A Walking and Running Biomechanical Analysis of Femoroacetabular Impingement

Abstract

Context: Femoroacetabular Impingement (FAI) is a bony deformity that leads labral tears, pain, and osteoarthritis. It is currently unknown how hip strength and walking and running biomechanics change over serial time points post-operatively in this population. Objective: Compare a battery of functional outcome measures pre- and post-operatively in FAI and healthy controls. Design: Causal comparative; Independent samples t-test for between subjects and matched pairs t-test for within subjects design, as well as correlations of variable relationships. Setting: Hospital and Research Laboratory. Participants: 12 unilateral FAI (11F, 1 M; age 30.6 ± 7.6, height 1.7 ± 0.1, weight 73.1 ± 13.1) and 10 controls (7F, 3 M; age 31.7 ± 6.1, height 1.7 ± 0.1, weight 68.4 ± 15.0). Intervention: Data were collected at an initial or pre-operative session (FAI within two weeks of hip arthroscopy) and again three- and six-months later. Main Outcome Measures: Clinical and radiographic data were collected at a local hospital, while all other data were collected in the laboratory. Patient related outcomes surveys (PROS) included the Hip Outcome Score and UCLA activity score. Max voluntary isometric hip and knee and strength were collected via hand held dynamometry. Walking and running data were collected via three-dimensional motion capture. Results: FAI participants PROS were lower than controls, except for the UCLA at sixmonths (8.7±1.6 vs. 8.8±1.9). The FAI group improved hip and knee flexion and extension strength over time, but remained weaker than controls. In sagittal and frontal plane muscles, the FAI group only had 67% of the strength as the controls. Hip external rotation strength was greater in FAI versus controls at both three- (21.1± 9.6 vs 10.7±4.6, P<0.05) and six-months (18.8±8.6 vs. 12.0±5.9). The decreased strength found in the FAI group correlated to their decreased HOS scores (r>0.4). Walking velocity in the FAI group was 17%, 12%, and 10% slower than controls at the pre-operative, threemonth and six months sessions, respectively. Hip motion was decreased in the sagittal and during walking, but not during running. The pelvis and hip frontal plane motions were reduced during both walking and running. The transverse plane motion during walking and running favored external rotation at the hip and lower leg, whereas the controls preferred an IR position. Conclusions: There are many differences between groups pre-operatively that persisted at both three- and six-months post-operatively. The FAI patients in this study had worse PROS, were weaker in most of their hip musculature, and displayed abnormal walking and running patterns that may be attributed to both pain and weakness. Therefore, full recovery from hip arthroscopy takes protracted periods of time greater than six-months. Keywords: Femoroacetabular-Impingement, Hip Arthroscopy, Labrum Tear, Hip Strength, Walking and Running Biomechanics.