The versatility of the Supinator to Posterior Interosseus Nerve (SPIN) transfer: Indications and outcomes, a Case Series

Transfer of the supinator motor branches to the posterior interosseous nerve (SPIN) was first described as a reliable method of restoration of digit extension in cases of paralysis when there is retained function in the 5th and 6th cervical nerve roots with loss of function in the 8th cervical nerve root. We performed a retrospective review of all the SPIN transfers that were performed in our unit which included 16 limbs in 14 patients over a 6-year period. The median age was 49 years (range 22-74). The average follow-up period was 15 months (range 6-24 m). Aetiology included spinal cord injury (SCI) in 5, plexus root avulsion in 3, degenerate spondyloradiculopathy in 3 and the final three patients had paralysis from oncological resection, inflammatory and compressive neuropathy respectively. Functional digit extension (MRC grade 3 and above) was achieved in 12/16 limbs. Patients with degenerative spine lesions had the worst outcome with a median of MRC grade 2 with a median time to surgery of 20 months (average age of 67), compared to 13 months in the SCI group (average age 32.8) and four months in the BPI group (average age 34.6). The SPIN transfer may be safely performed in a wide spectrum of pathologies including brachial plexus injuries, spinal cord injuries and neuritis. However, in degenerative spondyloradiculopathy we report inferior outcomes, which may be due to late referral, chronic denervation, possible involvement of the donor nerve and an older age group and potentially diminished rehabilitation and neural plasticity potential.