More Than Epineurium Deep: Characterizing Peripheral Nerve Damage Using High-Resolution Micro-Computed Tomography for Simulated Peripheral Nerve Lacerations.

Purpose: Nerve damage because of acute traumatic lacerations is challenging to assess and is typically evaluated using loupes or an operating microscope. However, defining the zone of injury clinically is limited to evaluating the epineurium and/or transected nerve ends for visible injury, with tactile changes corresponding with nerve damage not evident in the acute setting. During surgical nerve repair or reconstruction, adequate debridement of the damaged tissue is essential, as fascicular health influences the regenerative potential of the nerve. This study used a novel high-resolution imaging method to characterize the extent of nerve damage resulting from 3 common mechanisms of traumatic lacerations. Methods: Twelve human upper extremity cadaveric specimens were used to simulate common injuries using a knife, broken glass, or table saw in flexor tendon zones II or V. The distance of nerve damage measured from the transected end was visually estimated by experienced peripheral nerve surgeons under loupe magnification. The length of nerve damage was measured radiographically using micro-computed tomography and then compared with visually estimated damage. Results: Radiographic image analysis revealed fascicular disruption extending proximally and distally from the transection, which was underestimated by visual assessment 9.5 mm on average in knife injuries, 7.8 mm in broken glass injuries, and 12.1 mm in table saw injuries. The extent of radiographic damage was similar in proximal and distal nerves, and in knife and broken glass lacerations, but most extensive in table saw lacerations. Conclusions: Nerve damage was greatest in table saw lacerations. Radiographic imaging showed fascicular damage extending beyond the surgeon's visual assessment of epineural damage, indicating that the internal damage to nerves from traumatic lacerations was underappreciated by surgeons. The impact this underestimated damage has on regenerative potential of an injured nerve requires further investigation. Type of study/Level of evidence: Diagnostic V.