Nerve De-tensioning Effects of Conduits: A Quantitative Cadaveric Analysis Comparing Conduit-Assisted and Direct Digital Nerve Repairs
Emily Jewell, MD1; Benjamin Loflin, MS2; Stephen Schlecht, PhD2; Jeffrey A. Greenberg, MD3; Sameer K Puri, MD4; Brandon S. Smetana, MD3
1Reid Health, Richmond, IN; 2Indiana University, Indianapolis, IN; 3Indiana Hand to Shoulder Center, Indianapolis, IN; 4Resident, Department of Orthopaedic Surgery, Indiana Hand to Shoulder Center, Indianapolis, IN
Introduction: An optimal environment will eliminate undo strain that is placed upon a nerve laceration after repair. We hypothesize that the use of a conduit when compared to a suture only repair will displace the strain experienced by a nerve away from the laceration site.
Materials & Methods: 30 digital nerves were harvested from five fresh frozen cadavers and were speckled for later strain mapping. They were then divided into three groups of 10 nerves which were lacerated at their midpoint then repaired based upon their assigned cohort: direct repair with suture only (“SO”), conduit assisted repair with approximating sutures at the nerve laceration site (“CAR”), and conduit only repair without approximating sutures (“CO”). All nerves were loaded using an Instron device while being filmed using a high-resolution image capture system. Digital image correlation, a non-contact strain mapping technique, was then used to determine the strains experienced during the loading process throughout the entire nerve length, and specifically at the nerve laceration site as well as at both of the conduit to epineural suture junctions if a conduit was used. Ultimate load to failure was also recorded.
A one-way ANOVA was used to compare strain at each measured site between the three different testing groups, between the three sites of measured strain within each group, as well as ultimate load to failure between groups.
Results: At failure, the strain seen at the nerve laceration site in the SO group (0.87 +/- 0.42) was significantly greater than the two cohorts where conduits were utilized: CAR (0.18 +/- 0.27) and CO (0.20 +/- 0.25) (P<0.05). The use of a conduit increased the ultimate load to failure from the SO group (0.45 +/- 0.27N) compared to the CAR (1.20 +/- 0.32N) and CO (0.96 +/-0.29N) cohorts (P<0.5). With the use of a conduit, approximately 11% of the total strain experienced by the nerve during the loading process was seen at the nerve laceration site. However, with a suture only repair, approximately 85% of the total strain seen by the specimen was localized to the nerve laceration site.
Conclusions: The use of a conduit during nerve repair effectively de-tensions the nerve laceration site by shielding it from the majority of strain experienced by the nerve during an applied load. De-tensioning the nerve repair site is one modifiable factor that may help optimize the environment for a nerve during the healing process.
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