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Reverse End-to-Side Motor Nerve Transfer for Augmentation of Ulnar Nerve Intrinsic Function
John R. Barbour, MD, Kirsty U. Boyd, MD, Santosh Kale, MD, Marci S. Bailey, RN, MSN, Susan E. Mackinnon, MD
Washington University School of Medicine, Division of Plastic and Reconstructive Surgery, Saint Louis, MO

Introduction: Following peripheral nerve injury, prolonged muscle denervation can lead to irreversible muscle atrophy despite eventual nerve regeneration and re-innervation.  A reverse end-to-side (RETS) transfer of the anterior interosseous nerve (AIN) to the motor component of the ulnar nerve is used to augment, or “supercharge”, motor recovery in proximal ulnar nerve injuries that are in-continuity (i.e. Sunderland II or III) by providing a source of motor axons in closer proximity to the intrinsic hand muscles.  Experimental studies have shown that a RETS motor nerve transfer can lead to re-nervation of a denervated motor nerve, improved muscle mass, higher motor end plate counts, and increased nerve fibers.  Because of our satisfaction with this procedure, we report our early results in 35 patients undergoing RETS transfer for augmentation and preservation of intrinsic hand function.

Methods: Thirty-one consecutive patients undergoing the procedure over the two-year period between August 2009 and August 2011 were retrospectively analyzed.  Preoperative electromyography results were reviewed. Patient demographics, details of the original nerve injury, indications for procedure, and pre-operative and post-operative measures of intrinsic muscle function (grip and pinch strength) were recorded. 

Results: Thirty-one patients underwent AIN to ulnar nerve RETS procedures (Male: 61% (19/31), age 44±18 years; Female: 39% (12/31), age 54±9 years).  The presence of axonal injury with motor action potentials (MUPs) was confirmed in all patients, suggesting an in-continuity injury.  All patients underwent the RETS nerve transfer in combination with release of Guyon’s canal +/- anterior transposition of the ulnar nerve at the elbow.  All patients have demonstrated some functional recovery of ulnar nerve intrinsic function following nerve decompression and RETS motor nerve transfer.  No donor morbidity was noted in any patient. Details regarding MRC grade, pinch and grip strength are being collected.

Conclusions: For ulnar nerve injuries in which incomplete, or delayed, regeneration is anticipated, a RETS nerve transfer might be useful to augment the regenerating nerve with additional axons in closer proximity to the target muscle, leading to quicker reinnervation.  In theory, this technique does not impede the normal recovery of the in-continuity nerve and has no donor site morbidity.  Factors influencing the success of the procedure include the degree of compression, adequate release of Guyon’s canal, and the degree of proximal injury (Sunderland II/III).  In our experience, this procedure has been an excellent addition to the surgical management of patients with ulnar intrinsic weakness.       

RETS Graph

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