Using precisely controlled bidirectional orthopedic forces to assess flexibility in adolescent idiopathic scoliosis: comparisons between push-traction film, supine side bending, suspension, and fulcrum bending film.

Study Design: A prospective study.

Objective: To validate the effectiveness of push-traction film (PTF) in assessment of curve flexibility in adolescent idiopathic scoliosis.

Summary Of Background Data: There is no agreement among surgeons about the most advantageous method in flexibility evaluation of scoliosis. As all methods available provide the orthopedic force from one direction and use a single torque, it is difficult for them to achieve the postoperative correction; also they could not meet the needs for different types of curves.

Methods: Precisely controlled bidirectional (push and traction) orthopedic forces were applied for curve flexibility evaluation in 31 consecutive adolescent idiopathic scoliosis patients. The correction rate (CR) of postoperation, supine side-bending, suspension, and fulcrum bending radiographs were compared with PTF in instrumented main thoracic (MT) and thoracolumbar/lumbar curves. Correlation and linear regression analyses were also been done to find the best predictor among the four methods.

Results: In MT group, CR of PTF was significantly higher than that of side bending (P = 0.010) and suspension (P = 0.000) but not significantly different from that of fulcrum bending (P = 0.335). In TL/L group, CR of PTF was significantly higher than that of suspension (P = 0.000), but not significantly different from that of side bending (P = 0.681) and fulcrum bending (P = 0.382). There was no significant difference between CR of PTF and postoperation in both MT (P = 0.122) and TL/L (P = 0.068) groups. Correlation and linear regression analyses showed that PTF provided the highest correlation of the four methods, with the postoperative angle in both MT (r = 0.957) and MT/L group (r = 0.779).

Conclusion: To our knowledge, this was the first report about using precisely controlled bidirectional correction forces for curve flexibility evaluation. Although it did not achieve the best CR among the four methods studied, correlation and regression analyses confirmed that PTF was a more stable and accurate method to predict flexibility. We believe that further exploration of a more rational push-traction force ratio would help to obtain a better flexibility.