Introduction

Brachial plexus injuries (BPI) are among the most severe and debilitating peripheral nerve injuries. These often result from high energy trauma. In panplexal injuries, where all 5 nerve roots (C5, C6, C7, C8, T1) are affected, the prognosis is particularly poor due to total loss of motor function and sensation in the affected limb. The resulting paralysis and sensory deficit significantly impact a patient’s ability to perform even basic daily activities, thus contributing to severe disability and a reduced quality of life.

The management of complete BPI poses one of the most intricate challenges for peripheral nerve surgeons. The complexity of brachial plexus anatomy and the variability in injury patterns result in diverse clinical presentations and treatment options, often making standardized protocols difficult to establish. Surgical strategies depend on various factors, including the timing of intervention, intraoperative findings, and the availability of donor nerves. Reconstruction options range from nerve grafting and nerve transfers to tendon and free functional muscle transfers, particularly in late-presenting cases.

Advancements in nerve transfers continue to offer new options hope to patients who previously had limited surgical options. Nerve transfers and functional muscle transfers have emerged as transformative approaches, enabling meaningful recovery of motor function in many cases. Additionally, Dorsal Root Entry Zone (DREZ) lesioning has become an essential tool for managing the chronic neuropathic pain that often accompanies severe nerve injuries, addressing one of the most debilitating symptoms of BPI.

This review aims to provide a comprehensive overview of surgical techniques pivotal in the management of complete BPI, including nerve transfers and functional muscle transfers. By synthesizing current literature, this review aims to offer an in-depth understanding of these approaches, emphasizing the importance of personalized care tailored to each patient’s unique injury and clinical needs.

Nerve Grafting

Exploration of the brachial plexus and nerve grafting is essential when possible. In the senior author’s practice, magnetic resonance imaging (MRI) neurography is used to provide information on the potential availability of a graftable root. Additionally, physical examination may sometimes provide an indication on availability of a graftable root supported by a positive Tinel’s sign and tenderness in the neck. Importantly, we do not explore the brachial plexus and nerve graft after 9 months from the time of the injury, as the postoperative functional results are poor. If there is suspicion for a multilevel brachial plexus injury with a high energy mechanism of injury it is important to explore thoroughly the supraclavicular and infraclavicular brachial plexus to ensure that all injuries are identified.

In the senior author’s experience, an initial plan to graft from the C5 root to the musculocutaneous nerve was changed in 1 patient when a second distal injury was found where the musculocutaneous nerve was avulsed from the biceps muscle distally. This necessitated instead, conversion subsequently to a functional free muscle transfer for reconstruction of elbow flexion.

Ideally, where possible, nerve grafting and nerve transfers should be combined in a “belt and suspenders” approach to maximise reinnervation of potential targets. Nerve grafting has the advantage of potentially providing more axons to reinnervate a target muscle and hence greater power of the reinnervated muscle. Nerve transfers, conversely, often have faster reinnervation potential, but a lower ceiling on the final strength of the reinnervated muscle.

Nerve Transfers

Nerve transfers have become a cornerstone in restoring function for patients with severe brachial plexus injuries, particularly root avulsion injuries. In root avulsion injuries, the nerve roots are torn from the spinal cord, disrupting the native pathways for motor and sensory signals. Nerve grafting is not possible in this scenario because there is no intact nerve root to graft to proximally. Nerve transfers address this challenge by redirecting functional, healthy nerves from other parts of the body to reinnervate the damaged area of the brachial plexus, effectively bypassing the avulsed roots.

The time interval between the injury and nerve transfer surgery is crucial for favorable outcomes. Even when nerve grafting is feasible, nerve transfers sometimes can result in reduced co-contractions due to more focused reinnervation of target muscles. This is particularly applicable in reinnervation of shoulder muscles in brachial plexus birth injuries (BPBI). Additionally, because nerve transfers are performed closer to the target muscles, reinnervation occurs more quickly, even when surgery is delayed. Where there is a nerve root available for grafting, early exploration of the brachial plexus within 4-6 months is gaining traction. Bentolila et al. recommended that the intervention delay be no more than 4 months and reported that a delay greater than 7 months yielded unfavorable results. In our practice, we prefer nerve transfers to be perfomed within 6 months from the time of the initial injury, for improved outcomes.

Nerve Transfers for Restoration of Shoulder Function

Nerve transfers are a fundamental technique in the surgical management of brachial plexus injuries, particularly for restoring shoulder movement, which is essential for upper limb function. Among the most well-established techniques is the spinal accessory nerve (SAN) to the suprascapular nerve (SSN) transfer. ^, This procedure, first described in 1972 by Kotani et al., has been extensively studied and is widely regarded as a reliable method for addressing shoulder paralysis. Studies have demonstrated that the intact distal branch of the SAN can be effectively transferred to a denervated SSN, yielding relatively favorable outcomes. By reinnervating the supraspinatus and infraspinatus muscles—both key for shoulder stability and controlled arm movement—this transfer improves shoulder abduction and external rotation, which are often severely compromised in complete BPI cases. This procedure is essential as it lays the foundation for other functional improvements by providing a stable shoulder, facilitating more effective use of the hand and forearm in daily activities. The SAN-SSN transfer also contributes to shoulder endurance, which is vital for prolonged or repetitive upper limb tasks.

The SAN-SSN transfer can be performed through either an anterior or posterior approach. Studies have demonstrated no statistically significant difference in overall functional outcomes between the 2 approaches. The primary challenge with the anterior approach includes the relatively long reinnervation distance to the target muscle. A workaround that has been described is an extensile approach involving partial detachment of the trapezius muscle from the clavicle which allows more distal exposure of the suprascapular nerve distal to the suprascapular notch. This extended exposure also allows identification of additional, undetected suprascapular nerve injuries when using the anterior approach.

The posterior approach is generally favored if there is suspicion of a proximal suprascapular nerve injury, which often occurs with scapular fractures. Some surgeons routinely prefer the posterior approach for SAN to SSN transfer, as the nerve transfer bypasses all potential injuries to the SSN proximal to the suprascapular notch and reinnervates the SSN closer to its targets. ^, Our preference is to perform the SAN to SSN nerve transfer from the posterior approach in the presence of scapular fractures or other high energy trauma around the shoulder. In the senior authors’ experience isolated SAN to SSN nerve transfer without a second nerve transfer for reinnervation of the axillary nerve in panplexus injuries can provide restoration of active shoulder abduction from about 30 to 90 degrees. This is dependent on various factors such as the patient’s age, body mass index (BMI) and compliance to postoperative rehabilitation. Restoration of shoulder external rotation through reinnervation of the infraspinatus muscle is more variable, and depends again on various factors.

The contralateral C7 (cC7) transfer has also been used for reconstruction of shoulder function, with more guarded results. This involves harvesting the C7 nerve root from the uninjured side and transferring it to the injured brachial plexus. After its first description in 1991 by Gu et al. , cC7 transfer has been shown to improve functionality in the hand, elbow, and shoulder, depending on the targeted recipient nerve. However, the overall outcomes of cC7 nerve transfer for improving shoulder function have remained equivocal in the current literature. Sammer et al. investigated the role of isolated cC7 nerve transfer to the axillary or suprascapular nerve in patients with panplexal BP injury, which showed nonfavorable outcomes. Their study found that only 23.1% of patients had an MRC score of > 3, and none had an MRC score of 5. Trezis showed similar outcomes, where 20% of patients with a cC7 to axillary nerve transfer achieved an MRC score of >3. Based on these studies isolated cC7 nerve transfer may not be an effective option for improving shoulder function in patients with panplexal BP injury . Studies employing multiple nerve transfers, such as combining cC7 transfer with SAN-to-SSN transfer, have demonstrated significantly better outcomes for shoulder function, suggesting that additional nerve transfers enhance functional recovery in these cases .

Nerve Transfers for Restoration of Elbow Function

Elbow flexion is often the priority of surgeons in brachial plexus reconstruction. Several nerve transfers targeting the musculocutaneous nerve have been described to restore elbow flexion. In panplexal injuries, potential donor nerves include the spinal accessory nerve, intercostal nerves, phrenic and contralateral C7. The first nerve transfer for elbow flexion was performed by Seddon in 1963 by grafting 1 intercostal nerve to the musculocutaneous nerve, opening up new prospects for treating BPIs.

The SAN, a purely motor nerve, is a good option for reconstruction of elbow flexion due to its easy accessibility during supraclavicular exploration. ^, It contains approximately 1500 to 3000 myelinated axons, and when used for elbow flexion, an intervening nerve graft is usually required. Sami et al. published a series involving 44 patients who underwent nerve transfer between a branch of the accessory nerve and the musculocutaneous nerve with a sural nerve graft. After a follow-up period of 36 ± 13 months, 72% of patients showed overall reinnervation (Grades M1–M5) of the biceps muscle. Functional reinnervation (Grades M3–M5) was observed in 20 patients (51.3%) at final follow-up. Of these, 9 patients achieved Grade M3, 11 achieved Grade M4, and none reached Grade M5.

The MCN is a mixed nerve comprising both motor and sensory fibers. Following nerve transfer surgery, some motor fibers may mistakenly connect to the sensory fibers of the MCN terminating distally in the lateral antebrachial cutaneous nerve during regeneration, which can reduce the transmission of nerve axons to the motor fibers of the target muscles. However, the biceps branch of the MCN solely contains motor fibers directed to the biceps muscle. As a result, the SAN can be transferred to the biceps branch of MCN using a longer interposition nerve graft as an alternative.

Intercostal nerves are another popular choice of donor nerve in panplexal injuries. 41.9% of patients achieved M3 or M4 elbow flexion after ICNs to MCN transfer in a study reported by Maldonado et al. utilizing intercostal nerves. Intercostal nerves can often be combined with phrenic nerves to provide adequate elbow extension and flexion. Malungpaishope et al. investigated outcomes after transfer of the fourth to sixth intercostal nerves to the long head of triceps and phrenic nerve to the MCN, resulting in M3 or better elbow extension in 7 out of 10 patients along with elbow flexion MRC ≥ 3 in 9/10 patients. Although effective, phrenic nerve transfer requires careful patient selection, as the phrenic nerve plays a crucial role in respiratory function. Patients with compromised pulmonary function may not be suitable candidates for this procedure due to the potential risk of respiratory complications. While some studies report no symptomatic pulmonary dysfunction following phrenic nerve transfer, others have observed diaphragmatic paralysis, reduced inspiratory capacity, and the risk of respiratory failure years after surgery. ^, The phrenic nerve as a donor is more popular in Asia, and less commonly used in the USA, where there is a significant concern for donor site morbidity.

Although the SAN and intercostal nerves offer more motor axons than the phrenic nerve, the latter is a popular donor for nerve transfers to the musculocutaneous nerve due to its high amplitude and dense rhythmic discharge. ^, The phrenic nerve was first adopted in 1970 by Gu et al. to reconstruct elbow flexion. Its location in the supraclavicular region often places it directly in the operative field, and due to its contributions from C3 and C4, it is often spared in cases of complete root avulsion. Gu and Ma found that the recovery of biceps strength and contraction occurred earlier with phrenic nerve transfer compared to SAN or intercostal nerve transfer, with 84.6% of patients recovering muscle strength of M3 or greater. ^,

Nerve Transfers for Restoration of Hand Function

The contralateral C7 (cC7) root transfer to the median nerve, utilizing either a vascularized or nonvascularized ulnar nerve graft as a bridge, is one of the few effective techniques for restoring wrist and finger flexion and hand sensation. Introduced by Gu et al. in 1991, this procedure demonstrated satisfactory outcomes in 7 of 9 cases. In a subsequent report involving 14 patients who underwent contralateral C7 transfer to the median nerve for restoring wrist and finger flexion, 50% (7 patients) achieved ≥ M3 muscle power. Additionally, sensation in the median nerve territory recovered to S3 in 12 patients, while the remaining 2 patients achieved S2-S1 and S0 recovery each. When the cC7 was transferred to the radial nerve, 66.7% of cases (4 out of 6) regained wrist and finger extension with ≥ M3 power. Sensory recovery of the first web area reached S3 in 5 patients and S2-S1 in 1 patient.

Gu et al. advocated for a 2-stage transfer approach to optimize outcomes. This involved using the posterior division of the cC7` from the unaffected side with a pedicled ulnar nerve graft to the median nerve on the affected side. In the first stage, the pedicled ulnar nerve graft is detached distally and flipped proximally to coapt to the cC7. In the second stage, the proximal ulnar nerve on the affected side is sectioned and coapted to the median nerve. An alternative approach is to utilize a free vascularized ulnar nerve graft to bridge the defect between the cC7 and the affected median nerve. Using these techniques, finger and wrist flexion can often be restored after about 2 years. The efficacy of hand reanimation can vary due to various factors such as patient age and compliance to postoperative rehabilitation and retraining.

The C7 nerve is particularly advantageous for brachial plexus reconstruction due to its substantial number of over 25,000 myelinated fibers—significantly more than other commonly used donor nerves. It contains a mix of motor and sensory axons, making it suitable for reconstructing both motor-dominant nerves, such as the suprascapular nerve, and complex mixed nerves, like the median nerve. Despite its large number of axons, permanent donor-side morbidity following division of the C7 nerve is minimal.

A disadvantage of the cC7 nerve transfer is the need to activate the contralateral donor upper extremity to initiate movement in the reconstructed upper extremity. Experience suggests this is routine in adults, with children, however able to shift cortical control of the transferred portion of the cC7 nerve to the contralateral motor cortex, enabling more natural control of cC7-innervated muscles over time.

Functional Muscle Transfer

When donor nerves are unavailable, nerve grafting has failed, or in cases of delayed presentation (typically beyond 12 months), muscle transfer offer a viable alternative for functional restoration. Success rates can vary significantly, influenced by the functional suitability of the muscle and the associated complication rates. Adams et al. reported a failure rate of 15.4% in their study on free functional gracilis transfer for restoring elbow or finger flexion. Muscles commonly utilized for biceps substitution include the latissimus dorsi, rectus femoris, vastus lateralis, and gracilis. Free muscle neurotization can be performed as a single-stage procedure involving direct innervation most often with 2–3 intercostal nerves or the spinal accessory nerve. Alternatively, this can be performed as a 2-stage process, where a nerve graft is initially connected to a proximal donor nerve and subsequently banked subcutaneously in the arm. However, these procedures are not without challenges. Potential drawbacks include vascular compromise leading to muscle loss or suboptimal strength postreinervation due to inadequate axonal input, inappropriate tensioning, or loss of active muscle fibers.

The choice of donor muscle used for transfer is also subject to debate. While the latissimus dorsi is favored for its large size and rapid return to function, some authors argue that it, along with the rectus femoris, lacks the unique excursion and pedicle characteristics of the gracilis muscle, which make the latter particularly suitable for restoring elbow flexion. Ahmed et al. compared single vs double gracilis muscle transfers for restoring elbow flexion in patients with brachial plexus injuries, and reported significantly better outcomes with the double transfer technique. Their study also emphasized the importance of the nerve used for neurotization, with the spinal accessory nerve yielding superior results. Younger patients were also found to have a more favorable outcomes.

Our preference is to perform a single stage functional free gracilis transfer innervsted by the spinal accessory nerve for reconstruction of elbow flexion in patients with chronic, complete BPI as the spinal accessory nerve has been shown to be superior to intercostal donor nerves. Additionally, having the functional muscle focus only on elbow flexion allows it to perform 1 function, across 1 joint, in an effective fashion.

DREZ Lesioning for Pain Management

Neuropathic pain is a common and challenging symptom for patients with brachial plexus avulsions, particularly in cases of complete BPI. Dorsal Root Entry Zone (DREZ) lesioning is a specialized surgical technique designed to alleviate chronic pain by disrupting nociceptive neuron activity in the dorsal horn, thereby blocking pain signal transmission to the brain. Two primary methods are used for DREZ lesioning: radiofrequency (RF) ablation and microsurgical DREZotomy. A systematic review and meta-analysis by Shekouhi et al. evaluated the safety and efficacy of DREZ lesioning for managing pain in patients with brachial plexus avulsions, analyzing data from 917 patients. Among these patients, 655 (71.4%) reported substantial pain relief at their most recent follow-up. The study also found that microsurgical DREZotomy was significantly superior to RF-assisted lesioning in terms of reductions in Visual Analog Scale (VAS) scores and a lower risk of motor deficits. In our practice, we will consider DREZ lesioning for patients after about 5 years from the time of the injury. This allows neuropathic pain to stabilize in intensity after the initial injury. Additionally, as DREZ lesioning potentially has serious, life-threatening complications, this allows patients to carefully consider and trial other options for management of chronic neuropathic pain before considering DREZ lesioning as a surgical option.

Examples of panplexal brachial plexus reconstruction

Case 1: Reconstruction of Shoulder and Elbow Function With Nerve Grafting and Nerve Transfers

A 17-year-old male who suffered a complete brachial plexus injury following a motorcycle accident was operated on by the senior author. The patient presented with total motor and sensory function loss in the affected left upper limb. MRI showed a postganglionic C5 injury, postganglionic C6 injury with a proximal neuroma, C7 preganglionic avulsion, and pseudo-ganglionic avulsion of C8 and T1 roots with a large pseudo-meningocele ( Fig. 1 ). The surgical plan included a combination of nerve grafting and nerve transfers to restore functional outcomes, focusing on key techniques that have shown efficacy in cases of severe BPI.

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