Optimization of Brachialis to AIN Nerve Transfer for Recovery of Finger Flexion in Tetraplegia
Stanley Bazarek, MD, PhD, Brigham & Women's Hospital, Boston, MA and Justin M Brown, MD, Massachusetts General Hospital, Boston, MA
Introduction: Nerve transfers have recently been applied toward functional restoration following tetraplegia. Hand function is rated the top priority in this population. Outcomes have been limited in the literature, but recovery of finger extension via transfer of the supinator nerve branches to the PIN has shown consistent success, while restoration of finger flexion has been variable. The use of distal nerve donors, such as the ECRB or pronator teres have shown good results, but C5 injury often leaves only the more proximal brachialis branch of MCN available. This transfer has demonstrated poor results in the hands of numerous surgeons. We believe this is due to the technique being employed in these cases.
Materials & Methods: Surgery was performed in patients with both acute and chronic cervical cord injury. Pre-operative evaluation included both physical exam and electrophysiological studies. In C5 patients of international classification levels 0-2, brachialis was deemed the only reasonable donor to reconstruct finger flexion. One of two strategies was employed in these cases. First, if pre-operative evidence showed innervation of finger flexors, followed by intra-operative verification, a sural nerve graft was utilized and tunneled to the forearm for later (9-12 month) transfer to the AIN. Second, if there was evidence of denervation in the finger flexors in a patient less than 1 year from the injury, a direct brachialis to AIN transfer was performed, including meticulous neurotization of the AIN proximal to cubital fossa. Because the "pure? AIN fascicle is often not able to directly reach the brachialis branch, an elbow flexion brace was used to overcome a gap of up to 5 cm and this was slowly extended over 6-12 weeks to avoid rupture of the repair site.
Results: Both direct brachialis repair with progressive extension and the 2-stage indirect repair via sural graft to AIN produced an average MRC grading of 4.
Conclusions: The restoration of finger flexion in the tetraplegic patient can be reliably achieved through transfer of the nerve to the brachialis to the AIN if one of the strategies above is followed. These strategies have demonstrated a reliably superior result to those from the brachialis to "AIN fascicle" as previously published by multiple authors.
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