Background/Purpose: Inadequate clinical response in a substantial portion of total hip arthroplasty (THA) patients, ¹ as well as gait deficits after THA ² have been well-documented. However, the relationships between different types of outcome measures is not always obvious. A more detailed understanding of the relationships between clinical scores and gait variables could lead to new management strategies that would improve outcomes in both domains. The purpose of this study was to determine whether gait variables are related to clinical scores before or after THA, and whether changes in gait variables are related to changes in clinical scores.

Methods: From an IRB-approved repository, we identified 125 subjects (Age 61 ± 10 years; BMI 29 ± 5 kg/m²; 62 Female, 63 Male) who had been evaluated before and 1 year after primary unilateral THA. Harris Hip Scores (HHS) were used to summarize clinical status (preop 57 ± 14, postop 91 ± 11). From standard gait analysis data, we selected 3D peak external hip moments and sagittal plane dynamic hip range of motion (HROM) from trials collected at each subject’s self-selected normal walking speed. Pearson correlations revealed that speed was significantly correlated with several gait variables before or after surgery, and that change in speed was significantly correlated with change in HHS and gait variables (R = 0.199 to 0.660, p values ≤ 0.026). We therefore decided to use first order partial correlation coefficients to evaluate relationships between HHS and gait variables while controlling for speed.

Results: There were significant correlations between preop HHS and HROM (R_|speed = 0.296, p = 001), postop HHS and the peak external rotation moment (R_|speed =0.234, p=0.009) and the change in HHS and the change in both HROM (R_|speed = 0.252, p = 0.005) and peak internal rotation moment (R_|speed= 0.270, p = 0.002). There were no other statistically significant relationships (p ≥ 0.158).

Conclusion: To our knowledge, this is the first study linking specific gait variables to clinical outcome measures. After controlling for the relationship between walking speed and both clinical and gait variables, higher preop- and postop- clinical scores, or more clinical improvement, was associated with higher values of range of motion or hip rotational moments. Because the hip abductors play an important secondary role in maintaining rotational control during stance, we found the relationships between HHS and rotational moments particularly notable. It is possible that addressing subtle abductor dysfunction in the transverse plane could improve both gait and clinical outcomes for some patients. Future prospective studies, however, are needed to fully evaluate the time-course of clinical recovery and gait recovery.

References: 1) Hawker et al., Arthritis Rheum 2013; 65(5):1243-5. 2) Ewen et al., Gait Posture 2012; 36(1):1-6.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/relationships-between-clinical-outcome-measures-and-gait-variables-before-and-after-total-hip-arthroplasty/