Targeted Muscle Reinnervation-an Up-to-Date Review: Evidence, Indications, and Technique

Abstract

Targeted muscle reinnervation (TMR) is a surgical technique originally created to improve prosthetic function following upper extremity amputation. TMR has since been shown to be effective in the prevention and treatment of chronic postamputation phantom and residual limb pain in both upper and lower extremity amputees and for neurogenic pain in the nonamputee patient population. This article provides a current review of the various indications for TMR and surgical techniques, organized by amputation site, timing, and regional anatomy.

Keywords: myoelectric prosthesis; nerve transfers; painful neuromas; targeted muscle reinnervation.

Fig. 1

Example of delayed shoulder TMR for myoelectric prosthesis control. The patient is a 42-year-old male with a previous right upper extremity trauma complicated by infection requiring shoulder disarticulation who presented with no pain but poor myoelectric prosthetic control. Of note, a pedicled latissimus muscle flap was previously required for soft tissue coverage and preop findings were as follows: triceps 0/5, deltoid 1 to 2/5, remnant proximal biceps 2/5, latissimus muscle flap 2/5 (retained voluntary contracture). ( A ) demonstrates the planned incision two finger-breadths below the clavicle medial to sternal notch then laterally and inferiorly along deltopectoral groove. ( B, C ) demonstrate the nerves dissected and ready for transfer to motor targets with Video 1 displaying the target motor nerve being stimulated. ( D ) demonstrates the coaptations performed with 7–0 prolene in end-to-end epineural fashion: (1) MCN to the motor branch of the clavicular head of pec major (elbow flexion), (2) median nerve to lateral pectoral nerve (medial and upper sternal head of pec major muscle; hand close), (3) radial nerve to medial pectoral nerve (lower lateral pec major sternal head; elbow extension and finger/thumb extension), (4) ulnar nerve to thoracodorsal nerve (not shown in the figure). ( E ) A medially based, pedicled adipofascial flap was raised and inset ( F ) between the clavicular and sternal heads of the pec major to buffer signaling of elbow flexion (MCN to clavicular head) and elbow extension (radial to sternal head) for the surface electrodes. MCN, musculocutaneous nerve; TMR, targeted muscle reinnervation.

Fig. 2

Example of delayed BKA-TMR performed via a prone and supine approach. The patient is a 45-year-old man status post-right traumatic BKA 4 years prior who presented with symptomatic neuromas and phantom limb pain. Nerve transfers were first performed in prone positioning through the popliteal fossa. ( A ) displays the patient in the prone position with a planned incision using the fibular head as a guide. ( B ) displays the TN dissected with vessel loops around motor nerve targets. ( C ) displays the CPN dissected out with LSN. ( D ) displays the coapted nerve transfers (1) TN to the motor branch of FHL, (2) CPN to the motor branch of soleus, (3) MSN to the motor branch medial gastrocnemius, and (4) LSN to the motor branch lateral gastrocnemius. ( E ) Displays the patient now positioned supine with motor and sensory nerve targets dissected. Video 2 displays the nerve stimulator on the motor targets. ( F, G ) Display the coapted nerve transfers (5) SN to motor branch vastus medialis, (6) MFCN to motor branch to sartorius. BKA, below-knee amputation; CPN, common peroneal nerve; FHL, flexor hallucis longus; LSN, lateral sural nerve; MFCN, medial femoral cutaneous nerve; MSN, medial sural nerve; SN, saphenous nerve; TMR, targeted muscle reinnervation; TN, tibial nerve.

Fig. 3

Example of delayed hand TMR. The patient is a 62-year-old female who suffered an avulsion amputation of the right thumb with failed replantation at an outside hospital, now status post multiple debridements and skin grafting with a symptomatic neuroma of the digital nerve to the thumb. ( A, B ) Displays the markings for the simultaneous open carpal tunnel release to easily access the thenar motor branch of the median nerve and the skin flaps that will be raised. Her first metacarpal was also noted to be prominent and painful, so this was also debrided (circular region). ( C ) Displays the dissected common digital nerve to thumb after distal transection to healthy fascicles and thenar motor branch (vessel loop). Video 3 demonstrates the thenar motor branch being stimulated. ( D ) Displays approximation of the common digital nerve to thumb and thenar motor branch just prior to coaptation. TMR, targeted muscle reinnervation.

Fig. 4

Example of acute TMR of the GON performed immediately following an oncologic resection in a middle-aged woman. ( A ) Demonstrates the lipomatous tumor resected by surgical oncology with ( B ) GON dissected and skeletonized (arrow) with the retractor assisting with visualization of the deeper motor compartments of the posterior neck for target motor nerve branches to accept the coaptation. Video 4 displays the dissection and demonstrates checkpoint stimulation of the target motor nerve to semispinalis capitis. ( C ) Closure of the muscle compartments after TMR. GON, greater occipital nerve; TMR, targeted muscle reinnervation.