On dynamic behavior of bone: Experimental and numerical study of porcine ribs subjected to impact loads in dynamic three-point bending tests

W, Zeng S, Wu Y. Evaluation of the mechanical properties of porcine kidney

With the development of medical diagnosis and treatment, knowing the mechanical properties of living tissues becomes critical. The aim of this study was to investigation material properties of the fresh porcine kidney and the parametric characterization of its viscoelastic material behavior. The material investigation included uniaxial tension tests in different strain rates, relaxation tests, as well as hydrostatic compression tests on the samples extracted from the fresh porcine kidney cortex. Tension tests and relaxation tests were performed by a planar dog-bone specimen with a micron loading testing machine. Hydrostatic compression tests were performed on the kidney cylinder sample which was placed in a compression chamber. Furthermore, a nonlinear viscoelastic model recently proposed by us was employed to characterize the tension data at different strain rates and relaxation test data. The the experimental and numerical results show that the stress-strain relations of the porcine kidney cortex at different strain rates in tension are presented for the first time and a higher strain rate results in higher ultimate strength and initial Young modulus but a lower rupture strain. A damage-dependent visco-elastic model is employed to model the tension data at different strain rates and relaxation data and exhibits a good agreement with the experimental data, which also demonstrates that the damage has an obvious influence on the stress-strain relation. Through comparison with the existing reference covering the uniaxial compression data, it seems that the mechanical behavior of the porcine kidney cortex manifests a stress state-dependent mechanical behavior. The ultimate strength and rupture strain are larger in compression than that in tension.

Biomechanical properties of the bone during implant placement

Background

In this research the biomechanical properties of a bone model was examined. Porcine ribs are used as experimental model. The objective of this research was to investigate and compare the biomechanical properties of the bone model before and after implant placement.

Methods

The bone samples were divided in three groups, Group 1 where ALL-ON-FOUR protocol was used during pre-drilling and placing the implants, Group 2 where ALL-ON-FOUR protocol was used during pre-drilling, and implants were not placed, and Group 3 consisting of intact bones served as a control group. Static and dynamic loading was applied for examining the model samples. Kruskal–Wallis statistical test and as a post-hoc test Mann–Whitney U test was performed to analyze experimental results.

Results

According to the results of the static loading, there was no significant difference between the implanted and original ribs, however, the toughness values of the bones decreased largely on account of predrilling the bones. The analysis of dynamic fatigue measurements by Kruskal–Wallis test showed significant differences between the intact and predrilled bones.

Conclusion

The pre-drilled bone was much weaker in both static and dynamic tests than the natural or implanted specimens. According to the results of the dynamic tests and after a certain loading cycle the implanted samples behaved the same way as the control samples, which suggests that implantation have stabilized the skeletal bone structure.

Lepidium sativum: Bone healer in traditional medicine, an experimental validation study in rats

India is a land of spices and medicinal plants. Ayurvedic medications and methods are commonly practised in India for curing several ailments. Lepidium sativum (garden cress) is an important herb that belongs to Brassicaceae family. It is believed that the plant has its origin in Ethiopia but is now cultivated throughout the world. The plant is well-known in Ayurveda for its beneficial properties it holds. The present study describes the fracture healing property of the methanolic and aqueous extract of Lepidium sativum seeds. For the study, 21 Charles foster rats were used. They were grouped into three groups each containing seven rats: control, methanolic, and aqueous group. Rats were anesthetized using ether vapors and fractures were induced in each rat from all the three groups using hand held three-point bending technique. The broken bone fragments were then stabilized using splints. The control group was administered with normal saline, along with food and water, post-fracture. The methanolic group was administered with the methanolic extract of Lepidium sativum seeds at dose of 400 mg/kg given orally, post-fracture along with food and water. The third group received aqueous extract of the seeds in doses of 550 mg/kg orally, along with daily food and water intake for a period of 8 weeks. The results were evaluated both radiologically and biochemically. X-rays were done on day 0, 2^nd week, and 4^th week post-fractures to look for the callus formation and serum levels for calcium, phosphorus, and alkaline phosphatases were evaluated on 0 day, 1 week, 2^nd week, 4^th week, 6^th week, 8^th week, and 10^th week post-injury. It was observed at the end of the study period that the methanolic group had significant callus formation starting at the 2^nd week itself post-fracture. The serum levels of calcium, phosphorus, and alkaline phosphatases at 4^th, 6^th, and 8^th weeks had significant P values in the methanolic group rats.