Quantitative Analysis of Stress-Stretch Curves in Canine Lumbar Vertebrae Using Modified Logistic Functions.

BACKGROUND: The mechanical characteristics of bone are crucial for comprehending its functionality and response to different load conditions, which are essential for advancing medical treatments, implants, and prosthetics. By employing mathematical modeling to analyze the mechanical properties of bone, we can assess stress and deformation under both normal and abnormal conditions. This analysis offers valuable perspectives on potential fracture risks, the effects of diseases, and the effectiveness of various treatments. Therefore, researchers are attempting to find an adequate mathematical description of the mechanical properties of bone. METHODS: Experimental stress-stretch external loading curves were obtained through investigations of canine vertebrae. The obtained experimental curves were fitted using the SciPy Python library with a slightly modified logistic function (logistic function plus additional const). RESULTS: The resulting coefficient of determination R2 (R squared) for most curves was near 0.999, indicating that an appropriate fitting function was selected for the description of the experimental stress-stretch curves. CONCLUSIONS: The stress-stretch behavior of canine vertebrae can be described using a logistic function modified by adding additional parameters for the most accurate fitting results.

Experimental and theoretical investigation of aortic wall tissue in tensile tests.

BACKGROUND: Understanding the mechanical properties of aortic tissue is essential for developing numerical computation tools and assessing the risk of aortic aneurysm fractures. Tensile tests using aortic wall specimens allow for the determination of stress and strain depending on the location and direction of the sample. OBJECTIVE: The aim of this study was to perform a mechanical tensile test using canine aorta samples and create a numerical model of aortic tissue tension from the processed data. METHODS: Dogbone-shaped samples were dissected from canine aortic segments. The initial measurements were made at zero tension and the tensile tests were conducted at 10 mm/min until rupture. Force and stretch data were used to obtain engineering and true stress-strain curves. The true stress-strain curves were taken until the maximum strength was obtained, after which they were smoothed and fitted using a logistic function with three coefficients. These curves were then used as material mechanical properties for a numerical model of the aortic tissue tension. A simplified rectangle form was used to mimic the middle of the dogbone-shaped portion of the tissue specimen. Experimental displacement data were collected for the boundary conditions of the finite element 3D model. RESULTS: The experimental data processing revealed that the logistic function described the nonlinear behaviour of the aorta soft tissue with an accuracy of 95% from the start of the tension to the media layer rupture. By applying numerical simulations, we obtained a correspondence of the load curve with an RMSE = 0.069 for the theoretical and experimental external tension data. CONCLUSION: The numerical investigation confirmed that the non-linear soft tissue was validated by applying a logistic function approach to the mechanical properties of the aortic wall.

Histomorphometry and µCT scan analysis of osteoporosis in spayed female dogs.

Background: Both humans and small animals suffer from similar metabolic and structural diseases that impact the musculoskeletal system; however, instead of studying animal disease in its own right, animals are more often used as models for research into various human ailments, such as osteoporosis. There are few studies indicating that animals may suffer from osteoporosis, which raises the question of why small animals, which we believe to be equally susceptible, receive so little attention. With this research, we hope to draw the attention of researchers to the fact that the examination of animals for this disease is just as important as the examination of humans; human osteoporosis research receives a great deal of attention, while animals and their health are neglected. Aims: We aimed to analyze the bone volume fraction (BV/TV) and thickness of first (L1) and second (L2) lumbar vertebrae samples from five cadavers using histomorphometric analysis. In addition, we aimed to investigate one cadaver using microcomputed tomography (µCT) imaging. Methods: The L1 and L2 vertebrae from five dog carcasses were used to evaluate the BV/TV and the trabecular thicknesses. We used precise sampling criteria, and also developed a methodological approach to the study of the vertebrae. Using semi-automated methods, we performed histomorphometric analysis and µCT data analysis. Results: We used five dog cadavers in this research. During the histomorphometry study, we observed that the lowest L1 BV/TV ratio was 7.88% and the highest was 23.08%. The L2 vertebrae BV/TV ranged from 11.58% to 23.7%. The L1 and L2 lumbar trabeculae thicknesses were also measured. L1's smallest trabecula was 17.34 microns and its largest was 31.88. The L2 vertebrae trabecula thickness was 18.76-30.75 microns. BV/TV and trabecular thickness were positively correlated (and vice versa). The two-tailed p value was less than 0.00001. This difference is statistically significant. After µCT analysis, we discovered regions in the vertebral body with low porosity; these cavities are usually filled with connective tissue. The bone tissue in these areas is more vulnerable, meaning fracture risk has increased. Conclusions: Animals should not just be considered as models for osteoporosis in humans, but also as potential patients. A single test, such as histomorphometry, may not be sufficient; more advanced technology, such as µCT, is required, since it reveals the pores that make the vertebral column more brittle and susceptible to fracture.

Empirical case report of the mechanical properties of three spayed canine lumbar vertebrae.

Background: Today, animals, like humans, suffer from spinal illnesses, which are aggravated in old age. Much emphasis is placed on diagnosis and treatment, but little focus is given to the spine's mechanical properties. Degenerative spine diseases are a major problem throughout the world. According to the World Health Organization, osteoporosis is a world-class public problem that reduces bone mass, resulting in bone fracturing and increased risk of bone fracturing. Therefore, the mechanical investigation of vertebrae can provide more information about the development of osteoporosis.s. Case Description: For our case report, we used spayed mongrel lumbar vertebrae samples obtained from a canine which was about 8 years old and weighed 28 kg. The dog was diagnosed with a mammary tumor, and its owners decided to euthanize the dog. All consent forms were filled. Conclusion: Mechanical tests were performed on three vertebrae, and a notable difference was observed in the first cycle of the first vertebra (L1). Second-order polynomials for displacement and seventh-order polynomials for pressure were proposed for describing the stress-strain relationship of the vertebrae under the cyclical loads. Our research protocol has been broken down into several parts. After measuring the area of the loaded surface, the largest area was in the L2 vertebra (176 ± 16 mm; 177 ± 3 mm) and the smallest was in the L7 vertebra (156 ± 4 mm; 151 ± 33 mm). The smallest distance was recorded between the first (L1) and seventh (L7) lumbar vertebrae (L1) (15.17 ± 0.93 mm), and the largest distance was recorded between the L3 and L4 vertebrae of the lumbar (19.8 ± 3.7 mm).

Monopolar electrocautery use in minimally invasive urosurgery: Case report of ectopic ureter management in a bitch.

Background: Ureteral ectopy is a congenital anomaly, affecting young dogs, predominantly bitches. The main complication of the disease is urinary incontinence, which leads to low life quality for both animals and their owners. However, only two less invasive surgical management options are reported. Laser ablation is quite popular, while monopolar electrocautery use is very rare. Case Description: A 3-month and 1-week-old, 1.7 kg female Poodle was admitted to the Vetamicus clinic with severe urinary incontinence and moisture-associated dermatitis. After diagnosing intramural ectopy type during computed tomography scan and video cystoscopy, a search for surgical management options began. We proceeded with the monopolar cauterization technique, where a semirigid Karl Storz monopolar coagulating ball electrode is used to cut a mucous membrane partition between the ureter and urinary bladder. No complications occurred during or after the surgery. Ureter successfully healed and full continence was achieved together with sporadically using phenylpropanolamine syrup. Conclusion: The present case indicates that monopolar electrocautery use in intramural ectopy type management and possibly other urinary tract pathologies might be strongly beneficial.