Computed tomography measurement of acetabular dimensions: normal values for correction of dysplasia

Abstract

Background: A successful periacetabular osteotomy includes reliable planning based on radiographs and CT scanning. However, we lack normative CT values in planning realignment of the osteotomized acetabulum.

Patients and methods: We retrospectively studied 70 hips that had been CT-scanned. Patients who showed no signs of developmental disturbances in either of the hip joints were eligible for the study. Sex differences were also studied.

Results: The AA-angle, CE-angle, ACE-angle and AcetAV-angle, depicting frontal, sagittal and horizontal alignment, averaged 3 degrees (SD 4 degrees ), 41 degrees (7 degrees ), 31 degrees (5 degrees ) and 21 degrees (7 degrees ), respectively. The upper normal value (+ 2SD) for the AA-angle was 12 degrees , normal range (+/- 2SD) for CE-angle was 27 degrees -55 degrees , lower normal value (- 2SD) for the ACE-angle was 22 degrees , and normal range (+/- 2SD) for the AcetAV-angle was 6 degrees -35 degrees . However, comparison of mean angles in women with those in men showed a statistically significant difference for the AA-angle and AcetAV-angle, but we found no significant differences between the mean figures for right and left hips.

Interpretation: Knowledge of the normal dimensions of the acetabulum is essential in the diagnosis of the type and severity of DDH, as well as in preoperative planning. Accurate estimation of the normal contact surface orientation permits correct realignment of the osteotomized acetabulum.