RADIOGRAPHIC DIAGNOSIS OF LUNG LOBE TORSION

Clinical data, thoracic radiographs, ultrasonographic exams, and histopathologic reports in 13 dogs and two cats with confirmed lung lobe torsion were reviewed. Age of dogs ranged from 4 months to 11.5 years, (mean of 6.4 years) and several breeds of large and small dogs were represented. Right middle lobe torsion was predominant in large dogs (five of eight large breed dogs) and left cranial lobe torsion was more commonly seen in small dogs (three of five small-breed dogs). Two domestic short-hair cats, 10 and 14 years of age, had right cranial and right middle lobe torsion, respectively. Underlying thoracic disease was found in only five of 15 patients. On thoracic radiographs, increased lobar opacity and pleural effusion were found in all patients (100%). Small dispersed air bubbles were found within the affected lobe of 13 patients (87%). This pattern, which was the result of vesicular emphysema, was variably extensive, and became more evident on follow-up radiographs in five of six dogs. The lobar bronchi could be seen in only eight of 15 patients (54%), and appeared irregular, focally narrowed or blunted in six of the eight patients, and displaced in five of the eight. Other common radiographic findings included mediastinal shift (nine), curved and dorsally displaced trachea (seven), and axial rotation of the carina (seven). Ultrasonography was used in seven patients and considered generally useful, although variable signs were observed.     

ULTRASONOGRAPHIC TECHNIQUE AND NORMAL ANATOMIC FEATURES OF THE SACROILIAC REGION IN HORSES

The purpose of this study was to establish the normal percutaneous ultrasonographic appearance of anatomic structures within the equine sacroiliac region. Percutaneous ultrasonography was performed in a cranial-to-caudal direction in 10 normal adult live horses. The following structures were examined in detail: supraspinous ligament, lumbar and sacral spinous processes, thoracolumbar fascia and its caudal extension, tubera sacralia, ilial wings, dorsal and lateral portions of the dorsal sacroiliac ligaments, lateral part of the sacrum, and the lateral sacral crest. After ultrasonography, all animals were euthanized and detailed dissection of the lumbosacropelvic region was performed in six horses. Four lumbosacropelvic specimens were frozen and sectioned transversely for evaluation of cross-sectional anatomy. Gross anatomic findings were correlated with ante-mortem ultrasonographic images. On percutaneous ultrasonography, all horses had tubera sacralia with a mild-to-moderate roughened surface with occasional irregular hyperechoic mineralizations located within the apophyseal cartilage of younger horses. At the level of the tuber sacrale the caudal extension of the thoracolumbar fascia joined the dorsal portion of the dorsal sacroiliac ligament and assumed two different configurations relative to the dorsal portion of the dorsal sacroiliac ligament, with the predominant configuration of the thoracolumbar fascia located medial to the dorsal portion of the dorsal sacroiliac ligament. The less frequently encountered configuration had the thoracolumbar fascia positioned dorsal to the dorsal portion of the dorsal sacroiliac ligament. Caudal to the tuber sacrale the dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia consolidated to form a single, fused structure with a common insertion on the sacral spinous processes. A large variability in linear fiber pattern, echogenicity (small focal hypoechoic areas), ligament height, and cross-sectional measurements was identified in the fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia of normal horses. Diagnosing mild-to-moderate desmitis of the fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia based solely on ultrasonography may therefore be difficult. To correlate ultrasonography with histology, samples of a fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia with bilateral hypoechoic lesions were submitted for histology and revealed diffuse mild-to-moderate loss of fiber density, multifocal fibrocyte degeneration, and cartilagenous metaplasia with multifocal, mild myofiber mineralization, which was compatible with age-related changes. As controls, sections of ultrasonographically normal fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia from three horses demonstrated similar but milder histologic findings, which were considered normal.     

TOTAL SKIN ELECTRON THERAPY TECHNIQUE FOR THE CANINE PATIENT

Cutaneous epitheliotropic T‐cell lymphoma in canine patients is a radiation sensitive tumor but total skin electron therapy is used only rarely. Our purpose was to evaluate dose distribution from a total skin electron therapy technique using 6 MeV electron beams. The treatment was comprised of 12 fields, with the dog in lateral recumbency in a stride position at an extended distance from the source. Uniformity, flatness and symmetry were determined for each beam. The composite percent depth dose profile for all beams was measured in solid water phantoms and skin dose was determined on a canine cadaver using thermoluminescent dosimeters. The resulting d_max of the composite beams was 1 mm and dose variation over the skin was 6.8%, with the extremities having the most uneven dose distribution. Dimensions of the fields were adequate to obtain an effective treatment profile for the entire thickness of canine epidermis and the technique was feasible for clinical application. Individual tailoring of the protocol to deal with hot and cold spots may be necessary and set up will likely involve a significant time commitment for the therapy team.     

CONTRAST ENHANCEMENT OF EXTRADURAL COMPRESSIVE MATERIAL ON MAGNETIC RESONANCE IMAGING

Gadolinium‐enhancement of compressive extradural material is detected occasionally with magnetic resonance (MR) imaging in dogs. Our goal was to characterize contrast enhancement of extradural compressive material associated with intervertebral disc herniation, and to evaluate the association between enhancement and histopathologic findings and the onset of clinical signs. Ninety‐three dogs with a total of 99 lesions diagnosed as intervertebral disc herniation on MR imaging were assessed. Images were evaluated for lesion location, type of herniation, degree of compression, intramedullary T2‐weighted (T2W) intensities, and contrast enhancement. In 23 dogs, surgically removed compressive material was evaluated histopathologically for hemorrhage, inflammation, neovascularization, fibroplasia, fibrosis, mineralization, necrosis, and chronicity. Contrast enhancement of extradural compressive material, meninges, and both the compressive materials and meninges was present in 51.5%, 39.4%, and 17.2% of lesions, respectively. Extradural enhancement occurred more frequently in extrusions than protrusions (P=0.001). Meningeal enhancement and more severe neurologic deficits were significantly associated with a shorter duration of clinical signs (P=0.04 and 0.01, respectively). Intramedullary T2W hyperintensities, present with 44.4% of lesions, were associated with more severe neurologic deficits (P=0.001). Lesions with extradural enhancement were more often considered subacute to chronic in duration and more frequently associated with hemorrhage compared with nonenhancing material; however, no statistically significant association was established between contrast enhancement and histopathologic findings. Contrast enhancement of extradural compressive material and the meninges was found to be common with intervertebral disc herniation, and should not be interpreted as a specific sign of a mass lesion such as neoplasia.     

Mechanical Comparison of 3.5 mm Broad Dynamic Compression Plate,Broad Limited‐Contact Dynamic Compression Plate,and Narrow Locking Compression Plate Systems Using Interfragmentary Gap Models

Objectives— To compare (1) pullout properties between 3.5 mm cortical and locking screws, and (2) mechanical properties and gap displacements between the 3.5 mm broad limited‐contact dynamic compression plate (LC‐DCP), broad dynamic compression plate (DCP), and narrow locking compression plate (LCP), during axial loading of plate‐stabilized diaphyseal fragments with an interfragmentary gap. Study Design— In vitro mechanical testing of implanted polyurethane foam (PUF) hollow cylinders that simulated compact or osteopenic diaphyseal bone. Sample Population— (1) Five cortical and locking screws and (2) 4 PUF‐plate constructs for each plate type; using high‐ and low‐density (0.8 and 0.32 g/cm³) cylinders. Methods— (1) Screws were completely extracted at 5 mm/min. (2) Plated constructs were axially compressed at 300 N/s for 10 cycles from 5 to 355 N to determine gap displacement during physiologic loading, followed by single cycle increasing load to failure. Results— Pullout properties were not different between screw types. All plate constructs had yield loads over 3 times trotting loads. Gap closure occurred with LC‐DCP and DCP constructs, but not LCP constructs. LCP construct properties were most similar to LC‐DCP and DCP construct properties in the low‐density model. Conclusion— All plate systems sustained physiologic limb loads. Only LCP constructs maintained some gap integrity, although LC‐DCP and DCP screws were placed in neutral position. Clinical Relevance— The LCP system is more likely than LC‐DCP and DCP systems, with neutrally positioned screws, to maintain a planned interfragmentary gap, although gap strains range from 0% to 15% across the 2 mm gap during a trot load.     

Evaluation of a Collagenase Generated Osteoarthritis Biomarker in Naturally Occurring Canine Cruciate Disease

Objective— To determine the clinical value of a novel osteoarthritis (OA) biomarker in detecting canine cruciate disease.
Study Design— Cross sectional clinical study.
Animals— Dogs (n=22) with cranial cruciate ligament (CCL) rupture and 12 control dogs.
Methods— Concentrations of collagenase-generated cleavage epitope of type II collagen (Col2-3/4C_{long mono}, or C2C) in serum, urine, and joint fluid were compared between a group of dogs with CCL rupture and a control group. Correlation of C2C concentrations to the clinical stage of stifle OA was also evaluated.
Results— There were no significant differences in C2C concentrations in serum, urine, and joint fluid between groups ( P >.05). Subjective scores of lameness, joint effusion, osteophytosis were significantly more severe in the CCL rupture group compared with the control group ( P <.05). There was no significant correlation of C2C concentrations with clinical stage of stifle OA ( P >.05).
Conclusion— This OA biomarker did not detect pathology associated with CCL rupture. Our results suggest that collagenase-specific degradation of type II collagen in articular cartilage may not be involved in the early stage of naturally occurring canine cruciate disease, and that pathology associated with naturally occurring CCL rupture is different from that of experimental OA model.
Clinical Relevance— C2C is not clinically useful in detecting CCL rupture in dogs.     

External Fixator Clamp Reuse Degrades Clamp Mechanical Performance

Objective— To determine the effects of clamp reuse for the Kirschner–Ehmer (KE); Securos; and the IMEX–SK clamp.
Study Design— Experimental bench test of mechanical properties.
Methods— Specially designed fixtures were used to mechanically test 18 clamps of each type with respect to 6 mechanical variables: fixator pin slippage, connecting bar slippage, fixator pin rotation, connecting bar rotation, and clockwise and counterclockwise clamp–bolt axis pivot. Each clamp was tested 6 times for each variable at 7.68 Nm of clamp–bolt tightening torque. Results were compared using repeated measures ANOVA.
Results— For the IMEX–SK clamp, a significant degradation in the force required to cause slippage was found for connecting bar slippage and fixator pin rotation; however, this clamp also had a significant increase in the force to initiate slippage for clockwise clamp–bolt axis pivot with reuse. The Securos clamp had significant degradation in connecting bar slippage, connecting bar rotation, and fixator pin rotation whereas the KE clamp had significant degradation in connecting bar slippage only.
Conclusions— All 3 external fixator clamp types degraded in 1 or more movement variables in their ability to resist motion with reuse. The IMEX and Securos clamps were more subject to degradation than the KE clamp and this may have clinical importance for fixator composite rigidity.
Clinical Relevance— Fracture-reduction stability is related to the ability to resist motion within a clamp. The unpredictable nature of degradation we found cautions against repeated use. Clinicians should consider reuse of external fixator clamps with the knowledge that repeated use degrades clamp mechanical performance.     

ULTRASONOGRAPHIC ASSESSMENT OF LARYNGOHYOID POSITION AS A PREDICTOR OF DORSAL DISPLACEMENT OF THE SOFT PALATE IN HORSES

Dorsal displacement of the soft palate is an important cause of poor performance in racehorses, yet its etiology is not fully understood. Diagnosis requires treadmill videoendoscopy, which is not widely available. The relationship of the larynx, the hyoid apparatus, and the remainder of the skull may be important in predisposing horses to dorsal displacement of the soft palate. We hypothesized that this relationship could be accurately assessed in unsedated horses through ultrasonographic examination. Fifty-six racehorses presented for evaluation of poor performance were subjected to treadmill videoendoscopy and resting ultrasonography. Using ultrasound-assisted percutaneous measures of laryngo-hyoid position, the relationship between selected anatomic structures and the occurrence of dorsal displacement of the soft palate was evaluated. A significant relationship was found between the depth of the basihyoid bone at rest and the occurrence of dorsal displacement of the soft palate at exercise ( P =0.03). Other measures of laryngohyoid position were not found to be associated with dorsal displacement of the soft palate. Thus, there is an association between the occurrence of dorsal displacement of the soft palate at exercise and the resting position of the basihyoid bone, whereby on average a more ventral location of the basihyoid bone is present in horses with dorsal displacement of the soft palate. The pathophysiologic implications of this finding are not fully understood but, based on our findings, ultrasound examination is of value in assisting in the diagnosis of dorsal displacement of the soft palate.