High Cable Forces Deteriorate Pinch Force Control in Voluntary-Closing Body-Powered Prostheses

Abstract

BackgroundIt is generally asserted that reliable and intuitive control of upper-limb prostheses requires adequate feedback of prosthetic finger positions and pinch forces applied to objects. Body-powered prostheses (BPPs) provide the user with direct proprioceptive feedback. Currently available BPPs often require high cable operation forces, which complicates control of the forces at the terminal device. The aim of this study is to quantify the influence of high cable forces on object manipulation with voluntary-closing prostheses.MethodAble-bodied male subjects were fitted with a bypass-prosthesis with low and high cable force settings for the prehensor. Subjects were requested to grasp and transfer a collapsible object as fast as they could without dropping or breaking it. The object had a low and a high breaking force setting.ResultsSubjects conducted significantly more successful manipulations with the low cable force setting, both for the low (33% more) and high (50%) object’s breaking force. The time to complete the task was not different between settings during successful manipulation trials.ConclusionHigh cable forces lead to reduced pinch force control during object manipulation. This implies that low cable operation forces should be a key design requirement for voluntary-closing BPPs.

Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment

“…For work with occupational heat exposure, biological or chemical hazards, large weights or widely ranging ambient temperatures, there is no other technology. Development of body-powered technology currently is only conducted by a small number of individuals and groups (e.g., Randall Alley [ 147 , 148 ], Bob Radocy [ 40 , 149 ], Bradley Veatch [ 74 , 150 , 151 ], Dick Plettenburg’s group [ 152 – 156 ], Aaron Dollar’s group [ 157 ] and John Sensinger’s group [ 158 ]).…”

“…But actual motor skills including fine motor skills are acquired only by sufficiently specific and sufficiently extensive training [ 165 , 166 ]. To no surprise, absent proficiency of large shoulder and trunk muscles to perform fine grasps with a body-powered control in untrained non-amputees causes their control attempts to deteriorate at higher pinch forces in a study that makes a great case for training [ 156 ]. Also, absent sufficient specific training appeared to be the reason of fatigue in most non-using amputees when trying out body-powered arms, whereas the only actual daily user of a body-powered arm in that case series did not exhibit any significant restriction (study subject number seven [ 167 ]).…”

Characterizing the Force-Motion Tradeoff in Body-Powered Transmission Design

“…However, users of BP prostheses still express a lack of satisfaction with their devices [3]. A major component is the high forces required from the user to operate the prosthesis, which leads to dissatisfaction [7] as well as worsened force control and fatigue concerns [19], [20].…”

Reimagining Prosthetic Control: A Novel Body-Powered Prosthetic System for Simultaneous Control and Actuation

“…The high operation forces for BP prostheses contribute to their relatively high rejection rates [15]. Apart from fatigue and pain as primary drawbacks, high cable operation forces have also been found to deteriorate pinch force control accuracy in voluntary closing (VC) prostheses [38]. Notably, Hichert et al [39] report that users of BP prostheses perceive and control low operation forces better than high forces.…”