Posterior approach for accessory-suprascapular nerve transfer: an electrophysiological outcomes study

Anterior vs. posterior approach for spinal accessory nerve transfer to suprascapular nerve in brachial plexus injury: a systematic review and meta-analysis of comparative studies

Spinal accessory nerve (SAN) to suprascapular nerve (SSN) transfer is an effective surgical option for traumatic brachial plexus injuries (BPIs) when nerve grafting is not applicable. It is performed via two approaches: anterior and posterior. Despite the theoretical advantages of the posterior approach, clinical trials have yielded variable outcomes. This study aimed to compare the outcomes of anterior and posterior approaches for SAN to SSN transfer in restoring the Range of motion (ROM) and strength of shoulder abduction and external rotation in BPIs. We searched PubMed, Embase, Cochrane Library, Scopus, and Web of Science to identify studies comparing anterior and posterior approaches for SAN to SSN transfer. Quality assessment was performed using the Cochrane RoB2 tool and Newcastle-Ottawa Scale. via RevMan 5.4, meta-analyses were conducted. We identified eight comparative studies with 311 patients (n = 140 for posterior transfer, n = 171 for anterior transfer). Both approaches showed comparable outcomes with statistically significant advantages to the posterior approach by a modest but meaningful difference in shoulder abduction ROM (MD: 8.98°, 95% CI: 1.19 to 16.78, P = 0.02, I² = 0%) and in the Modified Medical Research Council (MRC), The posterior approach was associated with 4.78 times higher odds of achieving a grade ≥ M3 on the MRC scale (OR: 4.78, 95% CI: 1.43 to 15.96, P = 0.01, I² = 0%). We suggest that when functional gains are a priority, surgeons consider the posterior approach while still accounting for patient/surgeon specific factors and injury details.

Prevalence of Concomitant Distal Suprascapular Nerve Injury in Patients with Root-Level Brachial Plexus Palsy: A Clinical Anatomic Study of Injury Pattern

BACKGROUND

Root-level suprascapular nerve palsy is commonly reconstructed by means of spinal accessory nerve transfer in brachial plexus injury, but some patients do not recover. The authors hypothesize that this relates to concomitant undetected lesions distal to the nerve transfer coaptation.

METHODS

A total of 67 patients with plexus injury and C5/C6 root involvement were included in this prospective study between March of 2021 and October of 2022. During spinal accessory to suprascapular nerve transfer, the entire suprascapular nerve was explored using cresenteric clavicular osteotomy, and anatomic variations and injury patterns categorized.

RESULTS

Proximal root involvement was C5 to C6 ( n = 8), C5 to C7 ( n = 13), C5 to C8 ( n = 17), or C5 to T1 ( n = 29). Mean time from injury to surgery was 5.6 months. The suprascapular nerve was found to be injured in 16 of 67 cases (24%). In 9 cases (13%), the lesion was proximal to the suprascapular fossa. In 3 cases (4%), the suprascapular nerve was injured both proximally and within the fossa, and in 4 cases (6%), in the fossa or distal to it. Therefore, in 7 cases (10%), a traditional suprascapular nerve transfer would not successfully bypass the zone of injury of the suprascapular nerve in the fossa. Of the 16 cases of concomitant suprascapular nerve injury, 1 of 8 in occurred in C5 to C6 root injury, 4 of 13 of C5 to C7 root injury, 5 of 17 of C5 to C8 root injury, and 6 of 39 in total paralysis.

CONCLUSIONS

Concomitant distal suprascapular nerve injury in brachial plexus stretch palsy occurred in 24% of the cases. This warrants attention from the surgeon to identify distal lesions and to perform the nerve transfer beyond any secondary lesions.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Insights into the Medial Pectoral Nerve Transfer for Shoulder Abduction in Brachial Plexus Injuries: A Retrospective Case Series Analysis

BACKGROUND

Treatment priority in C5, C6, and C7 brachial plexus root avulsion is the recovery of shoulder function through reinnervation of shoulder muscles. The medial pectoral nerve is a potential donor for axillary nerve transfer, but outcomes are sparsely reported. This study reports the results of medial pectoral nerve transfer to the axillary nerve.

METHODS

We conducted a retrospective analysis of 12 patients with traumatic brachial plexus injury (C5, C6, and C7 root avulsion) who underwent medial pectoral nerve transfer to the axillary nerve. Sociodemographic and clinical characteristics, including electromyography findings, were documented. We assessed postoperative shoulder abduction strength and range of motion. Statistical analyses compared presurgery and postsurgery outcomes and contrasted our results with those from a study using spinal accessory nerve transfer to the suprascapular nerve.

RESULTS

Postsurgery, the mean shoulder abduction range of motion was 65.45°, with a median strength of M2. Significant improvement was noted compared to preoperative values. However, outcomes did not significantly surpass those from spinal accessory nerve transfer. Electromyography showed a low incidence of motor unit action potentials in the deltoid.

CONCLUSIONS

Medial pectoral nerve transfer to the axillary nerve did not yield superior results in shoulder abduction and deltoid reinnervation in our group of patients. At present, different nerve donors may also need to be considered for deltoid muscle reinnervation in patients with C5, C6, and C7 root avulsion to achieve better shoulder abduction recovery.

Comparison of Outcomes of Spinal Accessory to Suprascapular Nerve Transfer Versus Nerve Grafting for Neonatal Brachial Plexus Injury

Neonatal brachial plexus injuries may cause critical limitations of upper extremity function. The optimal surgical approach to address neonatal brachial plexus injuries has not been defined. In this systematic review, we compare clinical results after spinal accessory to suprascapular nerve transfer and nerve graft techniques among patients with neonatal brachial plexus injury. [Orthopedics. 2022;45(1):7-12.].

Outcomes of Shoulder Functions in Spinal Accessory to Suprascapular Nerve Transfer in Brachial Plexus Injury: A Comparison between Anterior and Posterior Approach

Background  Restoration of shoulder functions is important in brachial plexus injury (BPI). The functional outcomes of spinal accessory nerve (SAN) to suprascapular nerve (SSN) transfer by the anterior supraclavicular approach and the posterior approach is a matter of debate. This article aims to compare the outcomes of the shoulder functions by the SAN to the SSN transfer using the two approaches. Methods  Retrospective data was collected in 34 patients who underwent SAN to SSN transfer from January 2016 to June 2018. Group A included 16 patients who underwent nerve transfers by anterior approach, and Group B included 18 patients who underwent nerve transfers by posterior approach. Functional outcomes were measured by grading the muscle power as per the British Medical Research Council (MRC) grading (graded as M) and the range of motions (ROM) of the shoulder at 6 months and 18 months. Results  Early recovery was seen in group B with 7 patients (39%) showing M1 abduction power at 6 months as compared with one patient (6%) in group A . This difference was statistically significant ( p value = 0.04). At 18 months, 10 patients (62%) in group A had good recovery (MRC grade ≥3), while 13 patients (72%) in group B had a good recovery. This difference was not found to be statistically significant (Fisher exact test p value = 0.71) There was no statistical difference in the outcomes of ROM in shoulder abduction, external rotation, and motor power at 18 months of follow-up. Conclusions  Early recovery was observed in the anterior approach group at 6 months, however, there was no significant difference in the outcomes of shoulder functions in muscle power and ROM in the two groups at 18 months of follow-up.

ANALYSIS OF FATTY DEGENERATION OF THE TRAPEZIUS MUSCLE AFTER USE OF ACCESSORY NERVE

Objective:

To investigate, through magnetic resonance imaging, the occurrence of fatty degeneration of the trapezius in adult patients undergoing nerve transfer procedure, using the spinal accessory nerve.

Methods:

A total of 13 patients meeting the criteria of unilateral brachial plexus injury and more than one year of postoperative care after nerve transfer surgery underwent an MRI scan of the trapezius. A T1-weighted 3D sequence was used, with the IDEAL technique using 8.0 mm cut thickness, 8.0 mm cut spacing, TR of 100 ms, TE of 3.45 ms, flip angle of 10 degrees, 20 cuts, on the sagittal plane. The images of the upper, transverse and lower parts of the trapezius muscle were then classified according to the degree of fatty degeneration, compared with the contralateral side, using the Goutallier score.

Results:

For the upper trapezius there was a change of the degeneration state in 23% (p = 0.083), for the transverse section there was a change in 84.6% (p = 0.003), for the lower one there was a change in 92.3% (p = 0.002).

Conclusion:

The upper trapezius did not undergo significant degeneration after transfer. The lower and transverse trapezius suffered fatty degeneration in most patients, indicating severe functional impairment. Level of Evidence IV, Case series.

Outcomes of Spinal Accessory-to-Suprascapular Nerve Transfers for Brachial Plexus Birth Injury

PURPOSE

The results of a spinal accessory nerve-to-suprascapular (SAN-SSN) nerve transfer for brachial plexus birth injuries (BPBIs) have thus far been presented only in limited case series. Our study evaluates the recovery of shoulder function of patients who underwent an SAN-SSN for BPBI as an isolated procedure or as part of a multinerve reconstruction (MNR) surgery.

METHODS

We retrospectively reviewed the medical records of patients at a single institution who underwent an SAN-SSN after BPBI. Inclusion criteria were patients with both preoperative and a minimum 12-months postoperative active movement scale (AMS) scores. Patients for whom the primary surgery involved tendon transfers were excluded. The primary outcome measures were AMS scores for shoulder abduction, forward flexion, and external rotation and secondary outcomes included the need for further shoulder surgery to improve function.

RESULTS

Seventy-three patients met the inclusion criteria. Forty-three patients (58.9%) obtained functional shoulder motion (AMS ≥ 6) of at least 1 of 3 planes (abduction/flexion/external rotation) following surgery, with 13 patients (17.8%) achieving full recovery of 1 of these shoulder motions against gravity (AMS = 7). Fifty-six patients (76.7%) did not undergo subsequent tendon transfers or corrective osteotomies to augment shoulder function. The MNR procedures were performed in 46 patients (63%), of whom 45.7% gained a functional recovery. In 27 patients for whom SAN-SSN nerve transfer was conducted in isolation, 81.5% gained functional shoulder motion. However, isolated SAN-SSNs were conducted at a later age than MNR procedures (13.2 vs 4.8 months) and had higher preoperative AMS scores. The anterior and posterior approaches for SAN-SSN were both found to be effective when used for SAN-SSN in BPBI. When the follow-up duration cutoff was set to 3 years, the outcomes were found to be superior.

CONCLUSIONS

In 76.7% of the patients, SAN-SSN was able to recover function that was sufficient to prevent tendon transfers and corrective osteotomies. A cutoff of 3 postoperative years should be used as a benchmark for analyzing the results of this procedure.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Combined Radial to Axillary and Spinal Accessory Nerve (SAN) to Suprascapular Nerve (SSN) Transfers May Confer Superior Shoulder Abduction Compared with Single SA to SSN Transfer

BACKGROUND

The restoration of shoulder function after brachial plexus injury is a high priority. Shoulder abduction and stabilization can be achieved by nerve transfer procedures including spinal accessory nerve (SAN) to suprascapular nerve (SSN) and radial to axillary nerve transfer. The objective of this study is to compare functional outcomes after SAN to SSN transfer versus the combined radial to axillary and SA to SSN transfer.

METHODS

This retrospective chart review included 14 consecutive patients with brachial plexus injury who underwent SAN to SSN transfer, 4 of whom had both SA to SSN and radial to axillary nerve transfer.

RESULTS

SAN to SSN transfer achieved successful shoulder abduction (≥M3) in 64.3% of this cohort (9/14). During the long-term follow-up, patients achieved an average increase of 67.5° in shoulder abduction. There was no association between motor recovery and time from injury to surgery, age, body mass index (BMI), sex, or smoking status. The 4 patients who had SAN to SSN combined with radial to axillary nerve transfer demonstrated a statistically significant increase in the range of abduction (median, 90° vs. 42.5°, respectively; P = 0.022) compared with those who had SAN to SSN transfer alone; however, the difference in Medical Research Council (MRC) grades (MRC > M3) did not reach statistical significance (P = 0.07).

CONCLUSIONS

Patients with brachial plexus injury and an intact C7 root could benefit from radial to axillary transfer in addition to SAN to SSN transfer. There was no association between recovery of shoulder abduction and time interval from injury to surgery, age, sex, smoking, and BMI.

Endogenous automatic nerve discharge promotes nerve repair: an optimized animal model

Exogenous electrical nerve stimulation has been reported to promote nerve regeneration. Our previous study has suggested that endogenous automatic nerve discharge of the phrenic nerve and intercostal nerve has a positive effect on nerve regeneration at 1 month postoperatively, but a negative effect at 2 months postoperatively, which may be caused by scar compression. In this study, we designed four different rat models to avoid the negative effect from scar compression. The control group received musculocutaneous nerve cut and repair. The other three groups were subjected to side-to-side transfer of either the phrenic (phrenic nerve group), intercostal (intercostal nerve group) or thoracodorsal nerves (thoracic dorsal nerve group), with sural nerve autograft distal to the anastomosis site. Musculocutaneous nerve regeneration was assessed by electrophysiology of the musculocutaneous nerve, muscle tension, muscle wet weight, maximum cross-sectional area of biceps, and myelinated fiber numbers of the proximal and distal ends of the anastomosis site of the musculocutaneous nerve and the middle of the nerve graft. At 1 month postoperatively, compound muscle action potential amplitude of the biceps in the phrenic nerve group and the intercostal nerve group was statistically higher than that in the control group. The myelinated nerve fiber numbers in the distal end of the musculocutaneous nerve and nerve graft anastomosis in the phrenic nerve and the intercostal nerve groups were statistically higher than those in the control and thoracic dorsal nerve groups. The neural degeneration rate in the middle of the nerve graft in the thoracic dorsal nerve group was statistically higher than that in the phrenic nerve and the intercostal nerve groups. At 2 and 3 months postoperatively, no significant difference was detected between the groups in all the assessments. These findings confirm that the phrenic nerve and intercostal nerve have a positive effect on nerve regeneration at the early stage of recovery. This study established an optimized animal model in which suturing the nerve graft to the distal site of the musculocutaneous nerve anastomosis prevented the inhibition of recovery from scar compression.

Landmarks for Identifying the Suprascapular Foramen Anteriorly: Application to Anterior Neurotization and Decompressive Procedures

BACKGROUND

Additional landmarks for identifying the suprascapular nerve at its entrance into the suprascapular foramen from an anterior approach would be useful to the surgeon.

OBJECTIVE

To identify landmarks for the identification of this hidden site within an anterior approach.

METHODS

In 8 adult cadavers (16 sides), lines were used to connect the superior angle of the scapula, the acromion, and the coracoid process tip thus creating an anatomic triangle. The suprascapular nerve's entrance into the suprascapular foramen was documented regarding its position within this anatomical triangle. Depths from the skin surface and specifically from the medial-most point of the clavicular attachment of the trapezius to the suprascapular nerve's entrance into the suprascapular foramen were measured using calipers and a ruler. The clavicle was then fractured and retracted superiorly to verify the position of the nerve's entrance into the suprascapular foramen.

RESULTS

From the trapezius, the nerve's entrance into the foramen was 3 to 4.2 cm deep (mean, 3.5 cm). The mean distance from the tip of the corocoid process to the suprascapular foramen was 3.8 cm. The angle best used to approach the suprascapular foramen from the surface was 15° to 20°.

CONCLUSION

Based on our study, an anterior suprascapular approach to the suprascapular nerve as it enters the suprascapular foramen can identify the most medial fibers of the trapezius attachment onto the clavicle and insert a finger at an angle of 15° to 20° laterally and advanced to an average depth of 3.5 cm.

Evaluation of nerve transfer options for treating total brachial plexus avulsion injury: A retrospective study of 73 participants

Despite recent great progress in diagnosis and microsurgical repair, the prognosis in total brachial plexus-avulsion injury remains unfavorable. Insufficient number of donors and unreasonable use of donor nerves might be key factors. To identify an optimal treatment strategy for this condition, we conducted a retrospective review. Seventy-three patients with total brachial plexus avulsion injury were followed up for an average of 7.3 years. Our analysis demonstrated no significant difference in elbow-flexion recovery between phrenic nerve-transfer (25 cases), phrenic nerve-graft (19 cases), intercostal nerve (17 cases), or contralateral C₇-transfer (12 cases) groups. Restoration of shoulder function was attempted through anterior accessory nerve (27 cases), posterior accessory nerve (10 cases), intercostal nerve (5 cases), or accessory + intercostal nerve transfer (31 cases). Accessory nerve + intercostal nerve transfer was the most effective method. A significantly greater amount of elbow extension was observed in patients with intercostal nerve transfer (25 cases) than in those with contralateral C₇ transfer (10 cases). Recovery of median nerve function was noticeably better for those who received entire contralateral C₇ transfer (33 cases) than for those who received partial contralateral C₇ transfer (40 cases). Wrist and finger extension were reconstructed by intercostal nerve transfer (31 cases). Overall, the recommended surgical treatment for total brachial plexus-avulsion injury is phrenic nerve transfer for elbow flexion, accessory nerve + intercostal nerve transfer for shoulder function, intercostal nerves transfer for elbow extension, entire contralateral C₇ transfer for median nerve function, and intercostal nerve transfer for finger extension. The trial was registered at ClinicalTrials.gov (identifier: NCT03166033).

Nerve Transfers to Restore Shoulder Function

The restoration of shoulder function after brachial plexus injury represents a significant challenge facing the peripheral nerve surgeons. This is owing to a combination of the complex biomechanics of the shoulder girdle, the multitude of muscles and nerves that could be potentially injured, and a limited number of donor options. In general, nerve transfer is favored over tendon transfer, because the biomechanics of the musculotendinous units are not altered. This article summarizes the surgical techniques and clinical results of nerve transfers for restoration of shoulder function.

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.

Nerve transfer helps repair brachial plexus injury by increasing cerebral cortical plasticity

In the treatment of brachial plexus injury, nerves that are functionally less important are transferred onto the distal ends of damaged crucial nerves to help recover neuromuscular function in the target region. For example, intercostal nerves are transferred onto axillary nerves, and accessory nerves are transferred onto suprascapular nerves, the phrenic nerve is transferred onto the musculocutaneous nerves, and the contralateral C₇ nerve is transferred onto the median or radial nerves. Nerve transfer has become a major method for reconstructing the brachial plexus after avulsion injury. Many experiments have shown that nerve transfers for treatment of brachial plexus injury can help reconstruct cerebral cortical function and increase cortical plasticity. In this review article, we summarize the recent progress in the use of diverse nerve transfer methods for the repair of brachial plexus injury, and we discuss the impact of nerve transfer on cerebral cortical plasticity after brachial plexus injury.