SUMMARYPortosystemic shunts were ligated over a gauged stainless steel rod in 160 dogs and 15 cats, using a midline celiotomy. The diameter of the rod varied with the size of the shunt and the diameter of the portal vein cranial to the shunt. Shunts were narrowed to the smallest diameter that did not cause signs of portal hypertension such as cyanosis of the stomach, pancreas, and small intestine. A slight discoloration was accepted only if the heart rate, end-expiratory CO2%, or arterial blood pressure (if available) did not deviate more than 15% from the values that were recorded at the beginning of the surgical procedure. The perioperative mortality (0-30 days) was 29%. The most common cause of death was euthanasia because of hypoplasia of the portal vein cranial to the shunt. Animals with intrahepatic shunts had a significantly lower probability of survival than animals with extrahepatic portocaval or portoazygos shunts. In dogs, large breed and a high body weight were also significant risk factors for non-survival. Age had a significant effect on risk of non-survival, with an increased risk for older dogs, irrespective of the breed of the dog (large breed vs. small breed). The probability of survival without recurrence of hepatoencephalopathy (HE) after 1 and 4 years was 61.3% and 55.7%, respectively. The only variable that was significantly associated with non-recurrence of HE was the breed of the dog, there being a lower probability for large breeds. Among the animals that survived surgery for more than 30 days, there was a significant higher probability of recurrence of HE in cats than in dogs.

Medial coronoid disease (MCD) encompasses lesions of the entire medial coronoid process (MCP), both of the articular cartilage and the subchondral bone. To detect the earliest signs of MCD, radiography and computed tomography were used to monitor the development of MCD in 14 Labrador retrievers, from 6 to 7 weeks of age until euthanasia. The definitive diagnosis of MCD was based on necropsy and micro-computed tomography findings. The frequency of MCD in the dogs studied was 50%. Radiographic findings did not provide evidence of MCD, ulnar subtrochlear sclerosis or blunting of the cranial edge of the MCP. Computed tomography was more sensitive (30.8%) than radiography (0%) in detecting early MCD, with the earliest signs detectable at 14 weeks of age. A combination of the necropsy and micro-computed tomography findings of the MCP showed that MCD was manifested as a lesion of only the subchondral bone in dogs <18 weeks of age. In all dogs (affected and unaffected), there was close contact between the base of the MCP and the proximal radial head in the congruent joints. Computed tomography and micro-computed tomography findings indicated that the lesions of MCD probably originated at the base of the MCP.

This study describes the timing of development of the trabecular structure of the ulnar medial coronoid process (MCP) in the dog. The right MCPs of nine healthy golden retrievers, aged 4 to 24 weeks, without signs of secondary joint disease were dissected and scanned with microcomputed tomography (micro-CT) at a voxel size of 34 m to determine histomorphometric parameters. Bone volume fraction and mean trabecular separation show a reciprocal pattern in time, reflecting an initial high bone density (and low trabecular separation), and then a sharp drop in density at 8 -10 weeks, followed by a gradual increase to high values at 24 weeks. With a similar bone volume fraction as in young bone, the older bone shows thicker trabeculae and a more plate-like structure. This is reflected in the much smaller number of trabeculae and the lower surface/volume ratio at higher age. An anisotropic structure of the trabeculae with an orientation in the direction of the proximodistal axis of the ulna is already present at 6 weeks after birth. This primary alignment was perpendicular to the humeroulnar articular surface, matching the direction of the compressive forces applied to the MCP by the humeral trochlea. The secondary alignment appeared at 13 weeks after birth and was directed along the craniocaudal axis of the MCP, toward the attachment of the anular ligament. In comparison with data from long bones and vertebrae, the findings of a high bone volume fraction and a well-defined trabecular alignment at a very early age are remarkable. The high bone volume fraction is possibly a remnant of the fetal trabecular structure, as dogs are relatively immature at birth compared to other animals. Soon after the start of steady locomotion, the trabecular structure changes into a more mature-like structure. The early trabecular alignment is possibly a reflection of the early load-bearing function of the MCP in the elbow joint. Anat Rec Part A 278A: 514 -519, 2004.

Left-right symmetrical distal limb conformation can be an important prerequisite for a successful performance, and it is often hypothesized that asymmetric or uneven feet are important enhancing factors for the development of lameness. On a population level, it has been demonstrated that uneven footed horses are retiring earlier from elite level competition, but the biomechanical consequences are not yet known. The objectives of this study were to compare the functional locomotor asymmetries of horses with uneven to those with even feet.Hoof kinetics and distal limb kinematics were collected from horses (n = 34) at trot. Dorsal hoof wall angle was used to classify horses as even or uneven (<1.5 and >1.5° difference between forefeet respectively) and individual feet as flat (<50°), medium (between 50° and 55°) or upright (>55°). Functional kinetic parameters were compared between even and uneven forefeet using MANOVA followed by ANOVA. The relative influences of differences in hoof angle between the forefeet and of absolute hoof angle on functional parameters were analysed using multiple regression analysis (P<0.05).In horses with uneven feet, the side with the flatter foot showed a significantly larger maximal horizontal braking and vertical ground reaction force, a larger vertical fetlock displacement and a suppler fetlock spring. The foot with a steeper hoof angle was linearly correlated with an earlier braking-propulsion transition. The conformational differences between both forefeet were more important for loading characteristics than the individual foot conformation of each individual horse. The differences in vertical force and braking force between uneven forefeet could imply either an asymmetrical loading pattern without a pathological component or a subclinical lameness as a result of a pathological development in the steeper foot.

Medial coronoid disease (MCD) is a common joint disease of dogs. It has a multifactorial aetiology, but the relationship between known causal factors and the disease has yet to be elucidated. As most of the published literature is clinical and it reports changes associated with advanced disease, it is not known whether the changes reflect the cause or consequences of the condition. The aim of this study was to investigate early micromorphological changes occurring in articular cartilage and to describe the postnatal development of the medial coronoid process (MCP) before MCD develops. Three litters of MCD-prone young Labrador retrievers were purpose-bred from a dam and two sires with MCD. Comparisons of the micromorphological appearance of the MCP in MCD-negative and MCD-positive joints demonstrated that MCD was initially associated with a disturbance of endochondral ossification, namely a delay in the calcification of the calcifying zone, without concurrent abnormalities in the superficial layers of the joint cartilage. Cartilage canals containing patent blood vessels were only detected in dogs <12 weeks old, but the role of these channels in impaired ossification requires further investigation. Retained hyaline cartilage might ossify as the disease progresses, but weak areas can develop into cracks between the retained cartilage and the subchondral bone, leading to cleft formation and fragmentation of the MCP.

Cellular senescence, that is, the withdrawal from the cell cycle, combined with the acquirement of the senescence associated secretory phenotype has important roles during health and disease and is essential for tissue remodeling during embryonic development. Osteoclasts are multinucleated cells, responsible for bone resorption, and cell cycle arrest during osteoclastogenesis is well recognized. Therefore, the aim of this study was to investigate whether these cells should be considered senescent and to assess the influence of hypoxia on their potential senescence status. Osteoclastogenesis and bone resorption capacity of osteoclasts, cultured from CD14+ monocytes, were evaluated in two oxygen concentrations, normoxia (21% O2) and hypoxia (5% O2). Osteoclasts were profiled by using specific staining for proliferation and senescence markers, qPCR of a number of osteoclast and senescence‐related genes and a bone resorption assay. Results show that during in vitro osteoclastogenesis, osteoclasts heterogeneously obtain a senescent phenotype. Furthermore, osteoclastogenesis was delayed at hypoxic compared to normoxic conditions, without negatively affecting the bone resorption capacity. It is concluded that osteoclasts can be considered senescent, although senescence is not uniformly present in the osteoclast population. Hypoxia negatively affects the expression of some senescence markers. Based on the direct relationship between senescence and osteoclastogenesis, it is tempting to hypothesize that contents of the so‐called senescence associated secretory phenotype (SASP) not only play a functional role in matrix resorption, but also may regulate osteoclastogenesis.

The clinical history and diagnosis of a dog with leishmaniasis involving both elbow joints and the skin is described. The dog, a female, five-year-old crossbreed, had been imported from Majorca (Balearic Islands, Spain) four years before the diagnosis was made. For two years, the dog had had bilateral forelimb lameness. Physical examination revealed swollen, painful and crepitating elbow joints. Furthermore, an ulcerating dermatitis was found on the concave surface of the left pinna and necrotising margins on both ears. Radiographs of the elbow joints revealed complete destruction of the joint surfaces with dislocation of the radius and the ulna, compatible with severe osteolytic arthritis. The diagnosis of leishmaniasis was confirmed by a direct agglutination test.

Bone is a dynamic tissue adapting to loading according to “Wolff's law of bone adaptation.” During very early life, however, such a mechanism may not be adequate enough to adapt to the dramatic change in environmental challenges in precocial species. Their neonates are required to stand and walk within hours after birth, in contrast to altricial animals that have much more time to adapt from the intrauterine environment to the outside world. In this study, trabecular bone parameters of the talus and sagittal ridge of the tibia from stillborn but full‐term precocials (calves and foals) were analyzed by micro‐CT imaging in order to identify possible anticipatory mechanisms to loading. Calculated average bone volume fraction in the Shetland pony (49–74%) was significantly higher compared to Warmblood foals (28–51%). Bovine trabecular bone was characterized by a low average bone volume fraction (22–28%), however, more directional anisotropy was found. It is concluded that anticipatory strategies in skeletal development exist in precocial species, which differ per species and are most likely related to anatomical differences in joint geometry and related loading patterns. The underlying regulatory mechanisms are still unknown, but they may be based on a genetic blueprint for the development of bone. More knowledge, both about a possible blueprint and its regulation, will be helpful in understanding developmental bone and joint diseases. J. Morphol. 277:948–956, 2016. © 2016 Wiley Periodicals, Inc.