Evaluation of ground reaction force in walking of below knee amputees based on sample entropy

Introduction: Abnormal pressure during daily activities, including walking, is known as a risk factor in knee joint degeneration in knee amputees. The aim of this research was to analyze ground reaction force (GRF) and sample entropy in below-the-knee amputees. Methods: This study was a descriptive-cross-sectional type, and 20 people with below-knee amputations of the right leg (TT group) and 20 people without amputations (control group) participated. VICON motion analysis system was used to evaluate the ground reaction force during walking. Two linear and non-linear methods were used to analyze GRF data. Sample entropy was chosen as a nonlinear analysis method. ANOVA statistical test was used for inter-group comparison of GFR components and dependent t-test was used to check the difference between legs in TT group. All statistical steps were performed by SPSS software with p<0.05. Result: The amount of GRF force in the control group was significantly higher in the vertical (first and third peak) and anterior-posterior components and lower in the second peak of the vertical component than in the TT group (p<0.05). Also, the entropy value in all GRF components and in both legs of the TT group was significantly lower than the control group (p<0.05). Conclusion: According to the results, the amount of force exerted on the joints of the TT group is not symmetrically distributed between the two legs, so the probability of developing osteoarthritis in the healthy leg joint will be higher. The reduction of the entropy value is a sign of the absence of natural fluctuations in the GRF, which indicates less adaptation and coordination of the lower body joints during walking.