Online Exclusive

Mechanical Testing of Medical Implants

Posted in Testing Equipment by Camilla Andersson on May 11, 2012

Implants and the materials used for their production undergo extensive tests, which include the evaluation of the static and dynamic mechanical properties of the raw materials, components and systems. Many of these tests are internationally standardised. Other testing procedures are specific to a given application. In all cases, advanced testing instruments and clamping fixtures, along with flexible, programmable testing software, help in the determination and analysis of the relevant data.

Manufacturers of medical implants must demonstrate that they have carefully considered the risks of component or system failure and satisfactorily mitigated against them. To this end, such products undergo a variety of mechanical tests prior to their approval, from simple tensile tests on material specimens, through combined compression, torsion or flexure tests, up to the simulation of pressure pulsation on complete implant systems under defined ambient conditions. The examples below illustrate the wide range of testing applications.

Knee replacements: Fatigue behaviour of tibial trays
Fatigue fracture of knee tibial trays has been one of the most commonly reported failure mechanisms in Total Knee Replacements (TKR). It is caused by loss of underlying bone support underneath the implant, which renders the latter mechanically unstable. Cyclic loads imparted by walking cause fatigue cracks, ultimately leading to catastrophic failure. The ISO 14879-1 standard1 specifies a set of test parameters for determining the fatigue properties of different tibial tray designs.

In practice, servo-hydraulic test systems such as Instron's model 8870 have been found eminently suitable both for determining fundamental material properties such as the resistance to fatigue crack propagation, and testing of the entire tibial tray. One half of the tibial tray is secured in a clamping fixture, simulating a fully supported condyle. The other, unsupported condyle is then subjected to physio¬logically representative loading.

 Figure 1. Compact and space-saving servo-hydraulic test system, prepared for testing the fatigue properties of tibial trays for total knee replacements.

A fatigue testing system used frequently for this type of test is Instron's model 8872, a compact table-top test instrument (Figure 1). With a nominal load capacity of 25 kN it is particularly suited for static and dynamic testing of materials and components for biomedical applications. Its adjustable crosshead with integral servo-hydraulic actuator, which accommodates the load cell, and a corrosion-resistant base with T-slot table and drain channel, make the instrument eminently suitable for testing in a saline bath, as well as a wide range of other tests. The Console software provides extensive features for PC control of the testing system, including signal generation, calibration, limit setup and status monitoring. In addition, the Wavematrix block programming software can be used for cyclic tests.

Typically, when performing such measurements under dynamic loads, acceleration forces are acting on parts of the system, which are superimposed on the actual forces applied to the specimen. Therefore, the load cells will also record forces resulting from their own movement and that of the clamping fixtures attached to them. Dynacell load cells (with load capacities ranging from 250 N to 2500 kN) reduce these effects even at high test frequencies. In conjunction with the associated 8800 Digital Controller, they enable the automatic compensation of acceleration forces as well as inertial errors such as those caused by hydrodynamic effects that occur when testing in a fluid bath.

Spinal columns: Static, torsion and fatigue testing
In spinal constructs, high loading may lead to catastrophic failure. Hence, static testing must be performed to evaluate the compressive, tensile and torsional loads leading to the fracture of the spinal construct. In addition, service life testing is also critical, as fatigue fracture is more common in actual practice than catastrophic failure. Loading typically is applied with a constant-amplitude, load-controlled sinusoidal waveform, with tests running in excess of five million cycles. The ASTM F1717 standard2 specifies test methods for both static and fatigue testing. Testing is usually done with blocks of ultrahigh molecular weight polyethylene (PE-UHMW) rather than vertebrae, to eliminate vertebra-induced variance.

 Figure 2. Electro-dynamic testing systems offer exceptional response and high accuracy across a wide frequency range for fatigue testing of spinal constructs.


Universal testing systems are generally well suited for static tensile and compressive testing. Standard test software packages (e.g. Instron's Bluehill 3) can be used to record load-displacement curves and perform the calculations specified in the standard. Table-top torsion testers such as the 55MT MicroTorsion systems offered by Instron (designed for multiple revolutions) are suitable for application of torsional loads.

If an angle of rotation of ±135° is sufficient, the model 8874 fatigue testing system is an efficient solution for handling both axial and torsional fatigue testing. The biaxial, table-top servo-hydraulic instru¬ment features a dual-column frame and a combined dynamic actuator for axial and torsional loading in the upper crosshead. Once again, the 8800 digital electronic controller and the Dynacell load cell in conjunction with the Console and/or WaveMatrix software are ideal complements to the system.

If you need to test the durability of spinal constructs and require exceptional response and accuracy across a wide frequency range, Instron's all-electric test instruments (such as the ElectroPuls E1000, Figure 2), combined with the WaveMatrix software, provide the necessary capabilities. These advanced instrument feature a digital control system for easy loop tuning based on specimen stiffness.

The system is fed from a single-phase ac power supply and requires no other utilities for basic operation (such as pneumatic air, hydraulics or water).

Stents: Efficient fatigue testing of materials and structures

 Figure 3. A multi-specimen fixture assists manufacturers of cardio¬vascular implants in the evaluation of the fatigue strength of nickel titanium (Nitinol) and stainless steel materials and structures.


Traditionally, testing of stents and stent grafts to standards such as ASTM F2477–07.3 involves subjecting complete devices to pressure pulsation simulating blood flow for a prespecified number of cycles. To enable a representative sample of specimens to be evaluated and to reduce overall test time, multiple specimens must be tested on a single system.

To cater to this requirement, Instron has developed a multispecimen fixture for the ElectroPuls E3000 test instrument (Figure 3). Each specimen station features a fatigue-rated load cell, precision alignment and grips that are unique to the material or structure undergoing test. The entire assembly is submerged in a temperature-controlled bath to test the specimens in vitro. The test is controlled by the WaveMatrix software, which features integrated temperature control of the fluid bath, a live display of each load cell reading and trend monitoring of forces to determine specimen fracture.

Wide-ranging experience
The solutions described above only represent a cross-section of a diverse spectrum of standardised and application-specific testing solutions developed by Instron in close partnership with users from the medical device industry. A more comprehensive overview can be found on the website In all cases, the test system manufacturer's application specialists will be prepared to configure, in close cooperation with manufacturers and users, testing systems tailored to specific testing requirements, and to develop unconventional solutions for challenging testing tasks.

1. ISO 14879-1: Determination of endurance properties of knee tibial trays
2. ASTM F1717: Standard Test Methods for Spinal Implant Constructs in a Vertebrectomy Model
3. ASTM F2477–07: Standard Test Methods for in vitro Pulsatile Durability Testing of Vascular Stents


Find more content on:
No votes yet

Login to post comments

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

it is truly exceptionally

it is truly exceptionally informatic post for youngsters, and trust they will appreciate well in the wake of perusing this post. xarelto recall

Its my words too

rugby live online 2015

England Rugby World Cup 2015 Live Stream, Live Scores, RWC 2015 Live Telecast In USA, Australia, Canada, India, Watch Rugby Live Online Free, Tv Broadcast Rights

2015 rugby world cup live streaming

do you know that...

Manufacturers of medical implants must demonstrate their ability to produce quality work.

I like this post,And I guess

I like this post,And I guess that they having fun to read this post,they shall take a good site to make a information,thanks for sharing it to me.
link Building

about his or her health than

about his or her health than the patient.” To fuel this transformation, patients need better tools and better information.
manually do backlinks

He stated that some early

He stated that some early clinical experiments and trials in China on tissue engineering products were revealing responses that were not predicted by the in vitro and other preclinical tests, largely as a result of the effect of degrading polymer systems. This is clearly of major significance for the whole field of
High pr do follow links


They could be compiled by anyone, although a lot of the information is normally explored with regard to articles accuracy and reliability. An average well being website can have questions in addition to photographs and even video clip regarding the material staying mentioned. Particular goods including foods and drinks linked to wellbeing may be discussed along with queries are usually welcomed.

Thanks a lot It is an incomparable

Thanks a lot It is an incomparable writing and the topic discussed with the delightful reading.

SuperGirl Jacket

Are u serious about it?

You'll be less likely to acquire some illnesses if you eat healthy. This is an critical benefit of a healthy diet. Eating foods full of vitamins and minerals will permit the body to improve control illness and you will be wholesome along with happy. This will conserve your funds when you will not be visiting the physician as much or taking numerous prescription drugs.

such a great med technology

such a great med technology

I really enjoy simply reading

I really enjoy simply reading all of your weblogs. Simply wanted to inform you that you have people like me who appreciate your work. Definitely a great post. Hats off to you! The information that you have provided is very helpful.

It’s a tremendous post. I am

It’s a tremendous post. I am truly grateful for this blog and I was in fact looking for something impressive like this should stay longer here, read all the post very nice posting you have cigspromocode

Thank you for your post, I

Thank you for your post, I look for such article along time, today i find it finally. this post give me lots of advise it is very useful for me. david lovely

I think you should explore

I think you should explore the articles on your website, You should also cover different different categories for articles as you writes awesome. Thanks for sharing this great article with us.

copa america final

copa america 2015 final live stream
Final copa america 2015 live stream

Copa America 2015 Final Live Streaming-Stream, Live Telecast In India, USA, Watch Copa America Live Online, Live Scores, Predictions,

gold cup 2015 live stream
wimbledon 2015 live stream

Took me time to understand

Took me time to understand all of the comments, but I seriously enjoyed the write-up. It proved being really helpful to me and Im positive to all of the commenters right here! Its constantly nice when you can not only be informed, but also entertained! I am certain you had enjoyable writing this write-up.Buy Bed Sheets Online

Wimbledon 2015 Tennis Grand

Wimbledon 2015 Tennis Grand Slam Is going to start and if you are looking for wimbledon tennis live streaming, then you must try this page. wimbledon 2015 live streaming

good job

Thank you so much for the post you do. I like your post and all you share with us is up to date and quite informative..
Agen Bola
Agen Sbobet Online


I like , thanks for share..
Agen Judi Online

You completed a few fine

You completed a few fine points there. I did a search on the subject and found nearly all persons will go along with with your blog.

regole scacchi

This is a wonderful article,

This is a wonderful article, Given so much info in it, These type of articles keeps the users interest in the website, and keep on sharing more ... good luck. Luxury Bedding Uk

I will recommend this to all

I will recommend this to all my friends as I find the information here really interesting ? can't wait for another article from you! lembrancinhas do george pig

Really great post, Thank you

Really great post, Thank you for sharing This knowledge.Excellently written article, if only all bloggers offered the same level of content as you, the internet would be a much better place. Please keep it up! smart happy birthday wishes

Hello, I have browsed most of

Hello, I have browsed most of your posts. This post is probably where I got the most useful information for my research. Thanks for posting, maybe we can see more on this. Are you aware of any other websites on this subject.

payday advance

This post is probably where I

This post is probably where I got the most useful information for my research. Thanks for posting. packers and movers pune to hyderabad

Thanks for sharing have a

Thanks for sharing have a look at our's blog
eid mubarak 2015

great article

I havent any word to

I havent any word to appreciate this post.....Really i am impressed from this post....the person who create this post it was a great human..thanks for shared this with us.

klik disini

The system is fed from a

The system is fed from a single-phase ac power supply and requires no other utilities for basic operation (such as pneumatic air, hydraulics or water).how do you get more followers on instagram | apps to get more likes on instagram

Father's Day is a celebration

Father's Day is a celebration honoring fathers and celebrating fatherhood, paternal bonds, and the influence of fathers in society. Many countries celebrate it on the third Sunday of June, though it is also celebrated widely on other days by many other countries. | fathers day messages

Thanks :)

copa america 2015 live

I would love to stop by. But,

I would love to stop by. But, I think it might have to wait until this summer. I did not know that Serlkay had ever expanded its size. I must say that a succesful family owned business in this day and age is a very refreshing sight! As well as this is a very refreshing site!
General health tips

I would like to thank you for

I would like to thank you for the efforts you have made in writing this article. I am hoping the same best work from you in the future as well. In fact your creative writing abilities has inspired me to start my own BlogEngine blog now. Really the blogging is spreading its wings rapidly. Your write up is a fine example of it.
buy 50 instagram followers no password


Mothers Day ideas Mothers

This is something amazing

This is something amazing what i read over here.
Happy Mothers Day Greetings Card | Happy Mothers Day Cards Thank you for sharing

Hi there, I found your blog

Hi there, I found your blog via Google while searching for such kinda informative post and your post looks very interesting for me.
buy youtube views template

Proof that Stannis is not

Proof that Stannis is not only a religious looney tune, but also a MORON. What are the chances of the Wildings joining him now?

Game of Thrones Season 5 Episode

mothers day images-messages

So luck to come across your

So luck to come across your excellent blog. Your blog brings me a great deal of fun.. Good luck with the site.
Astuce Clash of Clans

MSBSHSE Result 2015 ssc


French Open 2015 Live

French Open 2015 Live Streaming : The French Open, often referred to as Roland Garros (officially: Les internationaux de France de Tennis, Roland Garros; also called Tournoi de Roland-Garros) is a major tennis tournament held over two weeks between late May and early June at the Stade Roland Garros in Paris, France.
French Open 2015 | French Open 2015 Live

champions league 2015

packers and movers

Hey!! good written information. Keep it up. you can also find more information about relocation. - packers and movers Bangalore marathahalli . packers and movers in bangalore movers and packers hyderabad

Mahresult ssc 2015 Manabadi

porsche boxster wheels

wow this good but ,I like your post and good pics may be any peoples not like because defrent mind all poeple ,
porsche boxster wheels

Awesome post thanks for

Awesome post thanks for sharing
CBSE Result, CBSE Result 2015, CBSE 2015 Result

mothers day 2015 will be

mothers day 2015 will be celebrate on the 10th may 2015 and you all guys are preparing for this big event. have a look
mothers day quotes mothers day gifts mothers day poems