The Effect of Conduit Length on Offloading Nerve Repairs Through Strain-Shielding: A Cadaveric Biomechanical Study.

Purpose: To determine whether the distance between conduit anchoring sutures and the neurorrhaphy influences local strain distribution at a primary nerve repair site in a cadaveric model. Methods: Median and ulnar nerves were harvested from cadaver limbs. Nerves were split between conduit-assisted repair at conduit lengths of 2, 4, and 6 mm, corresponding to anchor points of 1, 2, and 3 mm. All other nerves were allocated to standard primary repair. All nerves were loaded to failure at a loading rate of 20 mm/min. Strain was analyzed at the repair site and proximal and distal sites with two-dimensional digital image correlation. Results: The 6-mm conduit-assisted group demonstrated significantly lower strain at the repair site when compared with the 2- and 4-mm conduit-assisted groups. The 2- and 4-mm conduit-assisted groups had significantly higher strain at the repair site when compared to their respective proximal and distal sites. The 6-mm conduit-assisted repair group had a similar strain distribution when the repair site was compared to proximal and distal strain sites. Conclusions: The 6-mm conduit-assisted repair with anchor points positioned approximately 3 mm from the coaptation demonstrated lower repair site strain than shorter constructs, with no significant difference in strain at the repair site when compared to proximal and distal sites. Clinical relevance: Conduit-assisted nerve repair requires sufficient anchor-point positioning to function as a strain-shielding device. When using conduit-assisted nerve repair, shorter anchor points may not adequately offload the repair and may compromise the intended coaptation site, giving surgeons insight into optimal anchor-point positions for procedural planning.