Nerve Transfer for Restoration of Grasp in Tetraplegia: two strategies to improve the results of brachialis to AIN

Massachusetts General Hospital

S. Bazarek

In tetraplegia, nerve transfer for grasp has favored the brachialis branch of the musculocutaneous nerve as the donor. This was commonly sutured directly to a fascicle of the median nerve that favored AIN fibers. Results were less favorable compared with other nerve transfers in this population. This may be because the AIN is not fully formed at this level in most patients. Therefore, many axons are lost to less useful destinations, compromising results. To overcome this, we have 2 strategies. The first involves full isolation of the AIN fascicle from the median nerve using elbow flexion to overcome the remaining gap. Because this is technically challenging, we undertook as second strategy with a 2-stage operation using a graft from the brachialis with delayed hookup of the distal end to the AIN within the forearm. We present a case series of outcomes for grasp reanimation with both of these strategies. 4 patients (age 18-60) underwent direct repair in 6 limbs with a mean interval from injury to surgery of 8 months. 15 patients (ages 19 – 72) underwent the staged graft repair in 21 limbs with mean delay to surgery of 22 months. In the direct repair group, the median FPL MRC strength was 4/5 with interquartile range of 3-4. In fact, 67% were ≥3, with 38% reaching a 4/5. Median FDP function was 4 [2 – 4] with 90% achieving ≥3 and 76% reaching ≥4/5. In the 2-stage grafted repair FPL function was 4- [2 – 4] with 83% at ≥3 and 50% reaching ≥4. Median FDP function was 4 [4 – 4] with 90% ≥3 and 76% reaching ≥4/5 in this group. While the brachialis transfer is not the optimal transfer in this population (we favor pronator or ECRB), these strategies have improved our outcomes over a direct repair to the AIN fascicle.