Biomechanical Analysis of the Effect of Solid Ankle Cushion Heel And Dynamic Feet During Running of Individuals With Unilateral Transtibial Amputations

Objective :

Amputation of the lower limb due to the loss of a part of musculoskeletal structure reduces performance and increases injury during locomotion. The effect of various types of prosthetic feet during running has been analyzed in several studies. This study aims to conduct a biomechanical analysis of the effects of Although the Solid Ankle Cushion Heel (SACH) and dynamic-response feet on several kinetic variables during running in individuals with unilateral transtibial amputation.

Materials & Methods:

 In this quasi-experimental study, participants were 8 left-leg transtibial amputees who were selected using a convenience sampling method who were able to run and referred to Kosar Rehabilitation Center in Tehran, Iran from 2008 to 2012. To adapt to the feet, each foot was worn by the subjects for at least one week before the experiment. All subjects participated in three running sessions for evaluation; one session included the use of own foot (familiarization session), one session included the use of SACH foot, and one session included the use of dynamic-response foot. Only data from the two last sessions were used to compare the feet. Each subject ran in a 12-meter walkway three times at a speed of 2.5 m/s. The same running speed was used for the comparability of kinetic variables. Sport shoes were used to create an actual running condition. In each session, three successful trials were performed so that the foot was in full and perfect contact with the force plate. Kistler force plate and a three-dimensional motion capture system (Vicon) were used to collect kinetic and kinematic data, respectively. The camera and force plate data were sampled simultaneously at 200 and 1000 Hz, respectively. The trajectories of markers and analog data were filtered using the predicted mean square error filter in Vicon v. 1.7 software. The Kinetic variables were generated using the dynamic model of Vicon’s gait Plugin. The vertical ground reaction force was normalized for body weight. Five variables were selected for biomechanical analysis of feet. The maximum vertical ground reaction force, power, spring efficiency, plantar flexion in the amputated leg, and the symmetry ratio (percentage) of the maximum vertical ground reaction force between the amputated and intact legs were calculated. All values in each trial were averaged for each subject with each foot. Paired t-test and Wilcoxon test were used to analyze the data based on normality od distribution, considering a significance level of  P≤0.05.

Results:

 The results of paired t-test and Wilcoxon test showed that spring efficiency and maximum plantar flexion were significantly different between the SACH and dynamic-response feet (P≤0.05). The spring efficiency was greater with dynamic-response foot (P=0.05), while the maximum plantar flexion was greater with the SACH foot (P=0.05). There was no significant difference between the maximum vertical ground reaction force, maximum power absorption and generation in ankle, knee, and hip, maximum dorsiflexion moment, and the symmetry ratio of the maximum vertical ground reaction force between the amputated and intact legs.

Conclusion:

 During running, the spring efficiency with dynamic-response foot is greater than with SACH foot and is closer to the spring efficiency of a normal foot. Therefore, the dynamic-response foot has more natural performance than the SACH foot.