Inter-limb differences in patients following total hip arthroplasty four to five years after surgery: a cross-sectional study

Abstract Backgroundː Total hip arthroplasty (THA) is an effective procedure for patients with end-stage hip osteoarthritis. However, whether or not pre-operatively existing functional deficits are persisting several years post-surgery in the affected limb has not been thoroughly researched. Therefore, the primary aim of the study was to investigate differences between the operated and non-operated leg in hip strength, range of motion (ROM), balance, and gait in patients four to five years after undergoing THA. The secondary aim was to compare these values from the operated leg of the patients to those of the legs of healthy subjects. Methodsː Sixteen patients (age: 65.20±5.32 years) following unilateral THA (post-operation time: 4.7±0.7 years) and ten, healthy, age-matched control subjects (age: 60.85±7.57 years) were examined for maximum isometric hip muscle strength, active ROM of the hip joint, balance and gait on both limbs. Paired t-tests were used to assess the inter-limb differences in the THA group. Analyses of covariance (ANCOVA) were performed to compare groups, using age as a covariate. Results: The analysis of inter-limb differences in patients following THA revealed significant deficits on the operated side for hip abduction strength (p=0.02), for hip flexion ROM (p<0.01) and for balance in terms of the length of center of pressure (COP) (p=0.04). Compared to values of the control subjects, the patients demonstrated significantly reduced hip strength in flexion, extension and abduction (p<0.05) on the operated leg as well as reduced ROM measures in hip flexion, extension and abduction (p<0.05). Conclusions: Inter-limb differences as well as reduced hip strength and hip ROM compared with control subjects were still present four to five years after THA. These persisting asymmetries and deficits in patients following THA may be one explanation for the decrease in health-related quality of life (HRQoL) seen in patients over the years after surgery. Postoperative training focusing on strengthening hip muscles should be continued months and years after hip replacement in order to compensate persisting deficits and asymmetries. Trial registration: DRKS, DRKS00016945. Registered 12 March 2019 – Retrospectively registered, http://www.drks.de/DRKS00016945