Ex Vivo Biomechanical Comparison of the 2.4 mm UniLOCK® Reconstruction Plate Using 2.4 mm Locking Versus Standard Screws for Fixation of Acetabular Osteotomy in Dogs

Objective— To compare the accuracy of reduction and the biomechanical characteristics of canine acetabular osteotomies stabilized with locking versus standard screws in a locking plate. Study Design— Ex vivo biomechanical study. Sample Population— Cadaveric canine hemipelves and corresponding femurs (n=10 paired). Methods— Transverse acetabular osteotomies stabilized with 5‐hole 2.4 mm uniLOCK^® reconstruction plates using either 2.4 mm locking monocortical or standard bicortical screw fixation (Synthes^® Maxillofacial). Fracture reduction was assessed directly (craniocaudal acetabular width measurements and gross observation) and indirectly (impression casts). All constructs were fatigue‐tested, followed by acute destructive testing. All outcome measures (mean±SD) were evaluated for significance (P<.05) using paired t‐tests. Results— Craniocaudal acetabular diameters before and after fixation were not significantly different (21.9±1.2 and 21.5±1.2 mm; P=.45). No significant differences were observed in acetabular width differences between pre‐ and postoperative fixation between groups (locking ?0.4±0.4 mm; standard ?0.4±0.3 mm; P=.76). Grossly, there was no significant difference in the repairs and impression casts did not reveal a significant (P=.75) difference in congruency between the groups. No significant differences were found in fracture gap between groups either dorsally (locking 0.38±0.23 mm versus standard 0.22±0.05 mm; P=.30) or ventrally (locking 0.80±0.79 mm versus standard 0.35±0.13 mm; P=.23), and maximum change in amplitude dorsally (locking 0.96±2.15 mm versus standard 0.92±0.89 mm; P=.96) or ventrally (locking 2.02±2.93 mm versus standard 0.15±0.81 mm; P=.25). There were no significant differences in stiffness (locking 241±46 N/mm versus standard 283±209 N/mm; P=.64) or load to failure (locking 1077±950 N versus standard 811±248 N; P=.49). Conclusion— No significant differences were found between pelves stabilized with locking monocortical screw fixation or standard bicortical screw fixation with respect to joint congruity, displacement of fracture gap after cyclic loading, construct stiffness, or ultimate load to failure. Clinical Relevance— There is no apparent advantage of locking plate fixation over standard plate fixation of 2‐piece ex vivo acetabular fractures using the 2.4 mm uniLOCK^® reconstruction plate.     

Mycobacterium avium subsp. avium distribution studied in a naturally infected hen flock and in the environment by culture, serotyping and IS901 RFLP methods

Mycobacterium avium subsp. avium (MAA) of serotype 2 and genotype IS901+ and IS1245+ was cultured from 21 naturally infected hens (Gallus domesticus) from one smallholder aviary. From a total of 330 samples taken from hens, 124 mycobacteria were detected. Out of which MAA was detected in 103 (35.7%) of 288 tissues, in 4 (19.0%) of 21 swabs of cloacae and in 9 (42.9%) of 21 faeces samples, 8 other conditionally pathogenic mycobacterial species were also isolated. Tuberculous (TB) lesions were found in the liver, spleen and intestinal organs of seven hens. The isolates of MAA (n=58) from 16 infected hens (7 with TB lesions and 9 without TB lesions) were found to be of 3 IS901 RFLP types AE (n=48), AD (n=4) and E (n=6), where these MAA isolates are highly virulent to hens. Mixed infections with IS901 RFLP types (AE and AD) and (AE and E) were also evident in seven hens. From a total of 35 examined environmental samples, 23 mycobacterial isolates were detected. Out of which four (17.4%) MAA isolates of IS901 RFLP type AE and 19 (82.6%) other isolates of conditionally pathogenic mycobacteria were detected. The finding of identical IS901 RFLP types from both tissues and faecal isolates confirms that infected domestic hens are the principal source of infection for other susceptible hosts and lead to the contamination of the surrounding environment. The presence of different IS901 RFLP types in tissue isolates may indicate the repeated incidence of MAA infection and the occurrence of polyclonal infection.     

A TECHNIQUE FOR MAGNETIC RESONANCE IMAGING OF EQUINE CADAVER SPECIMENS

We tested an adaptation of a technique for performing magnetic resonance (MR) imaging of human cadaver limbs in the horse. The forelimbs from a normal horse were collected, frozen, and sealed with a paraffin-polymer combination prior to imaging with either a high- or midfield magnetic resonance scanner. Each forelimb was defrosted, scanned, and refrozen on two separate occasions. A five-point scale was used to evaluate the quality of each set of sagittal and transverse, T1-weighted images of each digit. There was no difference in image quality between first and second scans of either specimen (p > 0.05). We conclude that this technique allows investigators to bank tissue specimens for future magnetic resonance imaging without significant loss of image quality.     

The Effects of Implant Orientation, Canal Fill, and Implant Fit on Femoral Strain Patterns and Implant Stability During Catastrophic Testing of a Canine Cementless Femoral Prosthesis

Cementless femoral stems were placed into 12 normal greyhound femora. The implanted femora were divided into three groups by stem orientation and implant size and loaded in axial compression at a rate of 25 newtons (N) per second until failure. Rosette strain gauges were used to measure femoral principal strains at 500 N, 1,000 N, 1,500 N, and at maximum load. During maximum load, varus orientation of the femoral stem had significantly higher tensile hoop strains in the proximomedial cortex, whereas neutral orientation had higher tensile hoop strains along the cranial cortex. Femoral fractures occurred in these areas of peak tensile strain. There was no difference in maximum load between groups, therefore varus orientation did not predispose to fracture. Maximizing canal fill and implant fit increased implant stability.     

Incidence of antibodies against leptospira in the blood of breeding sows

Within a year, 4438 blood sera of sows coming from 25 farms of the Strakonice district were subjected to serological examination by the reaction of microagglutination lysis (RMAL) with 12 strains of Leptospira. The reaction was positive in 3.22% of all the blood sera. Separate significant titres were demonstrated in the reaction with the Leptospira organisms of four serological groups, including Grippotyphosa, Icterohaemorrhagiae, Hebdomadis and Australis. The reactions with the Leptospira of the Canicola serological group were observed only individually as coagglutination with a simultaneous occurrence of antibodies to Leptospira of the Grippotyphosa serological group. The highest number of reactions 119 (75.8%) was demonstrated in titre 400.     

USE OF TRANSCOLONIC 123I-IODOAMPHETAMINE TO DIAGNOSE SPONTANEOUS PORTOSYSTEMIC SHUNTS IN 18 DOGS

Transcolonic ¹²³I-Iodoamphetamine is rapidly absorbed across the colonic mucosa and binds to amine receptors in the liver and lungs. During the first ten minutes following colonic administration, a simple ratio of lung counts to lung counts plus liver counts provides an accurate estimate of the fraction of portal blood that bypasses hepatic sinusoids in dogs with portosystemic shunts. Studies were performed on 24 dogs with suspect portosystemic shunt. Shunt fraction values for 18 dogs with surgically confirmed portosystemic shunt were obviously higher than published values for normal dogs, and also significantly higher than values for the other six dogs, later confirmed to lack shunts. Postoperative studies were repeated on ten dogs with single shunt vessels 1–2 days after shunt closure. Total shunt ligation resulted in normal postoperative shunt fraction, whereas partial shunt ligation resulted in persistant elevation of shunt fraction. Transcolonic iodoamphetamine scintigraphy is noninvasive, easy to perform, and provides an accurate method to diagnose dogs with portosystemic shunt.