A prospective comparison of postoperative morbidity associated with the use of scalpel blades and lasers for onychectomy in cats

Abstract

This study compared patient discomfort for 10 d following feline onychectomies performed using a CO₂ surgical laser versus a scalpel blade. Both techniques appeared to result in discomfort of a similar duration, although the laser caused significantly less lameness than blade excision during the first 7 d.

Surgical lasers are becoming more common in veterinary medicine (1,2). The use of lasers to perform onychectomies in cats has been anecdotally advocated as being more humane than excision with a scalpel blade, citing reduced operative trauma, sealing of nerve endings, and less bleeding as reasons for justifying the increased cost to pet owners. A comparison of laser and traditional scalpel onychectomy has been previously published (3). This study found significantly less postoperative discomfort on the 1st d after surgery in those feet treated with the laser compared with those treated by scalpel excision. This difference was not present during the 2nd observation, 6 d later.

The purpose of the current study was to compare the decline of postoperative discomfort over a 10-day period in cat’s feet that have been declawed using a CO₂ surgical laser versus traditional excision with a scalpel blade.

All procedures were done in accordance with the policies of the University of Guelph’s Animal Care Committee. With owner consent, 9 healthy cats presented for elective onychectomy were randomly assigned (by drawing shuffled cards) to have either their right or left foot declawed with a CO₂ surgical laser (NovaPulse; Luxar, Bothell, Washington, USA), with a 0.4 mm tip and settings of 6W in continuous wave mode. The opposite foot was designated for routine excision with a #11 scalpel blade (Aesculap Ag, Tuttlingen, Germany). The order in which the feet were operated was also randomly assigned and 1 surgeon performed all of the surgical procedures. All cats were premedicated with SC injections of acepromazine (Atravet; Wyeth-Ayerst Canada, Guelph, Ontario), 0.05 mg/kg body weight (BW), and hydromorphone (Hydromorphone; Sabex, Boucherville, Quebec), 0.05 mg/kg BW. General anesthesia was induced by IV injection of a 1:1 combination of ketamine (Vetalar; Bioniche Animal Health, Belleville, Ontario) and diazepam (Diazapam; Sabex, Boucherville, Quebec), 0.1 mL/kg BW, and maintained with 100% oxygen and isoflurane (Aerrane; Baxter, Mississauga, Ontario). Each foot was scrubbed preoperatively with an aqueous 0.05% chlorhexidine gluconate solution. Intraoperative tourniquets were placed on the mid-antebrachium of both legs during the onychectomy. Regardless of group assignment, skin incisions were created around the base of each nail and the soft tissues were dissected to permit removal of the entire 3rd phalanx.(4) Following cleaning with gauze swabs moistened with sterile saline, the wounds were sealed with an external drop of cyanoacrylate tissue adhesive (Vetbond; 3M, Mississauga, Ontario) applied with a 1.0-mL syringe through a 25-gauge needle. Postoperative bandages were applied for the first 12 h. Hydromorphone (0.05 mg/kg BW) was administered, IM, as required during the first 12 h, and meloxicam (Metacam; Boehringer Ingelheim, Burlington, Ontario), 0.1 mg, PO, q24h, was administered for 3 d after surgery.

For the first 10 d after surgery, the cats were monitored and evaluated twice daily for lameness by observers blinded to the surgical procedures. The postoperative discomfort was rated from normal to nonweight bearing (Table 1) and recorded as a numeric score (0–3) for each foot. For analysis, the mean daily pain scores recorded from the 9 patients were determined for each treatment (laser versus blade) (Figure 1). A 2 factor (group and time) ANOVA accounting for repeated measures was fit to the data (SAS, Version 8; SAS Institute, Cary, North Carolina, USA). Univariate analysis and inspection of the residuals confirmed that the data were normally distributed and met the assumptions of the ANOVA (Shapiro Wilk test P = 0.4667). The F test from the ANOVA showed a significant difference between the 2 treatment groups when compared over the observation period (P = 0.0298). Significant daily improvement (reduced pain scores) was found for both groups (P < 0.0001) until postoperative day 8. Differences in the pain scores between the 2 groups were not significant when compared on individual days, and neither treatment group showed an observable lamness by day 9. Within the limits of comparison, these results are consistent with the previous report (3) and also show that lameness may persist for over 1 wk after surgery.

Table 1.

Descriptors for the postoperative evaluation of discomfort (lameness), following onychectomy

Pain score	Descriptors used for evaluation
0	Normal ambulation. No evidence of favoring the limb when walking.
1	Almost normal gait, but with slight or occasional limp.
2	Cat ambulates, but with a consistent, noticeable lameness.
3	Cat is nonweight bearing or carries the affected limb when walking.

Figure 1.

Mean and standard error (S_χ̄) of pain assessments made during the first 10 postoperative days after blade and laser onychectomies in 9 healthy cats.

Feline onychectomy with either scalpel blade or laser results in postoperative discomfort that can persist for several days. The cats in this study consistently favored feet that had been declawed with a scalpel blade more than those treated with the laser. The rate at which the postoperative discomfort declined did not seem to vary between the 2 treatments, and all animals were walking normally within 9 d. CVJ