Diagnosis and treatment of equine polysaccharide storage myopathy

Equine polysaccharide storage myopathy (EPSM) is a recently recognized metabolic condition with a high incidence in many breeds of horses and ponies. Clinical signs are extremely variable, but all can be related to underlying skeletal muscle dysfunction. Therapy employing a high-fat, high-fiber, low-starch, low-sugar diet and as much exercise as possible has proven to be extremely successful in control of this disorder. EPSM is progressive, and early detection and institution of therapy are vital.     

Fatal Myocardial Degeneration in an Adult Quarter Horse with Vitamin E Deficiency

A carcass of an adult female Quarter Horse that spontaneously died was received for general investigation at the veterinary diagnostic laboratory of North Dakota State University. Routine necropsy examination demonstrated multiple pale and firm foci in the heart that were histologically consistent with severe myocardial degeneration/necrosis and fibrosis. Analysis of a liver sample confirmed a suboptimal vitamin E level and a selenium value that was within reference range. Because there was no anamnestic indication for ingestion of cardiotoxic plants or evidence of other etiologic factors, vitamin E deficiency was concluded to have led to the development of the myocardial lesions, which precipitated acute heart failure resulting in sudden death.     

Comparison of Three Methods for Relief of Pain After Ear Canal Ablation in Dogs

This study compared three methods of pain relief in dogs that had total ear canal ablation with lateral bulla osteotomy. The hypothesis was that systemic opioids with preoperative local nerve blocks would provide superior pain relief. Thirty-one dogs with chronic otitis externa were included in the study. Dogs were randomly assigned to one of three protocols: systemic opioids alone (10 dogs, group 1), systemic opioids with bupivacaine splash block (11 dogs, group 2), and systemic opioids with preoperative local bupivacaine nerve blocks (10 dogs, group 3). Twenty-one dogs had bilateral ear ablation and 10 had unilateral ablation. Pain was assessed preoperatively, at extubation, 2 hours postextubation, and 1 day postoperatively by a single observer blinded to the analgesic protocol used. Pain scores were not significantly different within or between groups, nor did unilateral versus bilateral ablation have a significant effect on the score. Mean scores were less than 3 (scale 1 to 5) for all groups at all observation times. Rough recoveries were noted in 30% of group 1 dogs, 0% of group 2, and 20% of group 3 dogs. Ninety-four percent of dogs were moderately to heavily sedated at extubation. Sixty percent of group 3 dogs remained moderately to heavily sedated 2 hours postextubation. Rectal temperature, pulse rate, respiratory rate, and postoperative change in serum Cortisol levels were not significantly different between groups. Postoperative increase in blood glucose was significantly higher in groups 1 and 3 compared with preoperative levels. Twenty-three percent of the dogs required additional analgesia or tranquilization after surgery, as determined by the anesthetist; 1 dog in group 1, 2 in group 2, and 4 in group 3. Each of the three analgesic protocols provided similar pain relief in dogs undergoing total ear canal ablation.     

Efficacy of an Epidural Combination of Morphine and Detomidine in Alleviating Experimentally Induced Hindlimb Lameness in Horses

Amphotericin B-induced synovitis of the left tarsocrural joint was used to create a grade 3 of 4 lameness in 11 horses. Caudal epidural catheters were placed and advanced to the lumbosacral region. Baseline heart and respiratory rates were recorded and horses were videotaped at a walk and trot. Morphine sulphate (0.2 mg/kg) and detomidine hydrochloride (30 μg/kg) were administered to treated horses (n = 8) through the epidural catheter; an equivalent volume of physiologic saline solution was administered to control horses (n = 3) through the catheter. At hourly intervals after epidural injection for a total of 6 hours, heart and respiratory rates were recorded, and horses were videotaped walking and trotting. At the end of the observation period, video recordings were scrambled onto a master videotape. Lamenesses were scored by three investigators unaware of group assignment or treatment time. Lameness scores, heart rates, and respiratory rates were compared between groups using repeated measures analysis of variance. There was a significant decrease in lameness score after treatment with epidural morphine and detomidine ( P =.0003); average lameness scores of treated horses were less than grade 1 at each hourly observation for 6 hours after drug administration. Early in the observation period, heart rates significantly increased in control horses and decreased in treated horses ( P =.03). A similar trend occurred for respiratory rates ( P =.07). Results of this study demonstrate that epidural administration of a combination of morphine and detomidine is capable of providing profound hindlimb analgesia in horses.     

Structural Properties of Interlocking Nails, Canine Femora, and Femur-Interlocking Nail Constructs

Using standard material testing techniques (bending stiffness, torsional stiffness, and maximum torque to failure or yield torque), the structural properties of interlocking nails (IN), canine femora, and IN/femur constructs were determined. Specimens that were tested included: 6 and 8 mm diameter IN with 5 to 10 screw holes (n = 18), and intact canine femora (n = 10), which also, with an IN inserted, formed the intact construct (IC) group, (n = 10). Specimens in the IC group were first tested with an 8 mm diameter IN with zero screws, followed by one and two screws (4.5 mm diameter) in the proximal and distal femur. A fracture model construct (FMC), (n = 14), consisting of a transverse femoral osteotomy with a 3 mm gap, was used with either 6 mm or 8 mm IN. In the 6 mm FMC, one and two 3.5 mm screws were used sequentially in the proximal and distal femoral segment. In the 8 mm FMC, one and two 3.5 mm screws and one and two 4.5 diameter screws were used similarly. When bending forces were applied parallel to IN screw holes, mean IN stiffness was 20% less than with forces perpendicular to the holes (n = 18), (P <.05). Eight-millimeter IN were 220% stiffer in torsion and 270% stiffer in bending than 6 mm IN (P <.05). Six-millimeter IN had approximately 32% of the bending stiffness and torsional stiffness of intact femurs (P <.05). Eight-millimeter IN had 93% and 79% of the bending stiffness and torsional stiffness, respectively, of intact femurs. Intact femur constructs (8 mm IN with four, 4.5 mm screws) had 147% of the bending stiffness (P <.05), and similar torsional stiffness and maximum torque, as intact femora (P >.05). The mean values of 6 mm FMC with four screws (3.5 mm) were 21% and 33% in torsional stiffness and bending stiffness, respectively, of intact femora values. When tested in torsion, 8 mm FMC failed by bone fracture; 6 mm FMC, in contrast, underwent plastic deformation. In comparing FMC stabilized with an 8 mm IN with two screws (4.5 mm diameter) in each bone segment, to intact femurs, the maximum torque was similar, FMC torsional stiffness was 40% (P <.05), and FMC bending stiffness was 65% (P <.05). These 8 mm FMC percentages are comparable to human IN fracture model construct values, indicating that the 8 mm IN/four screw construct should provide adequate stabilization for many canine diaphyseal femoral fractures.