While the rodent model is commonly used for evaluating POP, one of the major disadvantages is that it is limited in its use in assessing topical and localized treatments such as devices or patches as the hindpaw is relatively small and the rodent may lick or bite at the injured paw. The rodent skin is also very different from human skin in that it heals primarily through contraction rather than re-epithelialization. Pigskin exhibits a higher degree of homology to human skin and has considerable correlation between contractile, metabolic and morphological features in skeletal muscle of human and pig. This model as has three important parameters that can be assessed in parallel:
The following abstract is from the publication in European J Pain, Sept 2013:
Management of acute pain related to surgical intervention, termed post-operative pain or POP, continues to be a major healthcare challenge. While the rat plantar incision model provides valuable data to researchers about the mechanisms mediating POP, the development of topical and localized treatments in small animal models is limited. To help address these issues, we describe here the characterization of a large animal model of incisional pain.
Pigs underwent full-skin incision or full-skin and muscle incision and retraction (SMIR). Withdrawal thresholds were determined using the Von Frey test at baseline, 0.5–12 h post-surgery and on days 1, 2, 3, 5 and 7 post-surgery. The analgesic effects of systemic morphine [0.1 or 1.0 mg/kg intramuscular (i.m.) dose] and local anaesthetic ropivacaine were studied. Spontaneous pain-like behaviours were scored and analysed. The effects on wound healing were evaluated by gross observation and by histopathological examination.
Pigs incurring SMIR demonstrated significantly increased mechanical hypersensitivity compared with pigs that underwent full-skin incision only (p < 0.05). Maximal analgesia was achieved with morphine (1 mg/kg i.m. dose) at 0.5 h post-treatment. Local treatment with ropivacaine was effective at increasing the withdrawal threshold to Von Frey filaments compared with saline control (p < 0.05) for a period of at least 6 h. Wounds healed normally with no signs of infection, redness or swelling.
We propose that the pig model of incisional pain can provide an appropriate translational model for validating new topical and localized treatments for POP in humans.
D. Castel, E. Willentz, O. Donnor, O Brenner, S. Meilin. Characterization of a porcine model of post-operative pain. European J Pain, Sept 2013,