Geometric measurements of the acetabulum in adult Malawians: radiographic study.

OBJECTIVES To determine the acetabular depth as well as acetabular and centre edge angles; to assess the influence of sex, if any, in these geometric measurements; and to determine the prevalence of hip dysplasia in adult Malawians. DESIGN A retrospective study. SETTING Queen Elizabeth Central Hospital (QECH) and Blantyre Adventist Hospital (BAH). MAIN OUTCOME MEASURES The acetabular and centre edge angles, acetabular depth and the prevalence of hip dysplasia were determined. MATERIALS AND METHODS Two hundred and fifty three bilateral radiographs of the hip from adults, 133 men and 129 women, were used to measure the acetabular depth, angle and centre edge angle using a calliper and goniometer. The radiographs were taken from patients with no underlying bone disease between January 1997 and February 2001 at QECH and BAH. RESULTS The prevalence of hip dysplasia was 11.54% for men and 13.16% for women with respect to centre edge angles but this difference by sex was not significant (P>0.1). However, the prevalence of hip dysplasia with respect to centre edge angle showed significantly more dysplasia in Malawian men than Nigerian and Chinese men (P<0.001 and P<0.05, respectively). Centre edge angles also showed a wider range in Malawian men (19-51 degrees right, and 15-52 degrees left) than women (18-45 degrees right, 20-46 degrees left). In both hips, the acetabular angles were more obtuse in men (35.52 degrees right, 34.21 degrees left) than women (29.43 degrees right, 29.29 degrees left), and this difference was significant (P<0.001). The ranges of acetabular angles were wider in women (11-38 degrees right, 8-40 degrees left) than men (24-49 degrees right, 20-40 degrees left). Acetabular depth was also greater in men than in women (P<0.01 right hip, P<0.02 left hip). CONCLUSION Sex influences geometrical measurements of the acetabulum. The prevalence of hip dysplasia with respect to centre edge angle was significantly higher in women than men and the prevalence for men with respect to centre edge angle was significantly different when compared with Nigerian and Chinese men. This information will assist clinicians in the region and Malawi in particular to interpret hip X-rays of African patients.