A Preliminary Study on Kinetic Analysis of Ground Reaction Force and Impulse During Gait in Patients With Total Hip Replacement and Implication for Rehabilitation.

Background: There is little research done on ground reaction forces (GRF) in terms of 3D impulses after total hip replacement (THR). This study aimed to investigate the GRFs and 3D impulses in four sub-phases of stance during gait in the patients undergoing THR.

Methods: A total of 10 pain-free THR patients and 10 healthy people were recruited. This is an observational and retrospective study. The gait data was collected between 2008 and 2014 and analyzed between 2020 and 2024. All the participants were included in the three-dimensional gait analysis. Gait parameters, phase durations, GRFs and impulses' key values during gait were calculated in four sub-phases of stance. Statistical comparisons were performed with generalized linear models including age, gender, body mass index and walking speed as interactive factors.

Results: It is found that (1) cadence, walking speed, stride length and step width in THR group were significantly decreased in compared with control group; (2) the THR decreased loading response duration in operative side and pre-swing duration in non-operative side compared with the control group, but the THR's two sides have similar duration proportions in sub-stance phases; (3) the THR group had lower GRFs than the control group in vertical direction but higher in the medial-lateral direction; (4) in operative side, the THR's impulses in loading response phase were lower than the control group in anterior-posterior direction, and (5) in non-operative side, the THR's impulse in pre-swing phase in anterior-posterior direction was higher than the control side.

Conclusion: The THR group showed slower walking speeds than the control group. The reasons could be from the decreased impulse in loading response phase, the decreased 2nd peak of GRF and the decreased pre-swing impulse in vertical direction in operative side. Clinicians are suggested to consider the information provided when designing relevant rehabilitation exercises on the related muscles and functions.