It is thought that underlying morphometric abnormalities of the hip joint may be associated with the onset, and potentially the progression of hip OA due to increased contact stresses on the articular cartilage. This study used 2D radiographic parameters (femoral neck-shaft angle [FNSA], acetabular index [AI], femoral head extrusion index [FHEI] and acetabular version [AV]), and 3D active shape models (ASMs) taken from 3T non-contrast MRI data to compare the hip joint morphometry in patients with hip OA and age-matched asymptomatic participants.
In summary, this study compared the geometry of the acetabulum and proximal femur in a study group of n=14 patients aged 50 years and over with a diagnosis of hip OA (K/L grade ≥ 2), with an age-matched control group of n=15 asymptomatic participants. Mean FNSA, AI and AV angles were all slightly larger in the control group compared to the study group. Mean FHEI values were significantly larger in the control group with most likely cause being superolateral migration of the femoral head in the OA group. Participants in both groups had anteverted acetabula with no evidence of retroversion being observed, and all mean measurements for the 2D morphometric parameters were within the reported normal ranges for adults. Labral pathology was evident in both control subjects and study subjects, and the TAL was clearly visible on all control group scans and ~77 % of the study group scans. A comparison of the ASMs identified the main characteristics in the OA study group to be asphericity of the femoral head and/or head-neck junction, presence of osteophytic bone growth around the region of the femoral head, obvious joint space narrowing, and superolateral migration of the femoral head. A slow recruitment rate resulted in only a small number of participants entering the study, however, the principal objective of this study, which was to examine joint morphology in patients with OA of the hip was achieved.
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