Purpose: The objective is to compare nerve densities in explanted polypropylene meshes in patients with or without chronic pain. Pain has supplanted recurrences as a complication of hernia surgery. The increased incidence of pain mirrors a parallel increase in the use of polypropylene meshes. Neither triple neurectomy nor careful nerve preservation has brought relief. Perhaps because we have forgotten that nerves, in response to some evolutionary mechanism, tend to regenerate, undergo changes imposed by prosthetic elements and architecture, mimicking entrapment and compartment syndromes.
Methods: A total of 33 hernia meshes have been analyzed: 17 excised due to severe pain, two for combined pain and recurrence, 14 sampled during revision for recurrence without pain. Each mesh had standardized sampling for histology and the nerves were highlighted by S100 stain. Nerve densities were assessed within the mesh spaces and in tissue outside the mesh.
Results: The density of nerves present in the standardized mesh samples of patients complaining of pain was much more elevated than in the mesh of those patients who had a recurrence but no pain. The difference was statistically significant (p < 0.001). Excluding two patients who had both pain and recurrence, the difference was even more marked (p < 0.0001).
Conclusions: Re-innervation and neo-innervation are known to take place following hernia repairs in indigenous tissue as well as through polypropylene meshes. However, when pain is an overriding issue dictating mesh explant, the degree of mesh innervation is significantly higher when compared to mesh excised for recurrence. That increase has been confirmed statistically.
Keywords: Hernia; Mesh; Mesh pain; Nerve counts; Nerve densities; Polypropylene.