Abstract
Background: It is often useful to gauge the flexibility of curves while assessing patients with scoliosis. Our aim was to discover if there were any reliable x-ray predictors of stiffness.
Methods: Previously the flexibility index has been shown to be an accurate measure of curve stiffness. A random selection of fifty x-ray sets was analyzed for parameters that might predict flexibility. These were then compared to the flexibility index generated from bending films. We recorded age; Cobb angle; bending film Cobb angle; Perdriolle rotation assessment; percentage wedging of the apical vertebrae and translation of the apex of the curve from a central sacral/cervical line. We then calculated the flexibility index. All measurements were taken from immediately pre operative standing AP x-rays and fulcrum bending films (1). The group was then assessed as a whole and subgroups were analyzed. Large curves (> 50 degrees) were compared to small (< 50 degrees) curves and thoracic curves were compared with thoracolumbar curves. Correlation between the flexibility index and the other parameters was then studied. We used Pearson correlation coefficient for parametric data and the Spearman rank correlation coefficient to study the non parametric data. P values were then assigned using a statistics software package.
Results: Age and apical translation were not related to curve stiffness. The Cobb angle was the only strong predictor of flexibility (p-0.002) looking at all curve types together. The Cobb angle was, however, more useful in larger curves and did not reach statistical significance in the small curve subgroup. In small curves Perdriolle rotational assessment was a more useful measurement (p-0.02). In the thoracic curve subgroup the percentage wedge of the apical vertebrae was a strong predictor (p-0.007).
Conclusion: Our sample had a strong bias toward an adolescent age group (5–61) mean age 17 and probably did not have enough of a spread to demonstrate the previous relationship between age and stiffness (2). The study re enforces the value of the Cobb angle in predicting curve stiffness but suggests caution using it in smaller curves. It also suggests a role for Perdriolle measurement in small curves and percentage apical wedge in thoracic curves.
The abstracts were prepared by Mr Colin E. Bruce. Correspondence should be addressed to Colin E. Bruce, Consultant Orthopaedic Surgeon, Alder Hey Children’s Hospital, Eaton Road, Liverpool, L12 2AP.
References:
1 Cheung KMC, Luk KDK. Prediction of correction of scoliosis with use of the fulcrum bending radiograph. J Bone Joint Surg Am. 1997; 79: 1144–1150. Google Scholar
2 Deviren et al. Predictors of flexibility and pain patterns in thoracolumbar and lumbar scoliosis. Sine2002 Nov 1 ;27(21):2346–9 Google Scholar
