A meta-analysis and systematic review: association of timing and muscle strength after nerve transfer in upper trunk palsy.

Abstract

A systematic review following PRISMA guidelines was conducted to address the PICO question: Does early (< 6 months) nerve transfer improve muscle strength outcomes when compared to late (≥ 6 months) nerve transfer for upper trunk palsy, as measured by the Medical Research Council (MRC) scale? The association between age and successful muscle function recovery was assessed as a secondary outcome. The quality of included studies was evaluated using the Methodological Index for Non-Randomized Studies (MINORS) tool. A total of 349 studies were screened, with 27 studies meeting criteria for systematic review, and 16 included in the meta-analysis. Most patients were young adult males who underwent a variety of different types of nerve transfers such as spinal accessory to suprascapular or triceps branch to axillary. Overall, 181 patients underwent nerve transfer within 6 months of injury, while 139 underwent nerve transfer after 6 months. Patients who underwent early nerve transfer had a 0.87 point higher postoperative MRC, compared to patients in the delayed period (p < 0.00001, n = 320), nearly a whole point difference in the MRC scale which is clinically significant and could make the difference between achieving functional muscle strength (MRC ≥ 3) or not. Additionally, patients who achieved functional postoperative muscle strength were 5.56 years younger than patients who did not (95% CI = [0.92, 10.20], n = 274). All included studies were of moderate quality according to MINORS, except one of poor quality. In conclusion, early nerve transfers for upper trunk palsy are associated with clinically and statistically significant improvements in muscle strength. When feasible, patients with persistent severe upper trunk palsy should undergo nerve transfer within 6 months post-injury.