Intraobserver and interobserver reliability of Catterall, Herring, Salter???Thompson and Stulberg classification systems in Perthes disease

OBJECTIVE: To assess the percentage agreement and intraobserver and interobserver reliability among Catterall, Salter-Thompson, Herring and Stulberg classification systems with special reference to the stage of treatment. METHODS: Anteroposterior and frog-leg radiographs of 10 patients were evaluated by 18 reviewers on two occasions. Each patient had three sets of radiographs of different stages of disease: before treatment, 6-12 months after the initiation of treatment and at least 5 years after the treatment. RESULTS: Interobserver-intraobserver agreement rates for Catterall (set 1), Salter-Thompson (set 1), Herring (set 1), Catterall (set 2), Herring (set 2) and Stulberg (set 3) were 0.6203-0.6862, 0.6037-0.5758, 0.5955-0.4946, 0.5782-0.3864, 0.3878-0.1133 and 0.7912-0.7733, respectively. CONCLUSIONS: The results of our study suggest the use of Catterall and Salter-Thompson systems prior to treatment and the Stulberg system at the end of the treatment at skeletal maturity. However, evaluation of the patients during the treatment period is still a dilemma and necessitates a new more reliable classification system.