Asymmetrical loading during sit-to-stand movement in patients 1 year after total hip arthroplasty

Background: Asymmetrical loading during functional performance can occur after total hip arthroplasty. We hypothesized that during sit-to-stand movements, the loading of the limbs of patients who undergo total hip arthroplasty is more asymmetrical than that of those who do not. The objective of the present study was to compare asymmetrical loading during the sit-to-stand movements of patients at 1 year after undergoing total hip arthroplasty, and that of healthy adults. Methods: Twenty-eight patients at 1 year after undergoing total hip arthroplasty and 16 healthy adults were included. We measured the vertical ground reaction force during the sit-to-stand movement for each leg and calculated the ratio of the peak vertical ground reaction force, and the ratio at the time of peak magnitude of the non-operated limb (control, right limb). Findings: The mean peak vertical ground reaction force ratio of the patients was 0.77 (0.2), and it was significantly lower than that of healthy adults. The vertical ground reaction force ratio for these patients at the time of peak magnitude of the non-operated limb was 0.72 (0.2), and was significantly lower than that of healthy adults. Interpretation: Loading on the operated leg during the sit-to-stand movement was lower than that on the non operated leg in patients at 1 year after undergoing total hip arthroplasty. Furthermore, loading during sit-to stand movement of patients 1 year after undergoing total hip arthroplasty was more asymmetrical than that of healthy adults. Even at 1 year after undergoing total hip arthroplasty, these patients performed the sit-to-stand movement asymmetrically.