Mandibular Osteodistraction for Correction of Deep Bite Class II Malocclusion in a Horse

Objective— To describe a technique for, and outcome after, mandibular osteodistraction in the horse.
Study Design— Clinical report.
Animals— Warmblood horse.
Methods— A half ring external fixator was applied on both sides of an osteotomy site performed on the mandible of a colt. A bite plate was placed on the upper incisors creating occlusion between lower and upper jaw. After a 5-day latency period, distraction was applied (1 mm/day) until the overjet was judged normal.
Results— Mandibular elongation and correction of brachygnathia was obtained without major complications. Six months after the procedure the overjet reduction was considered stable.
Conclusions— Mandibular osteodistraction can be considered for treatment of severe brachygnathia in yearlings.
Clinical Relevance— Distraction osteogenesis has the advantage of progressive elongation of the mandible, allowing concurrent bone remodeling and soft tissue adaptation. Severe mandibular incisor malocclusion in horses outside the maximal growth phase can be corrected using this technique.     

High serum troponin I concentration as a marker of severe myocardial damage in a case of suspected exertional heatstroke in a dog

A young, overweight dog presented with sudden onset lethargy and collapse following exercise in warm environmental conditions. Investigations revealed systolic hypotension, multiform ventricular premature complexes, irregular myocardial echogenicity with poor left ventricular systolic function and a markedly elevated troponin cTnI (180 ng/mL, reference range <0.3 ng/mL) consistent with severe myocyte damage. Infectious causes of myocarditis were ruled out on the basis of serological and polymerase chain reaction blood tests. Exercise-induced malignant hyperthermia was excluded from the history, an exercise tolerance test and genetic testing for the RYR1 V547A mutation. The diagnosis was myocardial damage secondary to suspected exertional heatstroke, from which the dog recovered uneventfully over a number of weeks and serum troponin normalised. This is the first case report in any species including man, documenting high troponin as a marker of severe myocardial damage following suspected heatstroke.     

Pinless External Fixation of Mandible Fractures in Cattle

Objective — This report describes our experience with a new technique for stabilization of mandibular fractures in cattle using a pinless external fixator.
Study Design — Mandibular fractures were stabilized with a pinless external fixator, which is a modification of a unilateral AO/ASIF (Association for the Study of Internal Fixation)-fixator in which pins are replaced with bone clamps.
Animals — Seven dairy cattle between 1 and 5 years of age.
Methods — Fracture stabilization was achieved by using the pinless external fixator. Postoperative management included intravenous administration of sodium chloride-glucose and antibiotics. A suspension of ruminal contents from a normal cow together with linseed and grass pellets was administered with a gastric tube.
Results — Three to 10 days after surgery six of seven cows masticated comfortably. The only failure was a yearling with a 10-day-old open infected fracture. This animal was slaughtered 9 days after surgery because of additional problems. In six cases there was enough callus formation 33 to 54 days after surgery to stabilize the fracture. The fixation devices were removed under heavy sedation. The major complication was bone sequestration at the fracture site, which required additional treatment.
Conclusion — The pinless fixator has proven satisfactory for external stabilization of unilateral horizontal ramus fractures of the mandible in cattle.
Clinical Relevance — The technique provides good stability without penetration of the medullary cavity and damage to the tooth roots. Other advantages of the technique include ease of application, minimal surgical trauma, and the short surgical time for application.     

A Comparison of the Effects of Unilateral Thyroarytenoid Lateralization Versus Cricoarytenoid Laryngoplasty on the Area of the Rima Glottidis and Clinical Outcome in Dogs with Laryngeal Paralysis

OBJECTIVE: To compare the clinical effects of unilateral thyroarytenoid lateralization versus unilateral cricoarytenoid laryngoplasty for the treatment of canine laryngeal paralysis. Study Design-A prospective, clinical trial. ANIMALS: Twenty client-owned dogs admitted to Glasgow University Veterinary Hospital (GUVH) between 1997 and 1999 with a diagnosis of laryngeal paralysis. METHODS: A thorough evaluation of each dog was undertaken that included history, physical and neurologic examinations, complete blood count, serum biochemistry profile, serum thyroxine (T4) level, and thyroid-stimulating hormone (TSH) assay. The exercise tolerance of each dog was investigated by assessing respiratory rate and arterial blood gas analysis at rest and after 5 minutes of mild exercise. Animals were included in the study on the basis of a definitive diagnosis of laryngeal paralysis made by endoscopic observation of the larynx in the lightly anesthetized patient. The animals were randomly assigned to 1 of 2 treatment groups: unilateral thyroarytenoid lateralization or unilateral cricoarytenoid laryngoplasty, with all procedures being performed by the same surgeon. Video images of the rima glottidis were recorded pre- and postoperatively using video endoscopy. Video images were digitized and the area of the rima glottidis measured using image-analysis software. An increase in the area of the rima glottidis was expressed as a percentage of the preoperative area. All animals were reassessed 6 weeks' postoperatively, and exercise tolerance tests were repeated. RESULTS: The mean increase in the area of the rima glottidis postoperatively when compared with the preoperative area was 140% for those animals undergoing unilateral thyroarytenoid lateralization (range, 120%-158%) and 207% for those animals undergoing unilateral cricoarytenoid laryngoplasty (range, 183%-228%). This difference was statistically significant (P < .0001). At the 6-week postoperative examination, there was no significant difference in improvement between the 2 groups when compared on either a clinical basis or exercise tolerance tests. The mean surgical time in the 2 groups was 25 minutes for thyroarytenoid lateralization and 43 minutes for cricoarytenoid laryngoplasty. This was a statistically significant difference (P = .002). CONCLUSION: Although increase in area of the rima glottidis was significantly greater after unilateral cricoarytenoid laryngoplasty compared with unilateral thyroarytenoid lateralization, no difference in clinical outcome could be detected. However, the cricoarytenoid laryngoplasty procedure required significantly more surgical time. CLINICAL RELEVANCE: Both unilateral cricoarytenoid laryngoplasty and unilateral thyroarytenoid lateralization are successful methods for the treatment of laryngeal paralysis; however, thyroarytenoid lateralization requires less surgical time to perform.