The Reliability of Preoperative Supine Radiographs to Predict the Amount of Curve Flexibility in Adolescent Idiopathic Scoliosis

Purpose: To determine the reliability of supine(SUP)long cassette radiographs as compared to side bending (SB) films in predicting curve flexibility in cases of adolescent idiopathic scoliosis (AIS). The value of side bending films is important in classification of AIS, as well as predicting curve flexibility. However, the reproducibility of side-bending films is highly variable depending on the experience of the technologist and the willingness of the patient to perform a maximal bend.

Methods: A total of 575 patients with a diagnosis of operative AIS having scoliosis films including standing long cassette anteroposterior (AP), lateral (LAT), side-bending (left and right) and supine preop films were evaluated. All curves were classified according to the Lenke classification, along with coronal parameters, Cobb measurements and sagittal data. Significance was set at p.

Results: For GroupI, MT supine films were highly predictive of MT-SB while TL/L supine films were also predictive of TL/L-SB and upright TL/L.(see Table).An equation was then derived to predict the value of the side-bending radiographs for each part of the curve (i.e. PT, MT and TL/L). For Group2, MT supine films were highly predictive of MT-SB and MT upright. MT standing TL/L supine films were highly predictive of TL/L-SB and TL/L standing. Group1 resulted in a strong statistical ability to predict a nonstructural PT curve(sensitivity=0.952,PPV=0.864,NPV=0.865) and also a nonstructural TL/L curve(sensitivity=0.958,PPV=0.916). Similarly, in Group2, we found a strong statistical ability to predict a nonstructural PT curve (sensitivity=1.00,PPV=0.982,NPV=1.00) and also a nonstructural MT curve (sensitivity=0.789,specificity=0.842,PPV=0.833,NPV=0.80).

Conclusions: A single preoperative supine X-ray is highly predictive of side-bending radiographs and can be used as an adjunct to predicting curve type, flexibility and structurality of a curve. This singular, reproducible and non-effort related radiograph can potentially replace the need for dual side-bending films.