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Quantification of femoroacetabular impingement and its contribution to hip pain

University of British Columbia

Cam and pincer morphologies (CPM) are important contributors to non-arthritic hip pain and potential precursors to hip osteoarthritis. Only some CPM hips develop pain and/or osteoarthritis, and it is not clear why. To elucidate the cause of symptoms in CPM hips, we need to identify the pathomechanisms. We recruited 33 participants, 9 with CPM and pain (CPM+), 13 with CPM and without pain (CPM-), and 11 controls to study proposed anterior impingement pathomechanisms using open MRI scanning combined with motion analysis. We assessed anterior impingement directly in squatting and sitting flexion, adduction, and internal rotation (FADIR) by quantifying anterior femoroacetabular clearance. CPM+ hips experienced impingement in active squatting ((mean(SD)) -11.9º(22.7º)) and passive sitting FADIR (-12.6º(17º)) postures, while CPM- hips experienced impingement in passive sitting FADIR (-4.7º(13º)) but not in active squatting (8.5º(14.6º)). Our results support the anterior impingement pathomechanism in CPM hips and highlight the effect of posture on anterior impingement. We then measured the 3D orientation of the acetabular rim in squatting and sitting FADIR compared to supine as a contributor to anterior impingement. Control hips orient their acetabular rim inferiorly in squatting (121.8º(4.7º), p<0.001) and sitting FADIR (104.3°(6.9°), p<0.001) compared to supine (73.9°(6.6°)). CPM+ did not orient their acetabular rim inferiorly compared to supine (80°(5.9°), p=0.097) in squatting (105.9°(30.8°)) and sitting FADIR (92.1°(22.6°)). CPM- inclined their acetabular rim inferiorly in active squatting (113.7°(23.9°),p=0.003) but not in sitting FADIR (92.7°(21.6°),p=0.51) compared to supine (76.1°(8.3°)). Open MRI scanning of hips cannot measure impingement dynamically during activities. Therefore, we assessed the accuracy of a subject-specific hip model driven with motion data to predict impingement compared to open MRI measures in squatting and sitting FADIR. We found an accuracy of about 1° for this model. Finally, we studied anterior impingement during walking using the validated model. We found diminished femoroacetabular clearance through the walking cycle in CPM+ (-13.8º(16.9º)) compared to CPM- (13.8º(19.9º),p=0.002) and control hips (17.6º(28.1º),p=0.015). Anterior femoroacetabular clearance showed a subject-specific pattern that depends on hip kinematics and morphotype. The subject-specific femoroacetabular clearance plotted along with hip kinematics demonstrate this model’s utility in identifying CPM hips experiencing anterior impingement during activity.

Text

2023-03-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/77682

Biomedical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/