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Papers of the Week

Papers: 20 Apr 2019 - 26 Apr 2019

Human Studies

2019 Oct

J Pain



Evaluation of post-surgical hyperalgesia and sensitization after open inguinal hernia repair: a useful model for neuropathic pain?


Wheeler DW, Bhatia A, Mani V, Kinna S, Bell A, Boyle Y, Chizh BA, Menon DK, Lee MC
J Pain. 2019 Oct; 20(10):1199-1208.
PMID: 31005594.


Cutaneous mechanical hyperalgesia can be induced in healthy volunteers in early-phase analgesic studies to model central sensitization, a key mechanism of persistent pain. However, such hyperalgesia is short-lived (a matter of hours), and is used only for assessing only single drug doses. In contrast, post-surgical peri-incisional hyperalgesia may be more persistent, and hence be a more useful model for the assessment of the efficacy of new analgesics. We undertook quantitative sensory testing in 18 patients at peri-incisional and non-operated sites before open inguinal hernia repair and up to the 24 post-surgical week. The spatial extent of punctate hyperalgesia and brush allodynia at the peri-incisional site were greatest at weeks 2 and 4, but had resolved by week 24. Heat allodynia, suggestive of local inflammation or peripheral sensitization, were not observed; instead, there were deficits in cold and heat sensory detection that persisted until week 24. The findings suggest that central sensitization contributes significantly to mechanical hyperalgesia at the peri-incisional site. The prolonged duration of hyperalgesia would be advantageous as a pain model, but there was considerable variability of mechanical hyperalgesia in the cohort; the challenges of recruitment may limit its use to small, early phase analgesic studies. Perspective: Peri-incisional mechanical hyperalgesia persists for at least 4 weeks after open inguinal hernia repair and reflects central sensitization; this may have utility as a model of chronic pain to assess the potential of anti-neuropathic analgesics.