Abstract
Supercharged end-to-side nerve transfer for severe cubital tunnel syndrome is a recently developed technique which involves augmenting the ulnar motor branch with anterior interosseous nerve (AIN). Previous studies suggested that this technique augments or “babysits” the motor end plates until reinnervation occurs, however, some authors suggested possible reinnervation by the donor nerve. We present two cases where this transfer was done for rapid progressive (6–9 months) cubital tunnel syndrome.
The first case was a 57 year-old right hand dominant female who presented to us with severe right cubital tunnel syndrome clinically, including intrinsic wasting and claw deformity. The patient had significant loss of function and visible atrophy to her hand intrinsics over the last few months. Electrodiagnostic studies confirmed the diagnosis of severe cubital tunnel syndrome demonstrating axonal loss, positive sharp waves and fibrillations in the ulnar nerve distribution distally. The patient underwent cubital tunnel ulnar nerve release, subcutaneous anterior transposition, Guyon's canal release along with an AIN to ulnar motor nerve end-to-side transfer. Patient-based functional outcome instruments were prospectively collected with improved overall pain and function as demonstrated from a quickDASH score of 9.1 1 year post-op in comparison to a score of 34.1 pre-op. Recovery was monitored clinically and electrodiagnostic studies at 6 months and 1 year post-operatively. She demonstrated improved intrinsic muscle bulk and strength. The nerve studies at one year showed reinnervation with large amplitude motor unit potentials in the 1st dorsal interosseous and abductor digiti minimi but the 5th finger sensory response remained absent. The second case was a 58 year-old right hand dominant male diagnosed with severe and progressive right cubital tunnel syndrome. Clinically, he had significant muscle wasting and weakness and confirmed denervation on electrodiagnostic studies. He underwent the same surgical procedure as described for the first case and follow-up regimen. The patient demonstrated improved pain score and significant overall function recovery with a quickDASH score of 11.4 one year post-op in comparison to 72.7 pre-op. Nerve studies at one year confirmed our clinical impression, showing ulnar nerve reinnervation with large amplitude motor unit potentials in the 1st dorsal interosseous, while sensory response remained absent.
It is yet unclear if end-to-side nerve transfers allow reinnervation of the target muscles. Previous studies have demonstrated clinical improvement with this transfer, however we are unaware of any electrodiagnostic studies demonstrating this effect. These two cases support the notion of reinnervation after an end-to-side procedure. Further studies are needed to assess outcomes of such nerve transfers.
