Preoperative factors associated with postoperative gait kinematics and kinetics after total hip arthroplasty.

OBJECTIVE: To determine how patient factors: age, sex, body mass index (BMI), clinical scores and physical exam findings, are associated with gait recovery after total hip arthroplasty (THA). METHOD: 145 subjects, who were evaluated with standard gait analysis, the Harris Hip Score (HHS), and a physical exam including passive range of motion (ROM), hip abductor strength assessment, before and after primary unilateral THA, were identified from an IRB-approved repository. Sagittal plane dynamic ROM and 3D peak external moments were averaged from operated-side normal-speed trials at each visit. We used linear regression analysis to evaluate the association among preoperative clinical factors and postoperative gait, with and without controlling for the influence of preoperative gait variables. RESULTS: Sagittal and transverse plane moments, and the peak abduction moment seen in early stance, significantly improved after THA (p < 0.001, effect size d = 0.22-1.04). The peak adduction moment did not change significantly (p = 0.646), although the change ranged from -2.7 to + 4.0 %Body weight × height (-80% to +315%). Preoperative gait, clinical factors and patient characteristics predicted up to 33% of the variability in postoperative gait. Notably, greater preoperative abductor strength was associated with higher postoperative adduction and external rotation moments (R = 0.197-0.266, p < 0.05) after adjusting for age, sex, BMI and preoperative gait. CONCLUSION: Preoperative clinical factors predicted several specific aspects of objectively-characterized postoperative gait function. Physical exam findings can augment the predictive ability of clinical outcome measures, and potentially help guide rehabilitation plans.