Is there any difference between anterior and posterior approach for the spinal accessory to suprascapular nerve transfer? A systematic review and meta-analysis

Functional and morphological evaluation of the trapezius muscle after spinal accessory nerve transfer to brachial plexus nerves

INTRODUCTION

The main innervation of the trapezius muscle is provided by the spinal accessory nerve. Several studies describe the contributions of cervical plexus roots to the trapezius muscle innervation, either directly or through connections with the spinal accessory nerve. There is no adequate understanding of how the trapezius muscle is affected after using the spinal accessory nerve in nerve transfer procedures with the usual technique, preserving at least 1 branch for the upper trapezius.

METHODS

We evaluated 20 patients with sequelae of traumatic brachial plexus injury who underwent surgical procedures for brachial plexus repair or free muscle transfer, which included the spinal accessory nerve transfer technique and were followed for a minimum of 1 year. The three portions trapezius muscle were evaluated by physical examination, magnetic resonance imaging (analysis of fatty degeneration) and electromyography.

RESULTS

In all evaluation methods, the middle and lower portions of the trapezius muscle showed more significant morphological and/or functional impairment than the upper portion, in most cases. There was a statistically significant difference in all the complementary exams results, between the affected side (with sacrifice of the nerve) versus the normal side, in the middle and lower portions of the trapezius muscle.

CONCLUSIONS

Physical examination alone is not sufficient to determine the residual functionality of the trapezius muscle. Magnetic resonance imaging and electromyography are useful tools to assess both morphological involvement of the trapezius muscle and nerve conduction impairment of the trapezius muscle, respectively. The results suggest that the middle and lower portions of the trapezius muscle are affected by previous SAN transfer and should be considered with caution for further muscle transfer procedures.

A Randomised Control Trial Comparing the Outcomes of Anterior with Posterior Approach for Transfer of Spinal Accessory Nerve to Suprascapular Nerve in Brachial Plexus Injuries

Background: In brachial plexus surgery, a key focus is restoring shoulder abduction through spinal accessory nerve (SAN) to suprascapular nerve (SSN) transfer using either the anterior or posterior approach. However, no published randomised control trials have directly compared their outcomes to date. Therefore, our study aims to assess motor outcomes for both approaches. Methods: This study comprises two groups of patients. Group A: anterior approach (29 patients), Group B: Posterior approach (29 patients). Patients were allocated to both groups using selective randomisation with the sealed envelope technique. Functional outcome was assessed by grading the muscle power of shoulder abductors using the British Medical Research Council (MRC) scale. Results: Five patients who were operated on by posterior approach had ossified superior transverse suprascapular ligament. In these cases, the approach was changed from posterior to anterior to avoid injury to SSN. Due to this reason, the treatment analysis was done considering the distribution as: Group A: 34, Group B: 24. The mean duration of appearance of first clinical sign of shoulder abduction was 8.16 months in Group A, whereas in Group B, it was 6.85 months, which was significantly earlier (p < 0.05). At the 18-month follow-up, both intention-to-treat analysis and as-treated analysis were performed, and there was no statistical difference in the outcome of shoulder abduction between the approaches for SAN to SSN nerve transfer. Conclusions: Our study found no significant difference in the restoration of shoulder abduction power between both approaches; therefore, either approach can be used for patients presenting early for surgery. Since the appearance of first clinical sign of recovery is earlier in posterior approach, therefore, it can be preferred for cases presenting at a later stage. Also, the choice of approach is guided on a case to case basis depending on clavicular fractures and surgeon preference to the approach. Level of Evidence: Level II (Therapeutic).