Feline Onychectomy

Introduction

Onychectomy is the surgical removal of the distal (third) digital phalanx (P3). This procedure is performed frequently in young cats as a primary surgery or at the time of gonadectomy. The forelimbs only (routinely) or all four paws (rarely) may be declawed however the latter requires the cat to be a totally indoors pet. Indications for onychectomy include destructive indoor scratching behavior, trauma, neoplasia, or infection. Onychectomy is estimated to be performed on at least 24% of all domestic cats in this country. The procedure has become controversial due to owner perceived postoperative pain, a relatively high rate of postoperative complications and anecdotal descriptions of negative behavioral side effects. Contrary to this belief, the scientific literature suggests that onychectomized cats ambulated normally by 9 days to 6 months postoperatively and declawing provided a protective effect against relinquishment to animal shelters which may result in euthanasia. Advances in perioperative analgesic protocols and refinement of surgical technique have improved the postoperative management of this procedure. Alternatives to declawing a cat with destructive scratching behaviors include repeated nail trimming, periodic application of plastic nail caps, behavioral training, or deep digital flexor tendonectomy.

Surgical Anatomy

The feline digit is composed of three phalanges. The third phalanx is comprised of an ungual crest which articulates with the second phalanx, and an ungual process which protrudes into the continually growing nail, also called the unguis. During onychectomy, the third phalanx is entirely or mostly removed. Paired dorsal elastic ligaments and axial and abaxial collateral ligaments span the joint space. Tendons of the common and lateral digital extensor muscles cross the dorsal surface of the 3rd to 5th digits. The deep digital flexor tendon attaches to the palmar flexor process portion of the ungual crest. Nail growth originates from the germinal epithelial tissue present in the ungual crest. This collection of dividing cells is located in the proximal and dorsal portion of the ungual crest, and if germinal epithelial tissue is incompletely removed claw regrowth can occur.

Anesthesia and Analgesia

Onychectomy requires general anesthesia. Adjunctive preoperative opioids and non-steroidal anti-inflammatory drugs have been shown to greatly improve postoperative comfort in cats. Buprenorphine (0.01 mg/kg intramuscularly) and application of a transdermal fentanyl patch (25 ug/hr) were shown to be the most effective opioids. Meloxicam (0.3 mg/kg subcutaneously) was proven more effective than butorphanol for pain control. Additionally, local anesthesia in the form of a ring block proximal to the paw is routinely performed. Bupivicaine (1 mg/kg) is distributed perineurally through a 25 gauge needle to selectively block nerve impulses in the sensory branches of the radial, median, and ulnar nerves (Figure 39-1). Bupivicaine has a 15 to 20 minute onset of action and lasts 6 to 8 hours.

Surgical Techniques

The most important component of any surgical technique for onychectomy is adequate removal of the third phalanx to avoid nail regrowth. Preparation of the paw aseptically is performed with surgical scrub and alcohol but without a need for clipping the hair. A tourniquet is applied for all but the laser technique to reduce intra-operative hemorrhage. Placement of the tourniquet distal to the elbow (proximal third of the antebrachium) is essential in preventing postoperative radial nerve dysfunction. For laser declaw, alcohol, due to its flammable nature, is avoided during surgical preparation and a tourniquet is not used.

Dissection Technique

With the cat in lateral recumbency, a #11 or 12 surgical blade is used to incise the skin along the distal ungual crest. Hemostatic forceps or Allis tissue forceps can be used to grasp the nail for manipulation. The third phalanx is extended and the skin overlying the P2-P3 articulation sharply incised. The ligamentous and tendonous attachments to the third phalanx are sharply transected using caution to not damage the digital pad (Figure 39-2). With proper technique, the smooth articular surface of the second phalanx should be easily visualized. Closure of the skin wound can be performed with small loosely tied absorbable suture or with tissue adhesive. When applying tissue adhesive (n-butyl cyanoacrylate), dried skin is compressed digitally in a medial to lateral direction and 1 to 3 drops are applied to the skin only. Subcutaneous application of adhesive will induce an inflammatory response that can be associated with postoperative draining tracts or persistent lameness.

Guillotine Technique

After tourniquet application and aseptic preparation, either a sterilized guillotine type (Resco) or scissors type (White) commercially available nail trimmer is used. The nail is grasped with forceps and the proximal cutting blade is placed between the ungual crest and the second phalanx. Care should be taken to avoid damage to the digital pad during cutting. A small portion of the palmar flexor process is often left with this method, but as long as the entire central and dorsal portions of the ungual crest are excised, nail regrowth rarely occurs. Skin closure is similar to the dissection technique.
 

Laser Technique

Proposed benefits of laser onychectomy include reduced hemorrhage, decreased postoperative pain, and the reduced need for a tourniquet, skin closure, or postoperative bandaging. A CO₂ laser with a 0.4 to 0.8 mm tip set at 4 to 6 watts is used to perform onychectomy similar to the scalpel blade dissection technique. When performing laser surgery, appropriate planning and technique is required to prevent injury to the patient, surgeon, and other personnel. Protection of inspired oxygen in the endotracheal tube from combustion is accomplished by wrapping the tube with saline moistened gauze. Careful technique is required to protect the digital pad and the second phalanx from laser damage. The surgeon and any staff in the room should wear approved laser protective eyewear and facemasks, and a smoke evacuator should be utilized to minimize inhalation exposure of vapor. Any excessive char is wiped away before suture or tissue adhesive skin closure. Skin closure as with all declaw techniques is optional however less hemorrhage is seen postoperatively when closure is performed.

Postoperative Management and Complications

Following onychectomy, a light bandage is often applied for the first 12 to 24 hours during hospitalization. This consists of a dry 4x4 gauze sponge, kling, and self adhesive material placed to the proximal antebrachium. Hemorrhage following bandage removal is usually minimal, but may require longer term bandaging. Care must be taken when applying any bandage postoperatively to prevent ischemic injury to the foot. All bandages are removed prior to patient discharge from the hospital. Shredded paper or commercially available recycled newspaper litter is used for 7 to 10 days in the litter-box at home to minimize possible wound contamination. Pain should be managed by oral opioids (Buprenorphine), a fentanyl patch, and/or oral meloxicam or robenacoxib postoperatively. Lameness occurring postoperatively can be affected by the technique and pain management protocol selected but is usually self limiting and resolves in 1 to 2 weeks. One report of flexor tendon contracture lameness, occurring 6 to 12 weeks postoperatively, required tendon release and was thought to be associated with excessive tissue trauma. Postoperative infections can be associated with subcutaneous tissue adhesive application and are best treated by opening the wound for drainage and allowing second intention healing with appropriate wound care. Nail regrowth, occurring in up to 10% of nail trimmer onychectomies, is often associated with draining tracts or fistula formation weeks to months after surgery. Radiographs will aid in the diagnosis, and treatment requires reoperation to remove the remaining ungual crest. Proper surgical technique and postoperative management will reduce the reported 24 to 50% complication rate associated with feline onychectomy.

Editor’s Note: Management of postoperative pain is recommended for 7-10 days postoperatively. Repeated use of metacam in cats has been associated with acute renal failure and death. Metacam solution for injection is approved for one-time use in cats before surgery to control postoperative pain associated with orthopedic surgery, spays and neuters.

Selected Readings

Holmberg DL, Brisson BA. A prospective comparison of postoperative morbidity associated with the use of scalpel blades and lasers for onychectomy in cats. Can Vet J 2006;47:162-163.

Curcio K, Bidwell LA, Bohart GV, Hauptman JG. Evaluation of signs of postoperative pain and complications after forelimb onychectomy in cats receiving buprenorphine alone or with bupivacaine administered as a four-point regional nerve block. J Am Vet Med Assoc 2006;228:65-68.

Romans CW, Gordon WJ, Robinson DA, Evans R, Conzemius MG. Effect of postoperative analgesic protocol on limb function following onychectomy in cats. J Am Vet Med Assoc 2005;227:89-93.

Romans CW, Conzemius MG, Horstman CL, Gordon WJ, Evans RB. Use of pressure platform gait analysis in cats with and without bilateral onychectomy. Am J Vet Res 2004;65:1276-1278.

Young WP. Feline onychectomy and elective procedures. Vet Clin North Am Small Anim Pract 2002;32:601-619, vi-vii.

Mison MB, Bohart GH, Walshaw R, Winters CA, Hauptman JG. Use of carbon dioxide laser for onychectomy in cats. J Am Vet Med Assoc 2002;221:651-653.

Patronek GJ. Assessment of claims of short- and long-term complications associated with onychectomy in cats. J Am Vet Med Assoc 2001;219:932-937.

Tobias KS. Feline onychectomy at a teaching institution: a retrospective study of 163 cases. Vet Surg 1994;23:274-280.

Ringwood PB, Smith JA. Anesthesia case of the month. J Am Vet Med Assoc 2000;217:1633-1635.

Martinez S, Hauptman J, Walshaw R. Comparing two techniques for onychectomy in cats and two adhesives for wound closure. Vet Med 1993;88:516-525.

Carroll GL, Howe LB, Peterson KD. Analgesic efficacy of preoperative administration of meloxicam or butorphanol in onychectomized cats. J Am Vet Med Assoc 2005;226:913-919.

Gellasch KL, Kruse-Elliott KT, Osmond CS, Shih AN, Bjorling DE. Comparison of transdermal administration of fentanyl versus intramuscular administration of butorphanol for analgesia after onychectomy in cats. J Am Vet Med Assoc 2002;220:1020-1024.

Dobbins S, Brown NO, Shofer FS. Comparison of the effects of buprenorphine, oxymorphone hydrochloride, and ketoprofen for postoperative analgesia after onychectomy or onychectomy and sterilization in cats. J Am Anim Hosp Assoc 2002;38:507-514.

Cooper MA, Laverty PH, Soiderer EE. Bilateral flexor tendon contracture following onychectomy in 2 cats. Can Vet J 2005;46:244-246.