INTERVERTEBRAL DISC DISEASE IN THREE LARGE FELIDS (PANTHERA SPP.) TREATED SURGICALLY.

Intervertebral disc disease (IVDD) in captive large felids is a commonly encountered syndrome that is usually treated medically, with surgical cases only sparsely documented in the literature. This case series describes the diagnosis, surgical treatment, and postoperative care of three cases of IVDD in large felids: an 8-yr-old male Bengal tiger (Panthera tigris tigris) with acute paraplegia, a 10-yr-old male tiger of unknown subspecies (Panthera tigris) with progressive tetraparesis, and a 17-yr-old female African lion (Panthera leo) with mild paraparesis. Two cases were diagnosed via magnetic resonance imaging (MRI) and the third was diagnosed with computed tomography myelography. Disc herniations were confirmed during surgery in all cases and via necropsy in two cases. Surgical procedures included a thoracolumbar dorsal hemilaminectomy in one tiger, a cervical hemilaminectomy in the other tiger, and a continuous lumbar dorsal hemilaminectomy in the lion. One tiger was euthanized approximately 1 wk after surgery and the other tiger was euthanized approximately 1 mon after surgery, following a lack of clinical improvement in both cases. The lion, however, improved markedly over several months after surgery before acutely declining secondary to spinal neoplasia. Analysis of these cases suggests that pursuing MRI and surgery as soon as possible after the onset of clinical signs and marking affected disc sites based on imaging to provide landmarks for the surgeon may improve long-term prognosis. Additionally, strict postoperative confinement in an accessible cage is beneficial to facilitate care and prevent overexertion while allowing early movement.

In vitro analysis and in vivo assessment of fracture complications associated with use of locking plate constructs for stabilization of caprine tibial segmental defects.

PURPOSE: Locking plate fixation of caprine tibial segmental defects is widely utilized for translational modeling of human osteopathology, and it is a useful research model in tissue engineering and orthopedic biomaterials research due to its inherent stability while maintaining unobstructed visualization of the gap defect and associated healing. However, research regarding surgical technique and long-term complications associated with this fixation method are lacking. The goal of this study was to assess the effects of surgeon-selected factors including locking plate length, plate positioning, and relative extent of tibial coverage on fixation failure, in the form of postoperative fracture. METHODS: In vitro, the effect of plate length was evaluated using single cycle compressive load to failure mechanical testing of locking plate fixations of caprine tibial gap defects. In vivo, effects of plate length, positioning, and relative tibial coverage were evaluated using data from a population of goats enrolled in ongoing orthopedic research which utilized locking plate fixation of 2 cm tibial diaphyseal segmental defects to evaluate bone healing over 3, 6, 9, and 12 months. RESULTS: In vitro, no significant differences in maximum compressive load or total strain were noted between fixations using 14 cm locking plates and 18 cm locking plates. In vivo, both plate length and tibial coverage ratio were significantly associated with postoperative fixation failure. The incidence of any cortical fracture in goats stabilized with a 14 cm plate was 57%, as compared with 3% in goats stabilized with an 18 cm plate. Craniocaudal and mediolateral angular positioning variables were not significantly associated with fixation failure. Decreasing distance between the gap defect and the proximal screw of the distal bone segment was associated with increased incidence of fracture, suggesting an effect on proximodistal positioning on overall fixation stability. CONCLUSIONS: This study emphasizes the differences between in vitro modeling and in vivo application of surgical fixation methods, and, based on the in vivo results, maximization of plate-to-tibia coverage is recommended when using locking plate fixation of the goat tibial segmental defect as a model in orthopedic research.