Boeckstyns 2013.

Study characteristics
Methods	Study type: RCT Follow‐up period: 24 months
Participants	Participants: 43 participants (22 intervention, 21 control) Injury: < 72 hours following injury, complete nerve laceration of the median or ulnar nerves or both in the distal third of the forearm Age range (years): 21–66 Sex: 9 female, 22 male (demographics provided for those attending 2‐year follow‐up)
Interventions	Intervention: collagen nerve guide conduit (23 nerves in 22 participants) Control: end‐to‐end suturing or nerve grafting (22 nerves in 22 participants, 21 direct repairs and 1 sural nerve graft). Note: data for sural nerve graft subsequently excluded from analysis.
Outcomes	Outcomes measured at 3, 6, 12, 18, and 24 months RMI Motor action potential Sensory action potential Safety (adverse events and complications)
Funding	No funding source declared
Conflicts of interest	Nerve conduit company employee featured on authorship
Notes	Nerve gap > 20 mm was an exclusion criterion. Trialists performed only 1 nerve grafting, which was excluded from the final analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	Quote: "We opened the randomization envelopes at the time of surgery after having measured the nerve gap and found the lacerations suitable for direct end‐to‐end suture or implantation of a short nerve graft."
Random sequence generation (selection bias)	Unclear risk	Details of sequence generation not provided.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	The participants and postoperative personnel were blinded to the treatment and subjective outcomes used.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	The evaluators were blinded to the treatment.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	11 participants did not have follow‐up at 24 months. 1 died, and the others did not attend follow‐up. Therefore, data were analysed for 18/22 participants in the conduit repair group and 13/21 participants in the direct suture group at 24 months. However, we judged the risk of bias unclear because there was no reported systematic difference in the way participant groups were followed up. There was only 1 participant with a nerve gap injury repaired using autologous nerve graft and the data were excluded from analysis. We deemed this a low risk of attrition bias in itself. We graded the risk of attrition bias overall as unclear as the reasons for loss to follow‐up were not detailed.
Selective reporting (reporting bias)	Low risk	All outcome measures were reported.
Other bias	Unclear risk	Nerve gaps were compared to direct repair. Length of defects repaired in the conduit group unclear. Quote: "We measured the nerve gaps to ensure that they did not exceed 20 mm but we did not record the measurements for further analysis." Comment: this could conceivably bias results to favour direct repair but we did not consider this a major concern. 1 participant underwent 2 nerve repairs (unit of randomisation was the participant). It is unclear how authors dealt with non‐independence of data in analysis.