Insufficient degrees of freedom in prosthetic wrist joints force users to make compensatory movements, which can result in residual limb pain and overuse syndromes. A new study’s findings indicate that the optimal compliance for a prosthetic wrist is specific to the phase of the motor task: a compliant wrist outperformed a stiff wrist during the reaching phase, whereas a stiff wrist exhibited more natural movements during the manipulation phase of heavy objects. Based on the results, the study’s authors encourage development of prosthetic wrists with switchable compliance.
The research team from the BioRobotics Institute of the Scuola Superiore Sant’Anna, Pontedera, Italy, hypothesized that a transradial prosthesis would allow simpler operation if its wrist were compliant during the reaching and grasping phase, and stiff during the holding and manipulation phase. To assess the hypothesis, the researchers compared a stiff and a compliant wrist while evaluating the extent of compensatory movements in the participants’ trunks and shoulders. The unimpaired participants used orthoses as they performed nine activities of daily living from the Southampton Hand Assessment Procedure.
The study was published in the July issue of IEEE Transactions on Neural Systems and Rehabilitation Engineering.
