In the November 16, 2016 edition of The Journal of Bone & Joint Surgery, Kim et al. improve our understanding of how blood flow is restored to the necrotic femoral head in Legg-Calve-Perthes disease. Using a series of perfusion MRI scans, the authors evaluated 30 hips with Stage-1 or -2 disease; 15 of the hips were treated conservatively, and 15 underwent one of three operative interventions.

Revascularization rates varied widely (averaging 4.9% ± 2.3% per month), but the revascularization pattern was similar, converging in a horseshoe-shaped pattern toward the anterocentral region of the femoral epiphysis from the posterior, lateral, and medial aspects of the epiphysis. The MRIs yielded no evidence of regression or fluctuation of perfusion of femoral heads, which casts some doubt on the proposed repeated-infarction theory of pathogenesis for this disease.

In a related commentary, Pablo Castaneda emphasizes that the study was not designed to evaluate the effects of different treatments, but he says knowing about an MRI pattern that is predictive of final outcomes in Legg-Calve-Perthes disease “has potential for improving our prognostic abilities.” Still, neither the commentator nor the authors suggest routinely obtaining serial MRIs in this patient population.