CAN PERFUSION MRI PERFORMED IN THE EARLY STAGES OF LEGG-CALVE-PERTHES DISEASE PREDICT LATERAL PILLAR INVOLVEMENT?

Purpose (a): Radiographic prognosticators of outcome for Legg-Calvé-Perthes disease (LCPD), e.g. lateral pillar classification, cannot be applied at the early stages, which is suboptimal since significant deformity of the femoral head can occur. The purpose of this study was to determine if perfusion MRI measurements of the femoral epiphysis obtained at the early stages of LCPD can predict the radiographic lateral pillar involvement at the maximum fragmentation stage. Methods (b): Twenty-nine patients were prospectively enrolled and had gadolinium-enhanced perfusion MRI in the early stages and were radiographically followed. Observers measured percent perfusion of the femoral head using MRI analysis software. Percent perfusion of the lateral third of the epiphysis was measured. Radiographs obtained at maximum fragmentation stage were used for the lateral pillar classification. Intraclass correlation coefficient and logistic regression were used for statistical analysis. Results (c): Mean age was 7.7±1.7 years (range 5.3-11.3 years). The mean time between MRI and the xray at maximum fragmentation was 8.2±5.5 months. Intraclass correlation of MRI measurements was 0.90 (95% CI of 0.83-0.95). In the hips that developed the lateral pillar A, B, or C, the mean percent perfusion of the lateral third of the epiphysis was 92±2%, 68±18%, and 46±12%, respectively (p=0.001). At the perfusion level of 90% and above in the lateral third of the epiphysis, the odds ratio of developing lateral pillar A vs. B or C was 72.0. At the perfusion level of 55% and below in the lateral third of the epiphysis head, the odds ratio of developing lateral pillar C vs A or B was 33.3. Conclusions (d): The lateral third epiphyseal perfusion measurements obtained at the early stages of LCPD using perfusion MRI were predictive of lateral pillar involvement at the maximum fragmentation stage. Significance: Perfusion MRI obtained early in LCPD may yield prognostic information to guide treatment decisions.