Nerve-targeted surgical treatments for spasticity: a narrative review

Spasticity is a potentially debilitating symptom of various acquired and congenital neurologic pathologies that, without adequate treatment, may lead to long-term disability, compromise functional independence, and negatively impact mental health. Several conservative as well as non-nerve targeted surgical strategies have been developed for the treatment of spasticity, but these may be associated with significant drawbacks, such as adverse side effects to medication, device dependence on intrathecal baclofen pumps, and inadequate relief with tendon-based procedures. In these circumstances, patients may benefit from nerve-targeted surgical interventions such as (i) selective dorsal rhizotomy, (ii) hyperselective neurectomy, and (iii) nerve transfer. When selecting the appropriate surgical approach, preoperative patient characteristics, as well as the risks and benefits of nerve-targeted surgical intervention, must be carefully evaluated. Here, we review the current evidence on the efficacy of these nerve-targeted surgical approaches for treating spasticity across various congenital and acquired neurologic pathologies.

Current perspectives on peripheral nerve repair and management of the nerve gap

From the first surgical repair of a nerve in the 6th century, progress in the field of peripheral nerve surgery has marched on; at first slowly but today at great pace. Whether performing primary neurorrhaphy or managing multiple large nerve defects, the modern nerve surgeon has an extensive range of tools, techniques and choices available to them. Continuous innovation in surgical equipment and technique has enabled the maturation of autografting as a gold standard for reconstruction and welcomed the era of nerve transfer techniques all while bioengineers have continued to add to our armamentarium with implantable devices, such as conduits and acellular allografts. We provide the reader a concise and up-to-date summary of the techniques available to them, and the evidence base for their use when managing nerve transection including current use and applicability of nerve transfer procedures.

Impact of Upper Limb Motor Recovery on Functional Independence After Traumatic Low Cervical Spinal Cord Injury

Cervical spinal cord injury (SCI) causes devastating loss of upper limb function and independence. Restoration of upper limb function can have a profound impact on independence and quality of life. In low-cervical SCI (level C5-C8), upper limb function can be restored via reinnervation strategies such as nerve transfer surgery. The translation of recovered upper limb motor function into functional independence in activities of daily living (ADLs), however, remains unknown in low cervical SCI (i.e., tetraplegia). The objective of this study was to evaluate the association of patterns in upper limb motor recovery with functional independence in ADLs. This will then inform prioritization of reinnervation strategies focused to maximize function in patients with tetraplegia. This retrospective study performed a secondary analysis of patients with low cervical (C5-C8) enrolled in the SCI Model Systems (SCIMS) database. Baseline neurological examinations and their association with functional independence in major ADLs-i.e., eating, bladder management, and transfers (bed/wheelchair/chair)-were evaluated. Motor functional recovery was defined as achieving motor strength, in modified research council (MRC) grade, of ≥ 3 /5 at one year from ≤ 2/5 at baseline. The association of motor function recovery with functional independence at one-year follow-up was compared in patients with recovered elbow flexion (C5), wrist extension (C6), elbow extension (C7), and finger flexion (C8). A multi-variable logistic regression analysis, adjusting for known factors influencing recovery after SCI, was performed to evaluate the impact of motor function at one year on a composite outcome of functional independence in major ADLs. Composite outcome was defined as functional independence measure score of 6 or higher (complete independence) in at least two domains among eating, bladder management, and transfers. Between 1992 and 2016, 1090 patients with low cervical SCI and complete neurological/functional measures were included. At baseline, 67% of patients had complete SCI and 33% had incomplete SCI. The majority of patients were dependent in eating, bladder management, and transfers. At one-year follow-up, the largest proportion of patients who recovered motor function in finger flexion (C8) and elbow extension (C7) gained independence in eating, bladder management, and transfers. In multi-variable analysis, patients who had recovered finger flexion (C8) or elbow extension (C7) had higher odds of gaining independence in a composite of major ADLs (odds ratio [OR] = 3.13 and OR = 2.87, respectively, p < 0.001). Age 60 years (OR = 0.44, p = 0.01), and complete SCI (OR = 0.43, p = 0.002) were associated with reduced odds of gaining independence in ADLs. After cervical SCI, finger flexion (C8) and elbow extension (C7) recovery translate into greater independence in eating, bladder management, and transfers. These results can be used to design individualized reinnervation plans to reanimate upper limb function and maximize independence in patients with low cervical SCI.

An assessment of co-contraction in reinnervated muscle

Aim: To investigate co-contraction in reinnervated elbow flexor muscles following a nerve transfer. Materials & methods: 12 brachial plexus injury patients who received a nerve transfer to reanimate elbow flexion were included in this study. Surface electromyography (EMG) recordings were used to quantify co-contraction during sustained and repeated isometric contractions of reinnervated and contralateral uninjured elbow flexor muscles. Reuslts: For the first time, this study reveals reinnervated muscles demonstrated a trend toward higher co-contraction ratios when compared with uninjured muscle and this is correlated with an earlier onset of muscle fatigability. Conclusion: Measurements of co-contraction should be considered within muscular function assessments to help drive improvements in motor recovery therapies.

Combined contralateral C7 to C7 and L5 to S1 cross nerve transfer for treating limb hemiplegia after stroke

BACKGROUND

Contralateral C7 to C7 cross nerve transfer has been proved to be safe and effective for patients with spastic arm paralysis due to stroke and traumatic brain injury. For the lower limb, contralateral L5 to S1 cross nerve transfer serves as a novel surgical approach. In many cases, patients with hemiplegia have both upper and lower limb dysfunction and hope to restore all limb functions within one operation. To cope with this demand, we performed combined contralateral C7 to C7 and L5 to S1 cross nerve transfer in two cases successfully.

CASE DESCRIPTION

Two patients were enrolled in this study. The first patient is a 36-year-old woman who had spasticity and hemiplegia in both upper and lower limbs on the left side after a right cerebral hemorrhage 14 years prior. The second patient is a 64-year-old man who suffered from permanent muscle weakness in his right limbs, especially the leg, after a left cerebral hemorrhage 7 years prior. Both patients underwent the combined nerve transfer to improve upper and lower limb motor functions simultaneously. During the 10-month follow-up after surgery, the limb functions of both patients improved significantly.

CONCLUSIONS

This study demonstrates the safety and benefits of combined contralateral C7 to C7 and L5 to S1 cross nerve transfer for hemiplegic patients after stroke. This novel combined surgical approach could provide an optimal choice for patients suffering from both upper and lower limb dysfunction, to reduce hospital stay while reducing financial burden.

Delayed nerve reconstruction for brachial plexus injuries: is the risk worth the reward?

OBJECTIVE

Nerve reconstruction after 6 months of denervation time in brachial plexus injuries (BPIs) can be inconsistent. A dilemma exists when the use of critical donor nerves for nerve transfers may lead to unreliable outcomes that would waste the donor nerve. The purpose of this study was to evaluate the long-term outcomes of elbow and shoulder function in patients with BPIs receiving nerve reconstruction in the delayed setting (i.e., 6-12 months after injury).

METHODS

Data from patients with delayed BPIs who received a nerve transfer (including proximal and distal nerve transfer/grafting) at a tertiary medical center were retrospectively collected from January 1999 to March 2020. Demographics, extent of injury, mechanism of injury, and reconstructive methods were collected. Patients were categorized into two groups: non-pan-plexus BPI (C5-6, C5-7, and C5-8) and pan-plexus BPI (C5-T1). Acceptable outcome was defined as elbow flexion ≥ M3 status or shoulder abduction ≥ 60°.

RESULTS

Sixty-four patients were included in the study. The average time from injury to nerve reconstruction was 236 (range 180-441) days, and the average follow-up time was 66 months. In the non-pan-plexus BPI group (n = 43 patients), 74.4% of patients demonstrated M3 elbow flexion, and 48.8% of patients demonstrated M4 elbow flexion. Double fascicular transfer yielded better results and faster recovery than a single fascicular transfer. In the pan-plexus BPI group (n = 21 patients), 38.1% of patients reached M3 elbow flexion and 23.8% attained M4 elbow flexion. In the non-pan-plexus BPI group, the recovery rate of acceptable shoulder abduction was 53.5%, but only 23.5% of pan-plexus patients with BPI achieved acceptable shoulder abduction.

CONCLUSIONS

Nerve reconstruction can effectively restore functional elbow flexion and acceptable shoulder abduction in non-pan-plexus patients with BPI in the delayed setting. However, neither acceptable elbow flexion nor shoulder abduction could be consistently achieved in pan-plexus BPI. Judicious use of the donor nerves in pan-plexus injuries is required, in addition to preserving a donor nerve for a backup plan such as free-functioning muscle transplantation or tendon transfers.

The association between number of intercostal nerves transferred and elbow flexion: a systematic review and pooled analysis

OBJECTIVE

This pooled analysis evaluates the association between the number of nerves transferred and postoperative outcomes after intercostal nerve (ICN) nerve transfer for elbow flexion.

METHODS

A systematic and pooled analysis of studies reporting individual patient demographics and outcomes after ICN-musculocutaneous nerve (MCN) transfer for traumatic brachial plexus injury was conducted. The primary outcome was the ability to attain an elbow flexion Medical Research Council (MRC) score of ≥4 at the final postoperative follow-up visit.

RESULTS

Ten studies were included for a total of 128 patients. There were 43 patients who underwent two ICNT, 77 patients who underwent three ICNT, and 8 patients who underwent four ICNT. The three groups did not differ in ability to achieve MRC ≥ 4 (2ICNT 48.8%, 3ICNT 42.9%, 4ICNT 50.0%, p = 0.789). The number of ICNs transferred was not associated with MRC scores ≥4 on the multivariable analysis (OR: 0.55, p = 0.126).

CONCLUSIONS

These results indicate that two ICN transfers may be as effective as three ICN and four ICN transfers and highlight the potential for nonsurgical factors to influence postoperative outcomes. Taken together, this pooled analysis leads us to question the utility of transferring >2 ICNs for MCN neurotization.

A Fresh Cadaver Study on the Innervation of Brachioradialis and Extensor Carpi Radialis Longus Muscles

PURPOSE

Distal nerve transfers have revolutionized peripheral nerve surgery by allowing the transfer of healthy motor nerves to paralyzed ones without causing additional morbidity. Radial nerve branches to the brachialis (Ba), brachioradialis (Br), and extensor carpi radialis longus (ECRL) muscles have not been investigated in fresh cadavers.

METHODS

The radial nerve and its branches were dissected in 34 upper limbs from 17 fresh cadavers. Measurements were taken to determine the number, origin, length, and diameter of the branches. Myelinated fiber counts were obtained through histological analysis.

RESULTS

The first branch of the radial nerve at the elbow was to the Ba muscle, followed by the branches to the Br and ECRL muscles. The Ba and Br muscles consistently received single innervation. The ECRL muscle showed varying innervation patterns, with one, two, or three branches. The branches to the Br muscles originated from the anterior side of the radial nerve, whereas the branches to the Ba and ECRL muscles originated from the posterior side. The average myelinated fiber counts favored the nerve to Br muscle over that to the ECRL muscle, with counts of 542 versus 350 and 568 versus 302 observed in hematoxylin and eosin and neurofilament staining, respectively.

CONCLUSIONS

This study provides detailed anatomical insights into the motor branches of the radial nerve to the Ba, Br, and ECRL muscles.

CLINICAL RELEVANCE

Understanding the anatomy of the radial nerve branches at the elbow is of utmost importance when devising a reconstructive strategy for upper limb paralysis. These findings can guide surgeons in selecting appropriate donor or recipient nerves for nerve transfer in cases of high tetraplegia and lower-type brachial plexus injuries.

Anatomy of Profunda Brachial Artery in the Axilla and Its Relationship With the Radial Nerve: Fresh-Cadaver Anatomical Study and Clinical Observations

PURPOSE

Dissection of the radial nerve in the axilla and upper portion of and posterior aspect of arm may be necessary for brachial plexus reconstruction, in axillary nerve paralysis, and in radial nerve injuries. The radial nerve is in intimate contact with the profunda brachial artery (PBA). The authors sought to describe the relationship of the PBA with the radial nerve.

METHODS

We dissected the PBA and the radial nerve bilaterally in 20 upper limbs from 10 fresh cadavers after subclavian artery injection with green latex. We studied the relationship of the PBA with the radial nerve, its branching patterns, and its diameters. In addition, we performed surgery on 5 patients with brachial plexus, radial, or axillary nerve injury in whom we dissected the PBA.

RESULTS

The PBA was present in all dissections, originating from the brachial artery (n = 19 specimens) close to the latissimus dorsi tendon or from the subscapular artery (n = 1 specimen). In 15 dissections, the PBA bifurcated into an anterior (AB) and a posterior (PB) branch. In one dissection, the AB was absent. The AB traveled toward the triceps medial head. The PB flanked the radial nerve posteriorly and traveled around the humerus, with the radial nerve passing between the medial and the lateral head of the triceps. The AB and PB were longer than the PBA and measured on average 53 mm (SD ± 33 mm) and 39 mm (SD ± 26 mm), respectively. Intraoperatively, the radial nerve could be exposed in the upper arm by pulling the triceps medial head anteriorly together with the AB. The PB was lateral to the radial nerve in the posterior arm approach.

CONCLUSIONS

In the upper arm, the radial nerve was not flanked by a single branch as postulated in anatomical textbooks but by 2 branches resulting from the bifurcation of the PBA.

CLINICAL RELEVANCE

Awareness of PBA anatomy is essential during radial nerve dissection from the anterior or posterior arm approach.

Global trends and outcomes of nerve transfers for treatment of adult brachial plexus injuries

The presentation, management and outcomes of brachial plexus injuries are likely to be subject to regional differences across the globe. A comprehensive literature search was performed to identify relevant articles related to spinal accessory to suprascapular, intercostal to musculocutaneous, and ulnar and/or median nerve fascicle to biceps and/or brachialis motor branch nerve transfers for treatment of brachial plexus injuries. A total of 6007 individual brachial plexus injuries were described with a mean follow-up of 38 months. The specific indication for accessory to suprascapular and intercostal to musculocutaneous transfers were considerably different among regions (e.g. upper plexus vs. pan-plexal), while uniform for fascicular transfer for elbow flexion (e.g. upper plexus +/- C7). Similarly, functional recovery was highly variable for accessory to suprascapular and intercostal to musculocutaneous transfers, while British Medical Research Council grade ≥3 strength after fascicular transfer for elbow flexion was frequently obtained. Overall, differences in outcomes seem to be inherent to the specific transfer being utilized.Level of evidence: III.

Key Considerations for Nerve Transfer Rehabilitation After Surgical Reconstruction for Brachial Plexus and Peripheral Nerve Injuries

Nerve transfer surgery is commonly used to treat patients with brachial plexus injuries. However, guidelines on postoperative rehabilitation are not clearly established. Nerve transfers require the patient to relearn how to recruit newly innervated muscle(s), which may not occur naturally or intuitively. Supervised therapy is a valuable resource to guide patients through their lengthy recovery (often >12 months) because target muscle strength is both obtained and functionally used in daily life. This article highlights 10 key principles that provide the foundation for rehabilitation following nerve transfer surgery after a brachial plexus injury. Due to the shortcomings of the current evidence base for nerve transfer rehabilitation, we have included our anecdotal experience to augment the existing literature. It is important to have a collaborative surgeon-therapist relationship to communicate regarding operative details, expected timelines for reinnervation, patient needs, and realistic expectations. We provide examples of how to tailor the exercise program to synergistically recruit both the donor and target muscle action, including how to appropriately advance exercises based on the current level of nerve return. We also discuss the role that fatigue plays in denervated muscle and how fatigue may affect the exercise demands placed on the target muscle during specific stages of recovery.

[Prosthetic Fitting Concepts after Major Amputation in the Upper Limb - an Overview of Current Possibilities]

BACKGROUND

The upper extremity and particularly the hands are crucial for patients in interacting with their environment, therefore amputations or severe damage with loss of hand function significantly impact their quality of life. In cases where biological reconstruction is not feasible or does not lead to sufficient success, bionic reconstruction plays a key role in patient care. Classical myoelectric prostheses are controlled using two signals derived from surface electrodes in the area of the stump muscles. Prosthesis control, especially in high amputations, is then limited and cumbersome. The surgical technique of Targeted Muscle Reinnervation (TMR) offers an innovative solution: The major arm nerves that have lost their target organs due to amputation are rerouted to muscles in the stump area. This enables the establishment of cognitive control signals that allow significantly improved prosthesis control.

PATIENTS/MATERIALS AND METHODS

A selective literature review on TMR and bionic reconstruction was conducted, incorporating relevant articles and discussing them considering the clinical experience of our research group. Additionally, a clinical case is presented.

RESULTS

Bionic reconstruction combined with Targeted Muscle Reinnervation enables intuitive prosthetic control with simultaneous movement of various prosthetic degrees of freedom and the treatment of neuroma and phantom limb pain. Long-term success requires a high level of patient compliance and intensive signal training during the prosthetic rehabilitation phase. Despite technological advances, challenges persist, especially in enhancing signal transmission and integrating natural sensory feedback into bionic prostheses.

CONCLUSION

TMR surgery represents a significant advancement in the bionic care of amputees. Employing selective nerve transfers for signal multiplication and amplification, opens up possibilities for improving myoelectric prosthesis function and thus enhancing patient care. Advances in the area of external prosthetic components, improvements in the skeletal connection due to osseointegration and more fluid signal transmission using wireless, fully implanted electrode systems will lead to significant progress in bionic reconstruction, both in terms of precision of movement and embodiment.

Retrograde peripheral nerve regeneration from sensory to motor pathways in rats: a new experimental concept in nerve repair

BACKGROUND

The polarity of nerve grafts does not interfere with axon growth. Our goal was to investigate whether axons can regenerate in a retrograde fashion within sensory pathways and then extend into motor pathways, leading to muscle reinnervation.

METHODS

Fifty-four rats were randomized into four groups. In Group 1, the ulnar nerve was connected end-to-end to the superficial radial nerve after neurectomy of the radial nerve in the axilla. In Group 2, the ulnar nerve was connected end-to-end to the radial nerve distal to the humerus; the radial nerve then was divided in the axilla. In Group 3, the radial nerve was divided in the axilla, but no nerve reconstruction was performed. In Group 4, the radial nerve was crushed in the axilla. Over 6 months, we behaviorally assessed the recovery of toe spread in the right operated-upon forepaw by lifting the rat by its tail and lowering it onto a flat surface. Six months after surgery, rats underwent reoperation, nerve transfers were tested electrophysiologically, and the posterior interosseous nerve (PIN) was removed for histological evaluation.

RESULTS

Rats in the crush group recovered toe spread between 5 and 8 days after surgery. Rats with nerve transfers demonstrated electrophysiological and histological findings of nerve regeneration but no behavioral recovery.

CONCLUSIONS

Ulnar nerve axons regrew into the superficial radial nerve and then into the PIN to reinnervate the extensor digitorum communis. We were unable to demonstrate behavioral recovery because rats cannot readapt to cross-nerve transfer.

Intercostal Nerve Transfer for Biceps Reinnervation in Obstetrical Brachial Plexus Palsy: A Preferred Reporting Items for Systematic Reviews and Meta-Analysis for Individual Patient Data Systematic Review using Individualized Fusion and Comparison to Supraclavicular Exploration and Nerve Grafting

Introduction

The objective of this study was to search existing literature on nerve reconstruction surgery in patients with obstetric brachial plexus palsy to determine whether treatment with supraclavicular exploration and nerve grafting produced better elbow flexion outcomes compared to intercostal nerve transfer.

Methods

This study was a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis for Individual Patient Data guidelines. A systematic search was conducted using multiple databases. An ordinal regression model was used to analyze the effect of using supraclavicular exploration and nerve grafting or intercostal nerve on elbow flexion with the two scores measured: elbow flexion Medical Research Council scores and Toronto active movements scale scores for elbow flexion.

Results

A final patient database from 6 published articles consisted of 83 supraclavicular exploration and nerve grafting patients (73 patients with Medical Research Council and 10 patients with Toronto score) and 7 published articles which consisted of 131 intercostal nerve patients (84 patients with Medical Research Council and 47 patients with Toronto scores). Patients who underwent supraclavicular exploration and nerve grafting presented with an average Medical Research Council score of 3.9 ± 0.72 and an average Toronto score of 6.2 ± 2.2. Patients who underwent intercostal nerve transfer presented with an average Medical Research Council score of 3.9 ± 0.71 and an average Toronto score of 6.4 ± 1.2. There was no statistical difference between supraclavicular exploration and nerve grafting and intercostal nerve transfer when utilizing Medical Research Council elbow flexion scores (ordinal regression: 0.3821, standard error: 0.4590, p = 0.2551) or Toronto Active Movement Scale score for elbow flexion (ordinal regression: 0.7154, standard error: 0.8487, p = 0.2188).

Conclusion

Regardless of surgical intervention utilized (supraclavicular exploration and nerve grafting or intercostal nerve transfers), patients had excellent outcomes for elbow flexion following obstetric brachial plexus palsy when utilizing Medical Research Council or Toronto scores for elbow flexion. The difference between these scores was not statistically significant.

Type of study/Level of evidence

Therapeutic Study: Investigating the Result of Treatment/level III.

A favourable suture method for size-mismatched nerve transfer: a case series of intercostal-to-musculocutaneous nerve transfer for brachial plexus injury

We review a nerve suture method for size-mismatched nerve transfers and report a case series involving patients with brachial plexus injury who underwent intercostal-to-musculocutaneous nerve transfer using this method.

Dynamic alternations of interhemispheric functional connectivity in brachial plexus avulsion injury patients with nerve transfer: a resting state fMRI study

Brachial plexus avulsion injury (BPAI) is a severe peripheral nerve injury that leads to functional reorganization of the brain. However, the interhemispheric coordination following contralateral cervical 7 nerve transfer remains unclear. In this study, 69 BPAI patients underwent resting-state functional magnetic resonance imaging examination to assess the voxel-mirrored homotopic connectivity (VMHC), which reveals the interhemispheric functional connection. The motor function of the affected upper extremity was measured using the Fugl-Meyer Assessment of Upper Extremity (FMA-UE) scale. The VMHC analysis showed significant differences between the bilateral precentral gyrus, supplementary motor area (SMA), middle frontal gyrus (MFG), and insula. Compared to the preoperative group, the VMHC of the precentral gyrus significantly increased in the postoperative short-term group (PO-ST group) but decreased in the postoperative long-term group (PO-LT group). Additionally, the VMHC of the SMA significantly increased in the PO-LT group. Furthermore, the VMHC of the precentral gyrus in the PO-ST group and the SMA in the PO-LT group were positively correlated with the FMA-UE scores. These findings highlight a positive relationship between motor recovery and increased functional connectivity of precentral gyrus and SMA, which provide possible therapeutic targets for future neuromodulation interventions to improve rehabilitation outcomes for BPAI patients.

Intercostal Nerve Transfers to Native Triceps or Free Muscle Flaps for Elbow Extension in Brachial Plexus Injuries

Intercostal nerve donors for traumatic brachial plexus injury reconstruction have been used to neurotize native muscles or free-functioning muscle transfers, with inconsistent outcomes reported. The aim was to record a substantial series, evaluate functional outcomes, and identify prognostic factors. We present a single-surgeon case series of 21 consecutive patients who underwent 21 transfer procedures to either native muscles or free-functioning muscles to reconstruct elbow extension over a 9-year period. Outcome parameters included target muscle power grade and timing of recovery. A Medical Research Council power grade ≥ M4 was achieved in 17 reconstructions. The free-functioning muscle group had significantly higher success rate and reached their best power grade 14 months earlier. Free-functioning muscle reconstruction with intercostal nerve transfer is a more complex procedure but has quicker functional recovery and greater reliability in achieving grade M4.

T12-L3 Nerve Transfer-Induced Locomotor Recovery in Rats with Thoracolumbar Contusion: Essential Roles of Sensory Input Rerouting and Central Neuroplasticity

Locomotor recovery after spinal cord injury (SCI) remains an unmet challenge. Nerve transfer (NT), the connection of a functional/expendable peripheral nerve to a paralyzed nerve root, has long been clinically applied, aiming to restore motor control. However, outcomes have been inconsistent, suggesting that NT-induced neurological reinstatement may require activation of mechanisms beyond motor axon reinnervation (our hypothesis). We previously reported that to enhance rat locomotion following T13-L1 hemisection, T12-L3 NT must be performed within timeframes optimal for sensory nerve regrowth. Here, T12-L3 NT was performed for adult female rats with subacute (7-9 days) or chronic (8 weeks) mild (SCImi: 10 g × 12.5 mm) or moderate (SCImo: 10 g × 25 mm) T13-L1 thoracolumbar contusion. For chronic injuries, T11-12 implantation of adult hMSCs (1-week before NT), post-NT intramuscular delivery of FGF2, and environmentally enriched/enlarged (EEE) housing were provided. NT, not control procedures, qualitatively improved locomotion in both SCImi groups and animals with subacute SCImo. However, delayed NT did not produce neurological scale upgrading conversion for SCImo rats. Ablation of the T12 ventral/motor or dorsal/sensory root determined that the T12-L3 sensory input played a key role in hindlimb reanimation. Pharmacological, electrophysiological, and trans-synaptic tracing assays revealed that NT strengthened integrity of the propriospinal network, serotonergic neuromodulation, and the neuromuscular junction. Besides key outcomes of thoracolumbar contusion modeling, the data provides the first evidence that mixed NT-induced locomotor efficacy may rely pivotally on sensory rerouting and pro-repair neuroplasticity to reactivate neurocircuits/central pattern generators. The finding describes a novel neurobiology mechanism underlying NT, which can be targeted for development of innovative neurotization therapies.

Combining Surgical Innovations in Amputation Surgery-Robotic Harvest of the Rectus Abdominis Muscle, Transplantation and Targeted Muscle Reinnervation Improves Myocontrol Capability and Pain in a Transradial Amputee

Adding robotic surgery to bionic reconstruction might open a new dimension. The objective was to evaluate if a robotically harvested rectus abdominis (RA) transplant is a feasible procedure to improve soft-tissue coverage at the residual limb (RL) and serve as a recipient for up to three nerves due to its unique architecture and to allow the generation of additional signals for advanced myoelectric prosthesis control. A transradial amputee with insufficient soft-tissue coverage and painful neuromas underwent the interventions and was observed for 18 months. RA muscle was harvested using robotic-assisted surgery and transplanted to the RL, followed by end-to-end neurroraphy to the recipient nerves of the three muscle segments to reanimate radial, median, and ulnar nerve function. The transplanted muscle healed with partial necrosis of the skin mesh graft. Twelve months later, reliable, and spatially well-defined Hoffmann-Tinel signs were detectable at three segments of the RA muscle flap. No donor-site morbidities were present, and EMG activity could be detected in all three muscle segments. The linear discriminant analysis (LDA) classifier could reliably distinguish three classes within 1% error tolerance using only the three electrodes on the muscle transplant and up to five classes outside the muscle transplant. The combination of these surgical procedure advances with emerging (myo-)control technologies can easily be extended to different amputation levels to reduce RL complications and augment control sites with a limited surface area, thus facilitating the usability of advanced myoelectric prostheses.

Nerve function restoration following targeted muscle reinnervation after varying delayed periods

Targeted muscle reinnervation has been proposed for reconstruction of neuromuscular function in amputees. However, it is unknown whether performing delayed targeted muscle reinnervation after nerve injury will affect restoration of function. In this rat nerve injury study, the median and musculocutaneous nerves of the forelimb were transected. The proximal median nerve stump was sutured to the distal musculocutaneous nerve stump immediately and 2 and 4 weeks after surgery to reinnervate the biceps brachii. After targeted muscle reinnervation, intramuscular myoelectric signals from the biceps brachii were recorded. Signal amplitude gradually increased with time. Biceps brachii myoelectric signals and muscle fiber morphology and grooming behavior did not significantly differ among rats subjected to delayed target muscle innervation for different periods. Targeted muscle reinnervation delayed for 4 weeks can acquire the same nerve function restoration effect as that of immediate reinnervation.

Brain plasticity and age after restoring elbow flexion with distal nerve transfers in neonatal brachial plexus palsy and nonneonatal traumatic brachial plexus injury using the plasticity grading scale

OBJECTIVE

Ulnar and/or median nerve fascicle to musculocutaneous nerve (MCN) transfers are used to restore elbow flexion following severe neonatal and nonneonatal brachial plexus injuries (BPIs). Restoring volitional control requires plastic changes in the brain. To date, whether the potential for plasticity is influenced by a patient's age remains unknown.

METHODS

Patients who had presented with a traumatic upper (C5-6 or C5-7) BPI were divided into two groups: neonatal brachial plexus palsies (NBPPs) and nonneonatal traumatic BPIs (NNBPIs). Both groups underwent ulnar or median nerve transfers to the MCN for elbow flexion restoration between January 2002 and July 2020. Only those who attained a British Medical Research Council strength rating of 4 were reviewed. The primary comparison between the two groups was the plasticity grading scale (PGS) score to determine the level of independence of elbow flexion (target) from forearm motor muscle movement (donors). The authors also assessed patient compliance with rehabilitation using a 4-point Rehabilitation Quality Scale. Bivariable and multivariable analyses were used to identify intergroup differences.

RESULTS

In total, 66 patients were analyzed: 22 with NBPP (mean age at surgery 10 months) and 44 with NNBPI (age range at surgery 3-67 years, mean 30.2 years; mean time to surgery 7 months, p < 0.001). All NBPP patients obtained a PGS grade of 4 at the final follow-up versus just 47.7% of NNBPI patients (mean 3.27, p < 0.001). On ordinal regression analysis, after nature of the injury was excluded because of excessive collinearity with age, age was the only significant predictor of plasticity (β = -0.063, p = 0.003). Median rehabilitation compliance scores were not statistically different between the two groups.

CONCLUSIONS

The extent of plastic changes that occur for patients to regain volitional control over elbow flexion after upper arm distal nerve transfers following BPI is influenced by patient age, with complete plastic rewiring more likely in younger patients and virtually ubiquitous in infants. Older patients should be informed that elbow flexion after an ulnar or median nerve fascicle transfer to the MCN might require simultaneous wrist flexion.

Assessment, patient selection, and rehabilitation of nerve transfers

Peripheral nerve injuries are common and can have a devastating effect on physical, psychological, and socioeconomic wellbeing. Peripheral nerve transfers have become the standard of care for many types of peripheral nerve injury due to their superior outcomes relative to conventional techniques. As the indications for, and use of, nerve transfers expand, the importance of pre-operative assessment and post-operative optimization increases. There are two principal advantages of nerve transfers: (1) their ability to shorten the time to reinnervation of muscles undergoing denervation because of peripheral nerve injury; and (2) their specificity in ensuring proximal motor and sensory axons are directed towards appropriate motor and sensory targets. Compared to conventional nerve grafting, nerve transfers offer opportunities to reinnervate muscles affected by cervical spinal cord injury and to augment natural reinnervation potential for very proximal injuries. This article provides a narrative review of the current scientific knowledge and clinical understanding of nerve transfers including peripheral nerve injury assessment and pre- and post-operative electrodiagnostic testing, adjuvant therapies, and post-operative rehabilitation for optimizing nerve transfer outcomes.

Axonal mapping of motor and sensory components within the ulnar nerve and its branches

OBJECTIVE

Intrinsic function is indispensable for dexterous hand movements. Distal ulnar nerve defects can result in intrinsic muscle dysfunction and sensory deficits. Although the ulnar nerve's fascicular anatomy has been extensively studied, quantitative and topographic data on motor axons traveling within this nerve remain elusive.

METHODS

The ulnar nerves of 14 heart-beating organ donors were evaluated. The motor branches to the flexor carpi ulnaris (FCU) and flexor digitorum profundus (FDP) muscles and the dorsal branch (DoBUN) as well as 3 segments of the ulnar nerve were harvested in 2-cm increments. Samples were subjected to double immunofluorescence staining using antibodies against choline acetyltransferase and neurofilament.

RESULTS

Samples revealed more than 25,000 axons in the ulnar nerve at the forearm level, with a motor axon proportion of only 5%. The superficial and DoBUN showed high axon numbers of more than 21,000 and 9300, respectively. The axonal mapping of more than 1300 motor axons revealed an increasing motor/sensory ratio from the proximal ulnar nerve (1:20) to the deep branch of the ulnar nerve (1:7). The motor branches (FDP and FCU) showed that sensory axons outnumber motor axons by a ratio of 10:1.

CONCLUSIONS

Knowledge of the detailed axonal architecture of the motor and sensory components of the human ulnar nerve is of the utmost importance for surgeons considering fascicular grafting or nerve transfer surgery. The low number of efferent axons in motor branches of the ulnar nerve and their distinct topographical distribution along the distal course of the nerve is indispensable information for modern nerve surgery.

Posterior Deltoid Function After Transfer of Branch to the Long Head Triceps Brachii of the Radial Nerve to the Anterior Branch of the Axillary Nerve

PURPOSE

The aim of this study was to evaluate the function of the posterior part of the deltoid after nerve transfer of the long head triceps branch of the radial nerve to the anterior branch of the axillary nerve in patients with an upper brachial plexus injury or isolated axillary nerve injury.

METHODS

We retrospectively reviewed 26 patients diagnosed with an upper brachial plexus injury or isolated axillary nerve injury who underwent nerve transfer of the long head triceps muscle branch of the radial nerve to the anterior branch of the axillary nerve in our institute between 2012 and 2017. Data on age, sex, the mechanism of injury, the pattern of injury, and operative treatment were collected from medical records. Preoperative and postoperative clinical examinations, including motor powers of shoulder abduction and extension according to Medical Research Council grading, were evaluated. At a minimum of 2 years after the operation, we evaluated the recovery of the posterior deltoid function using the swallow-tail test.

RESULTS

Twenty-two patients (84.6%) had recovery of posterior deltoid function confirmed by the swallow-tail test. There were 23 patients (88.5%) who achieved at least Medical Research Council grade 4 of shoulder abduction.

CONCLUSIONS

Nerve transfer from the branch to the long head triceps to the anterior branch of the axillary nerve is an effective technique for restoring deltoid function in an upper brachial plexus injury or isolated axillary nerve injury. This technique can provide shoulder abduction and shoulder extension, which are the functions of the posterior deltoid muscle.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Base of the Third Metacarpal as a Palpable and Reliable Landmark for Identifying the Median Nerve's Thenar Branch

PURPOSE

The objective of this study was to investigate whether the base of the third metacarpal can predict the location of the thenar branch (TB) of the median nerve and the accuracy of palpating the base of the third metacarpal.

METHODS

In 15 patients with ulnar nerve lesions around the elbow, we transferred the opponens motor branch to repair the deep terminal division of the ulnar nerve (DTDUN). Before surgery, we located the TB by palpating the base of the third metacarpal volarly. During surgery, we placed three needles at the following places: one at the entrance of the TB into the abductor pollicis brevis, another at the point where the TB contacted the thenar muscles, and third at the DTDUN's trajectory over the third metacarpal. We obtained fluoroscopic images and measured distances between the needles and structures with image software. We also examined the relationship between the TB, DTDUN, and the volar tubercle of the base of the third metacarpal in cadaver hands. Finally, we invited 22 surgeons to palpate the base of the third metacarpal on volunteer hands and verified their accuracy using fluoroscopy.

RESULTS

During surgery, after dissection and palpation of the TB, under fluoroscopy, we confirmed that the palpable bone prominence was the base of the third metacarpal. In cadaver dissections, we observed the TB crossing the volar tubercle of the base of the third metacarpal superficially from proximal to distal and from ulnar to radial. The DTDUN was, on average, 14 mm distal to the base of the third metacarpal distal limit. In total, 19 of the 22 surgeons correctly identified the base of the third metacarpal and consequently the trajectory of the TB.

CONCLUSIONS

The palpable base of the third metacarpal can be used to determine the trajectory of both the TB and DTDUN.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

The Cutaneous Branches of the Median and Ulnar Nerves in the Palm

PURPOSE

The dermatomal distributions of the ulnar and median nerves on the palmar skin of the hand have been studied thoroughly. However, the anatomic course of the median and ulnar cutaneous nerve branches and how they supply the skin of the palm is not well understood.

METHODS

The cutaneous branches of the median and ulnar nerves were dissected bilaterally in 9 fresh cadavers injected arterially with green latex.

RESULTS

We observed 3 groups of cutaneous nerve branches in the palm of the hand: a proximal row group consisting of long branches that originated proximal to the superficial palmar arch and reached the distal palm, first web space, or hypothenar region; a distal row group consisting of branches originating between the superficial palmar arch and the transverse fibers of the palmar aponeurosis (these nerves had a longitudinal trajectory and were shorter than the branches originating proximal to the palmar arch); and a metacarpophalangeal group, composed of short perpendicular branches originating on the palmar surface of the proper palmar digital nerves at the web space. The radial and ulnar borders of the hand distal to the palmar arch were innervated by short transverse branches arising from the proper digital nerves of the index and little finger. Nerve branches did not perforate the palmar aponeurosis in 16 of 18 cases.

CONCLUSIONS

The palm of the hand was consistently innervated by 20-35 mm long cutaneous branches originating proximal to the palmar arch and shorter branches originating distal to the palmar arch. These distal branches were either perpendicular or parallel to the proper palmar digital nerves.

CLINICAL RELEVANCE

Transfer of long proximal row branches may present an opportunity to restore sensibility in nerve injuries.

Updates in peripheral nerve surgery of the upper extremity: diagnosis and treatment options

The loss of function resulting from peripheral nerve injuries confers a significant burden to the patient and society. The treatment of peripheral nerve injuries requires an accurate diagnosis and formulation of a functional reconstructive plan. Advances in peripheral nerve imaging complement electrodiagnostic studies, and provide us with detailed information regarding the status of nerve injury, repair, and regeneration in order to prognosticate recovery and determine the need for surgical intervention. When direct nerve repair is not possible, the methods for bridging a nerve gap are the nerve autograft, allograft and conduit. While current research supports the use of conduits and nerve allografts for shorter nerve gaps, the nerve autograft still remains the gold standard for bridging a nerve gap. When direct nerve repair or nerve grafting fails, or is anticipated to be insufficient, nerve transfers are an alternative for reconstruction. Knowledge of axonal counts, upper limb innervation patterns, location and clustering of upper limb peripheral nerves allows for the design of new nerve transfers. The options of nerve transfers for radial, ulnar and median nerve injuries are outlined, as well as their outcomes. Nerve transfers are an attractive option for restoring motor and sensory function while minimizing donor site morbidity. However, one must consider their limitations, and preserve donor sites for secondary tendon transfer options. This article presents the latest information regarding the imaging of peripheral nerves, methods to bridge a nerve gap, and nerve transfers to aid the peripheral nerve surgeon in choosing a reconstructive plan.

Surgical management and outcomes of traumatic global brachial plexus injury: A concise review and our center approach

Global brachial plexus injury (GBPI) mainly affects adults and causes severe life-changing consequences that lead to the deterioration of patients' quality of life. Several surgical approaches have been described and reported in the literature to improve patients' functional ability. A literature review is done on PubMed/MEDLINE and Embase using specific keywords to retrieve relevant articles assessing different surgical approaches for GBPI management. Inclusion and exclusion criteria were applied, and eligible articles were included in the review. The literature survey revealed that various surgical options had been used to manage GBPI patients. In this concise review, we discuss and compare the different surgical approaches related to GBPI and its outcome in terms of restoring elbow flexion and extension, shoulder abduction, and wrist and hand function. The primary surgical intervention relies mainly on transferring single or multiple nerves with/without nerve grafts to restore the function of the targeted muscle. Different techniques using a variety of nerve donors and recipients are compared to assess the functional outcomes of each option. Moreover, further options are addressed for delayed GBPI injuries or failed nerve transfer procedures, as in free functional muscle transfer techniques. In addition, information about brachial plexus injury cases faced in our center is presented along with our center's approach to diagnosing and managing partial and GBPI cases.

Proximal forearm nerve branching patterns: an anatomical study and its clinical significance

OBJECTIVE

The aim of this study was to add to the understanding of nerve branching patterns in the proximal forearm and consider optimal nerve transfer options to address the various injuries that affect the function of the upper extremity.

METHODS

Eleven upper-extremity cadaveric specimens were dissected to expose the radial, median, and ulnar nerves in the proximal forearm. The site of origin of nerve branches from the major nerves was assessed, with measurements made in reference to the lateral epicondyle for the radial nerve branches and the medial epicondyle for the median and ulnar nerve branches. The distances to where these branches entered their respective muscles (muscle entry point) were assessed using the same landmarks. To plan a transfer, the length of the nerve branches was then calculated as the difference from the apparent origin from the main nerve trunk to the location where the nerve entered the muscle. Importantly, the nerve branch origin was established as the location of obvious separation from the main nerve trunk without additional fascicular dissection from the major nerve trunk. The number of branches was determined, and the diameter for each branch was measured using a Vernier caliper.

RESULTS

The radial nerve branch to the extensor carpi radialis brevis (ECRB) muscle had an average length of 50.7 mm and average diameter of 1.6 mm. The mean medial and lateral lengths of the radial branches to the supinator muscle were found to be 22.2 mm (diameter 1.4 mm) and 15.3 mm (diameter 1.3 mm), respectively. The anterior interosseous nerve (AIN) branch of the median nerve was found 67.8 mm distal to the medial epicondyle with a diameter of 2.3 mm. The flexor carpi ulnaris (FCU) muscle innervation from the ulnar nerve was provided by 3 or 4 branches in most specimens. The second and third of these branches were the longest, with means of 30.5 mm (diameter 1.4 mm) and 30.7 mm (diameter 1.3 mm), respectively.

CONCLUSIONS

While there is variability of the nerve branching pattern in the proximal forearm between specimens, the authors provide evidence of commonalities (branching patterns and distances) that can facilitate planning for upper-extremity nerve reconstructions. Importantly, all measurements are provided with reference to easily identified bony landmarks and to their muscle entry points to aid operative decision-making. These data complement the growing practice of nerve transfers in the upper extremity for a variety of pathologies.

Histological Compatibility in Distal Neurotizations: A Systematic Review

Considering the importance of defining the minimum number of axons between recipient and donor branches, that is, the definition of histological compatibility in distal neurotizations for the success of the procedure and the surgeon's freedom to choose individualized strategies for each patient, this systematic review was conducted to find out the most recent studies on the subject. The objective of this systematic review was to determine the importance of the number of axons and the relationship between axon counts in the donor and recipient nerves in the success of nerve transfer. A literature review was performed on five international databases: Web of Science, Scopus, Wiley (Cochrane Database), Embase, and PubMed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed (2020 version), a guide designed to guide the elaboration of systematic literature reviews. One hundred and fifty-seven studies were found, and 23 were selected based on the eligibility criteria. The articles presented were conclusive in determining the importance of the number of axons in the success of nerve transfer. Still, the relationship between the number of axons in the donor and recipient nerves seems more relevant in the success of transfers and is not always explored by the authors. The review of the articles has provided compelling evidence that the number of axons is a critical determinant of the success of nerve transfer procedures. However, the relationship between the number of axons in the donor nerve and that in the recipient nerve appears to be even more crucial for successful transfers, a factor that is not always adequately explored by authors in the existing literature. Level of evidence : Level IV, therapeutic study.

Extradural contralateral S1 nerve root transfer for spastic lower limb paralysis

The current study aims to ascertain the anatomical feasibility of transferring the contralateral S1 ventral root (VR) to the ipsilateral L5 VR for treating unilateral spastic lower limb paralysis. Six formalin-fixed (three males and three females) cadavers were used. The VR of the contralateral S1 was transferred to the VR of the ipsilateral L5. The sural nerve was selected as a bridge between the donor and recipient nerve. The number of axons, the cross-sectional areas and the pertinent distances between the donor and recipient nerves were measured. The extradural S1 VR and L5 VR could be separated based on anatomical markers of the dorsal root ganglion. The gross distance between the S1 nerve root and L5 nerve root was 31.31 (± 3.23) mm in the six cadavers, while that on the diffusion tensor imaging was 47.51 (± 3.23) mm in 60 patients without spinal diseases, and both distances were seperately greater than that between the outlet of S1 from the spinal cord and the ganglion. The numbers of axons in the S1 VRs and L5 VRs were 13414.20 (± 2890.30) and 10613.20 (± 2135.58), respectively. The cross-sectional areas of the S1 VR and L5 VR were 1.68 (± 0.26) mm 2 and 1.08 (± 0.26) mm 2, respectively. In conclusion, transfer of the contralateral S1 VR to the ipsilateral L5 VR may be an anatomically feasible treatment option for unilateral spastic lower limb paralysis.

The Clinical Outcomes of Spinal Accessory to Suprascapular Nerve Transfer Through a Posterior Approach

BACKGROUND

Spinal accessory nerve (SAN) to suprascapular nerve (SSN) transfer can restore function to the rotator cuff following brachial plexus injuries. The traditional anterior approach using the lateral branch of the SAN causes denervation of the lateral trapezius limiting shoulder elevation. Suprascapular nerve pathology at the suprascapular notch may be missed resulting in poor reinnervation of the rotator cuff. The posterior approach uses the medial SAN and allows decompression and visualization of the SSN at the notch and nerve transfer coaptation closer to the target muscles with a shorter reinnervation distance.

METHODS

This is a review of 28 patients from 2014 to February 2020 who underwent SAN to SSN nerve transfer via a posterior approach. Patients were evaluated for SSN pathology, external rotation power, and range of motion. Data were evaluated for high-energy trauma (HET) and low-energy trauma/nontraumatic etiology subsets.

RESULTS

A total of 8 HET (40%) patients had pathology identified at the suprascapular notch during the posterior approach, including SSN scarring, ruptures, neuromata-in-continuity, and ossification of ligaments. British Medical Research Council grade greater than or equal to 4 shoulder external rotation was achieved in 75% patients with median range of motion 137.5°.

CONCLUSIONS

Spinal accessory nerve to SSN transfer using a posterior approach allows visualization of pathology involving the SSN and coaptation of a medial SAN transfer close to the target muscles. Following HET, 8 cases (40%) had posterior pathology identified. Spinal accessory nerve to SSN transfer through a posterior approach shows improved external rotation power and range of motion.

The Role of Surgery in the Management of Radiation-Induced Brachial Plexopathy

Radiation-induced brachial plexopathy (RIBP) is a rare long-term complication of radiation therapy often causing pain, motor deficit, and overall quality of life reduction for affected patients. While a standard treatment for RIBP is yet to be established, management consists mostly of symptom management through the use of medications and physical therapy. There is a lack of evidence regarding the efficacy of surgical treatment. Omentoplasties and other vascularized flaps are commonly discussed options for eliminating neuropathic pain associated with RIBP. However, these approaches show no meaningful improvement in motor function. While limited, current literature suggests that nerve transfers may be an option for relief of neuropathic pain as well as restoration of motor function. This review of literature explores the options available to those affected by RIBP with a focus on the role of surgery.

Association of upper-limb neurological recovery with functional outcomes in high cervical spinal cord injury

OBJECTIVE

High cervical spinal cord injury (SCI) results in complete loss of upper-limb function, resulting in debilitating tetraplegia and permanent disability. Spontaneous motor recovery occurs to varying degrees in some patients, particularly in the 1st year postinjury. However, the impact of this upper-limb motor recovery on long-term functional outcomes remains unknown. The objective of this study was to characterize the impact of upper-limb motor recovery on the degree of long-term functional outcomes in order to inform priorities for research interventions that restore upper-limb function in patients with high cervical SCI.

METHODS

A prospective cohort of high cervical SCI (C1-4) patients with American Spinal Injury Association Impairment Scale (AIS) grade A-D injury and enrolled in the Spinal Cord Injury Model Systems Database was included. Baseline neurological examinations and functional independence measures (FIMs) in feeding, bladder management, and transfers (bed/wheelchair/chair) were evaluated. Independence was defined as score ≥ 4 in each of the FIM domains at 1-year follow-up. At 1-year follow-up, functional independence was compared among patients who gained recovery (motor grade ≥ 3) in elbow flexors (C5), wrist extensors (C6), elbow extensors (C7), and finger flexors (C8). Multivariable logistic regression evaluated the impact of motor recovery on functional independence in feeding, bladder management, and transfers.

RESULTS

Between 1992 and 2016, 405 high cervical SCI patients were included. At baseline, 97% of patients had impaired upper-limb function with total dependence in eating, bladder management, and transfers. At 1 year of follow-up, the largest proportion of patients who gained independence in eating, bladder management, and transfers had recovery in finger flexion (C8) and wrist extension (C6). Elbow flexion (C5) recovery had the lowest translation to functional independence. Patients who achieved elbow extension (C7) were able to transfer independently. On multivariable analysis, patients who gained elbow extension (C7) and finger flexion (C8) were 11 times more likely to gain functional independence (OR 11, 95% CI 2.8-47, p < 0.001) and patients who gained wrist extension (C6) were 7 times more likely to gain functional independence (OR 7.1, 95% CI 1.2-56, p = 0.04). Older age (≥ 60 years) and motor complete SCI (AIS grade A-B) reduced the likelihood of gaining independence.

CONCLUSIONS

After high cervical SCI, patients who gained elbow extension (C7) and finger flexion (C8) had significantly greater independence in feeding, bladder management, and transfers than those with recovery in elbow flexion (C5) and wrist extension (C6). Recovery of elbow extension (C7) also increased the capability for independent transfers. This information can be used to set patient expectations and prioritize interventions that restore these upper-limb functions in patients with high cervical SCI.

Phrenic Nerve as an Alternative Donor for Nerve Transfer to Restore Shoulder Abduction in Severe Multiple Root Injuries of the Adult Brachial Plexus

PURPOSE

Nerve transfer is the gold standard to restore shoulder abduction in acute brachial plexus injuries. The aim of this study was to compare the phrenic nerve (Ph) to the spinal accessory nerve (XI) as the donor nerve for this purpose.

METHODS

A retrospective chart review was performed on 136 patients with acute brachial plexus injuries who received a nerve transfer of the shoulder with either the Ph (94 patients) or XI (42 patients). Each group was divided into 3 subgroups based on the recipient nerve. The maximum degree of shoulder abduction was recorded after 2 years of postoperative follow-up. A generalized estimating equation model was performed to examine the variables affecting shoulder abduction over time.

RESULTS

The maximum degrees of shoulder abduction achieved were 61.9° ± 38.7° in patients with Ph and 51.1° ± 37.3° in patients with XI. More than M3 shoulder abduction was achieved by 67% of patients with Ph versus 59% of patients with XI. The regression analysis showed that the age at the time of surgery correlated more with the functional outcome over time than the choice of donor nerve.

CONCLUSIONS

In multiple root brachial plexus injuries, the Ph exhibited similar outcomes to the XI for shoulder abduction. Our routine exploration of the supraclavicular plexus exposes the Ph conveniently for nerve transfer. The phrenic nerve should be considered as an alternative when the XI is not available or is reserved for secondary reconstruction.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Selective upper trunk posterior division fascicular nerve transfer for proximal spinal accessory neuropathy: illustrative case

BACKGROUND

Spinal accessory nerve palsy can lead to severe shoulder pain and weakness, lateral scapular winging, and limitations in overhead activity. It most often occurs because of iatrogenic injury from procedures within the posterior triangle of the neck.

OBSERVATIONS

The authors present the case of a 39-year-old male with symptoms of right shoulder weakness and neck pain after a total thyroidectomy and right neck dissection. With ultrasound findings of a neuroma-in-continuity but no clinical or electromyographic signs of reinnervation at 6 months, surgical intervention was indicated. Operative exploration confirmed a very proximal injury and nonconducting neuroma-in-continuity of the spinal accessory nerve. A selective distal nerve transfer from the posterior division of the upper trunk was performed. At the 2.5-year follow-up, the patient demonstrated excellent recovery of full active shoulder abduction and forward flexion, return to full-time employment, and mild residual scapular winging.

LESSONS

Distal nerve transfers should be considered in cases of late presentation when primary repair is not possible or long interpositional grafts are required. Selective fascicular transfer from the posterior division of the upper trunk provides the advantages of a single incision, short reinnervation time, and synergistic donor function to facilitate motor reeducation.

Pulp-to-Pulp Pinch Reconstruction in a Tetraplegic Patient Utilizing Nerve and Tendon Transfers: A Case Report

In tetraplegia, hand reconstruction is of high priority. Key pinch reconstruction has been advocated for tetraplegia hand reconstruction because of the lack of donors for nerve and tendon transfers. We report a patient with mid-cervical tetraplegia who underwent nerve and tendon transfers in the right and left upper limbs seven months post-injury to reconstruct hand function. The particularity of our case resides in the left-hand thumb and index pulp-to-pulp reconstruction. For this, we transferred the nerve to the supinator to the posterior interosseous nerve and the nerve to the extensor carpi radialis brevis to the anterior interosseous nerve. During a second surgery, we relieved clawing by transferring the split flexor digitorum superficialis of the middle and ring fingers, motored by the brachioradialis, to the extensor apparatus of all fingers. Finally, to achieve better thumb palmar abduction, we osteotomized the scaphoid tubercle and fixed it to the distal radius while maintaining thenar muscle attachments. Five years after surgery, the patient was able to grasp and release small objects placed on a table after becoming left-handed. Here, we demonstrated that pinch-to-pinch reconstruction is possible, which increased hand use in daily activities, especially during eating and grabbing small objects over the table.

Anterior Interosseus to Ulnar Motor Nerve Transfers: A Canadian Perspective

BACKGROUND

The anterior interosseus nerve (AIN) to ulnar motor nerve transfer has been popularized as an adjunct to surgical decompression in patients with severe cubital tunnel syndrome (CuTS) and high ulnar nerve injuries. The factors influencing its implementation in Canada have yet to be described.

METHODS

An electronic survey was distributed to all members of the Canadian Society of Plastic Surgery (CSPS) using REDCap software. The survey examined 4 themes: previous training/experience, practice volume of nerve pathologies, experience with nerve transfers, and approach to the treatment of CuTS and high ulnar nerve injuries.

RESULTS

A total of 49 responses were collected (12% response rate). Of all, 62% of surgeons would use an AIN to ulnar motor supercharge end-to-side (SETS) transfer for a high ulnar nerve injury. For patients with CuTS and signs of intrinsic atrophy, 75% of surgeons would add an AIN-SETS transfer to a cubital tunnel decompression. Sixty-five percent would also release Guyon's canal, and the majority (56%) use a perineurial window for their end-to-side repair. Eighteen percent of surgeons did not believe the transfer would improve outcomes, 3% cited lack of training, and 3% would preferentially use tendon transfers. Surgeons with hand fellowship training and those less than 30 years in practice were more likely to use nerve transfers in the treatment of CuTS (P < .05).

CONCLUSIONS

Most CSPS members would use an AIN-SETS transfer in the treatment of both a high ulnar nerve injury and severe CuTS with intrinsic atrophy.

Following a Surgical Paradigm Shift Through the Adoption of Nerve Transfers Among Board-Eligible and Practicing Plastic Surgeons

BACKGROUND

Nerve transfers represent a new paradigm in the treatment of nerve injuries. Their current level of adoption among surgeons is unknown. This study evaluates the incidence of nerve transfers on case logs of board-eligible plastic surgeons over the past 14 years and surveys practicing nerve surgeons regarding their use of this technique.

METHODS

We queried the American Board of Plastic Surgery case log database for all nerve reconstruction Current Procedural Terminology codes from 2008 to 2021 and assessed trends and relationships between geographic region, examination year, and nerve transfer use. We surveyed nerve surgery professional societies to assess trends in practice, compared with a 2017 survey.

RESULTS

A total of 1959 nerve reconstruction cases were logged by 738 candidates from 2008 to 2021. Twelve percent of cases included nerve transfers. The proportion of nerve transfer codes (Z = -11.57; P < .0001) and the proportion of candidates performing nerve transfers (Z = -9.21, P < .0001) increased over the study period. Nerve transfers were associated with geographic region (χ² = 25.826, P = .0002), with most cases performed in the Midwest (26.4%). A higher proportion of practicing nerve surgeons reported performing nerve transfers in this survey than in our 2017 survey (χ² = 16.7, P < .001).

CONCLUSIONS

There has been an increase in nerve transfers logged in the past 14 years by board-eligible plastic surgeons, as well as increased use among currently practicing nerve surgeons. Although nerve transfer use is increasing among both plastic and orthopedic surgeons, a greater proportion of nerve reconstructions include nerve transfers in the plastic surgery cohort.

Is there any difference between anterior and posterior approach for the spinal accessory to suprascapular nerve transfer? A systematic review and meta-analysis

Dual nerve transfer of the spinal accessory nerve to the suprascapular nerve (SAN-SSN) and the radial nerve to the axillary nerve is considered to be the most feasible method of restoration of shoulder abduction in brachial plexus injuries. Supraspinatus muscle plays an important role in the initiation of abduction and its functional restoration is crucial for shoulder movements. There are two possible approaches for the SAN-SSN transfer: the more conventional anterior approach and the posterior approach in the area of scapular spine, which allows more distal neurotization. Although the dual nerve transfer is a widely used method, it is unclear which approach for the SAN-SSN transfer results in better outcomes. We conducted a search of English literature from January 2001 to December 2021 using the PRISMA guidelines. Twelve studies with a total 142 patients met our inclusion criteria. Patients were divided into two groups depending on the approach used: Group A included patients who underwent the anterior approach, and Group B included patients who underwent the posterior approach. Abduction strength using the Medical Research Scale (MRC) and range of motion (ROM) were assessed. The average MRC grade was 3.57 ± 1.08 in Group A and 4.0 ± 0.65 (p = 0.65) in Group B. The average ROM was 114.6 ± 36.7 degrees in Group A and 103.4 ± 37.2 degrees in Group B (p = 0.247). In conclusion, we did not find statistically significant differences between SAN-SSN transfers performed from the anterior or posterior approach in patients undergoing dual neurotization technique for restoration of shoulder abduction.

Treatment of C5 Palsy: An International Survey of Peripheral Nerve Surgeons

STUDY DESIGN

International survey.

OBJECTIVES

C5 palsy (C5P) is a neurological complication affecting 5-10% of patients after cervical decompression surgery. Most cases improve with conservative treatment; however, nearly 20% of patients may be left with residual deficits. Guidelines are lacking on C5P management and timing of surgical intervention. Therefore, we sought to survey peripheral nerve surgeons on their management of C5P.

METHODS

An online survey was distributed centered around a patient with C5P after posterior cervical decompression and fusion. Questions included surgeon demographics, diagnostic modalities, and timing and choice of operation. Responses were summarized and the chi-squared and Kruskal-Wallis H tests were used to examine differences across specialties.

RESULTS

A total of 154 surgeons responded to the survey, of which 59 (38%) indicated that they manage C5P cases. Average time prior to operating was 4.5 ± 2.2 months for complete injuries and 6.6 ± 3.2 months for partial injuries, with neurosurgeons significantly more likely to wait longer periods for complete (P = .01) and partial injuries (P = .03). Foraminotomies were selected by 19% of surgeons, while 92% selected nerve transfers. Transfer of the ulnar nerve to the musculocutaneous nerve was the most common choice (81%), followed by transfer of the radial nerve to the axillary nerve (58%).

CONCLUSION

Consensus exists among peripheral nerve surgeons on the use of nerve transfers for surgical treatment in cases with severe motor weakness failing to improve. Most surgeons advocate for early intervention in complete injuries. Disagreement concerns the type of nerve transfer employed, timing of surgery, and efficacy of foraminotomy.

Nerve Transfers for Brachial Plexus Reconstruction in Patients over 60 Years

Negative expectations regarding nerve reconstruction in the elderly prevail in the literature, but little is known about the effectiveness of nerve transfers in patients with brachial plexus injuries aged over 60 years. We present a series of five patients (1 female, 4 male) aged between 60 and 81 years (median 62.0 years) who underwent nerve reconstruction using multiple nerve transfers in brachial plexopathies. The etiology of brachial plexus injury was trauma (n = 2), or iatrogenic, secondary to spinal surgical laminectomy, tumor excision and radiation for breast cancer (n = 3). All but one patient underwent a one-stage reconstruction including neurolysis and extra-anatomical nerve transfer alone (n = 2) or combined with anatomical reconstruction by sural nerve grafts (n = 2). One patient underwent a two-stage reconstruction, which involved a first stage anatomical brachial plexus reconstruction followed by a second stage nerve transfer. Neurotizations were performed as double (n = 3), triple (n = 1) or quadruple (n = 1) nerve or fascicular transfers. Overall, at least one year postoperatively, successful results, characterized by a muscle strength of M3 or more, were restored in all cases, two patients even achieving M4 grading in the elbow flexion. This patient series challenges the widely held dogma that brachial plexus reconstruction in older patients will produce poor outcomes. Distal nerve transfers are advantageous as they shorten the reinnervation distance. Healthy, more elderly patients should be judiciously offered the whole spectrum of reconstructive methods and postoperative rehabilitation concepts to regain useful arm and hand function and thus preserve independence after a traumatic or nontraumatic brachial plexus injury.

Outcomes of immediate facial nerve reanimation with nerve transfer for facial nerve neoplasm-induced paralysis: a retrospective review

BACKGROUND

The purpose of this study was to evaluate the outcomes of our polyneural, zone-based reanimation approach for patients with neoplasm-induced facial paralysis.

METHODS

A retrospective review of consecutive patients who underwent facial reanimation surgery using multiple donor nerve transfers was undertaken. In each case, the selection of donor nerves was based on the availability of donor nerve and the viability of the motor endplate on the affected side. Sources of the neural inputs utilized included the remnant facial nerve stump, masseteric nerve, partial hypoglossal nerve, and branches of the contralateral facial nerve. Clinical outcomes were scored by expert raters. Ratings were undertaken using the modified House-Brackmann, eFACE and MEEI FACEgram scoring systems.

RESULTS

Between 2017 and 2020, 12 patients were included in the study (mean age 60 years; range 26-81 years). Eight patients (67%) achieved a grade III outcome on the modified House-Brackmann grading scale. Mean eFACE static and dynamic scores were 76 and 57 respectively, reflecting a high degree of symmetry at rest and moderate restoration of dynamic movement. Mean time to movement was 5.4 months (SD 1.9). Objective FACE-gram measurements confirmed restoration of midface movement with an average improvement in smile excursion and mouth angle excursion of 3.19 mm (SD 3.18) and 4.81° (SD 2.90) respectively.

CONCLUSION

Facial reanimation using multiple nerve transfers is effective in achieving improvements in facial function and symmetry.

The Effectiveness of Different Nerve Transfers in the Restoration of Elbow Flexion in Adults Following Brachial Plexus Injury: A Systematic Review and Meta-Analysis

PURPOSE

Restoration of elbow flexion is an important goal in the treatment of patients with traumatic brachial plexus injury. Numerous studies have described various nerve transfers for neurotization of the musculocutaneous nerve (or its motor branches); however, there is uncertainty over the effectiveness of each method. The aim of this study was to summarize the published evidence in adults with traumatic brachial plexus injury.

METHODS

Medline, Embase, medRxiv, and bioRxiv were systematically searched from inception to April 12, 2021. We included studies that reported the outcomes of nerve transfers for the restoration of elbow flexion in adults. The primary outcome was elbow flexion of grade 4 (M4) or higher on the British Medical Research Council scale. Data were pooled using random-effects meta-analyses, and heterogeneity was explored using metaregression. Confidence intervals (CIs) were generated to the 95% level.

RESULTS

We included 64 articles, which described 13 different nerve transfers. There were 1,335 adults, of whom 813 (61%) had partial and 522 (39%) had pan-plexus injuries. Overall, 75% of the patients with partial brachial plexus injuries achieved ≥M4 (CI, 69%-80%), and the choice of donor nerve was associated with clinically meaningful differences in the outcome. Of the patients with pan-plexus injuries, 45% achieved ≥M4 (CI, 31%-60%), and overall, each month delay from the time of injury to reconstruction reduced the probability of achieving ≥M4 by 7% (CI, 1%-12%).

CONCLUSIONS

The choice of donor nerve affects the chance of attaining a British Medical Research Council score of ≥4 in upper-trunk reconstruction. For patients with pan-plexus injuries, delay in neurotization may be detrimental to motor outcomes.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Successful retrograde regeneration using a sensory branch for motor nerve transfer

OBJECTIVE

The objective of this study was to test whether regenerating motor axons from a donor nerve can travel in a retrograde fashion using sensory branches to successfully reinnervate a motor nerve end organ.

METHODS

This study has two parts. In part I, rats (n = 30) were assigned to one of five groups for obturator nerve (ON)-to-femoral nerve transfer: group 1, ON-to-saphenous nerve (SN) distal stump; group 2, ON-to-SN proximal stump without femoral nerve proper (FNP) injury; group 3, ON-to-SN proximal stump with FNP crush injury; group 4, ON-to-SN proximal stump with FNP transection injury; and group 5, gold standard transfer, ON-to-motor femoral nerve (MFN) branch. At 8 weeks, retrograde labeling was done from the distal MFN, and the spinal cords were examined to assess the degree of obturator motor axon regeneration across the five groups. In part II, only group 4 was examined (n = 8). Through use of immunostaining and optical tissue clearing methods, the nerve transfer networks were cleared and imaged using light-sheet fluorescence microscopy to visualize the regeneration pathways in 2D and 3D models at 2- and 8-week time points.

RESULTS

Proximal FNP transection (group 4) enabled a significantly higher number of retrogradely regenerated motor axons compared with control groups 1-3. Moreover, group 4 had modest, but nonsignificant, superiority of motor neuron counts compared with the positive control group, group 5. Optical tissue clearing demonstrated that the axons traveled in a retrograde fashion from the recipient sensory branch to the FNP mixed stump, then through complex turns, down to distal branches. Immunostaining confirmed the tissue clearing findings and suggested perineurium disruption as a means by which axons could traverse across fascicular boundaries.

CONCLUSIONS

Sensory branches can transmit regenerating axons from donor nerves back to main mixed recipient nerves, then distally toward target organs. The extent of retrograde regeneration is markedly influenced by the type and severity of injury sustained by the recipient nerve. Using a sensory branch as a bridge for retrogradely regenerating axons can open new potential horizons in nerve repair surgery for severely injured mixed nerves.

Interfascicular Anatomy of the Motor Branch of the Ulnar Nerve: A Cadaveric Study

PURPOSE

The motor branch of the ulnar nerve contains fascicles that innervate the intrinsic musculature of the hand. This cadaveric study aimed to describe the organization and consistency of the internal topography of the motor branch of the ulnar nerve.

METHODS

Five fresh-frozen cadaveric specimens with an average age of 74 years (range, 65-88 years) were dissected. The ulnar nerve was exposed and transfixed to the underlying tissues to maintain its orientation throughout the dissection. The dorsal cutaneous branch (DCB) and the volar sensory branch were identified and reflected to expose the motor branch. The fascicles to the first dorsal interosseus (FDI), flexor pollicis brevis, and abductor digiti minimi (ADM) were identified. Internal neurolysis was performed distal to proximal to identify the interfascicular arrangement of these fascicles within the motor branch. The organization of these fascicles was noted, and the branch points of the DCB, FDI, and ADM were measured relative to the pisiform using a handheld electronic caliper.

RESULTS

The internal topography of the motor branch was consistent among all specimens. Proximal to the pisiform, the arrangement from radial to ulnar was as follows: volar sensory branch, flexor pollicis brevis, FDI/intrinsic muscles, ADM, and DCB. The position of these branches remained consistent as the deep motor branch curved radially within the palm and traveled to the terminal musculature. The locations of the average branch points of the FDI, ADM, and DCB with respect to the pisiform were as follows: FDI, 4.6 cm distal (range, 4.1-4.9 cm), 4.5 cm radial (range, 4.1-4.9 cm); ADM, 0.65 cm distal (range, 0.3-1.1 cm), 0.7 cm radial (range, 0.3-1.1 cm), DCB, 7.7 cm proximal (range, 4.2-10.1 cm), and 0.4 cm ulnar (range, 0.3-0.8 cm).

CONCLUSIONS

The internal topography of the ulnar nerve motor branch was consistent among the specimens studied. The topography of the motor branches was maintained as the motor branch turns radially within the palm.

CLINICAL RELEVANCE

This study provides further understanding of the internal topography of the ulnar nerve motor branch at the wrist level.

Distal Nerve Transfers in High Peroneal Nerve Lesions: An Anatomical Feasibility Study

The peroneal nerve is one of the most commonly injured nerves of the lower extremity. Nerve grafting has been shown to result in poor functional outcomes. The aim of this study was to evaluate and compare anatomical feasibility as well as axon count of the tibial nerve motor branches and the tibialis anterior motor branch for a direct nerve transfer to reconstruct ankle dorsiflexion. In an anatomical study on 26 human body donors (52 extremities) the muscular branches to the lateral (GCL) and the medial head (GCM) of the gastrocnemius muscle, the soleus muscle (S) as well as the tibialis anterior muscle (TA) were dissected, and each nerve's external diameter was measured. Nerve transfers from each of the three donor nerves (GCL, GCM, S) to the recipient nerve (TA) were performed and the distance between the achievable coaptation site and anatomic landmarks was measured. Additionally, nerve samples were taken from eight extremities, and antibody as well immunofluorescence staining were performed, primarily evaluating axon count. The average diameter of the nerve branches to the GCL was 1.49 ± 0.37, to GCM 1.5 ± 0.32, to S 1.94 ± 0.37 and to TA 1.97 ± 0.32 mm, respectively. The distance from the coaptation site to the TA muscle was 43.75 ± 12.1 using the branch to the GCL, 48.31 ± 11.32 for GCM, and 19.12 ± 11.68 mm for S, respectively. The axon count for TA was 1597.14 ± 325.94, while the donor nerves showed 297.5 ± 106.82 (GCL), 418.5 ± 62.44 (GCM), and 1101.86 ± 135.92 (S). Diameter and axon count were significantly higher for S compared to GCL as well as GCM, while regeneration distance was significantly lower. The soleus muscle branch exhibited the most appropriate axon count and nerve diameter in our study, while also reaching closest to the tibialis anterior muscle. These results indicate the soleus nerve transfer to be the favorable option for the reconstruction of ankle dorsiflexion, in comparison to the gastrocnemius muscle branches. This surgical approach can be used to achieve a biomechanically appropriate reconstruction, in contrast to tendon transfers which generally only achieve weak active dorsiflexion.

Posterior division of ipsilateral C7 transfer to C5 for shoulder abduction limitation

Background

Reparation of C5 by proximal selective ipsilateral C7 transfer has been reported for the treatment of neurogenic shoulder abduction limitation as an alternative to the reparation of the suprascapular nerve (SSN) and the axillary nerve (AXN) by distal nerve transfers. However, there is a lack of evidence to support either strategy leading to better outcomes based on long-term follow-up.

Objective

The purpose of the study was to investigate the safety and long-term outcomes of the posterior division of ipsilateral C7 (PDIC7) transfer to C5 in treating neurogenic shoulder abduction limitation.

Methods

A total of 27 cases with limited shoulder abduction caused by C5 injury (24 cases of trauma, 2 cases of neuritis, and 1 case of iatrogenic injury) underwent PDIC7 transfer to the C5 root. A total of 12 cases (11 cases of trauma and 1 case of neuritis) of C5 injury underwent spinal accessory nerve (SAN) transfer to SSN plus the triceps muscular branch of the radial nerve (TMBRN) transfer to AXN. The patients were followed up for at least 12 months for muscle strength and shoulder abduction range of motion (ROM).

Results

In cases that underwent PDIC7 transfer, the average shoulder abduction was 105.9° at the 12-month follow-up. In total, 26 of 27 patients recovered at least M3 (13 reached M4) (Medical Research Council Grading) of the deltoid. In cases that underwent SAN transfer to SSN plus TMBRN to AXN, the average shoulder abduction was 84.6° at the 12-month follow-up. In total, 11 of 12 patients recovered at least M3 (4 reached M4) of the deltoid.

Conclusion

Posterior division of ipsilateral C7 transfer is a one-stage, safe, and effective surgical procedure for patients with neurogenic shoulder abduction limitation.

Tendon Transfers, Nerve Grafts, and Nerve Transfers for Isolated Radial Nerve Palsy: A Systematic Review and Analysis

INTRODUCTION

Isolated radial nerve palsy is a debilitating injury that may potentially be reconstructed with either tendon transfers, nerve grafts, or nerve transfers. Currently, there is no consensus on the optimal technique for reconstruction. We performed a systematic review and analysis to determine which surgical intervention provides the best clinical outcomes.

METHODS

A systematic review was conducted according to PRISMA guidelines. Twenty-nine papers met inclusion criteria. Grading scales of function and strength were converted into a tripartite scoring system to compare outcomes between techniques. χ2 analyses were performed with a P value < .05.

RESULTS

Seven hundred fifty-four patients were analyzed. Tendon transfers resulted in the highest percentage of good outcomes (82%) and the lowest percentage of poor outcomes (9%). Tendon transfers were superior to nerve grafts and nerve transfers for restoration of wrist extension. Nerve transfers for wrist extension were superior to nerve transfers for finger extension. Nerve grafts and nerve transfers had equivalent rates of good and poor clinical outcomes.

CONCLUSIONS

This study analyzed reported outcomes of tendon transfers, nerve grafts, and nerve transfers for reconstruction of isolated radial nerve palsy. On pooled analysis, tendon transfers had higher rates of superior clinical outcomes as compared with nerve transfers and nerve grafts. Tendon transfers should be considered first-line reconstruction for isolated radial nerve palsy as nerve-based reconstruction is less predictable and reproducible.

Outcomes after Anterior Interosseous Nerve to Ulnar Motor Nerve Transfer

Background  Ulnar nerve lesions proximal to the elbow can result in loss of intrinsic muscle function of the hand. The anterior interosseous nerve (AIN) to deep motor branch of the ulnar nerve (DBUN) transfer has been demonstrated to provide intrinsic muscle reinnervation, thereby preventing clawing and improving pinch and grip strength. The purpose of this study was to evaluate the efficacy of the AIN to DBUN transfer in restoring intrinsic muscle function for patients with traumatic ulnar nerve lesions. Methods  We performed a prospective, multi-institutional study of outcomes following AIN to DBUN transfer for high ulnar nerve injuries. Twelve patients were identified, nine of which were enrolled in the study. The mean time from injury to surgery was 15 weeks. Results  At final follow-up (mean postoperative follow-up 18 months + 15.5), clawing was observed in all nine patients with metacarpophalangeal joint hyperextension of the ring finger averaging 8.9 degrees (+ 10.8) and small finger averaging 14.6 degrees (+ 12.5). Grip strength of the affected hand was 27% of the unaffected extremity. Pinch strength of the affected hand was 29% of the unaffected extremity. None of our patients experienced claw prevention after either end-to-end ( n  = 4) or end-to-side ( n  = 5) AIN to DBUN transfer. Conclusion  We conclude that, in traumatic high ulnar nerve injuries, the AIN to DBUN transfer does not provide adequate intrinsic muscle reinnervation to prevent clawing and normalize grip and pinch strength.