Development of the hip joints in unoperated children with cerebral palsy - A radiographic study of 76 patients

Background The aims of the present study were to assess the development of hip dysplasia in children with bilateral spastic cerebral palsy and to evaluate the factors that influence the progression. Patients and methods 76 children, 42 with spastic quadriplegia and 34 with diplegia, were included in the study. Their mean age at the first radiographic examination was 3.5 (1-11) years. The patients were followed up until operative treatment (54 subjects) or until the most recent radiograph in those who did not undergo hip surgery. The mean length of follow-up was 4.8 (1-13) years. On the initial and most recent radiographs, the migration percentage (NIP) was measured, which is the percentage of the femoral head lateral to the acetabular rim. Results The mean MP of the side with the largest displacement was 25% (-18-66) at the initial radiographic examination and 51% (9-100) at the last follow-up. The mean increase in MP was 7% (-2-33) per year. Linear multiple regression revealed that gait function and age were the most important variables that influenced the rate of MP progression. Children who could not walk had significantly greater MP progression per year (12%) than those who walked with or without support (2%). In the quadriplegics, the maximal yearly increase in MP was 13% under 5 years of age and 7% in older children. This difference was statistically significant, whereas no significant difference in relation to patient age was seen in the diplegics. Interpretation There is a pronounced trend towards displacement of the hips in quadriplegic CP patients who are under 5 years of age and cannot walk. Because hip dislocation may lead to severe problems, close follow-up is important in finding the appropriate time for hip surgery in order to avoid progression towards dislocation. The risk of severe hip dysplasia is considerably less in spastic diplegia.