Recovery in mechanical muscle strength following resurfacing vs standard total hip arthroplasty - a randomised clinical trial

Objectives: To evaluate the effect of resurfacing vs standard total hip replacement on post-surgery hip and knee muscle strength recovery in a prospective randomised controlled trial at the Department of Orthopaedics, University Hospital, Odense, Denmark. Methods: Forty-three patients were randomised into (A) standard total hip arthroplasty (S-THA) and (B) resurfacing total hip arthroplasty (R-THA). Pre-surgery assessment and follow-up were conducted (8,26 and 52 wks). Maximal isometric muscle strength (Nm) and between-limb asymmetry for the knee extensors/flexors, hip adductors/abductors, hip extensors/flexors were analysed. Results: Maximal knee extensor and hip abductor strength were higher in S-THA than R-THA at 52 wks post-surgery (P <= 0.05) and hip extensors tended to be higher in S-THA at 52 wks (P = 0.06). All muscle groups showed substantial between-limb strength asymmetry (7-29%) with the affected side being weakest (P <= 0.05) and hip flexors being most affected. Asymmetry was present in half of the muscle groups at 26 wks (P <= 0.05), and remained present for the hip flexors and hip adductors at 52 wks (P <= 0.05). Conclusions: R-THA patients showed an attenuated and delayed recovery in maximal lower limb muscle strength (in 2/6 muscle groups) compared to S-THA. Notably, the attenuated strength recovery following R-THA was most markedly manifested in the late phase (1 yr) of post-surgical recovery, and appeared to be due to the detachment of the lower half of the gluteus maximus muscle rather than implant design per se. Thus, the present data failed to support the hypothesis that R-THA would result in an enhanced strength rehabilitation compared to S-THA. Further, between-limb asymmetry remained present for hip flexors and adductors after 52 wks. Trial registration: NCT01229293 (C) 2011 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.