The Effect of Partial Rostral Hemimandibulectomy on Mandibular Mobility and Temporomandibular Joint Morphology in the Dog

Partial rostral hemimandibulectomy was performed in 10 adult dogs. The temporomandibular joints (TMJs) were examined radiographically and tomographically before surgery, and mandibular stability was evaluated before and immediately after surgery. Radiographic, tomographic, and hemimandibular mobility assessments were made again at months 3 and 6. The TMJs were examined grossly and histologically in five dogs euthanatized at month 3 and in five dogs euthanatized at month 6. Statistically significant hemimandibular instability (p less than 0.05) persisted in all subjects throughout the study. The radiographic appearance of the joints remained unaltered; however, space asymmetry was identified in postoperative tomograms of three dogs at month 3 and four dogs at month 6. The TMJs were grossly normal at necropsy. Histologically, there were degenerative changes in articular cartilage and subchondral bone in all of the joints. The authors conclude that partial rostral hemimandibulectomy causes TMJ degeneration, as a consequence of hemimandibular instability or abnormal loading, or both.     

Ventral Approach to the Pelvic Canal in the Female Dog

A ventral approach to the pelvic canal by bilateral pubic and ischial osteotomy was performed in five female dogs. The entire urogenital tract could be exposed and easily manipulated through this approach. All animals were ambulatory within 24 hours. Clinical union had formed in three of the four osteotomies by the time of euthanasia (months 2-4) in all animals. Incomplete union in some osteotomies indicated that exercise should be restricted for at least 4 months after the procedure. The procedure was determined to be clinically useful when wide exposure of the entire female urogenital tract is desired.     

Arytenoid Cartilage Movement in Resting and Exercising Horses

Endoscopic examinations of the larynx were recorded on 49 horses at rest and while exercising on a 5% inclined high-speed treadmill for 8 minutes at a maximum speed of 8.5 m/sec. Subjective laryngeal function scores at rest and while exercising were based on the degree and synchrony of arytenoid abduction. Arytenoid abduction was expressed as a left:right ratio of rima glottidis measurements. Horses with arytenoid cartilage asynchrony at rest (grade 2) could not be distinguished from normal horses (grade 1) when exercising because full abduction was maintained throughout the exercise period. Five horses with incomplete left arytenoid abduction at rest (grade 3) maintained full abduction during exercise; one grade 3 horse had dynamic collapse of the left side of the larynx. All horses with laryngeal hemiplegia at rest (grade 4) had dynamic collapse of the left side of the larynx during exercise. Forty-two horses with a resting left:right arytenoid abduction ratio greater than or equal to .71 consistently had complete arytenoid abduction at exercise. Seven horses with a left:right ratio less than .71 consistently showed dynamic collapse at exercise. There was no significant difference in the exercising left:right ratio between normal horses (grade 1) and grade 2 or grade 3 horses. These results suggest that horses with arytenoid asynchrony at rest do not suffer progressive collapse of the rima glottidis during exercise, and that incomplete arytenoid abduction at rest is an unreliable predictor of such collapse. Surgical treatment of all grade 2 horses and some grade 3 horses may be inappropriate.     

Palmar/Plantar Process Fractures of the Proximal Phalanx In 15 Horses

Fifteen fractures of the palmar or plantar process of the proximal phalanx in 15 horses are described. Ten were articular and five were nonarticular. Two modes of therapy were used depending on the location of the fracture. Nonarticular fractures were treated with stall rest or reduction in exercise, and articular fractures were treated with either surgical removal or internal fixation of the fragment. All horses that were operated on were sound within 6 months after surgery. Follow-up information was obtained on all horses through client questionnaire and race records in the racing breeds (Standardbred and Thoroughbred) and client questionnaire alone is the nonracing breeds (Quarterhorse and Arabian). Fourteen horses returned to an equal or better level of performance than before injury; one horse returned to a lower level of performance.     

Canine Lumbar Spinal Internal Fixation Techniques A Comparative Biomechanical Study

The stability (flexural rigidity) and strength of five canine spinal internal fixation techniques were quantitated and compared to each other and to the rigidity and strength of the intact spine. The techniques were applied to isolated canine lumbar spines (L2–L5) on which a complete spinal injury was surgically simulated at L3–L4. The spine-implant preparations were subjected to four-point bending and tested once to failure in flexion. The bending moment vs. L3–L4 angular deformation curves were recorded; rigidity and load sustained at failure (10° angular deformation) were compared. The combination of dorsal spinous process plate and dorsolateral vertebral body plate was the most rigid and most strong of the techniques tested. The dorsolateral vertebral body plate was the most rigid and most strong of the individual techniques, followed by the dorsal spinous process plate and the polymethylmethacrylate-pin technique. Vertebral body crosspins provided the least strength and stability of any of the techniques tested.     

Anesthetic Management of Equine Head Trauma A Case Report

A fractured frontal bone in an 8-year-old Arabian gelding was repaired surgically. The horse exhibited no detectable neurologic deficits before surgery. Anesthesia was induced with a combination of guaifenesin and sodium thiamylal and maintained on halothane in oxygen. Postoperatively, the neurologic status of the horse deteriorated, and it died. On postmortem examination, intracranial hemorrhage accompanied by pressure-induced malacia of the adjacent brain parenchyma was discovered. The hemorrhage was not associated with the surgical site. The authors hypothesize that increased intracranial pressure occurred in the perioperative period.     

Static and Dynamic Cerclage Wire Analysis

A new type of double loop cerclage wire, conventional single wire loop cerclage, and twist-type cerclage were evaluated. The double loop cerclage was applied using the Osteo Systems double loop tightener. Two groups of single wire loop cerclage were applied using the Osteo System loop tightener and the Richards loop tightener. Two groups of twist-type cerclage were applied using the Kirschner wire twister and side-cutting pliers. The test system allowed determination of the static tension produced by each wire, as weH as its ability to resist distraction. The double loop cerclage wires were the most effective in producing static tension and in resisting distraction. While the conventional single loop cerclage wires produced more static tension than the twist cerclage wires, they were less effective in resisting distraction.     

In Vivo Investigation of Communication Between the Distal Intertarsal and Tarsometatarsal Joints in Horses and Ponies

The frequency of communication between the tarsometatarsal and distal intertarsal joints was investigated in 27 horses and 12 ponies. After the injection of diluted latex into the tarsometatarsal joints using the plantarolateral approach, the horses and ponies were walked for 200 meters. Latex was found in the distal intertarsal joints of 19 of 73 tarsi (26% communication) at necropsy. In 3 tarsi, latex was also found in the proximal intertarsal and tar-socrural joints.     

Cardiovascular Effects of a Continuous Two-Hour Propofol Infusion in Dogs Comparison With Isoflurane Anesthesia

The cardiovascular effects during 2 hours of anesthesia with either a continuous propofol infusion or isoflurane were compared in the same six healthy dogs. Dogs were randomly assigned to be anesthetized with either propofol (5 mg/kg, IV administered over 30 seconds, immediately followed by a propofol infusion beginning at 0.4 mg/kg/min), or isoflurane (2.0% end-tidal concentration). The propofol infusion was adjusted to maintain a light plane of anesthesia. Dogs anesthetized with propofol had higher values for systemic arterial pressure due to higher systemic vascular resistance. Dogs anesthetized with isoflurane had higher values for heart rate and mean pulmonary artery pressure. Cardiac index was not different between the two groups. Apnea and cyanosis were observed during induction of anesthesia with propofol. At the end of anesthesia the mean time to extubation for dogs anesthetized with either propofol or isoflurane was 13.5 min and 12.7 min, respectively. A continuous infusion of propofol (0.44 mg/kg/min) provided a light plane of anesthesia. Ventilatory support during continuous propofol infusion is recommended.     

Surgical Anatomy for Desmotomy of the Accessory Ligament of the Superficial Digital Flexor Tendon (Proximal Check Ligament) in Horses

Dissections were performed to study the surgical anatomy for desmotomy of the accessory ligament of the superficial digital flexor tendon (proximal check ligament [PCL]). The surgical approach was initiated by incising the skin cranial to the cephalic vein and caudal to the distal radius. A palpable foramen in the antebrachial fascia that transmits a branch of the cephalic vein was used to advance deeper dissection. After the antebrachial fascia was incised, the fan-shaped PCL was exposed by retracting the en-sheathed tendon of the flexor carpi radialis muscle caudally. Desmotomy was performed gradually to avoid severing branches of the palmar carpal rete that pervade the ligament. Complete transection was evidenced by visualization of the membranous roof of the carpal canal distally, the muscle belly of the radial head of the deep digital flexor centrally, and loose areolar connective tissue along the caudal radius proximally. The vessels of the palmar carpal rete were visible coursing between the severed edges of the PCL. This report highlights relevant anatomic landmarks to facilitate an accurate desmotomy.