Developmental hip dysplasia (DDH) affects five to 13 percent of Caucasian adults. DDH is a shallow hip socket with increased risk for dislocation and arthritis. In this study, CT scans are used to find out how often both hips are affected. The anatomy of dysplastic hips was compared to normal, healthy hips.
Patients were included in the study before they had any corrective surgery. There was no sign of arthritis on X-rays or CT scans. Patients with unilateral hip pain (pain on one side) were examined and put into one of four groups. The groups included patients with DDH in the right hip, the left hip, and both hips. The fourth group of patients had borderline DDH in both hips. Patients in this last group were left out of the study.
The results of CT scans were compared based on gender (male versus female) and differences in hip anatomy. Rotation of the femur (thigh bone) and the angle of the femoral neck called anteversion were compared from the DDH groups to the normal (control) group.
They found a greater amount of anteversion (tilt or angle) in the normal group. Many of the DDH hips were already subluxed (partially dislocated) in the DDH group. The 3-D hip anatomy seen on CT scans helped show that increased rotation of the femur is linked with subluxation. There were no major differences between men and women.
The authors conclude that adults with hip pain and DDH on one side often have DDH on both sides. Subtle changes in hips previously thought to be “normal” are common in adults with unilateral DDH. Transverse pelvic CT scan is a good tool to find hidden DDH on the contralateral (opposite) side.
Long-term studies are needed to see if the abnormal stresses from DDH lead to arthritic changes on both sides in adults with known hip dysplasia on one side.