In this study, we developed a rat model of incisional pain. A 1-cm lon
gitudinal incision was made through skin, fascia and muscle of the pla
ntar aspect of the hindpaw in halothane-anesthetized rats. Withdrawal
responses were measured using von Prey filaments at different areas ar
ound the wound before surgery and for the next 6 days. A cumulative pa
in score based on the weight bearing behavior of the animals was also
utilized. The results of tests for withdrawal responses and scores bas
ed on weight bearing suggest that a surgical incision of the rat foot
causes a reliable and quantifiable mechanical hyperalgesia lasting for
several days after surgery. An incision that only included skin and f
ascia but not muscle in the foot caused less severe hyperalgesia durin
g the initial postoperative period. Distinct areas around the wound ha
d different withdrawal thresholds during the study period. Even remote
sites as much as 10 mm from the wound showed persistent mechanical hy
peralgesia. Selective denervations of the rat hindpaw prior to foot in
cision revealed both the sural and tibial nerves were responsible for
transmitting input from the incision that produces hyperalgesia. This
model should allow us to understand mechanisms of sensitization caused
by surgery and investigate new therapies for postoperative pain in hu
mans.