Abstract

Small gazelle species are typically excitable and often flighty in captivity. As such, physical or chemical restraint can be problematic and careful planning and an experienced team is needed to ensure the safe handling of the animal. In spite of this, traumatic injuries can result. Intra- and inter-specific aggression can also lead to injuries especially in intact males. Fractures of long bones are common in the worst-case scenarios, but traumatic joint injuries can also occur. These injuries can be insidious at first and potentially carry a worse prognosis to return to normal function. Three cases of stifle injuries in small gazelles at Busch Gardens Tampa Bay underwent surgical interventions with varied results. Standard small animal techniques were utilized keeping in mind the differences in the ruminant stifle.

Case 1

An intact 10-yr-old female Dorcas gazelle (Gazella dorcas) was immobilized to evaluate forelimb pedal osteomyelitis. Approximately 12 hr later she was found in sternal recumbency and weakly responsive to stimuli including hand restraint. She was treated for suspected renarcatization but on exam she was found to have luxated her right patella medially and had some internal rotation of the stifle. The gazelle was treated with 30 mg ketoprofen (Ketofen®, Fort Dodge Animal Health, Fort Dodge, IA, USA) i.v. and 25 mg naltrexone (ZooPharm, Laramie, WY, USA) and fasted overnight for further examination and possible surgery the next day. The next morning the gazelle was hand restrained and given a pre-anesthetic of 0.5 mg medetomidine (Domitor, Orion Corporation, Espoo, Finland) and 3 mg butorphanol (Torbugesic, Fort Dodge Animal Health, Fort Dodge, IA, USA) i.m., transported to the zoo hospital, intubated, and maintained on isoflurane (IsoSol®, VEDCO, Inc., St. Joseph, MO, USA). Examination found the animal in fair condition with a grade 3 medial patella luxation of the right stifle.¹ An anterior drawer sign was not present but the internal rotation was significant and different from the unaffected stifle. Radiographs demonstrated a bony density between the tibial eminences assumed to be an avulsion of the anterior cruciate ligament (ACL). The limb was prepped and draped routinely for exploration of the joint and attempts at a repair. A parapatellar approach from the medial aspect was chosen. The sartorius muscle was partially avulsed and bruised, the medial patellar tendon was torn, and the medial aspect of the joint capsule was ruptured. The joint was opened more along the tear on the medial aspect. The ACL was partially avulsed with a bony fragment attached from the anterior aspect of the tibia. The menisci were intact and lying in normal position. An extra-capsular repair was chosen for the ACL rupture so the joint was flushed and closed.¹ A hole was drilled across the tibial tuberosity at an angle about 30 degrees down from the horizontal. Fifty pound test monofilament line was threaded through this hole, tunneled under the patellar tendon and then anchored to a stainless steel screw placed in the lateral femoral condyle. Tightening of this suture greatly reduced the degree of internal rotation. A medial fixation was not deemed necessary as the joint appeared stable. The patella was returned to a normal position and held in place by imbricating the parapatella tendon and the fascia. Closure was routine and the gazelle recovered well. Immediate postoperative care comprised of stall rest, enrofloxacin (Baytril 100®, Bayer Corp., Agriculture Division, Animal health, Shawnee Mission, KS, USA) 100 mg p.o. s.i.d. for 10 days, and 75 mg etodolac (EtoGesic®, Fort Dodge Animal Health, Fort Dodge, IA, USA) p.o. s.i.d. Two weeks post surgery, the gazelle was sedated with medetomidine and butorphanol as before for suture removal and radiographs. The bone screw was still in place, the internal rotation resolved but the range of motion in the joint was reduced by 50%. The gazelle was returned to the herd 2 wk later. The original pedal osteomyelitis was recurrent and required several further interventions. Six months after the surgery this gazelle was euthanatized due to unmanageable pedal osteomyelitis. Necropsy confirmed this in both front feet along with a thyroid carcinoma.

Case 2

An intact 3-yr-old female Dorcas gazelle (Gazella dorcas) was manually restrained to examine the interdigital area of the left front limb. A proliferative and necrotic mass was excised and the gazelle given 300,000 IU penicillin G benzathine and procaine combination (PEN BP-48, Phoenix Scientific, Inc., Fort Dodge, IA, USA) s.c. A follow-up treatment was given 48 hr later again with manual restraint. When released the gazelle was lame on the right rear. The lameness was mild and another penicillin treatment was given under manual restraint 48 hr later. Five days later the gazelle had a grade 3/5 lameness in the right rear limb and the stifle was grossly swollen. The following day the gazelle was immobilized with 0.25 mg carfentanil (ZooPharm, Laramie, WY, USA), transported to the zoo hospital, intubated, and maintained on isoflurane. Physical exam revealed a grade 3 medial patellar luxation and radiographs confirmed this diagnosis.¹ Two days later the gazelle was immobilized again with 0.25 mg carfentanil, intubated, placed in dorsal recumbency, and prepped for surgery. A medial para-patellar incision was made from the proximal tibia that extended proximally ¼ the length of the femur. A large area of bruising was found in the sartorius with the tensor fascia lata and joint capsule torn open. The joint capsule was open enough to examine the joint. All structures appeared intact and there were no signs consistent with a torn cruciate ligament. The tear in the fascia lata was extended enough to freely move the patella back into position. The joint capsule was closed with 3-0 polydioxanone, the necrotic sartorius muscle was excised bluntly and the fascia lata closed in two layers of Lembert sutures. The parapatella tendon was also imbricated to the fascia lata with 2-0 polydioxanone in a Lembert pattern. Subcutaneous and skin closure was routine. The patella remained stable at the end of surgery. Two milligrams of butorphanol were given intra-operatively to slow and smooth out the recovery. Aspirin was dispensed at 650 mg p.o s.i.d. for 3 days for postoperative analgesia. Four days later the gazelle was fully weight bearing and moved to a larger pen for continued convalescence. While in this larger pen, several attempts to dart the gazelle failed due to her running and actually escaping into a secondary containment area before being herded into the primary pen. The gazelle was successfully immobilized and returned to the display and the remaining Dorcas herd 2 wk post surgery. Today this gazelle is still in the herd at Busch Gardens.

Case 3

A 3.5-yr-old hand-raised intact male Thomson gazelle (Gazella thomsonii) was housed with three females adjacent to an impala herd with an intact male. Several episodes of fence fighting were recorded. This male Thomason gazelle was examined after a 3 day period of intermittent non-weight bearing lameness that was worsening. The gazelle was immobilized with 0.5 mg carfentanil. On initial exam the right stifle was grossly swollen on the lateral aspect and had severe lateral instability with internal rotation. The gazelle was intubated and transported to the zoo hospital. Radiographs showed an area of periosteal reactive bone on the lateral distal femur. The following day the gazelle was immobilized again, intubated, placed in dorsal recumbency, and prepped for exploratory surgery of the right stifle. A left parapatellar approach was made extending from the tibial plateau and extends proximally up the distal 1/3 of the distal femur. Bruising and swelling was extensive in all layers of the soft tissues. The joint capsule was incised and both cranial and caudal cruciate ligaments were torn. The lateral collateral ligament was only partially avulsed. An extra-capsular ligament repair technique was performed as in case 1 with the addition of a medial screw placed near the medial femoral epicondyle and a medial suture being placed. Fifty pound test monofilament was used for the lateral suture and 40 pound test on the medial suture. The lateral suture was placed over the patella tendon in an effort to stabilize a very deranged joint, sacrificing range of motion in flexion. This technique had been used by one of the authors in dogs with severe traumatic injuries to the stifle and when healed provided a stable limb with limited range of motion in the stifle. Both sutures were secured with a crimped stainless-steel ring. The fragments of the cruciate were resected and the joint closed in a continuous layer. The soft tissues and skin were closed routinely. Recovery was slow but uneventful. Enrofloxacin 254 mg p.o. s.i.d. and etodolac 254 mg p.o. s.i.d. for 10 days were given for postoperative analgesia and infection control and to treat a concurrent infection of a fractured horn. The gazelle refused medicated feeds but ate romaine lettuce and hay well. The gazelle did well for 1 mo post surgery but failed to make any attempts to use the limb. Follow-up immobilization and radiographs demonstrated the failure of the lateral screw, migration of the crimped clips securing the sutures, medial patellar luxation, and an avulsion fracture of the tibial plateau. The limb was prepped as before and an incision was made over the previous one. The patella could not be reduced without lengthening the incision. This was thought to weaken the joint so a limb salvage procedure was opted for. The patella was sharply excised and a five-hole 12-mm wide plate designed for repairing fractures of the distal tibia was fitted on the medial aspect of the stifle. Two 1-inch stainless steel screws were placed above and below the joint. Soft tissues were closed over the plate and the skin closed in routine fashion. The stifle was very stable but the limb was left 6 cm shorter than the opposing limb. Recovery was prolonged but uneventful. Postoperative medications were again attempted as above with nearly complete compliance. One month post surgery the gazelle was able to toe touch and bear a small amount of weight on the limb but carried it at anything faster than a walk. This animal has been returned to the breeding group and continues to do well as of this writing.

Discussion

The sources of the stifle injuries in the above cases were all iatrogenic husbandry related; capture induced related, or as a result of incompatible species or individuals housed in close proximity.

In the first two cases, standard techniques from small animal orthopedic surgery appear to be a reasonable approach to traumatic injuries of the stifle. Patellar luxation have been reported in sheep, deer, goats, and llamas.^3,4 In the above cases, imbrication was sufficient to return the stifle to normal function but there is no reason not to expect other techniques to work (i.e., trochleoplasty) if indicated. A genetic predisposition for patellar luxation has been proposed for certain breeds of sheep.⁴ While trauma was the immediate cause of the luxations in the above Dorcas gazelle, genetic tendencies may need to be considered for a small population.

Several anatomic differences between dogs and ruminants should be noted. There is extensive fat stored in the ruminant stifle, the cranial cruciate has two distinct bands, and the absence of fabella in ruminants.² The fabella is an anchoring point for sutures for extracapsular stabilization techniques in dogs. This was overcome in case 1 and 3 by anchoring a bone screw near the epicondyles and placing the sutures over them. Other techniques are available for larger animals that would not require this screw placement. Fibular head transposition is a technique required for larger dogs (greater than 50 pounds) and would have likely been a better option for the Thomson gazelle. The complications seen in this case can all be ascribed to size of the animal, the flighty nature of this individual, and the added forces exerted on the lateral screw with the unorthodox placement of the lateral suture over the patellar tendon. The severe nature of the injury and the failure of the first surgery left limb salvage or amputations as the only viable options. Adapting readymade bone plates and commercial stainless screws allowed us the option of limb salvage first with reasonable results. Functional return to use and pain free convalescence are the main goals in any surgical procedure. Standard techniques can be adapted and utilized by the zoo clinician to provide care that may not be available otherwise or involve logistics that would delay the procedure.

Literature Cited

1.  Brinker WO, et al. 1990. Handbook of Small Animal Orthopedics and Fracture Treatment. W.B. Saunders Company, Philadelphia, Pennsylvania. Pp. 378–402.

2.  Ferguson JG. Surgical conditions of the proximal limb. In: Greenough PR, ed. Lameness in Cattle. W.B. Saunders Company, Philadelphia, Pennsylvania. Pp. 268–269.

3.  Kaneps AJ. 1996. Orthopedic conditions of small ruminants. Llama, sheep, goat, and deer. Vet. Clin. North Am. Food Anim. Pract. 12: 211–31.

4.  Shettko DL, et al. 2000. Diagnosis and surgical repair of patellar luxations in a flock of sheep. J. Am. Vet. Med. Assoc. 216: 564–566.