Effect of orthopedic implants on canine long bone compression stiffness: a combined experimental and computational approach.

Osteosynthesis for canine long bones is a complex process requiring knowledge of biology, surgical techniques and (bio)mechanical principles. Subject-specific finite element analysis constitutes a promising tool to evaluate the effect of surgical intervention on the global properties of a bone-implant construct, but suffers from a lack of validation. In this study, the biomechanical behavior of 10 canine humeri was compared before and after creation of a 10 mm bone defect stabilized with an eight-hole locking compression plate (Synthes®) and two locking screws on each fragment. The response under compression of both intact and plated samples was measured experimentally and reproduced with a finite element model. The experimental stiffness ratio between plated and intact bone was equal to 0.39 ± 0.06. A subject-specific finite element analysis including density-dependent elasto-plastic material properties for canine bone and automatic generation of orthopedic implants was then conducted to recover these experimental results. The stiffness of intact and plated samples could be predicted, with no significant differences with experimental data. The simulated stiffness ratio between plated and intact canine bone was equal to 0.43 ± 0.03. This study constitutes a first step toward the building of a virtual database of pre-computed cases, aiming at helping the veterinary surgeons to make decisions regarding the most suited orthopedic solution for a given dog and a given fracture.

Endocannabinoids in Body Weight Control.

Maintenance of body weight is fundamental to maintain one's health and to promote longevity. Nevertheless, it appears that the global obesity epidemic is still constantly increasing. Endocannabinoids (eCBs) are lipid messengers that are involved in overall body weight control by interfering with manifold central and peripheral regulatory circuits that orchestrate energy homeostasis. Initially, blocking of eCB signaling by first generation cannabinoid type 1 receptor (CB1) inverse agonists such as rimonabant revealed body weight-reducing effects in laboratory animals and men. Unfortunately, rimonabant also induced severe psychiatric side effects. At this point, it became clear that future cannabinoid research has to decipher more precisely the underlying central and peripheral mechanisms behind eCB-driven control of feeding behavior and whole body energy metabolism. Here, we will summarize the most recent advances in understanding how central eCBs interfere with circuits in the brain that control food intake and energy expenditure. Next, we will focus on how peripheral eCBs affect food digestion, nutrient transformation and energy expenditure by interfering with signaling cascades in the gastrointestinal tract, liver, pancreas, fat depots and endocrine glands. To finally outline the safe future potential of cannabinoids as medicines, our overall goal is to address the molecular, cellular and pharmacological logic behind central and peripheral eCB-mediated body weight control, and to figure out how these precise mechanistic insights are currently transferred into the development of next generation cannabinoid medicines displaying clearly improved safety profiles, such as significantly reduced side effects.

Intraosseous stress distribution and bone interaction during load application across the canine elbow joint: A preliminary finite element analysis for determination of condylar fracture pathogenesis in immature and mature dogs.

Distal humeral fractures are common fractures especially in immature small breed dogs. The pathogenesis is still unknown. For this study, a three- dimensional bone model of the canine elbow was created and finite element analysis performed in order to determine the relationship between fracture type and bone interactions. Fused and non-fused humeral condyles were considered. A failure criterion was implemented to simulate the pathogenesis until fracture. Our study results confirm the clinical observation that lateral condylar fracture is the most common fracture type, implying interaction with the radius. Medial and Y-fractures are less common and occur always in interaction with the ulna whereas the radius causes lateral condylar fracture. Additionally, the fracture type is sensitive to bone positioning during trauma. The pathogenesis of distal humeral fractures is more complex than generally reported in the literature.

Prediction of the mechanical response of canine humerus to three-point bending using subject-specific finite element modelling.

Subject-specific finite element models could improve decision making in canine long-bone fracture repair. However, it preliminary requires that finite element models predicting the mechanical response of canine long bone are proposed and validated. We present here a combined experimental-numerical approach to test the ability of subject-specific finite element models to predict the bending response of seven pairs of canine humeri directly from medical images. Our results show that bending stiffness and yield load are predicted with a mean absolute error of 10.1% (±5.2%) for the 14 samples. This study constitutes a basis for the forthcoming optimization of canine long-bone fracture repair.

Preactivation of the quadriceps muscle could limit cranial tibial translation in a cranial cruciate ligament deficient canine stifle.

Cranial cruciate ligament (CrCL) deficiency is the leading cause of lameness of the canine stifle. Application of tension in the quadriceps muscle could trigger cranial tibial translation in case of CrCL rupture. We replaced the quadriceps muscle and the gastrocnemius muscle by load cells and turn-buckles. First, eight canine limbs were placed in a servo-hydraulic testing machine, which applied 50% of body weight (BW). In a second phase, the CrCL was transected, and the limbs were tested in a similar manner. In a third phase, a quadriceps pretension of 15% BW was applied and limbs were again tested in a similar manner. Cranial tibial translation was significantly decreased in CrCL deficient stifles (p < 0.05) when quadriceps pretension was applied. These findings indicate that quadriceps pretension could play a role in the stability of a CrCL deficient stifle and should then be considered in rehabilitation programs and conservative treatment of CrCL rupture in dogs.

Inflammatory pseudotumours of the urinary bladder in dogs resembling human myofibroblastic tumours: a report of eight cases and comparative pathology.

Eight cases of inflammatory myofibroblastic tumours (IMT) of the urinary bladder in dogs are described, including their clinical, imaging, morphological, and histopathological aspects. Old small breed female dogs were more commonly affected. Haematuria was the main clinical sign, often associated with dysuria and crystalluria. The IMT appeared as single or multiple, polypoid, firm masses, measuring 1-7 cm. Histologically, the masses were well delineated, covered by a benign hyperplastic urothelium and diffusely infiltrated by a mixed inflammatory component. The cells were spindle-shaped, adopting a fascicular, pallisading or whirling organisation and were vimentin and variably desmin and actin positive. The nuclei were globular, containing open chromatin and prominent nucleoli. Mild to moderate pleomorphism and little mitotic activity were present. These morphological features are compatible with human myofibroblastic inflammatory tumours.