Abstract
BackgroundProsthetic arm research predominantly focuses on “bionic” but not body-powered arms. However, any research orientation along user needs requires sufficiently precise workplace specifications and sufficiently hard testing. Forensic medicine is a demanding environment, also physically, also for non-disabled people, on several dimensions (e.g., distances, weights, size, temperature, time).MethodsAs unilateral below elbow amputee user, the first author is in a unique position to provide direct comparison of a “bionic” myoelectric iLimb Revolution (Touch Bionics) and a customized body-powered arm which contains a number of new developments initiated or developed by the user: (1) quick lock steel wrist unit; (2) cable mount modification; (3) cast shape modeled shoulder anchor; (4) suspension with a soft double layer liner (Ohio Willowwood) and tube gauze (Molnlycke) combination. The iLimb is mounted on an epoxy socket; a lanyard fixed liner (Ohio Willowwood) contains magnetic electrodes (Liberating Technologies). An on the job usage of five years was supplemented with dedicated and focused intensive two-week use tests at work for both systems.ResultsThe side-by-side comparison showed that the customized body-powered arm provides reliable, comfortable, effective, powerful as well as subtle service with minimal maintenance; most notably, grip reliability, grip force regulation, grip performance, center of balance, component wear down, sweat/temperature independence and skin state are good whereas the iLimb system exhibited a number of relevant serious constraints.ConclusionsResearch and development of functional prostheses may want to focus on body-powered technology as it already performs on manually demanding and heavy jobs whereas eliminating myoelectric technology’s constraints seems out of reach. Relevant testing could be developed to help expediting this. This is relevant as Swiss disability insurance specifically supports prostheses that enable actual work integration. Myoelectric and cosmetic arm improvement may benefit from a less forgiving focus on perfecting anthropomorphic appearance.
Highlights
Prosthetic arm research predominantly focuses on “bionic” but not body-powered arms
We found that optimal usage entailed a relatively frequent switch of terminal devices, most notably between the voluntary closing (VC) and voluntary opening (VO) control type
Trying to build a prosthetic arm that works for work in forensic medicine taught us a number of things about current technology and its potential
Summary
Prosthetic arm research predominantly focuses on “bionic” but not body-powered arms. Any research orientation along user needs requires sufficiently precise workplace specifications and sufficiently hard testing. Work specific tasks [1] invariably define specific functional requirement profiles for workers (including prosthetic arms) [2]. Within body-powered control systems, voluntary opening (VO) and voluntary closing (VC) devices offer different profiles [5]. Assessment of current state and developments of prosthetic arms presented here has one particular aim. That aim is to enable the first listed author of this paper to keep working, at the front, within one of the most modern forensic pathology institutes and projects [6]. Since 2008, the first author develops, tests and refines solution oriented prosthetic arm components (as detailed in this case study)
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