Double Supinator Branch Transfer to Posterior Interosseous Nerve May Confer Superior Hand Opening Restoration Outcomes Compared to Single Branch: a Systematic Review and Meta-analysis

Introduction: Cervical spinal cord injury (SCI) and lower trunk brachial plexus injury (BPI) commonly result in hand paralysis. The supinator to posterior interosseous nerve (SPIN) transfer is a well-established surgical approach that can achieve restoration of hand opening with similar outcomes in SCI and BPI. Most often, the radial nerve has two branches to the supinator. Studies have reported utilization of either single or double supinator branches as donors for the SPIN transfer. The aim of this study was to study whether using one or both supinator branches can affect recovery of hand opening.

Methods: A systematic literature review was performed according to the PRISMA guidelines. All studies reporting outcomes of the SPIN transfer were included.

Results: A total of 16 studies with 108 patients and 152 SPIN transfers were included (132 with double and 20 with single supinator donor branches; 123 for SCI and 29 for BPI). Four of the 16 included studies reported use of a single motor supinator branch as a donor while the remaining 12 used both branches. The average time interval from injury to surgery was less than 12 months in each study. Finger extension (MRC ≥3/5) recovered in 65% (13/20) and 86.3% (114/132) of the single and double donor transfers (p=.016), respectively. Thumb extension restoration was achieved in 60% (12/20) and 83.3% (110/132) of the single and double branch transfers (p=.014), respectively. The median reported follow-up was more than 20 months per study. One patient in the cohort developed supination weakness; however, this patient had pre-existing biceps weakness. Four patients developed temporary wrist extension weakness.

Conclusion : Utilization of both supinator branches for the SPIN transfer might achieve superior hand opening outcomes in SCI and BPI, compared to the single supinator branch.