Three-dimensional CT measurement of adult acetabular dysplasia: technique, preliminary results in normal subjects, and potential applications.

Abstract

To assess a three-dimensional computed tomography (3DCT) technique for measurement of acetabular coverage in adults. We used 3DCT to define the geometric centre of the femoral head and to measure centre-edge angles (CEAs) at 10 degrees rotational increments around the acetabular rim. The means, ranges, standard deviations and 95% confidence intervals for the CEAs at the various rotational increments were determined. Inter- and intra-observer variability was measured. The normal values are compared with two example cases of acetabular dysplasia. The normal hips of 15 subjects aged 1949 years (mean 34.2 years) were measured. The 3DCT measurements are reproducible (mean difference interobserver, 1.7 degrees - 7.9 degrees; mean difference intra-observer, 0.6 degrees-6.9 degrees). Mean normal CEA at the lateral rim was 33 degrees with a 95% confidence interval of 23 degrees - 43 degrees. Mean normal CEAs at 10 rotational increments from anterior to posterior rim were determined, and graphed as a 'normal curve'. This new 3DCT method of assessing acetabular dysplasia is simple, reproducible, and applicable to diagnosis, quantification and surgical planning for adult acetabular dysplasia patients.