Proximal versus Distal Nerve Transfer for Biceps Reinnervation-A Comparative Study in a Rat's Brachial Plexus Injury Model

Using Transcranial Magnetic Nerve Stimulation to Differentiate Motor and Sensory Fascicles in a Mixed Nerve: Experimental Rat Study

BACKGROUND

 Accurately matching the correct fascicles in a ruptured mixed nerve is critical for functional recovery. This study investigates the use of transcranial magnetic stimulation (TMS) to differentiate motor and sensory fascicles in a mixed nerve.

METHODS

 In all 40 rats, the median nerve in the left upper arm was evenly split into three segments. The rats were separated into two groups. In Group A (20 rats), the segment with the highest amplitude during TMS was selected as the motor neurotizer and transferred to the musculocutaneous nerve. In Group B (20 rats), only the medial one-third segment was selected and transferred without using TMS. The results were compared using grooming tests, nerve electrophysiological studies, muscle tetanus contraction force measurements, muscle weight, and axon counts at 16 weeks.

RESULTS

 The grooming test showed that Group A performed significantly better than Group B at 12 and 16 weeks postoperatively. Tetanic muscle contraction force measurements also revealed that Group A had significantly better outcomes than Group B. However, electrophysiological testing, muscle weight, and axon counts showed no significant differences between the two groups.

CONCLUSION

 This study suggests that TMS can be used to distinguish motor fascicles from sensory fascicles in a mixed nerve. It is desirable to apply this technique intraoperatively to differentiate motor and sensory fascicles for appropriate nerve matching and to select the motor fascicles as a motor neurotizer for functioning free muscle innervation in human mixed nerve injury.

Spinal accessory nerve transfer for shoulder abduction has no benefit over supraclavicular exploration and nerve grafting in brachial plexus birth injury: a systematic review

Introduction

Brachial plexus birth injury (BPBI) has an incidence of 0.9 per 1,000 live births in the population. Techniques for repair classically include supraclavicular exploration and nerve grafting (SENG) and more recently nerve transfer, namely of the spinal accessory nerve (SAN) to the suprascapular nerve (SSN) to improve functional outcomes such as glenohumeral abduction and external rotation. This systematic review was conducted to evaluate whether spinal accessory nerve transfer produced significantly better outcomes for shoulder abduction in BPBI.

Methods

A search was conducted using Preferred Reporting Items for Systematic Reviews and Meta-Analysis Individual Patient Data guidelines. Standardized comparisons were made using the Mallet Score for shoulder abduction.

Results

10 full-text articles with itemized patient outcome measures were selected. 110 patients were identified with 51 patients in the SENG group and 59 patients in the SAN transfer group. The mean shoulder abduction Mallet score in the SENG group was 3.50 ± 0.84, while the mean Mallet score in the SAN transfer group was 3.58 ± 0.77, which displayed no significant differences (p = 0.9012). There was no significant relationship between the age at time of surgery and post-operative Mallet scores for shoulder abduction after SENG (p = 0.3720).

Discussion

Our systematic review found that there was no difference observed in post-operative outcomes of shoulder abduction when comparing SAN transfer and nerve grafting. Continued support for nerve grafting lies in the argument that it incorporates the patient's native neuroanatomy and allows for sensory reinnervation.

Rehabilitation protocols in neonates undergoing primary nerve surgery for upper brachial plexus palsy: A scoping review

INTRODUCTION

Surgical management is recommended in patients with severe neonatal brachial plexus palsy (NBPP) within the first 6 months of age to regain best possible function. Rehabilitation post-surgery remains relatively unexplored. This is a scoping review that explores, which rehabilitation modalities exist and how they vary for different microsurgical approaches in NBPP.

MATERIALS AND METHODS

A systematic search was conducted to include articles about upper trunk obstetric brachial plexus nerve microsurgery in pediatric patients that made mention of rehabilitation protocols. The aims of rehabilitation modalities varied and were grouped: "passive" movement to prevent joint contracture or stiffness, "active" or task-oriented movement to improve motor function, or "providing initial motor recovery". Surgical approach was described as either exploration of the brachial plexus (EBP) or nerve transfer without root exploration (NTwoRE). Technique was categorized into transfers and non-transfers.

RESULTS

Thirty-six full-text articles were included. Initiation of rehabilitation was 22.26 days post-surgery. Twenty-eight studies were EBP, and six were NTwoRE. Of studies classifiable by aims, nine were "passive", nine were "active", and five were "providing initial motor recovery". Only 27.7% of EBP studies mentioned active therapy, while 75.0% of NTwoRE studies mentioned active therapy. The average age of patients in the EBP procedure category was 7.70 months, and NTwoRE was 17.76 months. Within transfers, the spinal accessory to suprascapular group was more likely to describe an active shoulder exercise therapy, whereas contralateral C7 group was more likely to describe "initial motor recovery", especially through the use of electrostimulation. All articles on electrostimulation recommended 15-20-minute daily treatment.

CONCLUSION

Information on rehabilitation is limited post-nerve surgery in NBPP. However, when mentioned, the aims of these therapies vary with respect to surgical approach and technique. The type of therapy to employ may be a multifaceted decision, involving factors such as patient age, initial deformity, and goals of the care team.

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

Introduction

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

Methods

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

Results

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

Conclusion

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

Type of study/Level of evidence

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

The Impact of Exercise on Motor Recovery after Long Nerve Grafting-Experimental Rat Study

BACKGROUND

 Long nerve grafting often results in unsatisfactory functional outcomes. In this study we aim to investigate the effect of swimming exercise on nerve regeneration and functional outcomes after long nerve grafting.

METHODS

 A reversed long nerve graft was interposed between C6 and the musculocutaneous nerve in 40 rats. The rats were divided into four groups with 10 in each based on different postoperative swimming regimes for rehabilitation: group A, continuous exercise; group B, early exercise; group C, late exercise; and group D, no exercise (control group). A grooming test was assessed at 4, 8, 12, and 16 weeks postoperatively. Biceps muscle compound action potential (MCAP), muscle tetanic contraction force (MTCF), and muscle weights were assessed after 16 weeks. Histomorphometric analyses of the musculocutaneous nerves were performed to examine nerve regeneration.

RESULTS

 The grooming test showed all groups except group D demonstrated a trend of progressive improvement over the whole course of 16 weeks. Biceps MCAP, MTCF, and muscle weights all showed significant better results in the exercise group in comparison to the group D at 16 weeks, which is especially true in groups A and B. Nerve analysis at 16 weeks, however, showed no significant differences between the exercise groups and the control group.

CONCLUSIONS

 Swimming after long nerve grafting can significantly improve muscle functional behavior and volume. The effect is less evident on nerve regeneration. Continuous exercise and early exercise after surgery show more optimal outcomes than late or no exercise. Having a good habit with exercise in the early period is thought as the main reason. Further studies are needed to determine the optimal exercise regimen.

Supercharge End-to-Side Sensory Transfer to A Long Nerve Graft to Enhance Motor Regeneration in A Brachial Plexus Model—An Experimental Rat Study

Background Long nerve grafts will affect muscle recovery. Aim of this study is to investigate if supercharged end-to-side (SETS) sensory nerve transfer to long nerve graft can enhance functional outcomes in brachial plexus animal model.

Methods A reversed long nerve graft (20–23-mm) was interposed between C6 and musculocutaneous nerve (MCN) in 48 SD rats. The sensory nerves adjacent to the proximal and distal coaptation sites of the nerve graft were used for SETS. There were four groups with 12 rats in each: (A) nerve graft alone, (B) proximal SETS sensory transfer, (C) distal SETS sensory transfer, and (D) combined proximal and distal SETS sensory transfers. Grooming test at 4, 8, 12 and 16 weeks, and compound muscle action potentials (CMAP), biceps tetanic muscle contraction force, muscle weight and MCN axon histomorphologic analysis at 16 weeks were assessed.

Results Grooming test was significantly better in group C and D at 8 weeks (p = 0.02 and p = 0.04) and still superior at 16 weeks. There was no significant difference in CMAP, tetanic muscle contraction force, or muscle weight. The axon counts showed all experimental arms were significantly higher than the unoperated arms. Although the axon count was lowest in group C and highest in group D (p = 0.02), the nerve morphology tended to be better in group C overall.

Conclusion Distal sensory SETS transfer to a long nerve graft showed benefits of functional muscle recovery and better target nerve morphology. Proximal sensory inputs do not benefit the outcomes at all.

Double Fascicular Transfer Using Partially Injured Donor Nerves: Is It Powerful Enough to Restore Elbow Flexion in Acute Brachial Plexus Injuries?

BACKGROUND

 Loss of elbow flexion is a common sequela of acute brachial plexus injuries (BPIs). The Mackinnon/Oberlin-II double fascicular transfer (DFT) is a widely used method to restore this function in acute C5-6 or C5-7 injuries. This study attempted to evaluate if this technique can be applied reliably for cases involving C8 and/or T1 injuries.

METHODS

 Adult patients with acute BPIs who underwent the Mackinnon/Oberlin-II DFT in our center between 2008 and 2018 were retrospectively identified. Group I (n = 37) included patients with only C5-6 or C5-7 injury, while group II (n = 32) patients presented C5-8 ± T1 injuries. The demographic data, pre- and postoperative neurologic evaluations, electrodiagnostic studies, and grip strength assessment were collected.

RESULTS

 A total of 69 patients met the inclusion criteria. Preoperatively, the patients in group II presented poorer nerve conduction and electromyography in both the median and the ulnar nerves and the supply muscles. The percentage of M3 achievement in both groups was 91.9 versus 87.5% and M4 was 73.0 and 71.9%, respectively, which both were not statically significant but the achievement of group II was slower than the group I, 1 to 2 months slower, respectively. Both groups had 57.57 and 46.0% of the postoperative grip power compared with the healthy side, the result of shoulder abduction was not different (p = 0.480).

CONCLUSION

 With careful preoperative evaluation, early intervention, appropriate intraoperative functional fascicle selection, and aggressive postoperative rehabilitation, indications for the Mackinnon/Oberlin-II DFT technique can safely include acute C5-8 injuries and even partial T1 acute BPIs.

Can a Partially Injured Donor Nerve Restore Elbow Flexion in an Acute Brachial Plexus Injury in Rats?

BACKGROUND

Loss of elbow flexion commonly occurs following acute brachial plexus injury. The double fascicular transfer is often used in acute C5-C6 and C5-C7 root injuries, but is rarely applied in cases involving concomitant C8 or T1 root injury. The authors designed a rat model using varying severities of lower trunk injury to determine whether partial injury to the lower trunk affects nerve transfers for elbow flexion.

METHODS

There were four different rat groups in which 0, 25, 75, or 100 percent of the donor lower trunk remained intact. One-fourth of the cross-sectional area of the ulnar nerve was then transferred to the musculocutaneous nerve immediately. The authors assessed outcomes using a grooming test, muscle mass, retrograde labeling of sensory/motor neurons that regenerated axons, and immunohistochemical stain of regenerated axons.

RESULTS

Five months after nerve transfer, rats that underwent partial injury of the lower trunk fared significantly worse than the rats in whom the donor lower trunk remained 100 percent intact, but significantly better than the rats with 0 percent intact lower trunk. Rats with 25 or 75 percent of the lower trunk intact recovered equivalent function, at both the donor and recipient sites.

CONCLUSIONS

Although relatively weak compared with the 100 percent intact donor lower trunk group, the partially injured donor nerve was still functional; even though the nerve sustained a partial injury, the residual axons reinnervated the target muscles. The power of the muscles following either 25 percent or 75 percent injuries was equal after the recovery. Resorting to this approach may be useful in cases in which no alternatives are available.