The NEON trial: nerve repair vs. alignment for digital nerve injuries

This multicentre trial randomized 122 adult patients with suspected unilateral digital nerve injuries across 17 NHS hospitals. After surgical exploration confirmed nerve division, participants were randomized 1:1 to either:

Both groups received identical post-operative care and rehabilitation. The primary outcome was hand function measured by the Impact of Hand Nerve Disorders (I-HaND v2) scale at 12 months. The participants were blinded as to whether their nerve injury was sutured or not. Outcome assessors were similarly blinded to the allocation.

The study found no significant differences between treatment groups:

The results of this controversial RCT have challenged the surgical dogma that all digital nerve repairs must be sutured to optimise outcome and reduce neuroma risk. The nerve alignment alone group demonstrated trends toward equivalent or slightly better outcomes across most measures. This suggests that careful alignment of nerve ends may be sufficient for good functional recovery, potentially without the need for suturing. Importantly, the study demonstrated that reinnervation may occur effectively through alignment alone, possibly because suture material and the trauma of placing stitches might create a suboptimal environment for nerve regeneration.

The trial was terminated early due to slow recruitment (achieving 122 of the planned 478 participants). It is therefore fundamentally underpowered to definitely reject the null hypothesis. This was partly due to COVID-19 impacts but also due to challenge and debate within the hand surgery community regarding the trial design.

There was a series of correspondence published in the Journal of Hand Surgery that debated the appropriateness of randomly allocating participants to the nerve alignment alone group.4-6 These three letters demonstrate a pivotal debate in the hand surgery community that established the clinical equipoise for the NEON trial. The systematic review by Dunlop et al showed that only 24% of repaired digital nerves achieved good sensory recovery, with similar neuroma rates between repaired (4.6%) and non-repaired (5%) nerves, challenging the effectiveness of routine digital nerve suture repair.3 This was supported by a commentary that re-iterated these results and proposed the premise of the NEON trial.4 McArthur et al. then published a response letter critiquing this work, challenging these findings and reflecting the controversy and lack of equipoise within the community.5 Wormald et al. then contributed a commentary directly questioning "To repair or not repair a single digital nerve in adults?" articulating the clinical uncertainty that justified conducting the NEON RCT: to definitively compare surgical repair versus nerve alignment alone.6 This published academic discourse nicely demonstrates the critical importance of establishing equipoise in surgical trials.7

Whilst this initial lack of equipoise may have impacted the rate of recruitment to the study, although it is worth noting that 17 sites across the UK were open to recruitment by the time the study was closed as part of the NIHR post-pandemic reset. Despite these issues, it remains the largest randomized study of digital nerve repair to date and provides the best available evidence for clinical practice.

The NEON trial found no evidence supporting the superiority of suture repair over nerve alignment alone for isolated digital nerve injuries. These findings suggest that current surgical practice could be reconsidered, with treatment decisions becoming more individualized and judicious.