Abstract
Purpose
To assess the use of radiographic measurement compared to descriptive classification in the evaluation of Perthes' disease.
Method
Fifteen consultant Paediatric Orthopaedic surgeons, members of the BOSS Collaborative from different UK centres, were asked to rate a series of 100 healed AP radiographs of hips affected by Perthes' Disease from the Liverpool Perthes' Disease Register using the Stulberg' s grading. Two independent observers categorised roundness error using Digitimizer™ software. Kappa scores were used to determine the inter-observer concordance amongst the 15 observers for Stulberg classification. Lin concordance was used to determine roundness error assessment. The relationship between the two outcomes was explored statistically and graphically; considering the mean Stulberg grade recorded by the 15 observers as a continuous outcome.
Results
There was moderate to fair agreement regarding the Stulberg' s grading among the Consultant surgeons with an overall Kappa error of 0.377 (95% 0.353 – 0.393). The Lin concordance between the two independent observers evaluating roundness error was 0.50 (95% CI 0.36–0.64). There was a strong correlation between the Stulberg grading and roundness error measurement. Using a box and whisker chart the roundness error correlated well with modal Stulberg grade.
Conclusion
Roundness error appears to be a useful radiographic measure of hip shape in Perthes' disease by offering a continuous estimate of hip deformity. It correlates well with surgeon-reported hip shape and can be a useful tool in clinical trials.
