Supinator to posterior interosseous nerve transfer to restore hand opening in brachial plexus and spinal cord injury: a systematic review and individual patient-data meta-analysis.

Cervical spinal cord injury (SCI) and lower trunk brachial plexus injury (BPI) commonly result in hand paralysis. Although restoring hand function is complex and challenging to achieve, regaining volitional hand control drastically enhances functionality for these patients. The authors aimed to systematically review the outcomes of hand-opening function after supinator to posterior interosseous nerve (PIN) transfer. A systematic literature review was performed according to the PRISMA guidelines. A total of 16 studies with 88 patients and 119 supinator to PIN transfers were included (87 transfers for SCI and 32 for BPI). In most studies, the time interval from injury to surgery was 6-12 months. Finger extension and thumb extension (Medical Research Council grade ≥ 3/5) recovered in 86.5% (103/119) and 78.1% (93/119) of cases, respectively, over a median follow-up of 19 months. The rates of recovery were similar for the SCI and BPI populations (finger extension, 87.3% in SCI and 84.3% in BPI; thumb extension, 75.8% in SCI and 84.3% in BPI). Type of injury (OR 1.05, 95% CI 0.17-6.4, p = 0.95), time from injury to surgery (OR 1.01, 95% CI 0.8-1.29, p = 0.88), and age (OR 0.97, 95% CI 0.90-1.06, p = 0.60) were not associated with odds of a successful outcome. Duration of follow-up was significantly associated with successful finger extension (OR 1.15, 95% CI 1.01-1.30, p = 0.026). No donor-associated supinator weakness was reported postoperatively given that patients had an intact bicep muscle preoperatively contributing to supination. Supinator to PIN transfer is a safe and effective procedure that can achieve successful restoration of digital extension in the SCI and BPI population at similar rates. Duration of follow-up was associated with superior outcomes, which was expected.