Rate of Recovery of Finger Extension in Cervical Spinal Cord Injury following Supinator to Posterior Interosseous Nerve Transfer

Introduction: Nerve transfers (NTs) have demonstrated efficacy in improving patients’ functional outcomes following spinal cord injury (SCI). However, few studies provide a timeline for recovery following NTs and none provide a predictive model for what to expect as the ultimate outcome based on the findings of earlier timepoints. In this prospective cohort study, we evaluated the rate of recovery of finger extension in patients that underwent supinator nerve branches to posterior interosseous nerve transfer (SUP-PIN).

Methods: We assessed outcomes for finger extension at pre-operative and multiple post-operative timepoints using average finger extension force (FEF), the Medical Research Council (MRC) grading, and maximum range of finger extension (MRFE) from relaxation categorized into angle ranges of 0°, 1-15°, 16-30°, 31-45°, and 45°+.

Results: A total of 10 patients were included in the preliminary analysis. Pre-operatively, no (0%) patients had any measurable movement of finger extensors. 90% of patients demonstrated non-zero finger movement between 3- and 6-months post-operatively. At 6-months, 6 patients (60%) achieved MRCs >2 and MRFE angles >1-15° in all fingers (IAFs). These patients exhibited the greatest increase in FEF at the subsequent timepoints (average FEF at 18-months was 5.7 Newtons) and reached MRCs >4 and MRFE angles >30-45° IAFs at 16-months. 4 patients (40%) who did not reach MRCs >2 and MRFE angles >1-15° at 6-months had an average FEF of 3.1 Newtons at 18-months, and at 16-months, only 1 (25%) patient achieved MRCs >4 and MRFE angles >30-45° IAFs. The 18-month assessment marked the timepoint of plateau in functional recovery. Past the 18-month assessment, there was progressive recovery of FEF in 60% of patients, but MRCs and MRFE angles changed insignificantly.

Conclusion : Our findings suggest that patients reaching specific recovery benchmarks by 6-months are more likely to achieve greater finger extension function by 16-months and most functional gains stabilize around 18-months. Moreover, functional progress attained during the first 6-months following SUP-PIN appear pivotal for maximizing outcomes which underscores the need for early and effective rehabilitation strategies to optimize recovery trajectories.