Traditionally, the outcome of treatment of Perthes disease has been assessed by characterizing the shape of the femoral head, the structure of the acetabulum, and the interface between those two hip joint structures. The most common classification system in use today is that developed by Stulberg et. al. that categorizes the affected hip into one of five different classifications. The benefit of this system is that it has been shown to predict the likelihood of degenerative arthritis. However, this classification system is currently limited in its lack of high reproducibility.

Hitesh Shaw, Benjamin Joseph, and other investigators from Kasturba Medical College in Manipal, India sought to develop a method to depict reliable and continuous outcome measures for the treatment of Legg-Calve-Perthes disease. To accomplish this feat, they used image analysis software on anteroposterior and lateral radiographs of hips of skeletally mature individuals with healed Perthes disease.

The research team reported high reliability of measures of sphericity and congruency of the femoral head and acetabulum (a measure of how well the curvature of the femoral head and acetabulum match). These two continuous measures have yet to be correlated with other outcomes such as early arthritis and impingement.

Reference: Quantitative Measures for Evaluating the Radiographic Outcome of Legg-Calve-Perthes Disease. Shah H, Siddesh ND, Pai H, Tercier S, and Joseph B. The Journal of Bone & Joint Surgery PMID: 23426770