High ulnar nerve injury results in significant loss of hand function, with poor long-term outcomes due to the long re-innervation distance to the intrinsic muscles in the hand. Transfer of the anterior interosseous nerve (AIN) to the deep motor branch of the ulnar nerve (MUN) provides functional axons close to the target muscles, and is shown in several studies to produce functional instrinsic recovery. The purpose of this study was to evaluate the outcomes and efficacy of this procedure in a series from a single peripheral nerve injury unit in Birmingham, UK.
A retrospective review of medical records was conducted of patients who underwent AIN to MUN nerve transfer following high ulnar nerve injury. Data including demographics, injury details, surgical procedure, and outcomes were collected.
Sixteen patients were identified who had undergone AIN to MUN transfer with an average of 17 months follow up. Mean age was 39.4 years and median delay from injury to nerve transfer was 0.8 months. The injury site was above the elbow in 5 cases, at the elbow in 8 cases, and in the proximal forearm in 3 cases. The majority were sharp transection, with the remaining from blast injuries, traumatic traction, and one post neuroma resection. Transfer was performed end-to-end in 7 cases, hemi end-to-end in 7 cases, and supercharged end-to-side in 2 cases. Five patients achieved intrinsic muscle recovery of MRC 4+ and thirteen gained MRC 3 or above.
The AIN to MUN nerve transfer provides meaningful intrinsic recovery in the majority of traumatic high ulnar nerve injuries. This procedure should be routinely considered, however further research is required to determine the optimal technique.