We assessed the predictive value of the fulcrum bending radiograph in the context of alternate-level pedicle screw fixation of the scoliotic spine.

Methods: A prospective radiographic analysis of patients with thoracic adolescent idiopathic scoliosis who were managed operatively with alternate-level pedicle screw fixation at a single institution was performed. The Cobb angle was measured on posteroanterior standing coronal radiographs that were made preoperatively and one week postoperatively. The fulcrum flexibility percentage and the fulcrum bending correction index percentage were calculated.

Results: Forty-two patients were assessed. The mean age at the time of surgery was 14.6 years, and the mean number of fused levels was 9.4. On the preoperative radiographs, the mean values for the standing Cobb angle, the fulcrum bending radiograph Cobb angle, and fulcrum flexibility were 57.9 degrees, 21.8 degrees, and 62.7%, respectively. On the one-week postoperative radiographs, the mean Cobb angle was 15.4 degrees, the mean curve correction was 73.4%, and the mean fulcrum bending correction index was 122.1%. A significant, positive correlation was noted between the fulcrum bending radiograph angle and the fulcrum bending correction index, indicating that the fulcrum bending radiograph could predict the correction of flexible curves; however, for stiff curves, pedicle screws could provide more correction than the fulcrum bending radiograph predicted.

Conclusions: To our knowledge, this is the first study to demonstrate the predictive value of the fulcrum bending radiograph in the context of alternate-level pedicle screw fixation in patients with adolescent idiopathic scoliosis. Curve flexibility may dictate the degree of the fulcrum bending correction index, whereby a curve that is less flexible may achieve a greater fulcrum bending correction index. The fulcrum bending radiograph has potential predictive utility. In addition, pedicle screw constructs appear to have a better ability to correct scoliosis in comparison with hooks and hybrid constructs.