Hip dislocation in spinal muscular atrophy.

Hip conditions in 49 patients affected with spinal muscular atrophy were studied: 35 of these were affected with the intermediate form of the disease (patients were able to sit but not walk), and 14 with the mild form (patients were able to walk). The Perkins method was used to measure the migration percentage of the femoral head. Thirty-one percent of the patients affected by the intermediate form of the disease had normal hips, 38% had unilateral or bilateral subluxation, 11% had hip dislocation. In the mild form of the disease, 50% of the patients had normal hips, 28% had unilateral or bilateral subluxation, and 22% had a hip dislocation. In the intermediate form of the disease there was a linear correlation between migration percentage and age, and between migration percentage and scoliosis. In the patients affected with the mild form of the disease who were able to walk, and in the patients affected with the intermediate form and fitted with orthoses who were able to stand, or to walk, there was no hip dislocation. Hence, walking with or without orthoses seems to be an important factor in preventing hip dislocation.