By David Duclos, DVM, DACVD, For The Education Center
Originally Published In Veterinary Practice News, February 2018 – Download as a PDF
Griffey, an 11-year-old male miniature schnauzer, was presented for chronic inflammation, severe swelling and ulceration of P3 on the right forelimb, digit 3 (Figure 1). It appeared that the claw on the affected digit caused the patient significant discomfort and pain, provoking him to constantly bite and lick the site, aggravating the inflammation. It had been present for two years, and the swelling in the tissue around P3 was causing the affected digit to turn into the adjacent digit, causing ulceration on this adjacent tissue as well. Histopathology showed severe inflammatory response. The inflammation was possibly due to a small segment of cactus thorn stuck in the soft tissue, causing a chronic severe reaction in both the soft tissue and the bone. No signs of neoplasia or infection were present. The author decided to remove the distal phalanx of the digit using his CO2 laser.
Due to its high affinity for water, the CO2 laser wavelength provides efficient hemostasis during the surgery. This gives the surgeon an excellent view of the anatomic structures that need to be cut and removed, while avoiding damage to the structures that need to be spared.
Laser equipment and settings
A 45-watt, flexible, hollow waveguide VetScalpel® CO2 laser equipped with the VetScalpel® tipless, adjustable, focal spot size handpiece was used for the procedure.
During the entire procedure, the laser remained in continuous wave SuperPulse mode F1-4. This mode delivers 20 pulses per second at a 40 percent duty cycle. This means if the watts had been set at 25 at a 40 percent duty cycle, the tissue received 10 watts of average power. The watt setting was used at 25, 15, and 11 at various times during the procedure depending on how much power was needed. This means that the average power delivered to the tissue varied from 10 to 6 or 4.4 watts. The handpiece was set to 0.25-millimeter focal spot size.
The patient was positioned in lateral recumbency. The forelimb was clipped and aseptically prepared for surgery.
The patient was pre-anesthetized with dexmedetomidine (Dexdormitor®) and butorphanol tartrate (Torbutrol®). General anesthesia consisted of sevoflurane (SevoFlo®) in oxygen and was maintained via an endotracheal tube.
The phalanx amputation began with a laser skin incision without a tourniquet (no tourniquet is typically used for this laser procedure). A horizontal cutaneous incision was placed at the base of the claw and extended proximal to the digital pad (Figure 2-A). For the most efficient cut, the laser handpiece should be held perpendicular to and approximately 1 to 3 millimeters away from the target tissue (as shown in Figures 2-B and 2-C). Three laser passes were made before the incision was extended laterally on the left side (Figure 2-B). The skin on P2 was pulled back to help the surgeon maintain visibility of the surgical site. The incision was deepened until the joint between P3 and P2 was reached and carefully transected (Figure 2-C). (The surgeon knows when the joint capsule is transected because synovial fluid flows out into the surgical field.) The watts were decreased to the lowest setting mentioned above, i.e., 4.4 watts. From this point, the laser tip was directed at the bone of P3 (Figures 2-D and 2-E). (The surgeon knows that the laser is hitting P3 because sparks from the laser energy hitting bone may be seen.) The surgeon kept moving down and around P3 until the entire P3 was exposed. Keeping the laser tip pointed toward P3 and away from P2 allowed the surgeon to avoid damaging the articular surface of the distal P2. (Note that this bone surface, completely undamaged by the laser ablation, is shown in Figure 4.)
For the most efficient cut, the laser handpiece should be held perpendicular to and approximately 1 to 3 millimeters away from the target tissue.
The laser energy coagulated the digital vasculature, which helped maintain excellent visibility of the surgical field during the procedure. Any bleeding was controlled effectively by defocusing the laser beam. In case a blood vessel exceeds 0.6 millimeters, it can be ligated. The affected claw was grasped with curved Kelly-Rankin hemostatic forceps and reflected. Laser resection continued clockwise, circumferentially undermining P3, “peeling” it away from the associated digital pad (Figures 2-D and 2-E). The goal of such resection was to salvage the associated digital pad during the procedure (Figures 3 and 4) in order to be able to close the surgical wound efficiently and to preserve a weight-bearing surface.
The surgical site was rinsed with sterile saline solution and then blotted with a gauze pad (Figure 4). The surgeon closed wound by apposing the wound edges and using 3-0 monofilament nonabsorbable sutures, which were placed in a mattress pattern (Figures 5-A and 5-B). The patient was able to bear weight upon discharge from the hospital the day of the surgery.
A robenacoxib (Onsior®) injection was given during surgery; Tramadol, dispensed postoperatively, was to be administered twice daily for 14 days. An injection of cefovecin sodium (Convenia®) was given at surgery to provide a long-acting, broad-spectrum antibiotic effect during the first 14 days of healing. The owners were instructed to limit the dog’s activity for two weeks post-surgery.
The patient’s recovery was uneventful. The referring vet rechecked him every five days postoperatively, at which times the bandages were changed and the surgical site examined. The paw was kept wrapped until it healed, two weeks later. The sutures were removed in 14 days, after which the patient no longer licked the paw and resumed normal activity. On his last recheck at three weeks post-surgery, he was doing well and had been running and playing at normal activity for one week.
Dr. Duclos is a small-animal practitioner in Lynnwood, Wash., where he is the owner and clinical dermatologist at the Animal Skin & Allergy Clinic. He completed his residency in veterinary dermatology at the University of Pennsylvania. He is an associate clinical instructor for the Western University College of Veterinary Medicine in Pomona, Calif., and teaches senior veterinary students as externs at his clinic. He frequently hosts veterinary students from other Veterinary Medical Colleges around the US, and from veterinary colleges in Europe that are seeking to learn about the specialty of veterinary dermatology during their third and fourth year of veterinary school. In addition, Dr. Duclos teaches veterinary residents in dermatology who are seeking to learn more about laser surgery for two- to four-week externships sponsored by the American College of Veterinary Dermatology. He recently has begun to take part in the One Health initiative, recognizing that the health of people is connected to the health of animals and the environment. He authored a number of book chapters and scientific papers on various subjects in veterinary dermatology. He extensively lectures in the US, Canada, and Europe. Dr. Duclos is well known in the veterinary dermatology specialty for his expertise in CO2 laser surgery and for his interest in clinical photography.
This Education Center article was underwritten by Aesculight of Bothell, Wash., the manufacturer of the only American-made CO2 laser.