Otto Bock body-powered elbow

Backlocks are also found in some prosthetic elbows (Boston Elbow 111, LTI Otto Bock Body-Powered Elbow) as a means of holding elbow position in the absence of a drive torque. This ability allows users to park their prosthetic arm at any desired position and then remove (decouple) themselves from the arm s control. 

The Otto Bock Body-Powered Elbow mechanism uses a springlike clamp that locks down on a shaft when twisted in one direction but opens to release a shaft when twisted in the other. This is a unidirectional mechanism whose main advantage is simplicity. A similar mechanism can be found in some children s bicycles, where the child backpedals to brake the bike. A disadvantage of this type of mechanism is that over time the lock can slip because of wear and tear on the spring on the elbow shaft. 

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