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 a successful procedure to reduce pain and restore function in patients with end-stage hip osteoarthritis. However, whether or not pre-operatively existing deficits in strength, balance, range of motion (ROM) and gait are persisting several years post-surgery in the affected limb has not been thoroughly researched. Therefore, the aim of the study was to investigate inter-limb differences in patients who had undergone THA four to five years ago and to compare the values of the operated leg to controls. 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 controls (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 values of the operated leg to controls, 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 controls, 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 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