THE MORPHOLOGY OF THE FEMUR IN DEVELOPMENTAL DYSPLASIA OF THE HIP

We studied the morphometry of 35 femora from 31 female patients with d evelopmental dysplasia of the hip (DDH) and another 15 from 15 age- an d sex-matched control patients using CT and three-dimensional computer reconstruction models, According to the classification of Crowe et al 15 of the dysplastic hips were graded as class I (less than 50% sublu xation), ten as class II/III (50% to 100% subluxation) and ten as clas s IV (more than 100% subluxation). The femora with DDH had 10 to 14 de grees more anteversion than the control group independent of the degre e of subluxation of the hip. In even the most mildly dysplastic joints , the femur had a smaller and more anteverted canal than the normal co ntrol. With increased subluxation, additional abnormalities were obser ved in the size and position of the femoral head. Femora from dislocat ed joints had a short, anteverted neck associated with a smaller, narr ower, and straighter canal than femora of classes I and II/III or the normal control group.We suggest that when total hip replacement is per formed in the patient,vith DDH, the femoral prosthesis should be chose n on the basis of the severity of the subluxation and the degree of an teversion of each individual femur.