Oral session 1 : Rehabilitation Low-frequency electric muscle stimulation combined with physical therapy after total hip arthroplasty for hip osteoarthritis in elderly patients : a randomized controlled trial

Introduction: Total hip athroplasty (THA) improves function and quality of life in patients suffering from hip osteoarthritis (OA), especially in those above 75 years [1]. Though rapid recovery of functional capacity in these often elderly patients is essential from a medical and financial point of view, the factors that determine the outcome following THA for hip OA need further investigation. The influence of physical parameters, such as muscle strength, have rarely been studied. Both muscular atrophy and the loss of muscle strength which accompany hip OA limit functional recovery following this operation [2]. The purpose of this study was therefore to assess the effects of low-frequency electric muscle stimulation (LFEMS) associated with usual physiotherapy on functional outcome after THA for hip OA in elderly subjects. Methods: Twenty-nine subjects referred to the rehabilitation department of Dijon university hospital after THA for hip OA were randomized either in the intervention group (n = 16; 78 ± 8 years) which received simultaneous LFEMS of bilateral quadriceps and calf muscles (highest tolerated intensity, 1 hour sessions, 5 days/week, for 5 weeks) associated with conventional physical therapy including resistance training. , or in the control group (n = 13; 76 ± 10 years) which received conventional physical therapy alone (25 sessions). Main Outcome Measurements: Before and after: maximal isometric strength of knee extensors (KES), Functional Independence Measurement (FIM); after: 6-minute walk test (6-MWT) and 200-meter fast walk test (200-MFWT); duration of stay. Results: LFEMS was well tolerated. It resulted in a greater improvement in KES on the operated side (77% vs. 23%; p < 0.01), leading to a better balance of muscle strength between the operated and unoperated limb. The LFEMS group also showed a greater improvement in FIM scores, though improvements in the walking tests were similar for the two groups, as was duration of stay. Discussion: Our results suggest that LFEMS associated with conventional physiotherapy is superior to physiotherapy alone in increasing strength of the knee extensors. The LFEMS also led to a greater degree of independence as measured by the FIM. However, the duration of hospital stay was not reduced and the walking performances were not better in the LFEMS group compared to the control group. LFEMS resulted in a more even balance of strength between the 2 limbs, which can reduce the need for a walking aid. This could be one of the factors that accelerate the recovery of independence, as measured with the FIM. Moreover, this better balance could reduce gait asymmetry, and thus reduce the metabolic cost of walking, as well as the incidence of falls. The exact mechanisms involved in the effect of LFEMS are still a question of debate. Its impact is principally peripheral, and mainly associated with the increase in the aerobic capacity of muscles with a modification in myotypology. However, transfer of muscle strengthening resulting from the effect of LFEMS on motor function, previously described in cardiac diseases [3], has not been found in this study. Conclusion: In addition to conventional rehabilitation, LFEMS is a safe, well-tolerated therapy after THA for hip OA. It improves knee extensor strength, which is one of the factors of the functional outcome after THA, and leads to greater functional independence.