The Benefits of Body Power

Current upper-limb prosthetic options can be divided into four categories: functional aesthetic, activity specific, body powered, and externally powered or bionic. Body-powered devices can be further subdivided into categories based on operational mode, either voluntary opening (VO) or voluntary closing (VC), and design and configuration, hook, prehensor, or hand. Body-powered prostheses are simpler and lighter. They are also more affordable, therapeutic, functional, and reliable than most bionic alternatives. They also are typically less cosmetic than functional aesthetic options. Compared fairly in activities requiring rigorous, bimanual and bilateral performance, modern VC prehensor technology will outperform bionic hands or terminal devices (TDs). This technology also outperforms all VO systems and functional aesthetic prostheses. Body power captures musculoskeletal energy through efficient harness and cabling systems. VO systems often use this energy to power split hooks, which are reliable self-grasping tools, albeit with limited gripping force. VO hooks are excellent assistive aids, while VO hands have mostly been replaced by myoelectric options. Modern VC prehensors capture and multiply body energy into prosthetic function. Adult males can generate from a few ounces to more than 100 pounds of maximum grip force with VC prehensors, equivalent to an able-bodied adult male. Prostheses with this gripping force improve bimanual functional capability. VC prehensors are over 90 percent efficient compared to other body-powered systems that rarely generate more than 15 pounds of force. Bionic technology can provide only about 50 pounds of maximum prehension. Because body-powered devices do not rely on battery power, are not susceptible to the same level of concerns about damage or destruction caused by physical trauma or moisture, and have little need for repair or maintenance downtime, they are an excellent primary choice for the majority of individuals with a single-hand absence, particularly those with unilateral transradial amputations. Body power is also far less expensive, costing only 15-20 percent of bionic technology to purchase and maintain. Why, then, are body-powered devices prescribed less often than bionic? I venture that it's because the patient and many healthcare professionals believe that bionic is the best, most functional technology available and that body power is mostly looked upon as inferior. That assumption is flawed. Furthermore, the majority of individuals who have newly acquired hand loss are encouraged to use bionics. Historically, patients were first trained with body-powered prostheses to ensure they were good candidates for more advanced technology. In reality, body-powered devices provide cost-effective, comprehensive rehabilitation outcomes. It is still far less expensive to provide a high-performance, body-powered VC prosthesis and one or more activity-specific prostheses than it is to provide a single bionic limb. The case for modern, body-powered prostheses in the 21st century is viable and strong. Expect to see more exciting options in body-powered and activity-specific technology in the future. Robert "Bob" Radocy, MS, is the president and CEO of TRS, Boulder, Colorado. He earned a master of science degree in physical education and recreation from the University of Colorado, Boulder.

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Related posts:

High School Student Creates Prosthetic Hand

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Certified Prosthetist / Prosthetist-Orthotist (CP/CPO) Gates Prosthetics + Mobility Clinic — Mountain Home, AR

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