Abstract
After a fall of 15 feet in his habitat, a 14-month-old male polar bear was diagnosed with a fracture of the lateral humeral condyle with a subluxation of the medial condyle as well. From a lateral approach, the fracture was stabilized by two 5.5-mm interfragmentary cortical screws in lag fashion. The recovery was uneventful, although he would not tolerate a cast. After 3 months of confinement, he was reintroduced in his habitat successfully.
Introduction
A 14-month-old polar bear had a history of severe acute trauma due to a 15-foot fall. It resulted in a non-weightbearing lameness of the right front limb immediately after the fall. The bear was anesthetized (Telazol 500 mg, xylazine 340 mg by pole syringe) and referred to the hospital facilities of the zoo. General anesthesia was maintained with isoflurane in oxygen administered through an endotracheal tube in a semiclosed circle system. Physical examination was normal except for a moderate swelling of the right elbow. Radiographic images of the elbow on the craniocaudal view showed a closed articular intercondylar humeral fracture with a proximal displacement of the lateral condyle and a subluxation of the medial condyle. The bear recovered uneventfully from anesthesia and was confined to a small stall until surgery was performed 5 days after the injury.
General anesthesia was induced with a combination of zolazepam-tiletamine and xylazine injected intramuscularly (500–300 mg). After endotracheal intubation, anesthesia was maintained by means of inhalation of isoflurane in oxygen with spontaneous breathing. Preoperative radiographic images were obtained to evaluate accurately the fragment displacement. Blood samples from the left femoral vein were drawn and submitted for complete blood count and chemistry profile.
The bear was positioned in dorsal recumbency with its right front limb maintained extended with a rope around its paw hooked up to an engine lift. The limb was prepared for aseptic surgery.
Methods
A 20-cm skin incision was performed over the lateral distal third of the right humerus extending distally to the elbow joint. Blunt and sharp dissection provided exposure of the lateral condyle, epicondyle, and elbow joint. A large hematoma was present around the fracture. The fracture site was debrided and lavaged with sterile saline. Reduction of the fracture was achieved manually with some difficulty. Anatomic reduction was confirmed by palpating the congruity of the humeral articular surface. Then, the fracture was stabilized using two 18-gauge cerclage wires around the fragments. Interfragmentary compression was achieved with two 5.5-mm cortical screws in lag fashion. The first screw was inserted into the extensor fossa through the humeral condyles. The transcondylar lag screw was tightened until perfect joint congruity was achieved by palpating the articular surface through the joint incision. The second screw was placed proximally for rotational stability. After interfragmentary compression, the distal cerclage became loose and was removed. Anconeus muscle was approximated with polydioxanone USP 1 in a cruciate pattern. Subcutaneous tissue and skin were sutured with polyglactin 910 USP 1 in a simple continuous pattern and in an interrupted cruciate pattern, respectively. The surgical incision was protected by a semiocclusive dressing before a full limb cast was applied, including the foot with the carpus in flexion. Cefazolin sodium (10 mg/kg) was given IV during the surgery every 2 hours and ketoprofen (2 mg/kg IM) for a single dose. The following day, cephalexin monohydrate (15 mg/kg) was incorporated in his feed every 12 hours for 19 days combined with ketoprofen (1 mg/kg) every 24 hours for 3 days.
Results and Discussion
Recovery from anesthesia was uneventful, and the bear started to put weight on his cast immediately after 7 hours of anesthesia and 4 hours of surgery. The animal managed to remove his cast twice in 1 week and was then left without it in an indoor enclosure. Surgical incision healed properly, and he was fully bearing weight on his right front limb. Chemistry profile and complete blood count analysis were within normal limits.
Control radiographs were performed 3 weeks postoperatively under anesthesia. Radiographic images showed callus formation gradually bridging the fracture line. Joint congruity was excellent, and the two screws still in place. The bear was then moved outside in a small enclosure. A week after, he had access to a bigger enclosure with a pool. Two months later, control radiographic images showed proper healing with a large callus. At palpation, the right humerus was stable. The bear was finally moved into his habitat of origin with two other female polar bears. Since then, he is perfectly sound. He’s been very active with a normal growth.
Severe joint incongruity is frequently observed with humeral condylar fracture.1,2 Interfragmentary compression with internal fixation is essential to re-establish proper joint alignment.1,2 No particular intervention was performed on the medial condyle because the subluxation was corrected after the fracture reduction and interfragmentary compression. Although this surgery is common in companion animals, to our knowledge, this particular fracture is fatal in large animals. Also, orthopedic procedures are rarely reported in bears. This case reported here shows that internal fixation applied to fracture in bears is possible. The large and strong musculature of the bear made fracture reduction challenging. Surgical intervention shortly after the injury and the use of neuromuscular blocking drugs may have helped decrease surgery time and anesthesia as well. Polar bears can sustain long surgical procedures under general anesthesia, and lateral condylar fracture of the humerus can be treated successfully with two interfragmentary lag screws.
Literature Cited
1. Witz, M., O.M. Lepage, C. Lambert, et al. 2001. Brown bear (Ursus arctos arctos) femoral head and neck excision. J. Zoo. Wildl. Med. 32(4):494–499.
2. Olmstead, M.L. 1993. Fracture of the humerus. In: Slatter D (ed). Textbook of Small Animal Surgery. 2nd ed. W.B. Saunders, Philadelphia. Pp. 1716–1728.