The influence of control format and hand design in single axis myoelectric hands: assessment of functionality of prosthetic hands using the Southampton Hand Assessment Procedure.

BACKGROUND

It is important to measure the functional capabilities of a prosthesis in order to make informed decisions when prescribing a limb.

OBJECTIVES

To measure the functional of a range of commercial single degree of freedom hands to act as baseline comparisons for the newer multi-axis hands.

STUDY DESIGN

Form-board and self-timed tasks.

METHOD

Repeated measures with a single subject using a validated assessment tool. The test measured the function of three conventional, single axis, powered hands, controlled by five different myocontroller formats. One transcarpal device was also tested.

RESULTS

When controlled by the same type of two channel myoelectric controllers (proportional voluntary opening, voluntary closing) the overall functional scores were similar for all similar types of hand, with a maximum score of 94 out of 100. The smaller transcarpel hand had a score of 84. Only when a more limited single channel three state controller was used was the score much lower (81).

CONCLUSION

All of the hands were of a similar design and were set in a precision grip, but the precision grip did not achieve the highest individual grip score. Additionally, while the Southampton Hand Assessment Procedure (SHAP) score is dependent on the speed of execution of the task, the speed of the prosthesis did not have as great an impact on the score as the other variables.

CLINICAL RELEVANCE

This study provides comparative data between similar designs of commercial hands. This will allow clinicians to be better informed when they prescribe a device for a user.