Blood supply of the head of the femur in traumatic hip dislocation.

Traumatic dislocation of the hip causes circulatory embarrassment in the femoral head in both adult and immature rabbits. Damage to the extraosseous epiphyseometaphyseal vessels of blood supply and drainage is a major causative factor. Disturbance of circulation is most severe in immature rabbits and worsens with continued dislocation to finally reach a maximum within a period of 24 hours. In adult rabbits, the intraosseous epithyseo-metaphyseal anastomoses across the obliterated growth plate minimize the effects of damage to the extraosseous epiphyseal nutrient system. Early reduction of the dislocated hip enhances early and complete recovery of blood supply to the femoral head. Reduction of the dislocated hip delayed to 12 hours or longer does not benefit the rate and extent of the circulatory recovery of the femoral head. Histologically demonstrable aseptic necrosis of the femoral head occurs in the majority of rabbits, regardless of skeletal maturity or reduction. It is more common and extensive in immature rabbits. Abnormal roentgenologic features within the femoral head are observed infrequently between five and ten weeks after dislocation, despite the high incidence of aseptic necrosis.