A technique for maximizing biceps recovery in brachial plexus reconstruction

A systematic review of axon count measurement and reporting for nerve transfers in the upper extremity

INTRODUCTION

Axon counts in the literature vary by source and method, and no single source summarizes all brachial plexus nerves. This review aims to compile these counts in one article and assess comparability across studies.

METHODS

A systematic review was conducted in November 2023, according to the PRISMA guidelines. Four databases were assessed using different variations of the terms "nerve axon count* AND "upper extremity". 539 articles were found and screened, and after full text assessment of the pre-selected articles, 54 articles were finally retained. For these articles, the axon counts, SD, and ranges were collected for all upper extremities' nerves. If more than one article counted the axons of a specific nerve and if the difference between the counts was less than 100%, an average count was calculated.

RESULTS

In the 54 articles a total of 56 nerves were assessed. Axon counts of 18 nerves were done only in a single study. In the comparison between the averages in between studies, in 20 nerves the difference excided 100% between the highest and lowest value. For 16 nerves a metanalysis could been performed and presented in the article.

CONCLUSIONS

Our study revealed enormous differences in axon counts across various studies, reaching up to a factor of 87 between the averages from one study to another. Additionally, the quality of the methods of these studies varies, particularly since axon count is frequently reported as a secondary or tertiary outcome. This insight cautions surgeons against using axon counts from studies with differing methodologies to plan nerve transfers.

An Updated Evaluation of the Management of Nerve Gaps: Autografts, Allografts, and Nerve Transfers

Within the past decade, there have been multiple innovations in the field of nerve surgery. In this review, we highlight critical changes and innovations that have helped advance the field and present opportunities for further study. This includes the modification and clarification of the classification schema for nerve injuries which informs prognosis and treatment, and a refined understanding and application of electrodiagnostic studies to guide patient selection. We provide indications for operative intervention based on this nerve injury classification and propose strategies best contoured for varying injury presentations at differing time points. Lastly, we discuss new developments in surgical techniques and approaches based on these advancements.

Review of Outcomes After Peripheral Nerve Transfers for Motor Nerve Injury in the Upper Extremity

BACKGROUND

Modern nerve-to-nerve transfers are a significant advancement in peripheral nerve surgery. Nerve transfers involve transferring donor nerves or branches to recipient nerves close to the motor end unit, leading to earlier reinnervation and preservation of the musculotendinous units in proximal nerve injuries. After nerve reinnervation, function may be superior to traditional tendon transfer techniques in terms of strength and independent motion. Nerve transfer surgery has emerged as a promising treatment option for many cases of nerve injury that were previously expected to result in poor outcomes, such as proximal injuries, long nerve gaps, or unavailability of the proximal injured segment.

METHODS

A review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Publications that focused on upper extremity nerve transfers were included, and functional motor and sensory recovery was analyzed. Technique reports, case reports, brachial plexus injuries, and reports on multiple nerve injuries were excluded.

RESULTS

A total of 48 relevant articles were identified with search criteria, and we discuss functional outcomes on nerve transfers for ulnar nerve injury, musculocutaneous nerve injury, median nerve injury, and radial nerve injury that met inclusion criteria.

CONCLUSIONS

Nerve transfers are an option for restoring hand and forearm function in patients with peripheral nerve injuries adversely affecting their ability to function. The literature demonstrates positive functional outcomes after nerve transfer operations, and thus, the utility and variations have increased. We aim to provide an overview of the outcomes of current nerve transfer techniques for ulnar, radial, median, and musculocutaneous acquired/traumatic mononeuropathies in the hand and upper extremity.

A Comprehensive Review of Topography and Axon Counts in Upper-Extremity Peripheral Nerves: A Guide for Neurotization

Purpose

Currently, no comprehensive database detailing topography and axon counts exists. This study aims to review the axon counts and topography of the major peripheral motor nerves of the upper extremity to allow for optimal surgical planning for peripheral nerve reconstruction via neurotization.

Methods

Peer-reviewed journal articles were identified through PubMed, ScienceDirect, Google Scholar, and CENTRAL. Studies were included for review based upon the identification of the described topography or axon count of any upper-extremity peripheral motor nerve. Animal research, laboratory studies, and unpublished studies were excluded from our review. A total of 43 studies were identified, and 38 of these met the inclusion criteria. Statistical analysis was performed to determine axon count averages for all upper extremity motor nerves identified in the included studies.

Results

Thirty-eight studies were reviewed, giving insights into the topography and axon counts of the major peripheral nerves of the upper extremity, including the brachial plexus and its terminal branches as well as common donor nerves such as the spinal accessory nerve and intercostal nerves. Studies showed considerable variability in reported axon counts.

Conclusions

Existing data were relatively weak and included several case reports and series. Taking this into consideration, we posit that there is a need for further studies of upper-extremity nerve axon counts that include large study populations and more consistent methods of nerve specimen analysis.

Clinical relevance

Understanding the topographical anatomy of donor and recipient nerves, as well as appropriately matching the motor axon counts for each donor and recipient, is helpful in upper-extremity nerve reconstruction.

The prerequisites and clinical outcomes of ipsilateral C7 nerve root transfer to the upper trunk for adult C5-C6 brachial plexus injuries

PURPOSE

Although ipsilateral C7 nerve transfer is used for the treatment of C5-C6 brachial plexus injuries, accurately evaluating the functional quality of the donor nerve (ipsilateral C7 nerve root) is difficult, especially when the C7 nerve root is slightly injured. The purpose of this study was to determine the indicators to evaluate the quality of the ipsilateral C7 nerve and assess the clinical outcomes of this procedure.

METHODS

This study employed the following three indicators to assess the quality of the ipsilateral C7 nerve: (1) the muscle strength and electrophysiological status of the latissimus dorsi, triceps brachii, and extensor digitorum communis; (2) the sensibility of the radial three digits, especially the index finger; and (3) the intraoperative appearance, feel and electrophysiological status of the ipsilateral C7 nerve root. Transfer of the ipsilateral C7 nerve root to the upper trunk was implemented only when the following three tests were conducted, the criteria were met, and the clinical outcomes were assessed in eight patients with C5-C6 brachial plexus injuries.

RESULTS

Patients were followed-up for an average of 90 ± 42 months. At the final follow-up, all eight patients achieved recovery of elbow flexion, with five and three patients scoring M4 and M3, respectively, according to the Medical Research Council scoring. The shoulder abduction range of motor recovery averaged 86 ± 47° (range, 30°-170°), whereas the shoulder external rotation averaged 51 ± 26° (range, 15°-90°).

CONCLUSION

Ipsilateral C7 nerve transfer is a reliable and effective option for the functional reconstruction of the shoulder and elbow after C5-C6 brachial plexus injuries when the three prerequisites are met.

The Outcome of Spinal Accessory Nerve Transfer to the Musculocutaneous Nerve in Birth Brachial Plexus Palsy

PURPOSE

Patients with brachial plexus birth injury with limited intraplexal donors require the use of extraplexal donors. Concern regarding the potential for respiratory problems resulting from the harvest of intercostal nerves or the phrenic nerve suggests the need for other options. Transfer of the spinal accessory nerve (SAN) is one option for restoring elbow flexion in adult patients; however, there are few reports of the results of this transfer in brachial plexus birth injury. This study aimed to report the result of SAN transfer to the musculocutaneous nerve (MCN) in brachial plexus birth injury.

METHODS

Patients who had undergone SAN to MCN nerve transfer were included in this study. Patients were classified according to Narakas classification. The chart was reviewed for the time for recovery of elbow flexion according to the Active Movement Scale (AMS).

RESULTS

Eleven patients underwent SAN to MCN transfers with interpositional sural nerve grafts. Mean birthweight was 4,070 grams (range: 3,300-4,670). Mean time to operation was 6.5 months (range: 4-10). Of the 11 patients, two were of Narakas type 3, whereas the others were of type 4. One patient did not recover elbow flexion and underwent later tendon transfer, whereas the other 10 patients reached AMS grade M6 recovery. The median time for AMS grade M1 elbow flexion recovery was eight months (interquartile range: 6.2-8.8) and for AMS grade M5 was 26 months (interquartile range: 14.2-36.5).

CONCLUSIONS

Spinal accessory nerve to MCN transfer with an interposition nerve graft is a viable option for restoring elbow flexion. However, long-term outcomes of this procedure have yet to be fully demonstrated.

TYPE OF STUDY/LEVEL OF EVIDENCE

Case series IV.

Adult traumatic brachial plexus injuries: advances and current updates

Nerve grafting, tendon transfer and joint fusion are routinely used to improve the upper limb function in patients with brachial plexus palsies. Newer techniques have been developed that provide additional options for reconstruction. Nerve transfer is a tool for restoring upper limb function in total root avulsions where nerve grafting is not possible. In partial brachial plexus injuries, nerve transfers can greatly improve shoulder, elbow, wrist and hand function. Intraoperative electrical stimulation can be used to diagnose precisely which nerve is injured and to choose which nerve fascicles should be transferred. Finally, measuring the postoperative outcome can improve the evaluation of our techniques. The aim of this article was to present the current techniques used to treat patients with brachial plexus injury.

Optimizing donor fascicle selection in Oberlin's procedure: A retrospective review of anatomical variability using intraoperative neuromonitoring

BACKGROUND

Transfer of the fascicle carrying the flexor carpi ulnaris (FCU) branch of the ulnar nerve (UN) to the biceps/brachialis muscle branch of the musculocutaneous nerve (Oberlin's procedure), is a mainstay technique for elbow flexion restoration in patients with upper brachial plexus injury. Despite its widespread use, there are few studies regarding the anatomic location of the donor fascicle for Oberlin's procedure. Our report aims to analyze the anatomical variability of this fascicle within the UN, while obtaining quantifiable, objective data with intraoperative neuromonitoring (IONM) for donor fascicle selection.

METHODS

We performed a retrospective review of patients at our institution who underwent an Oberlin's procedure from September 2019 to July 2023. We used IONM for donor fascicle selection (greatest FCU muscle and least intrinsic hand muscle activation). We prospectively obtained demographic and electrophysiological data, as well as anatomical location of donor fascicles and post-surgical morbidities. Surgeon's perception of FCU/intrinsic muscle contraction was compared to objective muscle amplitude during IONM.

RESULTS

Eight patients were included, with a mean age of 30.5 years and an injury-to-surgery interval of 4 months. Donor fascicle was located anterior in two cases, posterior in two, radial in two and ulnar in two patients. Correlation between surgeon's perception and IONM findings were consistent in six (75%) cases. No long term motor or sensory deficits were registered.

CONCLUSIONS

Fascicle anatomy within the UN at the proximal arm is highly variable. The use of IONM can aid in optimizing donor fascicle selection for Oberlin's procedure.

Surgery for mononeuropathies

Advancement in microsurgical techniques and innovative approaches including greater use of nerve and tendon transfers have resulted in better peripheral nerve injury (PNI) surgical outcomes. Clinical evaluation of the patient and their injury factors along with a shift toward earlier time frame for intervention remain key. A better understanding of the pathophysiology and biology involved in PNI and specifically mononeuropathies along with advances in ultrasound and magnetic resonance imaging allow us, nowadays, to provide our patients with a logical and sophisticated approach. While functional outcomes are constantly being refined through different surgical techniques, basic scientific concepts are being advanced and translated to clinical practice on a continuous basis. Finally, a combination of nerve transfers and technological advances in nerve/brain and machine interfaces are expanding the scope of nerve surgery to help patients with amputations, spinal cord, and brain lesions.

Long-term functional recovery in C5-C6 avulsions treated with distal nerve transfers

BACKGROUND

In patients suffering from traction lesions of the brachial plexus, complete C5 and/or C6 root avulsion patients with C7 root preservation are relatively uncommon occurrences, but represent excellent candidates for surgical treatment, with satisfactory results. Shoulder abduction and extra-rotation, elbow flexion and forearm supination are lost functions restorable with surgical treatment.

METHODS

This single-center, prospective observational study involved a series of 27 young adults with C5 and/or C6 root complete avulsion and C7 preservation, which underwent surgical repair with double or triple nerve transfer.

RESULTS

Patients recovered a useful elbow flexion. Electromyographic and clinical signs of biceps reinnervation were observed in each UN-MC nerve transfer. The abduction strength recovery was M5 in 10 patients, M4 in 14 patients and M3 in 3 patients. The external rotation strength recovery was M5 in 4 patients, M4 in 18 patients, M3 in 3 patients and M2 in 2 patients. The elbow flection strength was M5 in 5 patients, M4 in 15 patients and M3 in 7 patients. Elbow extension was preserved in all cases.

CONCLUSIONS

The concept of 'peripheral rewiring procedures' represents an advance in the repair of the peripheral nerve injuries. Triple nerve transfer can be nowadays considered a standard treatment for isolated C5-C6 avulsions. We report our experience with the second-biggest casuistry in the literature on patients treated with this technique. We consider our outcome concerning functional recovery to be satisfying and comparable to data reported in the literature.

How many nerve fibers innervate the human glans clitoris: a histomorphometric evaluation of the dorsal nerve of the clitoris

INTRODUCTION

It is frequently quoted in mainstream media that the clitoris has "8000 nerve endings." However, no study has yet quantified the number of nerve fibers (axons) innervating the human clitoris. The dorsal nerves of the clitoris (DNCs) are the primary source of sensation and somatic clitoral innervation. Therefore, reporting the number of axons in the DNCs is an important step in our understanding of clitoral innervation and sexual response with implications for many fields of medical practice. The purpose of this study is to quantify the mean number of axons in the human DNCs and to report the approximate mean number of nerve fibers that innervate the human glans clitoris.

METHODS

DNC samples were obtained from 7 transmasculine patients undergoing gender-affirming phalloplasty surgery. At the time of nerve coaptation, a small excess of the DNC (5 mm) was collected for analysis at the proximal level of the clitoral body, just distal of the emergence of the DNCs from underneath the pubic symphysis. Samples were placed into 3% glutaraldehyde fixative, postfixed in 1% osmium tetroxide, and serially dehydrated in ethanol and toluene. Samples were then embedded in araldite, sectioned on an ultramicrotome into 1-μm cross sections, and counterstained with 1% toluidine blue. Histomorphometric evaluation was performed at 1000x magnification with a Leitz Laborlux S microscope and image analysis software (Clemex Vision Professional) to obtain an axon counts. Descriptive statistics were performed to yield a mean and standard deviation of the number of axons in the DNCs. Assuming anatomic symmetry between bilateral DNCs, mean total number of somatic nerve fibers innervating the human glans clitoris was obtained by doubling the mean count of the DNCs.

RESULTS

Seven sample DNCs were collected. Of those, 5 were analyzed as 2 did not have sufficient nerve tissue present. The mean number of nerve fibers in the human DNCs was 5140 (SD = 218.4). The mean number of myelinated nerve fibers innervating the human clitoris was 10,281 (SD = 436.8).

CONCLUSION

This study is the first to report the number of axons in the human DNC, at a mean 5140. Given the bilateral nature of clitoral innervation and symmetry of anatomic structures, the approximate mean number of myelinated axons that innervate the human glans clitoris is 10,280. When the uncaptured unmyelinated fibers and contributions from the cavernosal innervation are accounted for, it is clear that far Moree than 8000 axons innervate the human clitoris.

Approach to management of nerve gaps in peripheral nerve injuries

Peripheral nerve injuries (PNI) are a major clinical problem. In general, PNI results from motor vehicle accidents, lacerations with sharp objects, penetrating trauma (gunshot wounds) and stretching or crushing trauma and fractures. They can result in significant morbidity, including motor and/or sensory loss, which can affect significantly the life of the patient. Currently, the standard surgical technique for complete nerve transection is end-to-end neurorrhaphy. Unfortunately, there is segmental loss of the nerve trunk in some cases where nerve mobilization may permit end-to-end neurorrhaphy if the gap is less than 1 cm. When the nerve gap exceeds 1 cm, autologous nerve grafting is the gold standard of treatment. But in light of limited availability and concerned donor site morbidity, other techniques have been used: vascularized nerve grafts, cellular and acellular allografts, nerve conduits, nerve transfers and end-to-side neurorrhaphy. This review intends to present an overview of the literature on the applications of these techniques in repair of peripheral nerve injuries. This article also focuses on preoperative assessment, surgical timing, available options and future perspectives.

Transfer of a C7 Fascicle for the Pectoralis Major to the Suprascapular Nerve: A 3-Year Follow-Up Patient Series

BACKGROUND

In patients with C5-C6 brachial plexus injury, spinal accessory nerve transfer to the suprascapular nerve is usually performed for the restoration of shoulder abduction. In order to minimize donor deficits, we transferred one fascicle of the ipsilateral C7 root, dedicated to the pectoralis major muscle, to the suprascapular nerve.

METHODS

Ten patients with a mean age of 33 years (range, 19 to 51 years) were operated on at a mean delay of 4 months after their trauma (range, 2 to 7 months). Patients had C5-C6 brachial plexus palsy with avulsed roots on spinal magnetic resonance imaging scan. In addition to the partial C7 transfer, patients sustained nerve transfers to the posterior branch of the axillary nerve and to the motor branches of the musculocutaneous nerve for the biceps and brachialis muscles.

RESULTS

At a mean follow-up of 36 months (range, 29 to 42 months), mean shoulder abduction and external rotation ranges of motion were, respectively, 99 degrees (range, 60 to 120 degrees; p = 0.001) and 58 degrees (range, 0 to 80 degrees; p = 0.001). In nine patients, shoulder abduction strength was graded M4, according the British Medical Research Council grading scale, against 1.6 kg (range, 1 to 2 kg), and was graded M3 in one patient. External rotation strength was graded M4 in nine patients and M3 in one patient. Residual strength of the pectoralis major muscle was graded M4+ in every patient.

CONCLUSIONS

C7 partial transfer to the suprascapular nerve showed satisfactory results at long-term follow-up for active shoulder abduction and external rotation recovery in C5-C6 brachial plexus palsies. This technique replaced spinal accessory nerve transfer in the authors' practice.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Brachial Plexus Injuries - Review of the Anatomy and the Treatment Options

Brachial plexus injuries are still challenging for every surgeon taking part in treating patients with BPI. Injuries of the brachial plexus can be divided into injuries of the upper trunk, extended upper trunk, injuries of the lower trunk and swinging hand where all of the roots are involved in this type of the injury. Brachial plexus can be divided in five anatomical sections from its roots to its terminal branches: roots, trunks, division, cords and terminal branches. Brachial plexus ends up as five terminal branches, responsible for upper limb innervation, musculocutaneous, median nerve, axillary nerve, radial and ulnar nerve. According to the findings from the preoperative investigation combined with clinically found functional deficit, the type of BPI will be confirmed and that is going to determine which surgical procedure, from variety of them (neurolysis, nerve graft, neurotization, arthrodesis, tendon transfer, free muscle transfer, bionic reconstruction) is appropriate for treating the patient.

Nerve transfers in the upper extremity: A review

Injury of the brachial plexus and peripheral nerve often result in significant upper extremity dysfunction and disability. Nerve transfers are replacing other techniques as the gold standard for brachial plexus and other proximal peripheral nerve injuries. These transfers require an intimate knowledge of nerve topography, a technically demanding Intraneural dissection and require extensive physical therapy for retraining. In this review, we present a summary of the most widely accepted nerve transfers in the upper extremity described in the current literature.

FUNCTIONAL OUTCOME OF OBERLIN PROCEDURE

Objective:

To evaluate the functional outcome of patients with traumatic brachial plexus injury undergoing the Oberlin procedure.

Methods:

Eighteen patients were assessed, comprising 17 men (94.4%) and 1 woman (5.6%), mean age 29.5 years (range 17-46 years), with upper traumatic brachial plexus injury (C5-C6 and C5-C7). We assessed active range of motion of the elbow, elbow flexion muscle strength and hand-grip strength, and applied the DASH (Disabilities of the Arm, Shoulder and Hand) questionnaire.

Results:

Four patients (22.2%) did not achieve effective elbow flexion strength (BMRC Grade 3). Mean active range of motion was 100.2° (±45.6°), and we observed a mean percentage of strength recovery relative to the contralateral limb of 35.5% (0-66.3%). Elbow flexion (p = 0.0001) and hand-grip (p = 0.0001) strength levels were lower on the affected side.

Conclusion:

The surgical technique described by Oberlin for brachial plexus injuries proved effective for restoring elbow flexion and produced no functional sequelae in the hand. Bicep strength outcomes were better when surgery was performed within 12 months of injury. Level of evidence II, retrospective study.

Direct transfer of C7 pectoral fascicles to the suprascapular nerve in C5/C6 brachial plexus palsies: an anatomical study

We investigated a technique to reconstruct the suprascapular nerve in patients with C5/C6 brachial plexus palsies, using pectoral fascicles from the ipsilateral C7 root. Using a supraclavicular approach in eight cadavers, the suprascapular nerve was placed side by side with an anterior quadrant fascicle from the C7 root. Several criteria were assessed, including the fascicle length, the overlap between the two nerves and their respective diameters. The mean length of the C7 fascicles was 19.3 mm, with a mean overlap of 4.7 mm. The suprascapular nerve and the C7 fascicles had mean diameters of 2.2 mm and 2.1 mm, respectively. Pectoral fascicles from C7 seem to be an option for reconstruction of the suprascapular nerve in C5/C6 palsies. Clinical studies will be required to establish the potential limitations of this transfer, especially in cases with complex lesions of the suprascapular nerve.

The Surgical Management of Nerve Gaps: Present and Future

Peripheral nerve injuries can result in significant morbidity, including motor and/or sensory loss, which can affect significantly the life of the patient. Nowadays, the gold standard for the treatment of nerve section is end-to-end neurorrhaphy. Unfortunately, in some cases, there is segmental loss of the nerve trunk. Nerve mobilization allows primary repair of the sectioned nerve by end-to-end neurorrhaphy if the gap is less than 1 cm. When the nerve gap exceeds 1 cm, autologous nerve grafting is the gold standard of treatment. To overcome the limited availability and the donor site morbidity, other techniques have been used: vascularized nerve grafts, cellular and acellular allografts, nerve conduits, nerve transfers, and end-to-side neurorrhaphy. The purpose of this review is to present an overview of the literature on the applications of these techniques in peripheral nerve repair. Furthermore, preoperative evaluation, timing of repair, and future perspectives are also discussed.

Surgery for nerve injury: current and future perspectives

In this review article, the authors offer their perspective on nerve surgery for nerve injury, with a focus on recent evolution of management and the current surgical management. The authors provide a brief historical perspective to lay the foundations of the modern understanding of clinical nerve injury and its evolving management, especially over the last century. The shift from evaluation of the nerve injury using macroscopic techniques of exploration and external neurolysis to microscopic interrogation, interfascicular dissection, and internal neurolysis along with the use of intraoperative electrophysiology were important advances of the past 50 years. By the late 20th century, the advent and popularization of interfascicular nerve grafting techniques heralded a major advance in nerve reconstruction and allowed good outcomes to be achieved in a large percentage of nerve injury repair cases. In the past 2 decades, there has been a paradigm shift in surgical nerve repair, wherein surgeons are not only directing the repair at the injury zone, but also are deliberately performing distal-targeted nerve transfers as a preferred alternative in an attempt to restore function. The peripheral rewiring approach allows the surgeon to convert a very proximal injury with long regeneration distances and (often) uncertain outcomes to a distal injury and repair with a greater potential of regenerative success and functional recovery. Nerve transfers, originally performed as a salvage procedure for severe brachial plexus avulsion injuries, are now routinely done for various less severe brachial plexus injuries and many other proximal nerve injuries, with reliably good to even excellent results. The outcomes from nerve transfers for select clinical nerve injury are emphasized in this review. Extension of the rewiring paradigm with nerve transfers for CNS lesions such as spinal cord injury and stroke are showing great potential and promise. Cortical reeducation is required for success, and an emerging field of rehabilitation and restorative neurosciences is evident, which couples a nerve transfer procedure to robotically controlled limbs and mind-machine interfacing. The future for peripheral nerve repair has never been more exciting.

Elbow flexion reconstruction with nerve transfer or grafting in patients with brachial plexus injuries: A systematic review and comparison study

INTRODUCTION

Posttraumatic brachial plexus (BP) palsy was used to be treated by reconstruction with nerve grafts. For the last two decades, nerve transfers have gained popularity and believed to be more effective than nerve grafting. The aim of this systematic review was to compare elbow flexion restoration with nerve transfers or nerve grafting after traumatic BP injury.

METHODS

PRISMA-IPD structure was used for 52 studies included. Patients were allocated as C5-C6 (n = 285), C5-C6-C7 (n = 150), and total BP injury (n = 245) groups. In each group, two treatment modalities were compared, and effects of age and preoperative interval were analyzed.

RESULTS

In C5-C6 injuries, 93.1% of nerve transfer patients achieved elbow flexion force ≥M3, which was significantly better when compared to 69.2% of nerve graft patients (p < 0.001). For improved outcomes of nerve transfer patients, shorter preoperative interval was a significant factor in all injury patterns (p < 0.001 for C5-C6 injuries and total BP injuries, p = 0.018 for C5-C6-C7 injuries), and young age was a significant factor in total BP injury pattern (p = 0.022).

CONCLUSIONS

Our analyses showed that nerve transfers appear superior to nerve graftings especially in patients with a C5-C6 injury. Unnecessary delays in surgery must be prevented, and younger patients may have more chance for better recovery.

LEVEL OF EVIDENCE

Level II.

Results of Phrenic Nerve Transfer to the Musculocutaneous Nerve Using Video-Assisted Thoracoscopy in Patients with Traumatic Brachial Plexus Injury: Series of 28 Cases

BACKGROUND

The phrenic nerve can be transferred to the musculocutaneous nerve using video-assisted thoracoscopy, aiming at the recovery of elbow flexion in patients with traumatic brachial plexus injuries. There are few scientific papers in the literature that evaluate the results of this operative technique.

OBJECTIVE

To evaluate biceps strength and pulmonary function after the transfer of the phrenic nerve to the musculocutaneous nerve using video-assisted thoracoscopy.

METHODS

A retrospective study was carried out in a sample composed of 28 patients who were victims of traumatic injury to the brachial plexus from 2008 to 2013. Muscle strength was graded using the British Medical Research Council (BMRC) scale and pulmonary function through spirometry. Statistical tests, with significance level of 5%, were used.

RESULTS

In total, 74.1% of the patients had biceps strength greater than or equal to M3. All patients had a decrease in forced vital capacity and forced expiratory volume in 1 s, with no evidence of recovery over time.

CONCLUSION

Transferring the phrenic nerve to the musculocutaneous nerve using video-assisted thoracoscopy may lead to an increase in biceps strength to BMRC M3 or greater in most patients. Considering the deterioration in the parameters of spirometry observed in our patients and the future effects of aging in the respiratory system, it is not possible at the moment to guarantee the safety of this operative technique in the long term.

Axonal components of nerves innervating the human arm

OBJECTIVE

Axons traveling within the brachial plexus are responsible for the dexterous control of human arm and hand movements. Despite comprehensive knowledge on the topographical anatomy of nerves innervating the human upper limbs, the definite quantity of sensory and motor axons within this neural network remains elusive. Our aim was to perform a quantitative analysis of the axonal components of human upper limb nerves based on highly specific molecular features from spinal cord level to the terminal nerves at wrist level.

METHODS

Nerve specimen harvest at predefined harvesting sites (plexus roots and cords as well as major nerves originating from the brachial plexus innervating the arm and hand) was performed in 9 human heart-beating organ donors. Double immunofluorescence staining using antibodies against choline-acetyltransferase and neurofilament was performed to differentiate motor and sensory axons on nerve cross sections.

RESULTS

Three hundred fifty thousand axons emerge from the spinal cord to innervate the human upper limb, of which 10% are motor neurons. In all nerves studied, sensory axons outnumber motor axons by a ratio of at least 9:1. The sensory axon contribution increases when moving distally, whereas only 1,700 motor axons reach the hand to innervate the intrinsic musculature.

INTERPRETATION

Our results suggest that upper limb motor execution, and particularly dexterous coordination of hand movement, require an unexpectedly low number of motor neurons, with a large convergence of afferent input for feedback control. Ann Neurol 2017;82:396-408.

Brachial plexus injuries

Brachial Plexus Injuries result from a variety of causative mechanisms. They often present in a polytraumatic setting, and as such there is often a delay in their diagnosis and treatment. An understanding of the anatomy of the Brachial Plexus, and associated clinical pictures associated with injury, allows for early diagnosis and treatment. This review will consider the specific features of Brachial Plexus injuries relating to incidence, anatomy, mechanisms of injury, clinical presentation, and diagnostic evaluation.

Multiple nerve transfers for the reanimation of shoulder and elbow functions in irreparable C5, C6 and upper truncal lesions of the brachial plexus

In irreparable C5, C6 spinal nerve and upper truncal injuries the proximal root stumps are not available for grafting, hence repair is based on nerve transfer or neurotization. Between Feb 2004 and May 2006, 23 patients with irreparable C5, C6 or upper truncal injuries of the Brachial Plexus underwent multiple nerve transfers to restore the shoulder and elbow functions. Most of them (16 patients) sustained injury following motor cycle accidents. The average denervation period was 5.3 months. Shoulder function was restored by transfer of distal part of spinal accessory nerve to suprascapular nerve, and transfer of radial nerve branch to long head of triceps to the anterior branch of axillary nerve. Elbow function was restored by transfers of ulnar and median nerve fascicles to the biceps and brachialis motor branches of musculocutaneous nerve. All patients recovered shoulder abduction and external rotation; 7 scored M4 and 16 scored M3. Range of abduction averaged 1230(range, 800-1700). Full elbow flexion was restored in all 23 patients; 15 scored M4 and 8 scored M3. Patients with excellent results could lift 5 kgs of weight. Selective nerve transfers close to the target muscle provide an early and good return of functions. There is negligible morbidity in donor nerves. These intraplexal transfers are suitable in all cases of upper brachial plexus injuries.

Axon Counts Yield Multiple Options for Triceps Fascicular Nerve to Axillary Nerve Transfer

PURPOSE

To evaluate the relative axonal match between potential donor and recipient nerves, so that maximal reinnervation potential may be reached with the least chance of donor site morbidity.

METHODS

In 10 fresh-frozen cadaveric specimens, the main trunk and anterior, posterior, sensory and teres minor branches of the axillary nerve were identified, as were the radial nerve branches to the long, medial, and lateral heads of the triceps. The swing distances of the triceps fascicular nerve branches and the axillary nerve branches relative to the inferior border of the teres major muscle were recorded. Histomorphological analysis and axon counts were performed on sections of each branch.

RESULTS

The median number of axons in the main axillary trunk was 7,887, with 4,052, 1,242, and 1,161 axons in the anterior, posterior, and teres minor branches, respectively. All specimens had a single long head triceps branch (median, 2,302 axons), a range of 1 to 3 branches to the medial head of the triceps (composite axon count, 2,198 axons), and 1 to 3 branches to the lateral head of the triceps (composite average, 1,462 axons). The medial and lateral head branches had sufficient swing distance to reach the anterior branch of the axillary nerve in all 10 specimens, with only 4 specimens having adequate long head branch swing distances.

CONCLUSIONS

It is anatomically feasible to transfer multiple branches of the radial nerve supplying the medial, lateral, and sometimes, long head of the triceps to all branches of the axillary nerve in an attempt to reinnervate the deltoid and teres minor muscles.

CLINICAL RELEVANCE

Understanding the axon counts of the different possible transfer combinations will improve operative flexibility and enable peripheral nerve surgeons to reinnervate for both abduction and external rotation with the highest donor/recipient axon count ratios.

Donor Distal, Recipient Proximal and Other Personal Perspectives on Nerve Transfers

This article presents a personal overview of nerve transfers and emphasizes the various factors that contribute to outcome following these surgeries. There is no "one result" for all nerve transfers. The results will vary depending on factors relating to the donor nerve and the recipient nerve, the degree of the surgical difficulty of the specific procedure, and issues relating to preoperative and postoperative rehabilitation. The general issues that influence all nerve injury and recovery, such as age of the patient, comorbidities, and time since injury, pertain to nerve transfers as well.

Nerve Transfers to Restore Elbow Function

The purpose of this article is to provide an overview of the various nerve transfer options for restoration of elbow function. This article describes nerve transfer strategies for elbow flexion and extension including the indications, limitations, and expected outcomes based on current literature.

Vascularized Thoracodorsal to Suprascapular Nerve Transfer, a Novel Technique to Restore Shoulder Function in Partial Brachial Plexopathy

We describe the clinical outcome of a novel nerve transfer to restore active shoulder motion in upper brachial plexus injury. The thoracodorsal nerve (TDN) was successfully used as a vascularized donor nerve to neurotize to the suprascapular nerve (SSN) in a patient with limited donor nerve availability. At 4 years follow-up, he had regained useful external rotation of the injured limb, with no significant donor site morbidity. Shoulder abduction return was less impressive, however, and reasons for this are discussed. We provide a comprehensive review of the literature on this topic and a subsequent discussion on the details of this novel technique. This is the first reported case of TDN to SSN transfer, and also the first reported case of a vascularized TDN transfer in the English language literature. We advocate direct thoracodorsal to SSN transfer as a valid surgical option for the restoration of shoulder function in patients with partial brachial plexus avulsion, when conventional nerve donors are unavailable.

Nerve Transfers in the Upper Extremity: A Practical User's Guide

Nerve injuries above the elbow are associated with a poor prognosis, even with prompt repair and appropriate rehabilitation. The past 2 decades have seen the development of numerous nerve transfer techniques, by which a denervated peripheral target is reinnervated by a healthy donor nerve. Nerve transfers are indicated in proximal brachial plexus injuries where grafting is not possible or in proximal injuries of peripheral nerves with long reinnervation distances. Nerve transfers represent a revolution in peripheral nerve surgery and offer the potential for superior functional recovery in severe nerve injuries. However, the techniques have not been universally adopted due in part to a misconception that nerve transfers can only be understood and performed by superspecialists. Nerve transfer procedures are not technically difficult and require no specialized equipment. Numerous transfers have been described, but there are a handful of transfers for which there is strong clinical evidence. To restore shoulder abduction and external rotation in upper trunk brachial plexus injury, the key transfers are the spinal accessory to suprascapular nerve and the medial triceps branch to axillary nerve. For elbow flexion, the flexor carpi ulnaris branch of ulnar nerve to the biceps and brachialis branches of the musculocutaneous nerve is the key transfer. For ulnar intrinsic function, the distal anterior interosseous nerve to ulnar motor branch transfer has yielded excellent functional results. Nerve transfers form a therapeutic triad with traditional tendon transfers and functional motor unit rehabilitation which, when applied appropriately, can yield excellent functional results in complex nerve injuries. Nerve transfers are a powerful yet underused tool for proximal nerve injuries, which offer hope for traditionally discouraging injuries.

Motor Nerve Transfers

Brachial plexus and peripheral nerve injuries are exceedingly common. Traditional nerve grafting reconstruction strategies and techniques have not changed significantly over the last 3 decades. Increased experience and wider adoption of nerve transfers as part of the reconstructive strategy have resulted in a marked improvement in clinical outcomes. We review the options, outcomes, and indications for nerve transfers to treat brachial plexus and upper- and lower-extremity peripheral nerve injuries, and we explore the increasing use of nerve transfers for facial nerve and spinal cord injuries. Each section provides an overview of donor and recipient options for nerve transfer and of the relevant anatomy specific to the desired function.

Advances in nerve transfer surgery

Peripheral nerve injuries are devastating injuries and can result in physical impairments, poor functional outcomes and high levels of disability. Advances in our understanding of peripheral nerve regeneration and nerve topography have lead to the development of nerve transfers to restore function. Over the past two decades, nerve transfers have been performed and modified. With the advancements in surgical management and recognition of importance of cortical plasticity, motor-reeducation and perioperative rehabilitation, nerve transfers are producing improved functional outcomes in patients with nerve injuries. This manuscript explores the recent literature as it relates to current nerve transfer techniques and advances in post-operative rehabilitation protocols, with a focus on indications, techniques and outcomes.

[Recovery of elbow flexion in post-traumatic C5-C6 and C5-C6-C7 palsy: retrospective dual-center study comparing single and double nerve transfer]

Twenty-nine patients underwent single (n=15) or double (n=14) nerve transfer for post-traumatic elbow flexion palsy. Patients averaged 30.2 years, with a mean preoperative delay of six months and postoperative follow-up of 34.2 months. Sixty per cent of the single transfer patients recovered to BMRC grade M4 after an average of follow-up of 13.2 months. Eighty-five percent of double nerve transfer patients reached grade M4 after an average follow-up of 11 months. There were no significant differences between groups. Clinical assessment revealed motor or sensory deficit in seven cases, which did not cause any impairment. Patients with a C5-C6 injury had shorter recovery times and better strength in comparison with those with C5-C6-C7 injury. By restoring shoulder function, elbow flexion will be indirectly improved. This improvement can be partially attributed to the base of the arm being more stable.

The medial cord to musculocutaneous (MCMc) nerve transfer: a new method to reanimate elbow flexion after C5-C6-C7-(C8) avulsive injuries of the brachial plexus--technique and results

The aim of this paper is to report on our ample experience with the medial cord to musculocutaneous (MCMc) nerve transfer. The MCMc technique is a new type of neurotization which is able to reanimate the elbow flexion in multilevel avulsive injuries of the brachial plexus provided that at least the T1 root is intact. A series of 180 consecutive patients, divided into four classes according to the quality of hand function, is available for a long-term follow-up after brachial plexus surgery. The patients enrolled for the study have in common a brachial plexus palsy showing multiple cervical root avulsive injuries at two (C5-C6), three (C5-C6-C7) and four (C5-C6-C7-C8) levels. The reinnervation of the musculocutaneous nerve is obtained via an end-to-end transfer from two donor fascicles located in the medial cord. The selected fascicles are those directed principally to the flexor carpi radialis, ulnaris and, to a lesser degree, the flexor digitorum profundus. Under normal anatomic conditions, they are located in the medial cord, and their site corresponds to the inverted V-shaped bifurcation between the internal contribution of the median nerve and the ulnar nerve. The technique has no failure and no complications when the hand shows a normal wrist and finger flexion and a normal intrinsic function. In case of suboptimal conditions of the hand, the technique has proved technically more challenging, but still with 67% satisfactory results. In the four-root avulsive injuries, however, this method shows its limitations and an alternative strategy should be preferred when possible. EMG analysis shows a reinnervation in both the biceps and the brachialis muscles, explaining the high quality of the observed results. Moreover, this technique theoretically offers the possibility of a "second attempt" at a more distal level in case of failure of the first surgery. This procedure is quick, safe, extremely effective and easily feasible by an experienced plexus surgeon. The ideal candidate is a patient harbouring a C5-C6 avulsive injury of the upper brachial plexus with a normally functioning hand.

Brachial plexus injuries in adults: evaluation and diagnostic approach

The increased incidence of motor vehicle accidents during the past century has been associated with a significant increase in brachial plexus injuries. New imaging studies are currently available for the evaluation of brachial plexus injuries. Myelography, CT myelography, and magnetic resonance imaging (MRI) are indicated in the evaluation of brachial plexus. Moreover, a series of specialized electrodiagnostic and nerve conduction studies in association with the clinical findings during the neurologic examination can provide information regarding the location of the lesion, the severity of trauma, and expected clinical outcome. Improvements in diagnostic approaches and microsurgical techniques have dramatically changed the prognosis and functional outcome of these types of injuries.

Preoperative donor nerve electromyography as a predictor of nerve transfer outcomes

PURPOSE

We hypothesized that health of the donor nerve and corresponding muscle, as assessed by electromyography (EMG), could predict the outcome of nerve transfer surgery.

METHODS

A retrospective review was performed to investigate outcomes of nerve transfers for elbow flexion and shoulder abduction. Motor strength was graded preoperatively and after a minimum 1-year follow-up. Preoperative EMG results were classified as functionally normal or affected based on motor unit recruitment pattern and correlated with follow-up motor strength and range of motion.

RESULTS

Forty nerve transfers were identified: 27 were performed for elbow flexion and 13 for shoulder abduction. Overall, the 29 transfers in the normal EMG cohort showed significantly greater postoperative improvement in motor strength (Medical Research Council grade 0.2-4.1) than the 11 transfers in the affected EMG cohort (grade 0.0-3.0). In the shoulder cohort, normal donor nerves resulted in greater strength (grade 4.0 vs. 2.4) and active motion (83° vs. 25°) compared with affected donor nerves. Double fascicular transfers with 2 normal donor nerves demonstrated improved strength compared with double nerve transfers when 1 donor nerve was affected (grade 4.5 vs. 3.2).

CONCLUSIONS

Our findings demonstrate that a simple EMG classification that describes the quality of donor nerves can predict outcome as measured by postoperative motor strength and range of motion. Preoperative EMG evaluation should be considered a valuable supplementary component of the donor nerve selection process when planning brachial plexus reconstruction.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic II.

The 100 top-cited classic papers in hand surgery

The number of citations that a published article has received reflects the importance that paper has on that area of practice. In hand surgery, it is unknown which journal articles are cited most frequently. The purpose of this study was to identify and analyze the characteristics of the top 100 papers in the field of hand surgery. The 100 most cited papers were identified in the following journals; the Journal of Hand Surgery (American volume), the Journal of Hand Surgery (European volume), the Journal of Hand Surgery (British and European volume), The Scandinavian Journal of Plastic and Reconstructive and Hand Surgery, Hand Clinics, and the Journal of Plastic Surgery and Hand Surgery. The articles were ranked in order of the number of citations received. These classic 100 papers were analyzed for article type, their journal distribution, as well as geographic and institutional origin.

Tendon versus nerve transfers in elbow, wrist, and hand reconstruction: a literature review

Upper extremity reconstruction forces the surgeon to chose between several available procedures, among them tendon and nerve transfer. Few guidelines exist to assist the surgeon in this regard, and the authors, therefore, undertook a retrospective review of case series describing tendon and nerve transfer. The authors discovered a scarcity of robust reporting, particularly in regard to tendon transfer, making an objective comparison between the two techniques difficult. Tendon transfers are popular and familiar. Nerve transfers promise distinct advantages; however, excellent evidence of their superiority is lacking.

What has changed in brachial plexus surgery?

Brachial plexus injuries, in all their severity and complexity, have been extensively studied. Although brachial plexus injuries are associated with serious and often definitive sequelae, many concepts have changed since the 1950s, when this pathological condition began to be treated more aggressively. Looking back over the last 20 years, it can be seen that the entire approach, from diagnosis to treatment, has changed significantly. Some concepts have become better established, while others have been introduced; thus, it can be said that currently, something can always be offered in terms of functional recovery, regardless of the degree of injury. Advances in microsurgical techniques have enabled improved results after neurolysis and have made it possible to perform neurotization, which has undoubtedly become the greatest differential in treating brachial plexus injuries. Improvements in imaging devices and electrical studies have allowed quick decisions that are reflected in better surgical outcomes. In this review, we intend to show the many developments in brachial plexus surgery that have significantly changed the results and have provided hope to the victims of this serious injury.

Results of ulnar nerve neurotization to biceps brachii muscle in brachial plexus injury

OBJECTIVE

To evaluate the factors influencing the results of ulnar nerve neurotization at the motor branch of the brachii biceps muscle, aiming at the restoration of elbow flexion in patients with brachial plexus injury.

METHODS

19 patients, with 18 men and 1 woman, mean age 28.7 years. Eight patients had injury to roots C5-C6 and 11, to roots C5-C6-C7. The average time interval between injury and surgery was 7.5 months. Four patients had cervical fractures associated with brachial plexus injury. The postoperative follow-up was 15.7 months.

RESULTS

Eight patients recovered elbow flexion strength MRC grade 4; two, MRC grade 3 and nine, MRC <3. There was no impairment of the previous ulnar nerve function.

CONCLUSION

The surgical results of ulnar nerve neurotization at the motor branch of brachii biceps muscle are dependent on the interval between brachial plexus injury and surgical treatment, the presence of associated fractures of the cervical spine and occipital condyle, residual function of the C8-T1 roots after the injury and the involvement of the C7 root. Signs of reinnervation manifested up to 3 months after surgery showed better results in the long term.

LEVEL OF EVIDENCE

IV, Case Series.

Neurotization from two medial pectoral nerves to musculocutaneous nerve in a pediatric brachial plexus injury

Traumatic brachial plexus injuries can be devastating, causing partial to total denervation of the muscles of the upper extremities. Surgical reconstruction can restore motor and/or sensory function following nerve injuries. Direct nerve-to-nerve transfers can provide a closer nerve source to the target muscle, thereby enhancing the quality and rate of recovery. Restoration of elbow flexion is the primary goal for patients with brachial plexus injuries. A 4-year-old right-hand-dominant male sustained a fracture of the left scapula in a car accident. He was treated conservatively. After the accident, he presented with motor weakness of the left upper extremity. Shoulder abduction was grade 3 and elbow flexor was grade 0. Hand function was intact. Nerve conduction studies and an electromyogram were performed, which revealed left lateral and posterior cord brachial plexopathy with axonotmesis. He was admitted to Rehabilitation Medicine and treated. However, marked neurological dysfunction in the left upper extremity was still observed. Six months after trauma, under general anesthesia with the patient in the supine position, the brachial plexus was explored through infraclavicular and supraclavicular incisions. Each terminal branch was confirmed by electrophysiology. Avulsion of the C5 roots and absence of usable stump proximally were confirmed intraoperatively. Under a microscope, neurotization from the musculocutaneous nerve to two medial pectoral nerves was performed with nylon 8-0. Physical treatment and electrostimulation started 2 weeks postoperatively. At a 3-month postoperative visit, evidence of reinnervation of the elbow flexors was observed. At his last follow-up, 2 years following trauma, the patient had recovered Medical Research Council (MRC) grade 4+ elbow flexors. We propose that neurotization from medial pectoral nerves to musculocutaneous nerve can be used successfully to restore elbow flexion in patients with brachial plexus injuries.

Nerve transfers

Nerve transfers have been performed for many years, but the technique is further developing and gaining increased recognition as a time-tested procedure. The original operations are continually modified to treat a wide variety of peripheral nerve injuries, and yield reliable results. In addition, nerve transfers can be used in conjunction with tendon transfers or nerve grafts in order to best treat a specific patient's set of deficits. This review of nerve transfers briefly discusses the evolution of the technique, general principles, some specific transfers, post-operative rehabilitation, and their place on the reconstructive ladder.

Nerve transfers for the upper extremity: new horizons in nerve reconstruction

Nerve transfers are key components of the surgeon's armamentarium in brachial plexus and complex nerve reconstruction. Advantages of nerve transfers are that nerve regeneration distances are shortened, pure motor or sensory nerve fascicles can be selected as donors, and nerve grafts are generally not required. Similar to the principle of tendon transfers, expendable donor nerves are transferred to denervated nerves with the goal of functional recovery. Transfers may be subdivided into intraplexal, extraplexal, and distal types; each has a unique role in the reconstructive process. A thorough diagnostic workup and intraoperative assessment help guide the surgeon in their use. Nerve transfers have made a positive impact on the outcomes of nerve surgery and are essential tools in complex nerve reconstruction.

Arthroscopic release for shoulder internal rotation contracture secondary to brachial plexus birth palsy: clinical and magnetic resonance imaging results on glenohumeral dysplasia

Internal rotation contracture of the shoulder in brachial plexus birth palsy frequently leads to shoulder dysplasia. Six children underwent anterior arthroscopic release sparing the subscapularis. Clinical examination and MRI were performed preoperatively and repeated at the 5-year follow-up. MRI was carried out for assessment of glenohumeral dysplasia. Passive external rotation was improved by 63.3° without any limitation of active internal rotation. Active antepulsion/abduction was improved by 90°. Remodeling of the glenoid and improved coverage of the humeral head were observed in all cases. Shoulder arthroscopic release sparing the subscapularis seems to be an efficient procedure to restore external rotation without affecting active internal rotation.

Nerve transfers for the restoration of hand function after spinal cord injury

Spinal cord injury (SCI) remains a significant public health problem. Despite advances in understanding of the pathophysiological processes of acute and chronic SCI, corresponding advances in translational applications have lagged behind. Nerve transfers using an expendable nearby motor nerve to reinnervate a denervated nerve have resulted in more rapid and improved functional recovery than traditional nerve graft reconstructions following a peripheral nerve injury. The authors present a single case of restoration of some hand function following a complete cervical SCI utilizing nerve transfers.