Little data exists on the original morphology of acetabular dysplasia obtained from patients without radiographic advanced osteoarthritic changes. The aim of this study was to investigate the distribution and degree of acetabular dysplasia in a large number of patients showing no advanced degenerative changes using three-dimensional computed tomography (3DCT). Eighty-four dysplastic hips in 55 consecutive patients were studied. All 84 hips were in pre- or early osteoarthritis without radiographic evidence of joint space narrowing, formation of osteophytes or cysts, or deformity of femoral heads. The mean age at the time of CT scan was 35 years (range 15-64 years). 3D images were reconstructed and analyzed using recent computer imaging software (INTAGE Realia and Volume Player). Deficiency types and degrees of acetabular dysplasia were precisely evaluated using these computer software. The average Harris hip score at CT scans was 82 points. Twenty-two hips (26%) were classified as anterior deficiency, 17 hips (20%) as posterior deficiency, and 45 hips (54%) as lateral deficiency. No significant difference was found in the Harris hip score among these groups. The analysis of various measurements indicated wide variations. There was a significant correlation between the Harris hip score and the acetabular coverage (p < 0.001). Our results indicated wide variety of deficiency type and degree of acetabular dysplasia. Hips with greater acetabular coverage tended to have a higher Harris hip score.
