The construction of canine distal limb models used in teaching sonography identification of vegetal foreign bodies.

Musculoskeletal ultrasonography is a useful tool to identify radiolucent vegetal foreign bodies (VFBs). However, limited ultrasound experience and unfamiliarity with the normal sonographic appearance of anatomical structures can decrease clinician confidence. This study aimed to design a reusable silicone model that can teach VFB identification within the canine distal limb. Four canine hindlimbs were used to design the silicone models, and 12 canine distal forelimbs were constructed. The model was constructed using cadaver bones, barley grass (Avena fatua) seeds, and silicone to mimic the anatomy of the canine distal limb with a grass seed VFB. Limbs were randomly grouped based on grass seed locations: (1) the interdigital webbing, (2) the palmar surface of the canine forelimb immediately proximal to the metacarpal pad, (3) the dorsal surface of the distal limb immediately proximal to the proximal phalange, or (4) no grass seed (control) placed. Each limb was systematically ultrasounded and compared with cadaver limbs and clinical VFB cases. A comparison of ultrasonographic images validated the construction, revealing that the simulation model replicates the anatomical and echotexture characteristics of the normal canine distal limb. Furthermore, these models also have a likeness to clinical canine distal limb VFB cases and can be utilized as a training tool.

The validation of computed tomography derived radiodensity measurements of bone healing using histopathology.

BACKGROUND: The early identification of delayed bone healing or a non-union is vital for prompt treatment and superior patient outcomes. Current techniques rely heavily on operator skill for interpretation and hence their reliability and repeatability may be inconsistent. This study assessed the application of computed tomography (CT) derived densiometric measurements as a quantitative tool for the assessment of bone healing. METHODS: This prospective, longitudinal, method comparison study was performed using a recognised sheep tibial ostectomy model. Secondary bone healing was assessed at 2, 4, 6, and 8 weeks after the ostectomy was performed. CT densiometric measures of bone healing (Hounsfield units) were taken of the cis, trans, cranial and caudal cortices relative to the bone plate, with histological measurements (percentage of ossification) sourced from the same areas. Cis cortical densiometric data points were excluded from analysis due to significant beam hardening artefact from the bone plate (P < 0.001). A univariable linear regression was performed on the remaining data using averaged radiodensity (independent variable) and histomorphometric (dependent variable) measurements. RESULTS: The two measurements were significantly correlated (R2 = 0.623, P = 0.020) with a clear positive trend identified. CONCLUSION: This study suggests that radiodensity measurements may be a useful diagnostic and management tool for the monitoring of indirect bone healing.

Assessing colostral and serum immunoglobulin G in alpacas using Brix refractometry and total serum protein.

The adequate transfer of passive immunity is a critical factor in neonatal development and survivability. Although well documented in the dairy and equine industries, the recognition of inadequate immunoglobulin transfer on-farm and its impact on the ability of alpaca cria to thrive is largely unknown. Colostrum samples were collected from female alpaca within 24 h of parturition by the owners and whole blood collected from cria by the investigators between 1 and 7 days of age. Direct IgG concentration of milk and serum was determined using radial immunodiffusion assay (RID) and was indirectly estimated using optical and digital Brix refractometry for total solids and clinical refractometry for total serum protein. There was a strong correlation between optical and digital Brix refractometry, and colostral IgG concentration determined by RID. There was a moderate correlation between serum IgG concentration determined by RID and total serum protein in crias. Optical and digital Brix refractometry for colostral IgG estimation and total serum protein for serum IgG estimation are reliable, accurate and easy-to-use tools that can be used on-farm by trained, competent technicians to assess a failure of passive transfer in alpacas. A pilot study at one property only was performed, due to COVID-19 travel restriction interference. Further research is required to determine the reference intervals for these tools to be practical.

Safety evaluation of the Guardian device on the common carotid artery in sheep.

Background: Pulse pressure intensity in middle-aged adults is a risk factor for dementia. The Guardian device (The Brain Protection Company, Sydney, Australia) has been developed to reduce pulse pressure, as a potential therapy. Objectives: The aim of this study was to evaluate the safety of the Guardian, a novel pulse modulation device designed to reduce the intensity of the pulse pressure that penetrates into the cerebral small vessels. The Guardian is a helix that gently wraps around the common carotid artery (CCA) to slightly change its shape, to absorb pulsatility, without lowering flow. Methods: The Guardian was implanted bilaterally on the CCAs of 10 mature sheep for chronic implant periods of 3, 6 or 8 months. The ratio of internal device diameter to outer diameter of the CCA varied from 63% to 92% (n = 20). The implant position on the vessel was marked surgically at implant. Gross pathology and histopathology of the CCA were examined at 3- and 6-months post explant. Most devices were explanted using open surgery, however minimally invasive surgical explant techniques were examined in 2 animals to assess the potential of this approach for explant in humans if required. Results: The Guardian was successfully implanted with no adverse events, and minimally invasive explant appeared to be viable for removal. Following implant, the device was surrounded by a thin fibrous capsule, with similar pathology at 3- and 6-months. Minimal or no movement was observed. CCA sections appeared histologically normal, with no evidence of thrombosis, stenosis, fibrosis, chronic inflammatory response, or vessel degeneration. Conclusions: The feasibility of surgical implantation and biomaterial safety of the Guardian was confirmed over 8 months. Minimally invasive explant of the Guardian has the potential to be viable. Further work is required to demonstrate efficacy in vitro and/or in vivo before evaluation in humans.

The development of a systematic ultrasound protocol facilitates the visualization of foreign bodies within the canine distal limb.

Ultrasonography is an excellent investigative tool that can assist with the diagnosis of soft tissue conditions. In human medicine, ultrasonography is a fundamental diagnostic tool for the investigation of suspected vegetal foreign bodies (VFB), with protocol-based ultrasonography providing increased accuracy compared to lesion-focused examinations. Protocol-based ultrasonography is an emerging tool within the veterinary field, however, compared to human medicine is not routinely employed. The objective of this study was to develop a systematic ultrasound protocol to examine the distal limb for the visualization of vegetal foreign bodies (SUEDVEG). A 12 MHz linear and an 18 MHz high-frequency small-footprint linear array transducer was used on cadaver forelimbs (n = 6) and hindlimbs (n = 6) with images obtained from three common foreign body locations within the distal limb; 1; the interdigital webbing, 2; the palmar/plantar aspect of the phalanges and metacarpus and 3; the dorsal region of the phalanges and metacarpus. From these images, a 13-step systematic musculoskeletal protocol was developed and utilized on eight clinical cases or 10 limbs that had signs typical of distal limb VFB to preliminarily validate the proposed method. Vegetal foreign bodies were successfully identified and retrieved in seven (n = 8) clinical cases with method steps 9 and 11 (orthogonal views) identifying the majority of VFBs. The described ultrasound method appears highly useful for visualizing soft tissue locations of the canine distal limb known for tracking foreign bodies. Further studies are required to validate the described systematic examination method as the preferred clinical protocol over currently used lesion-focused exploration techniques.

Single Pedicle Advancement Flap Models for Teaching Veterinary Reconstructive Surgical Techniques.

Reconstructive surgical techniques are used in both general and referral veterinary practice to facilitate closure of challenging wound defects. During veterinary studies, there are often limited opportunities for students to practice these techniques on live patients or cadavers. Surgical models, including suture pads and ovariohysterectomy models, have been successfully incorporated into veterinary teaching, providing students with additional practice. Models to simulate veterinary reconstructive surgical techniques are lacking. In the current study, a single pedicle advancement flap model was designed. The design consisted of a silicone model secured by a plate, providing tension. Fifth-year veterinary science students (n = 34) were surveyed to assess the model's impact on surgical technique and confidence. Students were also assessed to determine surgical technique using the models. It was hypothesized that students who had two additional practice sessions using the models (Trial group, n = 17) would show greater improvement in technique than students who had no practice sessions between assessments (Control group, n = 17). Students strongly agreed (median score 5/5) that using the model helped to reinforce the subdermal plexus flap technique and improved their confidence in performing a subdermal plexus flap. Students from both groups performed significantly better in the follow-up assessment compared to the initial assessment. No significantly greater improvement was observed in technique between the control and the trial groups. Results suggest that the students' reconstructive surgical technique improved after a single practice session and that the single pedicle advancement flap model can be used synergistically with other teaching methods.

The investigation of bone fracture healing under intramembranous and endochondral ossification.

After trauma, fractured bone starts healing directly through bone union or indirectly through callus formation process. Intramembranous and endochondral ossification are two commonly known mechanisms of indirect healing. The present study investigated the bone fracture healing under intramembranous and endochondral ossification by developing theoretical models in conjunction with performing a series of animal experiments. Using experimentally determined mean bone densities in sheep tibia stabilized by the Locking Compression Plate (LCP) fixation system, the research outcomes showed that intramembranous and endochondral ossification can be described by Hill Function with two unique sets of function parameters in mechanical stimuli mediated fracture healing. Two different thresholds exist within the range of mechanical simulation index which could trigger significant intramembranous and endochondral ossification, with a relatively higher bone formation rate of endochondral ossification than that of intramembranous ossification. Furthermore, the increase of flexibility of the LCP system and the use of titanium LCP could potentially promote uniform bone formation across the fracture gap, ultimately better healing outcomes.

Tumor size as a predictor of lymphatic invasion in oral melanomas of dogs.

OBJECTIVE: To investigate putative associations between oral melanoma size and variables of histologic grade such as mitotic index, nuclear atypia, junctional activity, ulceration, lymphatic invasion, and degree of pigmentation. SAMPLE: 59 samples of oral melanomas from dogs sourced from 6 diagnostic laboratories within Australia. PROCEDURES: The size of each melanoma was microscopically measured, and each sample was evaluated for variables of histologic grade including mitotic index, nuclear atypia, junctional activity, ulceration, lymphatic invasion, and degree of pigmentation by a veterinary pathologist. The association between tumor size and histologic outcomes was then statistically evaluated. RESULTS: A significant relationship was identified between the size of oral melanomas and a single variable of histologic grade, lymphatic invasion, with larger tumors more likely to show lymphatic invasion. Further analysis revealed 2 applicable size thresholds for different clinical scenarios. Results indicated lymphatic invasion can confidently be ruled out for tumors < 6.5 mm in diameter (100% sensitivity) and ruled in for tumors ≥ 24.5 mm in diameter (100% specificity). CONCLUSIONS AND CLINICAL RELEVANCE: An association was found for oral melanomas of dogs between tumor size and lymphatic invasion.

Influence of plate-bone contact on cyclically loaded conically coupled locking plate failure.

INTRODUCTION: The maintenance of friction between locking plates and bone is not essential, so that they can be applied with a gap between the plate and underlying bone. We hypothesised that the presence of a gap under a locking plate with a conical coupling mechanism would reduce fixation stability or allow uncoupling of the locking screws from the plate. MATERIALS AND METHODS: Locking plates with two conically coupled locking screws were applied to 6 pairs of adult canine femora. One of each pair had plate to bone contact and the contralateral construct had a 2 mm plate to bone gap. Constructs were cyclically loaded in cantilever bending with 10 percent incremental increases every 1000 cycles at 2 Hz, starting at 250 N. The constructs were fatigued to failure. To evaluate fatigue life of the conical coupling, testing was repeated with aluminium tubing replacing the bone, to eliminate screw-bone cutout failure. RESULTS: The mean sustained loads and cycles to failure in the contact group (420.80, standard error [SE] 14.97 N; 7612.00, SE 574.70 cycles) were significantly greater than in the gap group (337.50, SE 14.97 N; 4252.00, SE 574.70 cycles), (p<0.001). Failure mode of all bone constructs was via screw cutout from the bone. Aluminium tubing constructs failed via screw or plate fatigue and breaking, with one construct having elevation of the plate over the screw head. DISCUSSION AND CONCLUSIONS: Elevation of locking plates with a conical coupling system by 2 mm from the bone reduced construct fatigue life but did not result in screw head uncoupling from the plate.