Abstract

Hip dysplasia is a common, progressive, coxofemoral degenerative joint disease of humans, dogs, and cats.⁸ It is a heritable disease in many breed of dogs, Maine coon cats, and Manx cats.³ It is occasionally reported in snow leopards (Uncia uncia), (J.O. Joslin, pers. comm.).

In domestic dogs and cats, several surgical techniques are routinely used to address the deterioration of joint integrity. These include total hip prostheses, pelvic and femoral osteotomies ^1,4,5,9,10 and excision of the femoral head and neck.¹¹ Selection of a specific orthopedic technique depends upon the age of the animal, breed, weight, and severity of the degeneration.² In general, total hip prosthesis are used in animals weighing more than 20 kg.²

A 9-yr-old intact male snow leopard weighing 37 kg was examined during quarantine in October 1998. The previous history included bilateral coxofemoral degeneration. Upon standardized radiographic examination (Orthopedic Foundation for Animals-OFA, Columbia, MO 65201 USA) the right femur was subluxated. Both femoral heads were flattened and large exostoses were noted on the dorsal-cranial rim of the acetabuli. Less than 50% of the left femoral head was within the acetabulum. Sclerosis was noted in both acetabuli and femoral heads. Both hips demonstrated an increased angle of inclination (coxa valga) with a femoral neck angle > 130°. These findings are compatible with radiographic signs of hip dysplasia.⁶ Bilateral total hip prostheses was chosen as the treatment of choice to most closely restore normal anatomic function.

Under the direction of the snow leopard Species Survival Plan (SSP), the leopard was placed with a conspecific female during the breeding season (January-March 1999). Breeding was unsuccessful and the leopard was conditioned to enter a crate for transportation to the College of Veterinary Medicine, University of Missouri in May 1999. The leopard was immobilized with 200 mg of tiletamine and zolazepam (Telazol, Fort Dodge Laboratories, Overland Park, KS 66210 USA) via blowdart.

The leopard was intubated with a 7-mm cuffed endotracheal tube and maintained on 2% isoflurane (Aerrane, Anaquest, Madison, WI 53713 USA) in 2 L/min oxygen during the course of the procedure. Continuous i.v. fluids (Lactated Ringer's Solution, Abbott Laboratories, North Chicago, IL 60064 USA) were administered during the procedure. One epidural injection of 4 mg preservative-free morphine sulfate (Abbott Laboratories) was administered 1 hr prior to surgery. Three i.v. injections of 1 g cefazolin (Ancef Injection, SmithKline Beecham Pharmaceuticals, Exton, PA 19341 USA) were administered i.v. at 90 min intervals. One 100-mg fentanyl transdermal patch (Duragesic Transdermal System, Janssen Pharmaceuticals, Titusville, NJ 08560 USA) was placed over the ipsilateral aspect of the cervical area 1 hr prior to the procedure. Fentanyl is released at 100 µ/hr transdermally for up to 72 hr (Janssen Pharmaceuticals).

Electrocardiography, esophageal stethoscopy, and direct palpation of femoral pulse monitored continuous heart rate and rhythm. End-tidal oxygen concentration (ETO2), saturated oxygen trends (SpO2), capillary refill time (CRT), body temperature, and carbon dioxide trends (CO2) were monitored throughout the procedure.

The right coxofemoral joint was replaced first, as it was the most severely affected joint. After surgical preparation, a standard approach⁷ through a craniolateral incision with a partial tenotomy of the deep gluteal muscle was performed to expose the coxofemoral area. The femoral head and neck were removed at a 130° angle to the axis of the femoral diaphysis with an oscillating bone saw (Synthes Inc., Paoli, PA 19301 USA). This facilitated placement of the femoral implant (K-9 II Femoral Component, Richards, Smith & Nephew, Inc., Memphis, TN 38116 USA) at a 130° angle to the femoral diaphysis. Reaming of the endosteal diaphysis was necessary to allow proper seating of the implant in the medullary cavity of the femur. The acetabulum was reamed with an Acetabular Reamer (Biomedtrix, Allendale, NJ 07401 USA) to place an acetabular cup made of a high-density polyethylene plastic (K-9 II Medium Acetabular Cup, Richards, Smith & Nephew, Inc., Memphis, TN 38116 USA). A 45° angle to the horizontal plane of the recumbent acetabulum was desired for placement of the acetabular cup. The acetabular cup was seated with bone cement (Dough-Type methylmethacrylate, Zimmer Inc., Warsaw IN 46580 USA) and allowed to set for 10 min. The femoral implant was then seated in the femoral marrow cavity with approximately 25 ml of bone cement (methylmethacrylate, Surgical Simplex P, Howmedica, Inc., Rutherford, NJ 07070 USA). The implant was also allowed to set for 10 min. Both types of bone cement contained cefazolin powder (SmithKline Beecham Pharmaceuticals). The femoral head was rotated into the acetabular cup by applying traction to the leg, manual pressure over the trochanter, and rotation of the distal leg internally. Once reduced, stability of the joint was assessed. The surgical site was copiously lavaged with sterile saline, excess bone cement fragments were removed, and the surgical site closed with 0 polydioxanone (PDS II, Ethicon, Inc., Somerville, NJ 08876 USA) in the joint capsule, tenotomy incision, and deep fascia. Superficial fascia was closed with 2-0 PDS. The subcutaneous tissues were apposed with 3-0 PDS and a subdermal suture line was placed with 4-0 monocryl (Ethicon, Inc.). The skin incision was closed with stainless steel staples (Visistat, Weck Closure Systems, Research Triangle Park, NC 27709 USA).

The leopard recovered without complication, and was transferred to the Animal Health Center of the Kansas City Zoo, Kansas City, MO. The cat began using the leg the same evening. No observable limp was noted. After 6 wk of recuperation, the leopard was immobilized and radiographed. The coxofemoral joint demonstrated continued stability and the leopard was transferred to its exhibit. All climbing structures were removed. The leopard was noted to use the right leg preferentially when ambulating in an anticline position, but all other movement was normal.

Six months later, the leopard was re-conditioned to enter the crate and the above procedure was performed on the left hip. The leopard had gained 2.5 kg in weight and keepers commented that its attitude appeared to have improved. Postoperative care was the same and the leopard recovered uneventfully. Postoperative radiographs demonstrated good positioning of the femoral implant and the acetabular cup. The right coxofemoral joint demonstrated a slight, nearly imperceptible cement line between the acetabulum and the acetabular cup. To lessen the chance of long term stress effects on the hips, access to climbing structures has been eliminated for 1 yr postoperatively. This snow leopard has recovered well. Its attitude has improved to the point that it now demonstrates an interest in enrichment items and there is a definite improvement in its overall behavior and attitude. It is hoped that this leopard will successfully breed with a conspecific female. While there is a chance that offspring could demonstrate the disease, not breeding this animal guarantees the loss of its direct genetic line. In conclusion, we believe this procedure was a complete success. This snow leopard continues to thrive and ambulates without an observable limp. A standard surgical approach, standard canine hip prosthetics, and anesthetic monitoring equipment can be used. No adverse effects from the fentanyl patch were noted and in both instances, the leopard removed the patch 7 days after surgery. The patch was placed on the same side as the repaired leg to prevent early removal with the surgically repaired limb. The cortical bone was much thicker than anticipated and additional effort was necessary to widen the marrow cavity to facilitate proper placement of the femoral implant. The mechanics of conditioning, transport, immobilization, surgery, and postoperative care demand patience and a well-coordinated effort between all parties involved.

Acknowledgments

The authors would like to thank Sea World/Busch Gardens entertainment divisions of Anheuser Busch Companies for paying for this procedure as part of their commitment to preserve wildlife. The authors also thank Dr. Keith Branson and Dr. John Dodam, anesthesiologists, Dr. Cristi Reeves Cook, Michelle Lancaster, Priscilla Foster and Mr. Randy Mertens of the UMC College of Veterinary Medicine for their assistance; Ms. Lani Stark RVT, Jennifer Pollard RVT, Ms. Tanya Howard, Mrs. Joni Hartman, Ms. Lori Holt, Mr. Richard Ward and Mrs. Penny Jolly of the Kansas City Zoological Gardens Animal Staff, and Mr. Loren Mosely, who constructed the transportation crate.

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