Targeted muscle reinnervation and advanced prosthetic arms

Abstract

Targeted muscle reinnervation (TMR) is a surgical procedure used to improve the control of upper limb prostheses. Residual nerves from the amputated limb are transferred to reinnervate new muscle targets that have otherwise lost their function. These reinnervated muscles then serve as biological amplifiers of the amputated nerve motor signals, allowing for more intuitive control of advanced prosthetic arms. Here the authors provide a review of surgical techniques for TMR in patients with either transhumeral or shoulder disarticulation amputations. They also discuss how TMR may act synergistically with recent advances in prosthetic arm technologies to improve prosthesis controllability. Discussion of TMR and prosthesis control is presented in the context of a 41-year-old man with a left-side shoulder disarticulation and a right-side transhumeral amputation. This patient underwent bilateral TMR surgery and was fit with advanced pattern-recognition myoelectric prostheses.

Keywords: amputation; prosthetic limb; shoulder disarticulation; targeted muscle reinnervation; transhumeral amputation.

Fig. 1

(A) Posterolateral view of angulation osteotomy in a transhumeral amputee. (B) X-ray of angulation osteotomy.

Fig. 2

Schematic of typical surgical plan for transhumeral targeted muscle reinnervation. (A) Anterior view. (B) Posterior view. Color-matched labels represent muscles and their source of innervation.

Fig. 3

Schematic of typical surgical plan for shoulder disarticulation targeted muscle reinnervation. Color-matched labels represent muscles and their source of innervation. In this example, the sternal head of pectoralis major is partitioned into two parts and reinnervated by the median and ulnar nerves.

Fig. 4

The case report patient with left shoulder disarticulation and right transhumeral amputation with loss of significant volar musculature. (A) Anteroposterior view. (B) Oblique view.

Fig. 5

Left chest with tissue expanders in place and planned latissimus rotation flap. Oblique views.

Fig. 6

Identification of ulnar, median, musculocutaneous, and radial nerves during left shoulder disarticulation targeted muscle reinnervation.

Fig. 7

Right transhumeral amputation neuromas.

Fig. 8

Right transhumeral amputation with healed free gracilis muscle transfer with overlying skin graft.

Fig. 9

Conventional myoelectric control for transhumeral amputation without targeted muscle reinnervation. Patients use an antagonistic muscle pair (biceps and triceps) to control each prosthetic degree of freedom. Therefore, for both elbow and hand mode, subjects produce an electromyographic signal (EMG) by attempting to move the lost elbow. To switch between elbow and hand modes, patients must signal a mode switch by cocontracting the biceps and triceps.

Fig. 10

Conventional myoelectric control for transhumeral amputation, with targeted muscle reinnervation. Patients use natively innervated biceps and triceps to control the elbow and reinnervated biceps and triceps to control the hand. Subjects produce an electromyographic signal (EMG) by attempting to move the corresponding joint in the lost limb. No mode switching is required.