Evaluating the Ability of Congenital Upper Extremity Amputees to Control a Multi-Degree of Freedom Myoelectric Prosthesis
Michael S. Gart, MD1, Brian Kaluf, CP, FAAOP2, Bryan J. Loeffler, MD1 and R. Glenn Glenn Gaston, MD1, (1)OrthoCarolina, Charlotte, NC, (2)Ability Prosthetics & Orthotics, Charlotte, NC
INTRODUCTION
Patients with congenital upper extremity amputations can generate the signals necessary to accurately control a multi-degree of freedom (DOF) myoelectric prosthesis despite never having learned to use their distal upper extremity.
METHODS
Patient records from a hand surgery clinic were screened for eligibility. Patients 8 years of age with unilateral, congenital transradial amputations were included. Patients with any inability to comply with the testing protocol (cognitive or visual impairment, non-English speaking) were excluded. A handheld electromyography unit with a graphical user interface (GUI) displayed on a laptop was used to record myoelectric signals and calibrate a pattern recognition control strategy. The complexity of control was increased incrementally from one to three DOF. The accuracy of the pattern recognition calibration and performance on a virtual Target Achievement Control (TAC) test were recorded as a percentage and as a ratio of successfully completed tasks/total tasks, respectively. The sound limb was tested first to control for ability to complete the testing protocol and to generate a paired sample data set with the congenital residual limb performance. Calibration accuracies for all patients were averaged by limb for one, two, and three DOF. Number of successfully completed tasks were averaged for all patients by limb and reported as the average number completed/total number of tasks.
RESULTS
Seven patients have completed the study protocol (average age 23.9 years). Average calibration accuracy for the pattern recognition control was 87.5%, 86.1%, and 83.1% for the sound limb and 88.1%, 88.1%, and 78.1% for the congenital residual limb using a one DOF, two DOF, and three DOF virtual prosthesis, respectively. The average completion rate on the TAC test was 0.86/1, 2.86/3, and 2.27/4 for the sound limb and 0.86/1, 2.71/3, and 3.00/4 for the congenital residual limb using a one DOF, two DOF, and three DOF virtual prosthesis, respectively. At three DOF, each patient's congenital residual limb matched or exceeded his/her sound limb on TAC testing.
CONCLUSIONS
Congenital upper extremity amputees are able to generate the signals necessary to control a multi-degree of freedom myoelectric prosthesis with accuracy comparable to their sound limb despite never learning to use their distal upper extremity. At three degrees of freedom, target achievement control testing demonstrated improved performance with the congenital residual limb compared with the sound limb. This preliminary research demonstrates congenital upper extremity amputees have the capacity to control modern myoelectric prostheses and may expand their options for prosthetic rehabilitation.
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