Vigdis S. Husby, Jan Helgerud, Siri Bjørgen, Otto S. Husby, Pål Benum, Jan Hoff
Total hip arthroplasty (THA) is a common procedure in orthopedic practice. In 2004, the reported rates (per 100,000 population) for primary THA in the United States, Canada, Australia, and New Zealand ranged from 70 to 150. The number is expected to increase as the population ages, more people live longer, and a greater percentage of the populationis obese. The main purpose of THA, besides pain relief, is to restore hip biomechanics leading to a minimal functional deficit, and to secure the longevity of the implant.
A large group of patients who have underwent THA still have mild to moderate long-term impairments postoperatively. The impairments include reduced walking efficiency, pain, muscle weakness of the hip abductors, contracture of the hip, gait disorders, and weakness of the hip extensors and flexors. Adequate strength of the muscles of the lower extremity and, in particular, the abductor muscles (rotating the leg to the side of the body) is required for a satisfactory gait pattern without limping and to prevent falls.
Maximal strength training (MST) is traditionally performed with high loads above 85% of 1-repetion maximum (1RM), few repetitions, and with explosive movements. MST has been carried out successfully in healthy subjects as well as patients with chronic obstructive pulmonary disease, and in patients with coronary artery disease.
To compare muscle strength, work efficiency, gait patterns, and quality of life in patients undergoing total hip arthroplasty (THA) we randomly assigned THA patients to either MST or a conventional rehabilitation program. Patients (n=24) with osteoarthritis as the main reason for THA were randomly assigned to perform MST (n=12) or conventional rehabilitation (n=12). The MST group performed maximal strength training in leg press and abduction with the operated leg only, 5 times a week for 4 weeks in addition to the conventional rehabilitation program. The conventional rehabilitation group received supervised physical therapy 3 to 5 times a week for 4 weeks.
1RM increased in leg press (two-legs) and in the operated leg separately in the MST group compared with the conventional group. 1RM abduction strength in the operated leg and the healthy leg increased in the MST group compared with the control. Rate of force development also increased in the MST group compared with the control. Work efficiency improved in the MST compared with the conventional group.
Conclusion: The present study demonstrates that MST is an appropriate treatment in an early postoperative phase after THA. Furthermore, MST improves muscular strength to a higher extent in the MST group compared with a conventional rehabilitation program, together with an improved work efficiency.