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.