Arthroscopic knee surgery does not modify hyperalgesic responses to heat injury

Background: Experimental studies suggest that surgical injury may up- or down-regulate nociceptive function. Therefore, the aim of this clinical study was to evaluate the effect of elective arthroscopically assisted knee surgery on nociceptive responses to a heat injury. Methods: Seventeen patients scheduled to undergo repair of the anterior cruciate ligament and 16 healthy controls were studied. The first burn injury was induced 6 days before surgery, and the second burn was induced I day after surgery with a contact thermode (12.5 cm(2), 47degreesC for 7 min) placed on the medial aspect of the calf contralateral to the surgical side. Ibuprofen and acetaminophen were given for 2 days before the first burn injury and again from the time of surgery. in the controls, the two burn injuries were separated by 7 days. Sensory variables included cumulated pain score during induction of the burn (visual analog scale), secondary hyperalgesia area, and mechanical and thermal pain perception and pain thresholds assessed before and I h after the burn injury. Results: The heat injuries induced significant increases in pain perception (P < 0.001) and decreases in pain thresholds (P < 0.02). Baseline heat pain thresholds were higher during the second burn injury in patients (P < 0.001) and controls (P < 0.01). However, there were no significant differences in pain to heat injury (P > 0.8), secondary hyperalgesia areas (P > 0.1), mechanical and thermal pain perception (P > 0.1), or mechanical and thermal pain thresholds (P > 0.08) in the burn area before surgery compared to after surgery. Conclusion: Arthroscopic knee surgery did not modify nociceptive responses to a contralaterally applied experimental burn injury.