Rasch A, Dalen N, Berg HE. Muscle strength, gait, and balance in 20 patients with hip osteoarthritis followed for 2 years after THA. Acta Orthopaedica 2010; 81: 183-188.

This study followed 20 patients for 2 years who had undergone a total hip replacement. Each subject had unilateral osteoarthritis, so the uninvolved leg served as the control. Data was collected just before surgery, at 6 months post-operatively, and at 24 months post-operatively. Data included isometric strength measurements of knee and hip muscle, gait parameters, and balance characteristics.

With regard to gait, the researchers found that the single limb support time became more symmetrical at both 6 months and 2 years compared to pre-operatively. The time spent in single limb support for both legs increased slightly producing a corresponding reduction in double limb support time. The authors suggest that these changes are consistent with reduction in pain that was reported by these subjects. Interestingly, the overall walking speed did not increase even after 2 years. 

Most of the hip and knee strength measures showed an increase from pre-op to 6 months post surgery. The strength values increased even more between 6 and 24 months. Generally, at 24 months the strength scores were not statistically different between the operated and non-operated limbs.  One important exception to these trends was the strength of the hip abductor muscles. The isometric strength at 6 months was less than preoperative value.  At 24 months the strength of the abductors exceeded the pre-op force but was still lest than the non-surgical leg. When the operated side abduction force was compared to the opposite limb, it was statistically less at all 3 testing times. 

Based on their findings, the authors proposed more emphasis on “supervised intense rehabilitation” in the early post-operative phase. They suggest that the self-report scales of function that show a “full recovery of pain” may not be sensitive enough to detect the weakness in the hip abductor muscles. They discuss other studies using MRI that have demonstrated persistent hip muscle atrophy after 2 years.

At Gray Institute®, the persistent weakness in the hip abductor muscles in these patients is a concern because of how it might impact the level of function that these patients attain after surgery. Patients with severe osteo-arthritis are so pleased with the reduction in pain, that they may not recognize the hidden functional impairments produced by the strength deficit. Or they might regain their pre-op functional status minus the pain, and fail to achieve the additional functional gains that the surgery might afford. It may not be until the individuals try to engage in more demanding functional activities like gardening, lifting, or golfing that the problems arise.

An additional perspective is that strength gains tested in an isometric-hold test may not be integrated into functional movements. Global functional movement tests allow rehabilitation and training practitioners to assess how well the patient is utilizing the gains in strength demonstrated in this study. These movements also assess balance. Movements that involve multiple regions of the body are likely to reduce the effect of the loss of proprioceptive input from the surgical hip. 

The 3DMAPS® (3D Movement Analysis & Performance System) Analysis Movements can identify residual deficits in these clients regarding the hip motion (mobility) and strength to control the motion (stability) while integrated with the rest of the body. An added benefit of 3DMAPS® is that the Analysis Movements properly tweaked provide the basis for training programs to resolve functional deficits based on the specific requirements of the desired functional task.