gms | German Medical Science

Objectives/Interrogation: Painful neuroma formation is a common and debilitating sequela of traumatic or oncologic nerve amputation. Studies suggest that isolating the nerve-end within a protective cap either at the time of amputation or during revision procedures may assist in the prevention of nerve-end neuromas. This study evaluated the local effects of novel porcine small intestine submucosa (pSIS) nerve caps with internal chambers on a terminal nerve end in an animal model.

Methods: The tibial nerves of fifty-seven (57) Sprague Dawley rats were transected, transposed and secured in a subcutaneous pocket of the lateral hindleg. The nerves were treated with a pSIS Nerve Cap (NC), pSIS Open Tube (OT), or were non-treated Surgical Controls (SC). Weekly pain response testing was performed by observing animals and assigning a semi-quantitative score (0-2) after mechanically stimulating transposed nerve ends, where zero was no response and two was a brisk withdrawal or vocalization. Samples were explanted at 8 and 12 weeks and stained with Hematoxylin and Eosin, Masson's Trichrome, or Neurofilament-200. Sample analysis included axonal swirling, axon optical density (OD), nerve width, cap remodeling, and tissue response.

Results and Conclusions: The NC group had significantly lower axonal swirling and pain response scores compared to the SC and OT groups. Nerve width was notably greater in the SC group compared to the NC group. The nerve caps and open tubes were considered non-irritants and exhibited similar remodeling. The SC group showed significantly lower axon optical density compared to all other groups. A lower axon optical density suggests a higher concentration of collagenous tissue, which is a characteristic of neuromas. Application of pSIS nerve caps in this animal model demonstrated increased axon optical density and decreased axonal swirling, distal nerve stump width and behavioral pain response. This suggests that nerve caps with internal chambers may support fibrin cable formation to facilitate axonal alignment; therefore, more reliably reducing the likelihood of painful neuroma formation.