Biomécanique des nerfs collatéraux digitaux – étude cadavérique

Injuries to digital collateral nerves after hand trauma are frequent and results from surgical treatment are poor. Characterization of mechanical behavior of healthy collateral nerves is necessary to produce numeric models and enhance the comprehension of nerve repair and regeneration process. There is no standard in the literature to characterize healthy nerve mechanics. The mechanical properties of the repaired nerve should be as similar as the healthy nerves, following the principles of mechanobiology. The aim of this study was to characterize the mechanical properties of human digital collateral nerves to look for a correlation with density as an intrinsic property of materials. 4 hands, 18 digital collateral nerves of 5 cm average length, were harvested and preserved by immersion in a NaCl 0.9 % solution to be tested. Each nerve was labelled to identify the corresponding finger during the tensile test. The nerves were positioned in a frame of emery paper, sutured and glued with ethyl-2-cyanoacrylate. Once positioned and aligned in the tensile test machine, Instron ® 3345 the tensile test was performed at speed of 6 mm min. During the test the nerve was continuously rehydrated with a NaCl 0.9 % solution. Density was measured using a Pycnometer and registered for each nerve. The test was recorded by a high-speed camera to identify the failure pattern according to wether the failure occurs in distal, middle and proximal area of the nerve. Finally, the diameter was measured using ImageJ software in a posterior image analysis. The results concern 3 thumbs, 2 index fingers, 6 middle fingers, 3 ring fingers and 4 pinky fingers There is no statistical significant difference between the studied variables among fingers. The failure pattern was distal in 72.22 %, middle 11.11 % and proximal in 16.67 % of the cases in contrast to the results presented by Goldberg et al. [Goldberg SH et al., 2007]. Our study presented a specific modulus characterization of human digital collateral nerves, we do not found other studies to compare our results. A pattern for each finger can be expected, but due to the scanty number of probes patterns do not emerge. We presented the human digital collateral nerve specific modulus constituted of 18 nerves. The failure pattern was distal in 70 % cases. Further studies in nerve composition must be conducted to enhance the knowledge of nerve biomechanical behaviour.