Abstract
Introduction Adult dysplasia of the hip (ADH) is a disorder of abnormal development of the hip
joint resulting in a shallow acetabulum and uncovering of the femoral head. Several
radiological measurements such as the Tönnis angle (acetabular index), lateral center
edge angle of Wiberg, and cross-sectional imaging parameters exist to calculate hip
dysplasia.
Aims The aim of this article was to describe a new ancillary linear measure of ADH on
cross-sectional imaging, the Birmingham Royal Orthopaedic Hospital (BROH) Femoral
offset.
Patients and Methods Anteroposterior radiographs of the pelvis and computed tomography imaging of 100
consecutive patients with suspected hip dysplasia were reviewed. Demographic details
and clinical indications were recorded. Tönnis angle was utilized to measure hip slope
on radiographs and the BROH femoral offset was calculated for each patient. Student's
t-test and one-way analysis of variance (ANOVA) were performed. Intraclass correlation
coefficient analysis was evaluated to assess the reliability between observers.
Results There was a total of 100 patients (128 hips) included in the study (60 with normal
Tönnis angle, 53 had dysplasia, and 15 had decreased Tönnis angle). The average BROH
femoral offset in the dysplastic cohort was increased in comparison to the normal
cohort with a statistically significant p-Value of 0.0001. The p-value was 0.00031 on ANOVA. The BROH femoral offset calculation revealed good intra-
and interobserver reliability of 0.9 and 0.9, respectively.
Conclusion The BROH femoral offset can be an additional index for measuring ADH that is easier
to calculate, and reproducible with good intra- and inter-observer reliability on
cross-sectional imaging.
Keywords
adult hip dysplasia - acetabular dysplasia - radiography - pelvic radiograph - Tönnis
angle - computed tomography
