Friction Measurement in the Biaxial Rocking Motion Hip Joint Simulator

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Vesa Saikko
Keyword(s):  
Hip Joint ◽  
Calf Serum ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Frictional Torque ◽  
Friction Measurement ◽  
Vertical Loading ◽  
Ultrahigh Molecular Weight ◽  
Rocking Motion ◽  
Hip Joint Simulator

The established biaxial rocking motion (BRM) hip joint simulator was complemented by a novel friction measurement accessory. This simple and practical system, which was easily added to an existing BRM design, is described in detail and shown to perform well in long-term wear tests and in comparative tests of 24 h duration involving several different bearing couples. The system was based on the measurement of frictional torque about the leaning axis of the lower component, the femoral head. In the 28 mm CoCr-on-ultrahigh molecular weight polyethylene articulation with diluted calf serum lubricant at body temperature and 1 kN static load, the maximum value of frictional torque during a cycle was 1.2 N m on the average. The alternative system based on the measurement of torque about the vertical loading axis was shown to be less sensitive and highly insensitive when contact area was small, as was the case with alumina-on-alumina.

Investigations on the wear behaviour of the temporary PMMA-based hip Spacer-G®

2003 ◽  
Vol 217 (1) ◽  
pp. 1-8 ◽  
Author(s):  
S Affatato ◽  
A Mattarozzi ◽  
P Taddei ◽  
P Robotti ◽  
R Soffiatti ◽  
...  
Keyword(s):  
Hip Joint ◽  
Calf Serum ◽  
Three Dimensional ◽  
Wear Particle ◽  
Sem Analysis ◽  
Wear Behaviour ◽  
Cement Spacer ◽  
Pmma Particles ◽  
Pmma Cement ◽  
Hip Joint Simulator

Total hip replacement has become one of the most successful orthopaedic procedures. However, complications due to infections may give serious problems and have devastating consequences for the hip implant. The use of a temporary three-dimensional polymethylmethacrylate (PMMA) cement spacer may be an alternative to solve infections in hip implants, improving the lives of patients awaiting reimplantation. In order to evaluate their wear behaviour, five PMMA Spacer-G® femoral heads were tested against five post-mortem pelves in a hip joint simulator with bovine calf serum as lubricant. The surface of the worn spacers was characterized by scanning electron microscopy (SEM) analysis; all the samples revealed a similar morphology, showing areas characterized by different degrees of wear. Particle debris was isolated from the lubricant and PMMA particles and bone fractions were quantified. The amount of debris was found to be higher than where no-temporary prostheses were used. However, this result is acceptable since wear debris is removed by lavage irrigation when the Spacer-G® is explanted. On the basis of these data, it is considered that the use of the cement Spacer-G® could be a promising approach to the treatment of complicated infections of the hip joint. Therefore, Spacer-G® is worthy of further research.

A Three-Axis Hip Joint Simulator for Wear and Friction Studies on Total Hip Prostheses

1996 ◽  
Vol 210 (3) ◽  
pp. 175-185 ◽  
Author(s):  
Vesa O Saikko
Keyword(s):  
Hip Joint ◽  
External Rotation ◽  
Frictional Torque ◽  
Hip Prostheses ◽  
Total Hip ◽  
Flexion Extension ◽  
Single Station ◽  
Wear And Friction ◽  
Total Hip Prostheses ◽  
Hip Joint Simulator

A three-axial, single-station hip joint simulator was designed and built for wear and friction studies on total hip prostheses. The design of the apparatus is described in detail. Continuous level walking is simulated. All three motion components, flexion-extension, abduction-adduction and internal-external rotation, are included. The motions are implemented electromechanically and the uniaxial load pneumatically. The load is measured continuously. For accurate measurement of wear, the apparatus has a loaded control joint, which also renders both the test and control joints self-centring, as they are loaded in series. The frictional torque of the test joint can be measured continuously throughout the wear test, which is an exceptional feature. Four tests of five million cycles each were completed using 32 mm diameter Co-Cr-Mo femoral heads and 5.6 mm thick, metal-backed, ultra-high molecular weight polyethylene acetabular cups as test specimens. Their wear and friction behaviour is described and discussed in relation to previous simulator studies and clinical observations. The lubricant was distilled water, maintained at body temperature. The wear of the cups was measured gravimetrically at intervals. The average wear rate was 3.9 mg/one million cycles, corresponding to 0.03 mm/year, and the average coefficient of friction was 0.01.

Effect of Head Surface Roughness and Sterilization Method on Wear of UHMWPE Acetabular Cups: Preliminary Hip Joint Simulator Results

2006 ◽  
Author(s):  
Anneli Jedenmalm ◽  
Walther Leardini ◽  
Mara Zavalloni ◽  
Saverio Affatato
Keyword(s):  
Surface Roughness ◽  
Hip Joint ◽  
Calf Serum ◽  
The Body ◽  
Acetabular Cup ◽  
Sterilization Method ◽  
Metal Head ◽  
Head Surface ◽  
The Impact ◽  
Hip Joint Simulator

More than one million hip joint replacements are performed each year in the world. However, the implants do not last forever due to material limitations, even though the operation is successful. The most common material combination used today is a CoCr head articulating against an UHMWPE (Ultra High Molecular Weight Polyethylene) acetabular cup. Several investigations have shown that the metal head is roughened inside the body and thus accelerating wear of the polymer cup. The sterilization method is also known to have effect on the wear properties. In vitro wear tests are however usually performed with as new implants. This investigation aimed at study the impact of head surface roughness on wear of both sterilized and non-sterilized acetabular cups. A total of nine acetabular cup and head pairs were wear tested in a hip joint simulator for 2Million cycles (Mc) with bovine calf serum as lubricant. Wear was determined by weighing of all cups. The heads were of CoCrMo and the average initial head surface roughness was 15nm (Ra), measured with a white light interference profilometer. The roughening was produced with a SiC paper producing circular multidirectional wear tracks to a surface roughness of about 400nm (Ra). The cups were of UHMWPE and the sterilized cups were 3Mrad gamma-radiated in nitrogen. The surface roughness after wear test was unchanged for the roughened heads, while the initially smooth heads were slightly roughened. Preliminary results show that the rough heads increase the wear of the cups 2-fold. The γ-irradiation affected both wear- and soak rate.

Third-Body-Wear as a Risk Factor in Joint Endoprosthetics

2005 ◽  
Vol 284-286 ◽  
pp. 995-998 ◽  
Author(s):  
Thomas Oberbach ◽  
Wilfried Glien ◽  
Christian Kaddick
Keyword(s):  
Hip Joint ◽  
Wear Behaviour ◽  
Third Body ◽  
Ceramic Component ◽  
Joint Gap ◽  
Alumina Particles ◽  
Joint Prostheses ◽  
Hip Joint Simulator

It is well known, that wear of the articulation partners of hip joint prostheses affect the long-term durability of the implants in vivo. The wear is dramatically increased if particles in the artificial joint gap act as third body. Those particles can also occur after a fracture of a ceramic component. Until now there are some different guidelines which coupling (metal-polyethylene, ceramic-polyethylene, ceramic-ceramic) should be used for revision. We tested and compared the wear behaviour of a ceramic-PE-pairing and a ceramic-ceramic-pairing under third body wear conditions with alumina-particles in a hip joint simulator.

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