Pathologic morphology of the dislocated proximal femur in children with cerebral palsy

We describe the gross and microscopic anatomic changes in the hip that resu lt from the deforming forces in children with neuromuscular imbalance. Twel ve dislocated proximal femora that had been resected from children with spa stic diplegia or tetraplegia were evaluated with respect to their gross. mi croscopic, and radiographic structure. The epiphyses were wedge shaped with deformation of the femoral head apparent in all cases. In addition to a se vere loss of articular cartilage, a furrowed erosion of epiphyseal bone sug gested a sustained, blunt, band-like force across the surface of the hip wh ere it opposed the acetabular labrum. The underlying physis of the capital femur was irregular with aberrant histologic structure, whereas that of the lesser trochanter was hypertrophic and angulated in a superior and anterio r direction. A significant degree of valgus was not noticeable in most spec imens. In summary, the spastic adductor and iliopsoas, responsible for the changes in the lesser trochanter, work in conjunction with the hip flexor a nd internal rotator muscles to subluxate the proximal femur. In the process , the superior rim of the acetabulum and capsule causes focal deformation o f the superolateral femoral head, creating a fulcrum upon which the hip the n progressively subluxates. The indentation locks the femoral head at the l ateral acetabular margin, preventing complete dislocation, but leading to b one pain consequent to cartilage erosion.