Movement quality of conventional prostheses and the DEKA Arm during everyday tasks

Abstract

Background: Conventional prosthetic devices fail to restore the function and characteristic movement quality of the upper limb. The DEKA Arm is a new, advanced prosthesis featuring a compound, powered wrist and multiple grip configurations.

Objectives: The purpose of this study was to determine if the DEKA Arm improved the movement quality of upper limb prosthesis users compared to conventional prostheses.

Study design: Case series.

Methods: Three people with transradial amputation completed tasks of daily life with their conventional prosthesis and with the DEKA Arm. A total of 10 healthy controls completed the same tasks. The trajectory of the wrist joint center was analyzed to determine how different prostheses affected movement duration, speed, smoothness, and curvature compared to patients' own intact limbs and controls.

Results: Movement quality decreased with the DEKA Arm for two participants, and increased for the third. Prosthesis users made slower, less smooth, more curved movements with the prosthetic limb compared to the intact limb and controls, particularly when grasping and manipulating objects.

Conclusion: The effects of one month of training with the DEKA Arm on movement quality varied with participants' skill and experience with conventional prostheses. Future studies should examine changes in movement quality after long-term use of advanced prostheses. Clinical relevance Movement quality with the DEKA Arm may depend on the user's previous experience with conventional prostheses. Quantitative analyses are needed to assess the efficacy of novel prosthetic devices and to better understand how to train people to use them effectively.

Keywords: Biomechanics in neuromuscular disorders; prosthetic design; testing of prosthetic and orthotic components; upper limb prosthetics.

Figure 1

Reach trajectory and speed. Unilateral (CAN) reaches are shown for one representative trial of each participant with the intact arm, DEKA Arm, and conventional prosthesis (Conv): (a) three-dimensional (Anterior–posterior: AP, Mediolateral: ML, Vertical) reach trajectories are shown from the beginning (dot) to end (x) of the reach phase. Note that for intact, right arm reaches, the ML axis has been reversed to match the left arm reaches. (b) Movement speed profiles are shown from the beginning of the reach until the end of the grasp phase. A long tail in the velocity profile represents a prolonged grasping phase. Intact arm reaches have no tails, indicating tight coupling between reaching and grasping.

Figure 2

Average non-dimensional jerk during reaches to (a) CAN and (b) BOX for each prosthesis user and for healthy controls. Error bars represent the standard deviation.

Figure 3

Average index of curvature during reaches to (a) CAN and (b) BOX for each prosthesis user and for healthy controls. Error bars represent the standard deviation.

Figure 4

Average number of submovements during the grasping phase of the (a) CAN and (b) BOX tasks for each prosthesis user and for healthy controls. Error bars represent the standard deviation.

Figure 5

Average number of submovements during the uncapping phase of the DEO task for each prosthesis user and for healthy controls. Error bars represent the standard deviation.