Clinical Context of Nerve Fascicle Transfer for Brachial Plexus Injury

Upper brachial plexus injuries involving the C5, C6, and occasionally C7 nerve roots frequently cause profound upper limb disability. Most commonly, high-energy traction injuries from motorcycle trauma disrupt the motor pathways controlling shoulder abduction and elbow flexion. Restoring active elbow flexion represents the primary functional objective in these reconstructive cases. Traditionally, surgeons relied upon lengthy supraclavicular nerve autografts. However, long regeneration distances often caused motor endplate degeneration before reinnervation could occur. Consequently, distal nerve fascicle transfer has transformed surgical reconstruction by delivering donor axons directly adjacent to target motor branches. Christophe Oberlin established this modern paradigm by transferring an ulnar nerve motor fascicle to the biceps motor branch. This technique achieved reliable motor recovery without causing donor deficits. Subsequently, investigators explored the median nerve as an alternative fascicular donor. Because both nerves originate from preserved lower trunk roots (C8-T1), surgeons can safely spare crucial hand motor function. Therefore, peripheral nerve surgeons increasingly perform distal fascicular neurotization to accelerate functional recovery. However, high-level prospective randomized evidence comparing the ulnar and median nerves has remained limited until recently.

Study Design and Surgical Randomization Protocol

To establish clinical equivalence, a prospective randomized clinical trial compared median and ulnar fascicle transfers directly. The surgical trial evaluated fifty consecutive patients treated between June 2013 and December 2018. All participants presented with documented traumatic C5-C6 or C5-C7 brachial plexus injuries requiring biceps motor reinnervation. Before surgery, investigators randomly allocated patients to receive either an ulnar nerve fascicle or a median nerve fascicle transfer. During the surgical exploration, microsurgeons applied intraoperative electrical nerve stimulation to confirm donor viability. Specifically, the surgical protocol required robust motor responses in the donor territories before coaptation. The surgical team excluded twelve patients intraoperatively because electrical stimulation demonstrated unequal fascicular conductivity between nerves. In addition, investigators excluded five patients who did not complete the required six-month postoperative follow-up. Consequently, thirty-three patients met all rigorous criteria for the final cohort analysis. The ulnar nerve fascicle transfer cohort comprised eighteen patients. Meanwhile, the median nerve fascicle transfer cohort included fifteen patients. All operative procedures maintained identical microvascular neurolysis and tension-free direct epineurial suturing techniques.

Comparative Functional Outcomes in Antigravity Elbow Flexion

Clinicians primarily assessed postoperative motor recovery by evaluating active elbow flexion against gravity. In the ulnar nerve cohort, fourteen out of eighteen patients, representing 78 percent, achieved successful antigravity elbow flexion. Similarly, the median nerve transfer group demonstrated excellent outcomes, with thirteen of fifteen patients, or 87 percent, restoring antigravity strength. Statistical analysis confirmed no significant difference between the two donor groups, with a p-value of 0.665. Furthermore, both surgical cohorts exhibited smooth postoperative recovery without catastrophic loss of distal hand motor strength. Clinicians observed that motor reinnervation occurred across comparable postoperative timelines in both cohorts. In addition, root involvement patterns (C5-C6 versus C5-C7 lesions) did not alter functional success rates when lower trunk donors remained healthy. Therefore, the data demonstrate that median nerve fascicles provide functional reinnervation equivalent to traditional ulnar transfers. Consequently, reconstructive surgeons can confidently select either donor nerve based on intraoperative conditions rather than perceived efficacy disparities.

Intraoperative Decision-Making and Donor Selection

Selecting the optimal donor fascicle requires meticulous microsurgical dissection and neurophysiological confirmation. During upper arm exposure, surgeons carefully identify the biceps motor branch originating from the musculocutaneous nerve. Next, the surgeon exposes adjacent median and ulnar nerve trunks within the medial bicipital groove. Microsurgeons utilize handheld intraoperative nerve stimulators to isolate expendable motor fascicles. Typically, ulnar fascicles innervating the flexor carpi ulnaris provide suitable motor donors. Alternatively, median nerve fascicles innervating the pronator teres or flexor carpi radialis serve as reliable donor sources. In this trial, twelve patients demonstrated uneven electrical responses, requiring surgeons to alter the randomized donor. Therefore, real-time electrical threshold testing remains indispensable during every reconstructive procedure. If one donor nerve exhibits diminished conduction or subtle stretch injury, surgeons should pivot immediately to the healthier alternative nerve. Moreover, this flexibility prevents reconstructive failure caused by undetected subclinical donor trauma. Ultimately, thorough intraoperative evaluation ensures predictable reinnervation while protecting intrinsic hand function.

Clinical Implications for Reconstructive Peripheral Nerve Surgery

These findings provide clear guidance for reconstructive hand and peripheral nerve surgeons managing severe plexus trauma. Historically, many centers relied almost exclusively on the classic Oberlin ulnar fascicle transfer. However, proving equivalence for median fascicle transfers expands surgical versatility significantly. When local scar tissue, direct trauma, or anatomical variations complicate ulnar nerve dissection, the median nerve offers an equal alternative. Furthermore, these findings reinforce the biological foundation of the double fascicular transfer technique. In double transfers, surgeons simultaneously neurotize the biceps and brachialis muscles using median and ulnar fascicles together. Because both individual transfers yield robust motor recovery, surgeons can deploy either fascicle with complete confidence. Additionally, early surgical intervention within six to nine months remains critical for success in traumatic brachial plexus reconstruction. Delayed referral allows progressive motor endplate loss, which impairs functional outcomes regardless of donor selection. Consequently, timely surgical intervention and adaptable donor fascicle selection produce optimal long-term functional recovery.

Frequently Asked Questions

What are the primary donor nerves for elbow reinnervation?

Surgeons primarily use expendable motor fascicles from the ulnar nerve or median nerve to restore active elbow flexion. Specifically, the classic Oberlin procedure transfers a flexor carpi ulnaris fascicle from the ulnar nerve into the biceps motor branch. Alternatively, surgeons transfer a flexor carpi radialis fascicle from the median nerve. Both techniques provide robust motor axons close to the target muscle, ensuring rapid, reliable functional recovery without sacrificing crucial hand motor power.

Does median nerve transfer cause donor site hand weakness?

Carefully performed median nerve fascicle transfer does not cause permanent hand weakness or functional impairment. Peripheral nerves possess internal redundancy, meaning redundant fascicles supply extrinsic forearm flexors. Surgeons utilize intraoperative electrical stimulation to identify redundant motor branches innervating the flexor carpi radialis or pronator teres. Consequently, harvesting an individual redundant fascicle leaves essential hand grasp and median sensory distribution fully intact. Patients typically retain complete forearm pronation and strong wrist flexion postoperatively without measurable functional deficits.

When should reconstructive surgeons consider double fascicular transfer?

Surgeons frequently consider double fascicular transfer when reconstructing complete elbow flexion paralysis in high-demand patients. This advanced technique combines an ulnar fascicle transfer to the biceps branch with a median fascicle transfer to the brachialis branch. Consequently, dual reinnervation of both major elbow flexors provides greater mechanical power and endurance than single-nerve neurotization. However, if intraoperative nerve stimulation reveals weakness in either donor trunk, surgeons should perform a single fascicular transfer using the healthiest donor.

Disclaimer: This content is for informational and educational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read here. Refer to the latest local and national guidelines for clinical practice.

References

1. Cho ÁB et al. A Prospective Randomized Comparison of Median and Ulnar Fascicle Transfers to the Biceps Motor Branch in Upper Brachial Plexus Injury. Hand (N Y). 2026 Oct 12. doi: 10.1177/15589447261487493. PMID: 42861488.


2. Oberlin C, Béal D, Leechavengvongs S, Salon A, Dauge MC, Sarcy JJ. Nerve transfer to biceps muscle using a part of ulnar nerve for C5-C6 avulsion of the brachial plexus: anatomical study and report of four cases. J Hand Surg Am. 1994;19(2):232-237.


3. Mackinnon SE, Novak CB, Myckatyn TM, Tung TH. Results of reinnervation of the biceps and brachialis muscles with a double fascicular transfer for elbow flexion. J Hand Surg Am. 2005;30(5):978-985.


4. Ray WZ, Mackinnon SE. Management of nerve gaps: autografts, allografts, nerve transfers, and end-to-side neurorrhaphy. Exp Neurol. 2010;223(1):77-85.