Non-invasive, objective determination of pain using pressure platform gait analysis : the effect of post-operative analgesic protocol and surgical method on limb function in cats following onychectomy
Our first objective was to perform pressure platform gait analysis on 26 adult cats that had or had not undergone bilateral forelimb onychectomy to determine peak vertical force (PVF) and vertical impulse (VI). The PVF and VI were collected from all limbs of each cat with a 2-m long pressure platform walkway. No significant difference was found for PVF and VI between cats that had or had not had onychectomy. Results suggest that bilateral forelimb onychectomy did not result in altered vertical forces measured more than 6 months after surgery in cats. Our second objective was to perform pressure-platform gait analysis on 27 adult cats to document the analgesic effects of topical administration of bupivacaine, IM administration of butorphanol, and transdermal fentanyl following onychectomy. Peak vertical force (PVF) and vertical impulse (VI) data were collected before and 1, 2, 3, and 12 days after unilateral (left forelimb) onychectomy. Two days after surgery, cats treated with bupivacaine had significantly lower PVF than did cats in the other groups. Results suggest that limb function following onychectomy is significantly better in cats treated with fentanyl transdermally or butorphanol IM than in cats treated with bupivacaine topically. Regardless of the analgesic regimen, limb function was still significantly reduced 12 days after surgery, suggesting that long-term analgesic treatment should be considered for cats undergoing onychectomy. Our third objective was to compare the level of post-operative limb function and discomfort in cats after scalpel and laser onychectomy as measured by pressure platform gait analysis on 20 healthy adult cats. Peak vertical force (PVF) and vertical impulse (VI) data were collected as described for the second objective. Cats in the laser group had significantly higher ground reaction forces (GRFs) on days 1 and 2 and significantly higher PVF ratio on day 12 when compared to cats in the scalpel group. Results suggest that cats have improved limb function following onychectomy when performed with a CO₂ laser as compared to with a scalpel.