"Perthes-like" changes in a free riding untreated congenital dislocated hip.

The development of avascular necrosis of the femoral head (AVN) after the treatment of congenital dislocation of the hip (CDH) is a well-known complication, but the coexistence in an old child of untreated CDH and ischemic changes of the femoral head has not been reported. Many authors and several years of clinical observation have shown that Perthes-like changes do not occur unless the two sides of the joint are in contact. The purpose of this paper was to report a case of Perthes-like disease that occurred in an untreated CDH, and to discuss the possible pathogenesis. The patient is an 8-year-old African American girl, who presented with a leg length discrepancy, and very mild complaints at the left hip. Physical examination revealed left hip stiffness with a positive Galeazzi sign. Pelvic radiographs showed a complete high riding dislocation of the left hip, with a small and dense femoral head. MRI showed a decreased signal of the entire femoral head. Hematologic and metabolic work-up was normal. Although the vascular theory seems to be well accepted in the pathogenesis of Perthes disease, it does not seem that the contact between the femoral head and the acetabulum is necessary to produce ischemic changes of the femoral epiphysis.