An Experimental Approach to Induce Trips in Lower-Limb Amputees

Summary

An experimental approach was developed to induce trips in lower-limb amputees. The goal was to create unexpected trips and induce meaningful tripping/recovery responses. The kinematic data from one transtibial amputee confirmed that such an approach effectively elicits reactive trip recovery responses.

Abstract

Reestablishing balance after a trip is challenging for lower-limb amputees and often results in a fall. The effectiveness of reestablishing balance following a trip depends on factors such as amputation level (transtibial or transfemoral) or which limb is tripped (prosthetic or sound/lead or trailing). Understanding the recovery responses can help identify strategies to avoid a trip becoming a fall and what trip-response functionality could be designed into a prosthesis. This study presents an experimental approach for inducing unexpected trips in individuals with amputation. Tripping was manually triggered by activating an electromagnetic device to raisea polypropylene wire to obstruct (bring to a near halt) theswinging limb during its mid-swing phase. A safety harness attached to a ceiling rail ensured participants did not hit the ground if they failed to reestablish balance following the trip (i.e., it prevented a fall from occurring). One transtibial amputee completed repeated walking trials in which a trip was induced around 1 out of 15 times to avoid it being anticipated. 3D kinematics were determined via two smartphones (60Hz) using the OpenCap software, highlighting that the experimental approach induced meaningful tripping/recovery responses dependent on which limb was tripped (prosthetic or sound). The presented methodology avoids using a rigid obstacle, potentially reducing the risk of injuries, and is inexpensive and easy to set up. Importantly it permits a trip to be unexpectedly introduced during the mid-swing phase of the gait and hence provides an approach for identifying real-world trip recovery responses. When tripping the sound limb, participants could 'disentangle' from the trip-wire (post-trip) by plantarflexing the ankle, but such action was not possible when tripping the prosthetic limb.

Introduction

It has been estimated that 57.7 million people worldwide live with limb amputation, of which ~ 65% occur in the lower limbs¹. Lower limb amputation may derive from several factors (e.g., acute traumatic events, disease progression, health complications, life-saving surgery, and congenital deformity). It has been associated with high mortality and morbidity rates for those with poor health conditions². In addition, mobility reestablishment after amputation is crucial to regaining independent living and life quality and is one of the most significant challenges for prosthesis users³.

Protocol

The University's ethics committee approved procedures, and the participant signed an informed consent form before participating.

1. Participant

NOTE: One Transtibial (TTA) amputee attending a local amputee rehabilitation center was invited and agreed to participate in the study. The participant was able to walk independently. Exclusion criteria were clinical conditions other than their amputation that could affect balance and mobility (e.g., neurological, orthopedic, or rheumatic disorders); ongoing pain, phantom pain, or pressure sores on the prosthetic limb, and difficulties understanding sim....

Results

The safety harness system was assumed to cause no interference in walking and proved effective in preventing falling when trip recovery strategies were unsuccessful. In addition, no injuries (e.g., skin abrasions, bruising) were reported. The noise generated by the release of the spring was not considered an intervening factor since the participants did not prevent tripping from occurring. Furthermore, the time between the instant the system was activated and the impact with the wire was around 60 ms. Thus, it was assume.......

Discussion

Although the present protocol brings preliminary results of an experiment designed to describe a trip protocol applied on a transtibial amputee, such an approach can also be safely applied to other amputees, e.g., transfemoral amputees, who are likely to have greater difficulties in recovering balance after a trip. The approach allowed the identification of the most pronounced actions executed to regain balance in response to an unexpectedly induced trip. The protocol can generally be deemed replicating real-world trippi.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Electromagnetic plates	Intelbras	https://www.intelbras.com/en/set-of-supports-with-electro-magnetic-lock-fe-150-kt-741-prata	Two electromagnetic plates (a fixed and a movable)
Full body safety harness	Generic	N/A	Safety rope 11 mm attached on a rail running 2 m above the head of the participants
Impact Goggle	Generic	N/A	One goggles with lower and side end closures
Insulator tape	3M	https://www.3m.com/3M/en_US/p/c/tapes/electrical/ptfe/	Used to obstruct vision at the lower and side edges of goggles
Open Pose	OpenPose	https://github.com/CMU-Perceptual-Computing-Lab/openpose	Open Pose is a open Software to movement analysis https://github.com/CMU-Perceptual-Computing-Lab/openpose
Open Sim	OpenSim	https://simtk.org/projects/opensim/	OpenSim is a softwware to analyse several movement parameters https://simtk.org/projects/opensim/
Polypropilene Wire	Generic	N/A	4 mm diameter
Triger system	Generic	N/A	The trigger system was home-made device, formed by a spring that pulls a lever that raises the wire approximately 10cm above the ground level
Video camera	Apple	https://apple.com	The video cameras of two smartphones (apple model 8 and 11) were used.