A Biomechanical Comparison of Headless Tapered Variable Pitch and AO Cortical Bone Screws for Fixation of a Simulated Lateral Condylar Fracture in Equine Third Metacarpal Bones

OBJECTIVE: To compare drilling, tapping, and screw-insertion torque, force, and time for the 4.5-mm AO and 6.5-mm Acutrak Plus (AP) bone screws, and to compare the mechanical shear strength and stiffness of a simulated complete lateral condylar fracture of the equine third metacarpal bone (MC3) stabilized with either an AO or AP screw. STUDY DESIGN: In vitro biomechanical assessment of screw-insertion variables, and shear failure tests of a bone-screw-stabilized simulated lateral condylar fracture. SAMPLE POPULATION: Eight pairs of cadaveric equine MC3s METHODS: Metacarpi were placed in a fixture and centered on a biaxial load cell in a materials-testing system to measure torque, compressive force, and time for drilling, tapping, and screw insertion. Standardized simulated lateral condylar fractures were stabilized by either an AO or AP screw and tested in shear until failure. A paired t test was used to assess differences between screws, with significance set at P < .05. RESULTS: Insertion and mechanical shear testing variables were comparable for AO and AP insertion equipment and screws. CONCLUSION: The 6.5-mm tapered AP screw can be inserted in equine third metacarpal condyles and is mechanically comparable with the 4.5-mm AO screw for fixation of a simulated lateral condylar fracture. CLINICAL RELEVANCE: Considering the comparable mechanical behavior, the potential for less-persistent soft-tissue irritation with the headless design, and the ability to achieve interfragmentary compression by inserting the screw in one hole drilled perpendicular to the fracture plane, the 6.5-mm tapered AP screw may be an attractive alternative for repair of incomplete lateral condylar fractures in horses.     

APPLICATION OF THE PIN-HOLE COLLIMATOR IN SMALL ANIMAL NUCLEAR SCINTIGRAPHY: A REVIEW

The pin-hole collimator is used to improve spatial resolution and magnify areas of interest. The pin-hole collimator has many applications in small animal veterinary scintigraphy. The principles of image formation for the pin-hole and parallel hole collimators are reviewed. The effects of distance on resolution and sensitivity are presented for the pin-hole and parallel hole collimators. Specific application of the pin-hole and parallel hole collimators. Specific application of the pin-hole collimator in veternary scintigraphy are discussed.     

Epoxy Putty for Free-Form External Skeletal Fixators

Objective —To evaluate the suitability of epoxy putty for use as a connecting beam material in a free-form external skeletal fixator.
Design —Mechanical evaluation of beams and the pin-material interface of commonly used methacrylates and the proposed epoxy putty.
Procedure —The apparent modulus, bending strength, and toughness of 10 beams of three methacrylates (Technovit, APEF System, Bone Cement) and three epoxy putties (Oatey Epoxy Putty, All-Metals PowerPoxy, and Plumber's PowerPoxy) were determined in three-point bending. The shear strength of smooth and roughened-shaft pins embedded in the three methacrylates and the Oatey Epoxy Putty was determined by pull-out testing.
Results —The epoxy putties had similar strength, greater apparent modulus, and reduced toughness when compared with the methacrylates. The shear strength of the smooth pin interface with the Oatey Epoxy putty was greater than that with the methacrylates. The interface with roughened pins was much stronger than that with smooth pins for all materials tested.
Clinical Relevance —Epoxy putty is a suitable material for free-form external fixators. It is easy to handle, inexpensive, and has suitable setting times and mechanical properties.     

Detection of Bacteria in Equine Synovial Fluid by Use of the Polymerase Chain Reaction

Equine synovial fluid aliquots were inoculated with Salmonella enteritidis, Escherichia coli, Actinobacillus equuli, Staphylococcus aureus , and Streptococcus zooepidemicus to obtain approximate concentrations of 1000, 100, 10, and 1 colony forming U/mL. Synovial fluid aliquots were also inoculated with an unquantitated inoculum of Bacteroides fragilis and Clostridium perfringens. Inoculated synovial fluid was incubated in trypticase-soy broth or Columbia broth for approximately 12 hours. Then aliquots were removed for DNA extraction and polymerase chain reaction (PCR) analysis for detection of a 531 base-pair segment of bacterial DNA corresponding to a region of the 16S ribosomal gene. Duplicate samples of inoculated synovial fluid were prepared for microbial culture. Bacteria were detected in all samples inoculated with bacteria but not in control synovial fluid samples. Under experimental conditions there was no difference between microbial culture and PCR analyses for detection of bacteria. Experimentally, PCR was able to detect bacteria in synovial fluid within 24 hours of inoculation.     

A comparison of epidural buprenorphine with epidural morphine for postoperative analgesia following stifle surgery in dogs

Objective To compare the efficacy of epidural buprenorphine with epidural morphine for post‐operative pain relief in dogs undergoing cranial cruciate ligament rupture repair. Study design A randomized, double blind clinical trial. Animals Twenty client‐owned dogs with cranial cruciate ligament rupture. Methods Dogs were randomly assigned to receive either epidural buprenorphine (4 µg kg^?1) or epidural morphine (0.1 mg kg^?1) in a total volume of 0.2 mL kg^?1. Epidural injections were performed immediately after induction of anesthesia. End‐tidal halothane and CO₂ were recorded every 15 minutes from the time of epidural administration of drug to extubation. A numerical rating pain score system was used by a blinded observer to evaluate analgesia beginning at extubation and continuing at specific intervals for 24 hours after surgery. Heart rate, respiratory rate, and blood pressure were recorded noninvasively at the same times. If pain score indicated moderate discomfort, rescue morphine at 1.0 mg kg^?1 was administered intramuscularly. Results There were no significant differences between groups with respect to pain score, heart rate, respiratory rate, indirect blood pressure, end‐tidal halothane or end‐tidal CO₂ at any time point. Fifty percent of dogs in the buprenorphine group and 50% of dogs in the morphine group required rescue analgesic medication. Time of systemic rescue morphine administration did not differ significantly between the two groups. There were no clinically observable side‐effects from epidural administration of either drug in any of the dogs of this study. Conclusions Epidural buprenorphine is as effective as epidural morphine for the relief of postoperative hindlimb orthopedic pain in dogs. Clinical relevance Buprenorphine appears to be an effective opioid for epidural use in healthy dogs. Buprenorphine may offer certain advantages over morphine for epidural use, such as lower abuse potential and, in some clinics, reduced cost and less wastage of drug.     

The effect of vitamin a supplementation on seminal characteristics and vitamin a absorption in stallions

Fourteen mature stallions were paired based on age and pretreatment spermatozoal output. One member of each pair was assigned to either 1) control (3 ml corn oil) or 2) treated (132,000 IU retinyl palmitate in 3 ml corn oil) experimental groups. Treatments were added to oat rations every other day. Seminal characteristics (gel free volume, gel volume, total seminal volume, percent progressively motile spermatozoa, number of spermatozoa per ml, percentage morphologically normal spermatozoa and spermatozoal membrane stability) and total scrotal width of each stallion were recorded before (February) and after three months of vitamin A supplementation (June). Plasma vitamin A was measured at 0,6,12,24, and 48 hours following the first and last treatments to document absorption. There were no treatment effects (p>.05) on seminal characteristics or scrotal width. Seasonal increases were recorded in gel-free volume, total seminal volume, percent spermatozoal motility, total spermatozoal output, percentage of morphologically normal spermatozoa, and total scrotal width. Plasma vitamin A was lower during the second collection period (June) than the first (February) in both treatment groups. Peak plasma vitamin A was observed 48 hours following ingestion of the first dose of the vitamin but at 12 hours following the last treatment.     

Evaluation of pacing site in dogs with naturally occurring complete heart block

Objective

To compare left ventricular synchronization and systolic performance with transvenous pacing of the right ventricular apex (RVA), left ventricular free wall (LVF) or simultaneous pacing of the RVA and LVF (BiV).

Animals, materials and methods

Seven canine patients with complete heart block. Prospective study evaluating effect of pacing site. Twenty four hours following implantation of transvenous BiV pacing systems, electrocardiograms and echocardiograms were assessed during pacing from the: (1) Right Atrial Appendage/RVA (RAA/RVA), (2) RAA/LVF, and (3) RAA/BiV.

Results

QRS duration was significantly shorter with BiV pacing versus LVF pacing (p < 0.001), or RVA pacing (p < 0.001). Echocardiographic indices of systolic performance fractional shortening (FS), ejection fraction (EF), cardiac output (CO) were significantly higher with BiV pacing than with pacing from the RVA (P = 0.023, 0.006, and 0.002 respectively). Cardiac output, measured by the biplane Simpson's method, was higher with LVF versus RVA pacing (P = 0.036). There was no difference in FS or EF when comparing LVF to RVA pacing. Tissue Doppler measurements of synchronization and systolic performance did not show any difference between pacing mode, but a significantly increased number of segments were seen to contract following aortic valve closure during LVF pacing (P = 0.0268) and RVA pacing (P = 0.0197) as compared to BiV pacing.

Conclusions

Findings suggest that BiV pacing improves cardiac output and systolic performance versus RVA pacing. This improvement however, is not reflected in tissue Doppler indices of synchronization and systolic performance.     

Localization of Oestrogen Receptors in the Epididymis During Sexual Maturation of the Domestic Cat

Oestrogens are involved in regulation of spermatogenesis and sperm maturation and are essential for male fertility. To study the role of oestrogens on epididymal function in the domestic cat, we analyzed the localization patterns of oestrogen receptors (ERs) within the epididymis of juvenile, pubertal and adults using immunohistochemistry. Cat epididymal tissues obtained during routine castrations were fixed in chilled Bouin's solution and processed for immunohistochemistry with ER-specific antibodies. For a certain receptor type, ER localization was influenced by donor age. In the juvenile epididymis, ERα was localized in the nuclei of epithelial cells of efferent ducts and undifferentiated epithelium of the ductus epididymis. During puberty, ERα localization in the undifferentiated epithelium of the epididymis shifted from the nuclei to the cytoplasm and plasma membrane. Oestrogen receptor-α level was highest in the pubertal and adult epididymis, especially within the cytoplasm and in plasma membranes of caput epithelial cells. This finding was suggestive of a role in fluid reabsorption within the efferent ducts and the epididymis. In corpus and cauda regions, ERα was less abundant, suggesting a minor role for oestrogens in sperm storage areas. Interestingly, localization of ERβ was neither influenced by age nor location within the epididymis and was ubiquitous throughout. Results demonstrate that oestrogen actions within the epididymis may be predominantly mediated through ERα during sexual maturation in the domestic cat.