Publication
This case series study was designed to provide an overview of the efficacy of an active pelvis orthosis (APO) against the fall risk after multidirectional slippages in transfemoral amputees (TFA). To achieve this goal, we investigated the dynamic stability after antero-posterior (AP) and diagonal (D) slippages, as assessed by the Margin of Stability (MoS) in both the frontal and the sagittal planes. Results revealed that the detection algorithm can actually signal a lack of balance in about 400 ms, for both AP and D slippages, for three over five amputees. However, it was also noticed that its performance decreased with the severity of the amputee's clinical status. Specifically, for most impaired amputees walking patterns are inherently less smooth thus the detection algorithm failed to detect abrupt modifications of gait patterns due to external perturbations. Results also demonstrated that the proposed assistive strategy can effectively promote balance recovery in the sagittal plane while subjects managed AP-slippages. On the other hand, the analysis of the stability in the frontal plane showed that the balance control does not systematically improve due to the APO assistance. Therefore, despite the APO could partially restrain the hip movement of the users in the frontal plane, balance control is mostly mediated by subjects' abd/adduction muscle groups leading them to adopt a context- and subject-dependent counteractive strategy to manage the lack of balance. Concluding, the outcomes of this preliminary study are promising and suggest to further investigate subject-specific tuning of the control algorithm underlying the APO-mediated assistance.