A targeted strengthening program for patients following total hip replacement
Investigators: Ms Clarissa Martin, Dr Bev Phillips, Prof Trevor Kilpatrick, Dr Helmut Butzkueven, Dr Niall Tubridy, Dr Elizabeth McDonald, Prof Mary Galea
Persistent lower limb weakness following total hip replacement (THR) is a largely under-recognized problem that prevents recovery of full function and may be associated with subsequent loosening of the prosthesis. Following THR, subclinical weakness in the muscles controlling hip position during walking and other daily activities is accompanied by altered joint biomechanics, leading to instability and loss of shock attenuation across the joint. This randomised controlled pilot study tests the relationship between strength training following THR and the extent of change in functional tasks and walking parameters.
Participants randomly assigned to the Experimental Group (E) undertake a customized program aimed at improving control and strength of muscles around the hip and knee twice-weekly for 8 weeks. Participants assigned to the Control Group (C) receive no supervised or structured exercises beyond those provided by the physiotherapist in the acute hospital (usual care). A blinded assessor assesses all participants on entry into the study, and at one week after completion of training. Outcome measures include: leg muscle power using a step test, WOMAC (Western Ontario McMaster Universities Osteoarthritis Index), Timed Up-and-Go test (TUG) , temporal and spatial parameters of gait measured by an instrumented mat, walking endurance , measured using the 6-minute walk test and net muscle moment at the hip during walking, measured using 3-D motion analysis (Fig. 1).
 Of 19 subjects recruited to the study so far, we have preliminary results for 13 patients (7 E, 6 C). There were no differences between the groups on any of the measures. Although there are too few subjects for adequate power in comparing the two groups, we have identified some interesting trends in the data. As expected, both groups showed improvement in functional status as measured by the TUG, step length and stride length. However, the Experimental group showed significant improvements in leg muscle power (p = 0.05), gait velocity (p = 0.04), step time (p = 0.03), and walking endurance (p = 0.01). There were no significant changes in the Control group on these variables. Analysis of the remaining variables is continuing.
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