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. 2026 Jul 6;100(4):867–875. doi: 10.1002/ana.78296

Neurophysiological Recovery Following Nerve Transfer Surgery to Restore Upper Limb Function after Cervical Spinal Cord Injury

Kyle J Missen 1,2, Justin M Brown 3, Ross M Mandeville 4, Harvey Wu 1, Sean Bristol 5,6, Peter K Broadhurst 7, Erin Brown 5,6, Christopher Doherty 5,6, Amy K Hanlan 2,5, Russell O'Connor 2,5, Lawrence R Robinson 7,8, Kayton Rotenberg 3, J Michael Hendry 9,10, Jana Dengler 11,12, Michael J Berger 1,2,5,✉
PMCID: PMC13587116  PMID: 42410673

Abstract

Objectives

Nerve transfer is a promising intervention for restoring hand and upper limb function after cervical spinal cord injury (SCI), but the timeline of neurophysiological recovery in humans remains unclear. This study aimed to define recovery profiles after nerve transfers to restore upper limb function.

Methods

Individuals with traumatic cervical SCI who received nerve transfer surgery in at least 1 limb were evaluated during routine clinical visits for up to 2 years post‐transfer. The primary outcome was the time to detect reinnervation, defined as the appearance of voluntary motor unit potentials on needle electromyography. Representative muscles were assessed for 5 nerve transfer procedures: (1) supinator to posterior interosseous nerve; (2) brachialis to anterior interosseous nerve (AIN); (3) extensor carpi radialis longus to AIN; (4) extensor carpi radialis brevis to AIN; and (5) axillary to triceps. In a subset of participants who continued needle electromyography after reinnervation was detected, an ordinal grading system characterized motor unit potential maturity and the presence of pathological spontaneous activity over time.

Results

A total of 44 individuals with traumatic cervical SCI were enrolled. Mean times to detect reinnervation were 6.9 months (supinator–posterior interosseous nerve), 10.4 months (brachialis–AIN), 9.6 months (extensor carpi radialis longus–AIN), 9.6 months (extensor carpi radialis brevis–AIN), and 9.0 months (axillary–triceps). Over time, reinnervated muscles showed reduced pathological spontaneous activity and progression from nascent to mature motor unit potentials.

Interpretation

These findings establish benchmark timelines for first detection of neurophysiological reinnervation after nerve transfer in cervical SCI, providing a foundation for setting clinical expectations, planning rehabilitation, and designing future interventional studies. ANN NEUROL 2026;100:867–875

Nerve transfer surgery is increasingly being used as a method to restore elbow extension, finger flexion, and finger extension in individuals with cervical spinal cord injury (SCI). 1 Several prospective studies 2 , 3 , 4 , 5 and one systematic review 6 highlight that nerve transfer surgery improves upper limb muscle strength and functional scores. However, these studies also demonstrate variability in treatment response between individuals and between different nerve transfers within the same individual. For example, Javeed et al 2 reported that at a median of 21 months after surgery, reinnervation of the finger flexors resulted in a median manual muscle strength score of 2, but the interquartile range (IQR) was 1–3, and nearly half of the individuals who underwent this transfer did not achieve antigravity strength. Variability between nerve transfer types has been demonstrated across studies, with motor outcomes typically superior for the radial branch of the supinator to posterior interosseous nerve (PIN) transfer to restore finger and thumb extensor strength, compared with the musculocutaneous branch of the brachialis to anterior interosseous nerve (AIN) transfer for finger and thumb flexion. 2 , 3 , 4 , 5

The reasons for interindividual and intertransfer variability in treatment response have not been investigated. As the fundamental goal of nerve transfer surgery is reinnervation of paralyzed muscle with new motor axons derived from a healthy donor nerve above the level of injury, it is intuitive that the time course and quality of reinnervation could pose barriers to recovery. It is well established that the time to reinnervation is inversely correlated with motor and functional outcomes in preclinical and clinical models of nerve injury. 7 , 8 , 9 The time to reinnervation is influenced, in part, by the distance regenerating axons must travel from the donor nerve to the target muscle. Axonal regeneration distances are typically shorter for finger and thumb extensor transfers compared with those for finger and thumb flexors (~4 cm for the supinator–PIN transfer 10 compared with ~7 cm for extensor carpi radialis brevis (ECRB)–AIN 11 and >15 cm for brachialis–AIN transfers 11 , 12 ). These longer regeneration distances likely contribute to slower reinnervation timelines and may help explain why extensor transfers generally yield superior motor outcomes.

Establishing neurophysiological recovery profiles is an important step toward further understanding the natural history of recovery after nerve transfer surgery, and determining whether limited or delayed reinnervation poses a barrier to successful outcomes. This information is also clinically relevant for setting patient expectations about the time course of recovery, and providing useful prognostic information for clinicians as they monitor the recovery process. Therefore, the purpose of this study was to evaluate neurophysiological recovery after nerve transfer surgery in SCI using data from needle electromyography (EMG) examinations. Specifically, we aimed to determine the time to reinnervation onset and characterize the progression of motor unit properties in recipient muscles after nerve transfer.

Methods

A portion of the data for this analysis was obtained from participants enrolled in a larger prospective, multicenter, open‐label, non‐randomized interventional cohort study of nerve transfer surgery in SCI (ClinicalTrials.gov, NCT05638191). A full description of the study setting, locations, names and numbers of approving ethical boards, and periods of recruitment, follow up, and data collection is available at https://clinicaltrials.gov/study/NCT05638191. An additional center not listed in the study registry contributed data on 14 participants who underwent similar surgical procedures, rehabilitation, and follow‐up evaluations. All study procedures were approved by local ethics boards, and written informed consent was obtained from all participants. This report adheres to the STROBE checklist for cohort studies.

Participants

All participants underwent unilateral or bilateral nerve transfer surgery, utilizing various combinations of procedures based on clinical indications. Eligibility for nerve transfer surgery is highly personalized. Generally, individuals with SCI are eligible if they have a suitable source of redundant donor axons, and experience poor/absent strength in either or both finger/thumb/elbow extension and finger/thumb flexion. 13 , 14 , 15 Typically, this means that presurgery motor level (defined by the International Standards for Neurological Classification of Spinal Cord Injury 16 ) is C5‐7, with grade 0–1 strength in recipient muscle groups. These classifications were determined from each patient's most recent preoperative inpatient chart notes. Before undergoing nerve transfer surgery, all participants underwent baseline electrodiagnostic examinations to rule out intercurrent peripheral nervous system conditions (eg, a brachial plexus lesion) and to assess the health of the donor nerves. Motor examinations were performed at the time of baseline EMG assessments to confirm the motor level of injury.

None of the participants had any medical, psychiatric, or cognitive comorbidity that may have influenced the study results. All participants were enrolled in a structured rehabilitation program, supervised by an experienced hand therapist, although the frequency and intensity of rehabilitation were not standardized.

Nerve Transfer Procedures

The surgical principles of nerve transfer are well described elsewhere. 17 , 18 , 19 All surgeons involved in the study were board‐certified plastic surgeons or neurosurgeons with extensive experience with nerve transfer surgery in SCI. The nerve transfer options for SCI are well defined. 20 The 5 main options are: (1) radial branch to supinator to PIN to restore finger/thumb extension; (2) musculocutaneous branch to brachialis to AIN, (3) radial branch to extensor carpi radialis longus (ECRL) to AIN, or (4) radial branch to ECRB to AIN to restore finger/thumb flexion; and (5) axillary to radial branch of the long head of triceps brachii to restore elbow extension. 21 , 22 The choice between using ECRL and ECRB as a donor nerve is surgeon‐dependent, and reflects a balance between reinnervation distance and preservation of wrist extension mechanics. Use of ECRB offers a more distal branching pattern 21 that may support earlier reinnervation, whereas use of the ECRL may better preserve central wrist extension by sparing the ECRB, consistent with tendon transfer principles, at the cost of potentially a longer reinnervation time. The ECRL–AIN and ECRB–AIN transfers may be preferred over the brachialis–AIN transfer due to their shorter distance for reinnervation, 11 but they are only available for individuals with C6–7 motor levels.

EMG Assessments

Needle EMG examinations of representative nerve transfer recipient muscles were performed by board‐certified electrodiagnosticians. Our group has previously published on electrodiagnostic approaches to postsurgical evaluation. 13 , 23 , 24 Standard anatomical landmarks were used to identify the muscles of interest, and in many cases, ultrasound was used to further confirm needle localization within these muscles. 25 The representative muscles tested in this study were the extensor digitorum communis for the supinator–PIN transfer, either the flexor pollicis longus or flexor digitorum profundus for the brachialis–AIN, ECRL–AIN, and ECRB–AIN transfers, and the long head of triceps brachii for the axillary–triceps transfer. Needle EMG evaluation of the representative muscles included characterization of pathological spontaneous activity (PSA; fibrillation potentials and positive sharp waves) and motor unit potential (MUP) morphology. MUP morphology was evaluated by the physiatrist, and described as absent (no detectable MUPs), nascent (small amplitude <500 μV, polyphasic), normal (amplitude 1–2 mV, bi‐ or triphasic), or chronic (amplitude >2 mV, bi‐ or triphasic) reinnervation. Denervation status was described in each representative muscle as present (PSA observed) or absent (no PSA observed).

Early in the recovery process, the donor muscle group often needs to be coactivated simultaneously with the recipient muscle of interest to elicit voluntary motor unit activity (donor augmentation). Participants were instructed to co‐contract the donor and recipient muscles to augment motor unit recruitment. Evaluations were conducted separately for each limb that underwent nerve transfer; thus, participants who received bilateral transfers could contribute data from both limbs to the analysis.

Follow‐Up Framework

The standard for our group is to schedule individuals with SCI who undergo nerve transfer for follow‐up assessments approximately every 3 months, up to 24 months postoperatively, to monitor motor recovery, identify barriers to progress, and evaluate potential adverse events. However, based on clinical experience indicating that evidence of reinnervation rarely emerges before 3 months post‐transfer, clinicians may advise patients to delay their visit until the 6‐month mark, provided no unexpected complications arise. In addition, logistical challenges, such as travel burden and accessibility, can limit the feasibility of frequent follow up for many individuals with SCI. Actual follow‐up times may therefore deviate from the ideal schedule. It should also be emphasized that the intervals between EMG assessments prevent us from directly observing the exact time of reinnervation. Instead, reinnervation must occur somewhere between the last visit (or the nerve transfer itself), which shows no MUPs, and the visit during which MUPs are first detected. As a result, the recorded time to reinnervation is an interval‐censored estimate and occurs later than the true biological onset of reinnervation.

Statistical Analysis

Kaplan–Meier survival analysis was conducted to estimate the time to reinnervation, starting from the date of nerve transfer surgery. The primary outcome was defined as the time, in months, to the first observable MUP on needle EMG examinations. Each limb was analyzed as a single event. If a limb received >1 nerve transfer (eg, double nerve transfer for finger extension and flexion), it counted as 1 limb in the analysis for each relevant transfer type. Incorporating bilateral limb data may introduce some non‐independence between observations from the same participant 26 and may influence the mean time to EMG‐detected reinnervation, because both limbs are typically assessed at the same visit; however, analyses were descriptive and no inferential comparisons assuming independence between limbs were performed. Limbs that showed no evidence of reinnervation at the participant's latest follow‐up assessment were right censored. Time to reinnervation for each nerve transfer type was summarized using restricted mean survival times (area under the Kaplan–Meier curve truncated at 24 months), 27 , 28 IQRs from Kaplan–Meier estimates, and cumulative incidence of reinnervation at 12 months (R package ‘survival’). Given the interval‐censored nature of EMG follow up and the limited temporal resolution for identifying the true biological onset of reinnervation, models evaluating predictors of reinnervation timing (eg, participant age, time from injury to surgery) were not performed.

We also assessed MUP morphology and PSA at each follow up to characterize MUP maturation and denervation status over the 2‐year follow‐up period. Classifications of MUP morphology and PSA were grouped into consecutive 6‐month bins (0–6, 6–12, 12–18, and 18–24 months post‐transfer), and the proportion of limbs showing each characteristic was calculated for each bin. Participants for whom MUPs were already present in all representative muscles at the first visit and who did not return for further evaluations (ie, those who completed only a single EMG assessment) were excluded from this additional analysis. All statistical analyses were performed using R software (version 4.1.3; R Foundation for Statistical Computing).

Results

Participants

A total of 44 individuals with traumatic cervical SCI who received nerve transfer in at least 1 limb participated in this study. Participant demographic information and injury characteristics are provided in Table 1. A total of 20 participants (45%) received transfers within 6 months of their injury, with a median time from injury to surgery of 6.2 months (IQR 5.1–17.5 months). A total of 31 participants (70%) received bilateral transfers, and 13 participants (30%) received unilateral transfers. The supinator–PIN transfer was performed on 70 limbs, the brachialis–AIN transfer was performed on 34 limbs, the ECRL–AIN transfer was performed on 9 limbs, the ECRB–AIN transfer was performed on 5 limbs, and the axillary–triceps transfer was performed on 11 limbs.

TABLE 1.

Participant Characteristics

Characteristic Total n = 44
Age, yr (mean ± SD) 37.1 ± 14.3
Sex, female, n (%) 9 (20%)
Neurological level of injury
C3, n (%) 1 (2%)
C4, n (%) 13 (30%)
C5, n (%) 18 (41%)
C6, n (%) 10 (23%)
C7, n (%) 2 (4%)
AIS grade
A, n (%) 27 (62%)
B, n (%) 12 (27%)
C, n (%) 4 (9%)
D, n (%) 1 (2%)
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Age is reported at the time of surgery. American Spinal Injuries Association Impairment Scale (AIS) grades were determined from preoperative International Standards for Neurological Classification of Spinal Cord Injury examinations.

Time to Reinnervation

A total of 152 follow‐up EMG assessments were conducted across the participant sample. The median time to first follow‐up EMG assessment was 6 months post‐transfer. Evidence of reinnervation in both limbs at the same time was observed in 83% (24/29) of participants with bilateral supinator–PIN transfers, 43% (6/14) of participants with bilateral brachialis–AIN transfers, 50% (1/2) of participants with bilateral ECRL–AIN transfers, 100% (1/1) of participants with bilateral ECRB‐AIN transfers, and 50% (2/4) of participants with bilateral axillary–triceps transfers. The time to reinnervation and survival curves for each transfer are presented in Fig 1.

FIGURE 1.

FIGURE 1

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Survival curves representing time to reinnervation. The mean time to reinnervation is shown in vertical dashed lines and to the right of the survival curves. Horizontal lines along the survival curves indicate censored observations. AIN = anterior interosseous nerve; ECRB = extensor carpi radialis brevis; ECRL = extensor carpi radialis longus; PIN = posterior interosseous nerve.

Reinnervation timelines differed across transfer types. For supinator–PIN transfers, evidence of reinnervation was first observed at approximately 3.3 months postsurgery. The proportion of limbs without reinnervation declined most notably between 5 and 7 months, with a mean time to reinnervation of 6.9 months (IQR 5.8–7.5 months). By 12 months, 92.9% of transfers demonstrated electrophysiological evidence of reinnervation.

Among transfers restoring finger and thumb flexion, the timing and proportion of reinnervation varied by donor nerve. ECRB–AIN and ECRL–AIN transfers demonstrated a mean reinnervation time of 9.6 months (ECRB–AIN: IQR 10.0–10.0 months; ECRL–AIN: IQR 6.9–11.9). All ECRB‐AIN transfers and 77.8% of ECRL–AIN transfers demonstrated evidence of reinnervation by 12 months. Brachialis–AIN transfers took longer to demonstrate evidence of reinnervation, with a mean time to reinnervation of 10.4 months (IQR 7.1–12.6 months). By 12 months postsurgery, reinnervation was observed in 69.4% of brachialis–AIN transfers.

For axillary–triceps transfers, the earliest evidence of reinnervation was observed at approximately 4.1 months post‐transfer, with a mean reinnervation time of 9.0 months (IQR 4.7–12.9 months). A total of 72.7% of transfers demonstrated reinnervation at 24 months postsurgery.

Two participants with brachialis–AIN transfers (1 limb each) were censored from the survival analysis, because they did not show evidence of reinnervation. Of these participants, 1 was lost to follow up before the mean brachialis–AIN reinnervation time (their latest follow up was ~7 months post‐transfer), and the other showed no evidence of reinnervation in 1 limb at their final follow‐up assessment at 24 months post‐transfer. One participant with axillary–triceps transfers (one limb) was lost to follow‐up at ~10.9 months post‐transfer and censored. No participants were censored for supinator–PIN, ECRL–AIN, or ECRB–AIN transfers.

MUP Properties and Denervation Status

MUPs and denervation status were characterized across follow ups according to the grading scheme outlined in the EMG Assessments section and binned into 6‐month periods. A total of 47 supinator–PIN transfers (limbs), 19 brachialis–AIN transfers, 8 ECRL–AIN transfers, 5 ECRB–AIN transfers, and 8 axillary–triceps transfers were evaluated in the sample.

Overall, MUPs assessed in all muscles progressively matured over the 24 months after surgery (Fig 2A). Within the first 6 months, most supinator–PIN MUPs were classified as nascent, with some normal and chronic MUPs appearing within the first year. By 24 months, all supinator–PIN transfers in the sample demonstrated evidence of reinnervation, with most MUPs classified as chronic or normal, although some remained nascent. In contrast, most AIN transfers showed no evidence of reinnervation within 6 months; however, by 12 months, the majority showed nascent MUPs, along with some normal and chronic MUPs. By 24 months, all AIN transfers demonstrated evidence of reinnervation, except for 1 limb that received a brachialis–AIN transfer. MUPs were relatively more mature at 24 months postsurgery after receiving ECRB–AIN transfers than after ECRL–AIN or brachialis–AIN transfers. Just over half of the triceps did not show evidence of reinnervation within the first 6 months post‐transfer, but MUPs progressively matured, and by 24 months, ~80% were classified as normal. No MUPs in the triceps were classified as chronic throughout the follow‐up period.

FIGURE 2.

FIGURE 2

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Neurophysiological recovery in nerve transfer recipient muscles. (A) Motor unit potential morphological characteristics and (B) pathological spontaneous activity in nerve transfer recipient muscles across a 2‐year follow‐up period. Representative muscles are the extensor digitorum communis (supinator–posterior interosseous nerve), flexor pollicis longus and flexor digitorum profundus (brachialis–anterior interosseous nerve, extensor carpi radialis longus–anterior interosseous nerve, extensor carpi radialis brevis–anterior interosseous nerve), and the long head of the triceps brachii (axillary–triceps). The number of transfers (limbs) in each bin is indicated above each bar. AIN = anterior interosseous nerve; ECRB = extensor carpi radialis brevis; ECRL = extensor carpi radialis longus; PIN = posterior interosseous nerve.

The proportion of muscles demonstrating PSA also progressively decreased over time (Fig 2B). Within 6 months postsurgery, the majority of representative muscles across all transfer types showed evidence of PSA. By 24 months, PSA was present in <5% of supinator–PIN muscles, approximately 36% and 29% of finger/thumb flexors after brachialis–AIN and ECRL–AIN transfers, and 40% of triceps. None of the ECRB–AIN transfer representative muscles demonstrated evidence of PSA by 24 months.

Discussion

This study aimed to determine the time to reinnervation, defined by the earliest observable MUP on needle EMG, in recipient muscles after nerve transfer surgeries to restore upper limb function in cervical SCI. Overall, reinnervation was detected earliest in muscles restoring finger and thumb extension, with the majority of supinator–PIN transfers demonstrating evidence of neurophysiological recovery within the first year after surgery. In contrast, reinnervation of finger and thumb flexors was detected later and varied by donor nerve, with ECRB–AIN transfers demonstrating more complete recovery by 12 months compared with ECRL–AIN and brachialis–AIN transfers. Axillary–triceps transfers demonstrated an intermediate recovery profile. These findings are consistent with prior reports that detectable muscle contraction (Medical Research Council grade 1) occurs earlier in the finger extensors (median 12 months) than in the finger/thumb flexors (median 18 months) in individuals with SCI who received late nerve transfers (median 21 months postinjury). 2 These findings can help clinicians set realistic expectations and design better rehabilitation timelines for patients undergoing nerve transfers after cervical SCI. Additionally, these results provide a framework for identifying atypical recovery after nerve transfer.

Perhaps the most important biological factor contributing to differences in reinnervation timing across transfer types is the distance from the nerve coaptation site to the motor target. In the present study, transfers associated with shorter coaptation‐to‐target distances demonstrated earlier reinnervation. Estimates suggest that this distance is approximately 4 cm for the supinator–PIN transfer (supinator deep head motor branch of radial nerve to extensor digitorum communis), 10 whereas it is approximately 7 cm for the ECRB–AIN transfer (ECRB branch of radial nerve to flexor pollicis longus or flexor digitorum profundus) 11 and >15 cm for the brachialis–AIN transfer (brachialis branch of the musculocutaneous nerve to flexor pollicis longus or flexor digitorum profundus). 11 , 12 Given that axonal regeneration proceeds at an approximate rate of 1 mm/day, 29 longer regeneration distances result in prolonged denervation. During this period, motor endplate degeneration, muscle fiber atrophy, and fibrosis may progressively reduce the target muscle's receptivity. 30 , 31 If reinnervation is not achieved within approximately 12–18 months, irreversible neuromuscular junction degeneration can occur. 32

These biological constraints likely also explain the variability in functional outcomes reported in the literature. In the present study, reinnervation on needle EMG was detected earlier in ECRB–AIN and ECRL–AIN transfers than in brachialis–AIN transfers. This is consistent with prior reports suggesting that functional outcomes are stronger when the radial branch to ECRB is used as the donor. 33 For instance, Bertelli and Ghizoni 12 reported that all limbs undergoing ECRB–AIN transfers achieved strong finger flexion (Medical Research Council grade 4), whereas using brachialis as a donor resulted in only 3 of 8 limbs achieving grade 3, and just 1 of 8 limbs achieving grade 4. Superior outcomes observed with the ECRB donor may also be attributed to its ample motor axon supply 34 and the fact that it is a more natural synergistic donor for finger flexion compared with the brachialis. Additionally, the ECRB–AIN transfer is more specific, as the donor is coapted directly into the AIN, whereas brachialis–AIN transfers are performed at a more proximal level of the median nerve where the fascicular pattern is less distinct, making it harder to ensure that the entire donor input is directed toward the intended AIN fibers. 35 It is important to acknowledge, however, that the optimal donor may vary among patients. For instance, the brachialis may be the only available donor to restore hand closure in individuals with a C5‐level injury. Thus, donor selection should be individualized based on patient‐specific considerations.

Throughout the 24‐month follow‐up period, we observed a progressive maturation of reinnervated MUPs in all recipient muscles. Early after reinnervation, needle EMG examinations revealed characteristics of immature reinnervated motor units, including small amplitudes and polyphasic patterns, in all recipient muscles. Over time, the MUPs became less polyphasic and increased in amplitude, reflecting ongoing terminal axon maturation and collateral sprouting into denervated muscle fibres. 36 Consistent with a slower time to reinnervation, finger/thumb flexors across all AIN transfer types, as well as triceps, remained polyphasic and showed a more prolonged period of PSA than the finger extensors. This pattern of motor unit remodeling is consistent with prior research, which demonstrated that reinnervated muscles in a non‐SCI model undergo extensive remodeling from nascent units to mature units over approximately 2 years. 37 We have recently demonstrated that even long after surgery (>18 months), motor units of nerve transfer recipient muscles in individuals with cervical SCI demonstrate instability upon repeated discharges, suggesting prolonged immaturity at the terminal axons and neuromuscular junctions. 38

Several limitations of our study should be acknowledged. First, the times to reinnervation we report are based on the first detection of reinnervation during scheduled follow ups. True reinnervation occurred between visits, so the interval‐censored nature of the data may lead to an overestimation of the true time to reinnervation. Thus, true reinnervation likely occurred earlier than reported. Second, our data are dichotomous and ordinal, which may lack the sensitivity to detect more subtle changes in muscle reinnervation and limit mechanistic insights into reinnervation timelines. Third, although all participants underwent structured postoperative rehabilitation, the frequency, intensity, adherence, and progression of rehabilitation were not systematically tracked over the 2‐year follow‐up period; therefore, we could not assess how rehabilitation exposure influenced neurophysiological or functional recovery. Fourth, some nerve transfer subgroups were small, and findings from these transfers should be interpreted accordingly. Finally, we did not formally assess the relationship between the reinnervation and maturation of recipient muscle motor units and improvements in upper limb function in this study. Although prior studies suggest that motor unit reinnervation and maturation are associated with recovery of force production, 37 reinnervation alone does not guarantee complete functional recovery. 39 Future studies should include more frequent monitoring to more precisely identify the onset of reinnervation and incorporate standardized functional assessments to quantify the relationship between reinnervation timing and upper limb functional recovery.

In summary, reinnervation timelines after cervical SCI nerve transfers followed a pattern consistent with the distance of regeneration, with earlier recovery detected in transfers involving shorter coaptation‐to‐target distances and more delayed, variable recovery in those requiring longer axonal growth. Nerve transfer recipient muscles demonstrated progressive maturation of MUPs and a reduction in denervation potentials over the 2‐year follow‐up period. By establishing expected electrophysiological timelines, these findings provide a framework for postoperative monitoring, patient counseling, and the design of rehabilitation protocols aligned with stages of neural recovery. They may also inform the development of predictive models and future interventions to accelerate axonal regeneration and optimize functional restoration. 40 , 41 , 42

Author Contributions

K.J.M., H.W., J.M.H., J.D., and M.J.B. contributed to the study's conception and design. J.M.B., R.M.M., S.B., P.B., E.B., C.D., A.K.H., R.O., L.R.R., and J.M.H. contributed to the acquisition and analysis of data. K.J.M. and M.J.B. contributed to drafting the text and preparing the figures. All authors approved the final draft.

Potential Conflicts of Interest

Nothing to report.

Acknowledgments

This project was supported by Michael Smith Health Research BC (HPI‐2022‐2835), Praxis Spinal Cord Institute (G2025‐11), Canadian Consortium of Clinical Trial Training Platform (CTTP‐2024‐04606), and the US Department of Defense (W81XWH2110986).

Data Availability

The data that support the findings of this study are available from the corresponding author upon reasonable request, subject to institutional ethics approval and applicable data‐sharing agreements.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request, subject to institutional ethics approval and applicable data‐sharing agreements.

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