Reverse End-to-Side (Supercharging) Nerve Transfer: Conceptualization, Validation, and Translation

Abstract

Partial nerve recovery either after expectant observation following an injury in-continuity or after nerve repair is not an uncommon occurrence. Historically, treatment strategies in these situations—late repair, revision repair, or acceptance of a mediocre result—were unsatisfying. The reverse end-to-side, or supercharging, nerve transfer was conceived to offer a more palatable option. Partially validated primarily through small animal research, supercharging has been rapidly translated to clinical practice. Many have extended the indications beyond the original intent, though the final place of this technique in the peripheral nerve surgeon’s armamentarium is still yet to be determined.

Reverse Shoulder Arthroplasty for Irreparable Rotator Cuff Tear After Radial to Axillary End-to-Side Transfer

“…It is well-recognized that delay in surgical intervention is an independent risk factor for poor outcomes because of irreversible changes in axonal regenerative capacity and motor endplate degradation known as end-stage muscle denervation that begins to occur as early as 3 months 12,31 . Absence of any recovery at 6 months suggests higher-grade injury with limited potential for recovery, and surgical intervention is reasonable after discussion with the patient 3,12,32 . This was our patient's situation, and he elected for both neurolysis and radial-to-axillary RETS transfer.…”

“…While 70% to 80% of low-grade neuropraxic or axonotmetic axillary nerve injuries will spontaneously resolve over many months, those that do not demonstrate any recovery, as in our case, may require surgical intervention to do so 3,4,30 . It is well-recognized that delay in surgical intervention is an independent risk factor for poor outcomes because of irreversible changes in axonal regenerative capacity and motor endplate degradation known as end-stage muscle denervation that begins to occur as early as 3 months 12,31 . Absence of any recovery at 6 months suggests higher-grade injury with limited potential for recovery, and surgical intervention is reasonable after discussion with the patient 3,12,32 .…”

“…While reverse shoulder arthroplasty (RSA) is the treatment of choice for severe cuff tear arthropathy 6-8 , it is historically contraindicated in the setting of deltoid compromise because of untenably poor outcomes including joint instability and limited range of motion 9,10 . In this report, we present the successful surgical management and return to activity of a 60-year-old patient with an irreparable cuff tear, glenohumeral osteoarthritis, and axillary nerve palsy through a staged approach with radial-to-axillary reverse end-to-side (RETS) “supercharging” 11 nerve transfer followed by RSA 12,13 .…”

Advancing glenohumeral dysplasia treatment in brachial plexus birth injury: the end-to-side spinal accessory to suprascapular nerve transfer technique

“…If intraoperative nerve stimulation at 0.5 mA demonstrates AMS scores of 4 or greater, no further surgery is performed — it is presumed that the child will recover function. If AMS scores of 4 or higher are only achieved with stimulation at 2 mA or greater, then a reverse ETS [ 21 ] of the suprascapular nerve with the spinal accessory nerve is performed (Fig. 4 ).…”

Muscle preservation in proximal nerve injuries: a current update

“…Supercharge end-to-side (SETS) neurotization is a surgical procedure that can theoretically restore the neurotrophic influence on the target muscles until their reinnervation (von Guionneau et al., 2021). Although their effectiveness has been experimentally proven (Daniel et al., 2022; Zavala et al., 2023), there are still some debates about its use in clinical practice (Davidge et al., 2015; Head et al., 2020; Isaacs, 2022). In particular, the widespread adoption of these ‘baby-sitting’ nerve transfers remains limited due to the lack of outcome standardization of such surgical interventions.…”