Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment.
Wolf Schweitzer, Michael J Thali, David Egger
PMID 29298708WHAT IT FOUND
For one forensic pathologist with below-elbow amputation, a customized body-powered arm supported heavy, sweaty, slippery work better than a myoelectric iLimb.
This is one person's experience, not proof either arm works.
Key findings
01For this one user, the customized body-powered arm was described as more reliable, comfortable, powerful, light-weight, cost-effective and needing less maintenance than the myoelectric arm.
02The myoelectric arm lost electrode control after 10 minutes with sweat exposure and developed electrode rashes that healed slowly over about 6 weeks.
03The user-designed shoulder anchor shifted pressure away from the brachial plexus and reduced the arm extension needed to actuate the gripper from around 12-15 cm to around 5 cm.
STILL TO COME
How it was doneWhat they foundWhat it means for OTs
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What it does not show
This is a case report of one person, who was also the author and developer of the arm, so it cannot show that the result applies to other amputees. The body-powered arm included several changes at once, including socket, cable, wrist, shoulder anchor, liner layering and terminal devices, so the contribution of any single component cannot be separated. The myoelectric arm was not redesigned in the same way, and many failures were attributed to inherent technology or manufacturer restrictions, so the comparison is not like-for-like. The work setting was extreme, with heavy slippery bodies, sweat, cold temperatures, long deployments and hazardous conditions, so it may not match lighter occupations. Outcome judgments were partly subjective, including manual skill level and sweat ratings, and no previously published academic tests were used.
Declared interests
The first author, Wolf Schweitzer, self-funded the work. Insurance funded body-powered and myoelectric technology, custom liners, a shoulder brace and custom wrists. The first author also privately invested about 6'000 CHF in myoelectric trials and 2'000 CHF in body-powered components. He was the user and developer.
The easy way to misread this
Do not conclude that a body-powered arm is proven better for physically demanding work. This is one person's case report, and the working arm combined a custom socket, cable system, wrist, shoulder anchor, liner layering and interchangeable terminal devices, so the contribution of any single component cannot be separated.