Stiffness Of The Bovine And Porcine Bones Biology Essay

Published:

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.

In human and animal body there are more than 200 bones present, including long, short, flat, sesamoid and irregular bone. In bone composed of 80% cortical bone and 20% of trabecular bone mass. There are three major component of bone; osteogenic cells (osteoblasts, osteoclasts and ostocytes), organic matrix (collagen and proteoglycans), and mineral. In that the osteogenic cell are involve the regeneration process, mineral are provides mechanical rigidity and load bearing strength and organic matrix are provides elasticity and flexibility to the bone. In human and animal bodies has so many function in the day to date life, therefore bone are involve the damage due to same forces. Because of that each and every bone in the body are undergoing remodelling process to adapt the biomechanical forces and removal of damage bone.

After child born the bone mass are increase during childhood and that reaches peak mass between the ages of 18-35 years in human, but that peak bone mass is primary determined by genetics of the particular animal or human, other than that affected by other factors such as nutrition, physical activity, pharmacology, and behaviours. After reaching peak bone mass level, bone resorption and bone formation are roughly balanced.

The cancellous bone or trabecular bone or spongy bone, it is very light bone, consist of some spaces and give honeycombed or spongy appearance to the bone. Bone matrix is filling with those spaces and highly vascularised than the compact bone. Due to this structure cancellous bone is providing structural support and flexibility to the whole bone without the compact bone. Therefore depending on the strength and flexibility need of the body cancellous bone was arranged on the bone, but it is not tolerate too much of the stress. It is mainly found at the ends of the long bone. Tibia bone is one of the long bone on lower hind leg bones; it is a largest bone in the lower hind leg bone and it functions is load bearing in the body, this bone reluctance to stress fracture. Therefore analysis of the stress forces on the body tibia is the good example, but can used human bone for that. In that situation can use animal bone models. It can provide uniform experimental material and allow for extensive testing of potential human therapies and disease analysis work. Therefore we select the bovine and porcine cancellous bone for our experiment purpose. This report subject is mechanical testing of cancellous bone and tried to find out if strength and stiffness of cancellous bone depends on bone density, species of animal, and testing condition.

ASTM D1621 and ISO 844 Standards

This is the standard testing methods regarding the mechanical behaviour of the cellular materials under compressive loads. This will compute the compressive stress at proportional limit load or compressive strength at maximum load and also compute the elasticity modulus for material. Therefore we can get standard data of compressive tests for research and development, quality control, acceptance or rejection under specification, and special testing purpose. But before doing this test methods there are specification of the material test for reference value. There should be always check the load ends of the specimen are parallel to each other and perpendicular to the sides, all the surfaces of the specimen should be free from the larger visible flaws or imperfection because gage marks on the specimen not affect the surface of the specimen, the direction of the compressive load must be anisotropy and at least minimum of five specimen must be tested for each experiment.

Materials and methods

Materials

Slices of bone samples (approximately 5mm) from bovine or porcine proximal tibias

Band saw

Core drill

Digital Vernier calipers (MW110-15DDL, Moore and Wright, UK)

Digital balance (CM 60-2N, Kern and Sohn, Germany)

Testing machine: Testing machine by ESH Testing Ltd, Brierley Hill, UK.

LVDT which permits measurements to a precision of +/- 0.1%

Load cell permits measurements to a precision of +/-1%

Ethanol

Methods

Thin slices (approximately 5mm) of 12 bone samples each from bovine and porcine proximal tibias were collected using a band saw.

The cancellous bone of approximately 9mm diameter was obtained from these samples using a core drill

The sample dimensions were measured using digital Vernier Calipers.

Each sample is placed in a vial containing ethanol for a week to dissolve the bone marrow.

The ethanol was changed every 3-4 days.

After one week the samples were removed from the ethanol, air-dried and measured the weights using a digital balance.

The samples from each species were divided into two groups of 6 each.

One group was subjected to "unconstrained loading" and the other group to "constrained loading".

The test specimens were conditioned at 23+/-20C and 50+/-5% relative humidity for 40hr prior to testing

The test was conducted in a standard laboratory atmosphere of 23+/-20C and 50+/-5% relative humidity.

Unconstrained loading:

Unconstrained loading test was conducted on 6 samples each from cows and pigs.

The sample was placed in a flat surface in a material testing machine and compressed using a flat ended surface of 25mm diameter at a rate of 0.5mm/min. (ASTM D 1621 and ISO 844 Standards)

The displacement of the flat- ended surface and the applied force were measured using an LVDT and load cell.

The displacement and force were digitally sampled at a frequency of 5Hz and stored on a PC.

Testing was continued until a yield point or a deformation of approximately 0.65mm was reached. (ASTM D 1621 and ISO 844 Standards)

Constrained loading:

Constrained loading was conducted on 6 samples each of bovine and porcine.

The sample was placed within an aluminum cylinder with an internal diameter of 9mm and a height of 5mm.

The cylinder with sample was placed on a flat surface in a material testing machine and was compressed using a flat-ended surface of diameter 8.9mm at a rate of 0.5mm/min. (ASTM D 1621 and ISO 844 Standards)

The displacement of the flat- ended surface and the applied force were measured using an LVDT and load cell.

The displacement and force were digitally sampled at a frequency of 5Hz and stored on a PC.

Result

All the data collected arranged in the EXCEL data sheet; in there we had consisted of force and displacement data for all 24 samples. In that 12 sample for bovine and other 12 samples for porcine, both had constrained and unconstrained loading. The stress and strain for each sample at different times were calculated using the below formula or given EXCEL formulary.

Strain = displacement /thickness

Stress = Force/cross sectional area (Ï€r2)

The stress-strain curve graph for each sample was drawn using EXCEL. The stiffness, compressive strength, zero strain point and failure strain were calculated by using those graphs. The maximum stress at the first hump was taken as the compressive strength even though the stress often rises to a larger value again at higher than the first hump as the first hump is the point where the pore structure first start to fail.

Compressive modulus or stiffness was calculated by dividing the stress and strain at any point on the straight portion of graph. The zero strain point was measured by extending a straight line from the steepest straight potion of the stress-strain curve towards the zero load line. The compressive failure strain is the strain at compressive failure minus the zero strain at which the failure occurs.

Bone density is determined by using the principle of densitometry, when the volume and bone weight are both known the bone density can calculate by using following equation for each samples.

Bone density=bone mass (Kg)/ bone volume (l)

(We measured bone mass as a gram (gr) and volume as a millimetre3 (mm3), it is very small therefore we converted in the density for gram/ centimetre3. And also mass of the bone took without bone marrow therefore this density must be apparent density for each of the sample).

By using EXCEL data we got stiffness, compressive strength, failure strain and zero strain point for all 24 test samples. By using above data we analyzed stiffness, compressive strength and compressive failure strain of each cancellous bone depend on the density. And also we got the analytical data for difference between the average stiffness, compressive strength and compressive failure strain of cancellous bone from cows and pig according to the density.

The average stiffness, compressive strength and compressive failure strain of cancellous bone from cows and pigs were plotted against their apparent density and compared the regression lines. Similarly, the average stiffness, compressive strength and compressive failure strain of cancellous bone from cows and pigs tested in constrained and unconstrained mode were plotted against their apparent density and compared the regression lines.Other than the above mention data we got different between the average failure strain of cancellous bone when tested in unconstrained and constrained mode according to the bone density. Those analytical data explain in the below.

Consider stiffness of the bovine and porcine bones

Figure 01- Figure 02

Under unconstrained loading, the stiffness of bovine bones shows a linear increase with increase in apparent density (slope=678.87). Where as bovine bone shown the stiffness decreases with apparent density in constrained loading (slope=-129.72). (Figure 01 & 02)

Figure 03 Figure 04

When considering the pig bone stiffness decreases with increase in apparent density (slope=-26.688) under unconstrained loading. In case of constrained loading pigs bone show the increases linearly with increase in apparent density (slope=245.66). (Figure 03 & 04)

Figure 05-the stiffness under constrained and unconstrained load of the bovine and porcine bones increased with the increased in the apparent density. In the chart bovine bone show a higher slope (316.81) than the porcine bone (47.759).

Figure 06 Figure 07

Considering bovine bone sample stiffness under constrained and unconstrained load increased very rapidly with the density, but when considering porcine bone sample stiffness under constrained and unconstrained load increased very slowly with the density. (Figure 06 & 07)

Table 01- Average values of the bovine and porcine bone samples

 

 

 

Weight (gr)

Vol.mm3

Density g/mm3

Stiffness(MPa)

Compressive strength(MPa)

Failure strain

Cow

Unconstrained

0.22936667

300.9571

0.76071

214.6541

7.942672

0.05796433

 

Constrained

0.22551667

307.3326

0.733324

146.7562

10.597127

0.1181775

Pig

Unconstrained

0.2579

292.6592

0.88883

134.5398

5.3235457

0.04998317

 

Constrained

0.25038333

287.3438

0.873688

111.278

5.58

-0.6353218

Considering average value of the both bovine and porcine bone samples, pig bone sample had high sample weight and density with less stiffness compare to the cow bone sample. (Table 01)

Considering of compressive strength for bovine and porcine bone

Figure 08 Figure 09

Under unconstrained loading, the compressive strength of bovine bones shows a linear increase with increase in apparent density (slope=-31.324), where as the bovine bone shown the compressive strength decreases with apparent density in constrained loading (slope=-9.0101). (Figure 08 & 09)

Figure10 Figure11

Under unconstrained loading, the compressive strength of porcine bones shows a linear increase with increase in apparent density (slope=-3.6207) where as the under constrained loading also the compressive strength of porcine bones shows a linear increase with increase in apparent density (slope=-21.576). (Figure 10 & 11)

Figure 12 the compressive strength under constrained and unconstrained load of the bovine and porcine bones increased with the increased in the apparent density. In the chart bovine bone show a slope (8.9158) similar to the porcine bone (8.2414).

Considering of failure strain for bovine and porcine bone

Figure13 Figure 14

Under unconstrained loading and constrained loading the stiffness of bovine bones shows a linear decreased increase with increase in apparent density (unconstrained loading slope=-0.2342) (constrained loading slope=-0.0711). (Figure 13 & 14)

Figure 15 Figure 16

Under unconstrained loading, the compressive strength of porcine bones shows a linear decrease with increase in apparent density (slope=-0.0656), where as the porcine bone shown the compressive strength increase with apparent density in constrained loading (slope=0.0778). (Figure 15 & 16)

Figure 17 the failure strain under constrained and unconstrained load of the bovine and porcine bones decrease with the increased in the apparent density. In the chart bovine bone show a slope (0.1805) little bit similar to the porcine bone (-0.026).

Discussion

When analyzed the stress-strain curve of the both species, can notice marginal variation happening on the stress during early phase of the strain. Normally can identify that variation prominently showed on the cow samples than the pig sample, also it was high degree on constrained sample than the unconstrained sample.

In this method only used the uni-axial constrained and unconstrained loading for the test samples at a rate of 0.5mm/min. When applying the load unconstrained cow samples stiffness of the bone was increased with the density but in pig sample it will decreased, and under constrained loading it was opposite, through the density cow samples stiffness was decreased and pig samples it was increased. In comparison of the compressive strength cow sample with density, unconstrained loading compressive strength was increased and constrained loading it was decreased, but pig sample both case it was increased. In that meaning according to the species of the animal change then affect the load change. But it can't say exactly because this test method used without bone marrow, therefore first this test has to do with the marrow. The degree of the removal of the marrow varies from bone species, age and other factor, therefore degree of the removal marrow may affect the all test analysis.

Other problem was when used the uni-axial constrained and unconstrained loading to samples, one type of the sample was change the shaped and other in fixed shape. After performed the test cow sample and pig samples had to different results.

Those above mentions variations happening due to the age, physiological status, dietary pattern or disease condition of the animal. Therefore can performed the testing trail for age, physiological status, and dietary pattern variation also the different species and within the species, and performed the all analytic and get the ideas of the bone.

Analyzing the degree of the mineralization of the cancellous bone, it combines with bone tissue response to stiffness. Because degree of the mineralization of the cancellous bone higher degree in the core and lower degree in the surface, therefore bone stiffness varies from the core to surface. In that this process may indicates some relationship of the bone re-modelling activity, in formation of the bone take place at the surface of the bone and that will get mineralized with the age and pack to the core of the bone.

If the evaluate the bone tissue by through the high resolution of micro-CT scanning, can describe the bone mineral density correlates with the stiffness and strength, and architecture of the bone quality, that lead to analyzed the bone quality and risk of fracture in bone in clinical studies. This micro-CT methods is 2D biased, if 3-D biased method used it can determine the architecture of bone mineral density is independent from the bone mechanical properties. And also using 3D biased method to analysis of the mechanical testing of bone specimens with bone architecture it provide additional information about architecture and bone mass is independent from the properties of the matrix tissue.

Writing Services

Essay Writing
Service

Find out how the very best essay writing service can help you accomplish more and achieve higher marks today.

Assignment Writing Service

From complicated assignments to tricky tasks, our experts can tackle virtually any question thrown at them.

Dissertation Writing Service

A dissertation (also known as a thesis or research project) is probably the most important piece of work for any student! From full dissertations to individual chapters, we’re on hand to support you.

Coursework Writing Service

Our expert qualified writers can help you get your coursework right first time, every time.

Dissertation Proposal Service

The first step to completing a dissertation is to create a proposal that talks about what you wish to do. Our experts can design suitable methodologies - perfect to help you get started with a dissertation.

Report Writing
Service

Reports for any audience. Perfectly structured, professionally written, and tailored to suit your exact requirements.

Essay Skeleton Answer Service

If you’re just looking for some help to get started on an essay, our outline service provides you with a perfect essay plan.

Marking & Proofreading Service

Not sure if your work is hitting the mark? Struggling to get feedback from your lecturer? Our premium marking service was created just for you - get the feedback you deserve now.

Exam Revision
Service

Exams can be one of the most stressful experiences you’ll ever have! Revision is key, and we’re here to help. With custom created revision notes and exam answers, you’ll never feel underprepared again.