Background/Purpose: We have previously reported that fatigue and hip abductor weakness are associated with reduced physical activity (PA) in women with hip osteoarthritis (OA). We speculated that excessive trunk motion during gait, assumed to be an adaptation to abductor weakness and/or pain, was the biomechanical factor underlying these previous findings. The purpose of the present study was to examine the association of frontal plane trunk motion with abductor strength, fatigue and PA. We hypothesized that in women with hip OA, increased frontal plane trunk movement is associated with decreased abductor strength, increased self-reported fatigue, and decreased PA. We further examined associations of trunk motion with pain and function.

Methods: We evaluated 25 women (age 62.0 + 10.2 yrs) with hip OA. Self-reported fatigue was measured by the Patient‐Reported Outcomes Measurement Information System (PROMIS) Fatigue Computer Adaptive Test. The HOOS was used to assess pain and function (ADL and sports/rec subscales). Trunk motion was assessed during level walking on a treadmill at self-selected speeds using conventional gait analysis method, and was defined by the peak angular displacement of the thorax-pelvic segment on the lateral side of the stance foot in reference to the lab coordinate system. The angle was measured for each gait cycle for each stance foot. The trunk angle was than separated by affected side and unaffected side trunk angle. Abductor strength was assessed in sidelying as peak isometric torque using a dynamometer. Finally, PA was assessed using the UCLA score, which ranges from a score of 1 (“wholly inactive”) to 10 (“regularly participate in impact sports…”). T-tests were used to compare affected side and unaffected side trunk lean. Pearson correlations were used to assess the association between trunk lean and outcome variables (abductor strength, fatigue, UCLA scores, and HOOS subscores). Lean to the affected side and unaffected sides were analyzed separately. Statistical analysis was done using SAS 9.4. 

Results: No difference between the magnitude of affected side trunk angle and unaffected side trunk angle was seen. (p=0.411). Higher affected side trunk lean was associated with higher fatigue, but not with abductor strength or UCLA (Table 1). Higher affected side trunk lean was also associated with worse HOOS pain, ADL, and Sports/Rec subscores (Table 1). Higher unaffected side trunk lean was associated with lower abductor strength, worse fatigue and lower UCLA scores (Table 1). Unaffected side trunk lean was not, however, associated with HOOS subscores.

Conclusion: The hypothesis that trunk lean was associated with fatigue, abductor strength, and PA was supported, but only when lean towards the unaffected hip was considered. Notably, only trunk lean towards the affected hip was associated with pain. Trunk lean towards the affected hip may be a compensation to reduce hip loads. In contrast, trunk lean towards the unaffected hip may be a compensation for lower abductor strength. Further study is needed to determine whether muscle or gait training may reduce fatigue and promote PA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-of-frontal-plane-trunk-motion-during-gait-with-abductor-strength-fatigue-and-physical-activity-in-women-with-hip-osteoarthritis/