Force track analysis of contemporary hip simulators

Calonius, Olof; Saikko, Vesa

doi:10.1016/s0021-9290(03)00166-0

Cited by 32 publications

(36 citation statements)

References 13 publications

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“…The more the local frictional force changes its direction in unit time, the faster is the generation of particles. Note 7 that the change of the sliding direction on the 'force track' of the hip during one walking cycle may be much higher than 360 degrees [6,9].…”

Section: Discussionmentioning

confidence: 99%

Performance analysis of the RandomPOD wear test system

Saikko

Kostamo

2013

Wear

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The type of relative motion between the bearing surfaces of prosthetic joints is known to strongly influence their wear behaviour. The previously validated 16-station wear simulator of the pin-on-disc type, called RandomPOD, was used to study the wear of a conventional, gamma-sterilized ultra-high molecular weight polyethylene (UHMWPE). The counterface was polished CoCr and the lubricant was diluted calf serum. Two test conditions were compared, random motion/random load and circular translation/static load. With random motion, the accumulated change of the direction of sliding was 2.8 times higher than that with circular translation. The test duration with both test conditions was 880 h. Random motion/random load resulted in a mean wear factor 23 per cent higher than that produced with circular translation/static load. The difference was statistically significant. The wear mechanisms however were similar and in agreement with clinical observations. As earlier studies have shown that the type of load is of secondary importance, the present study confirms the earlier findings that the type of relative motion is tribologically of fundamental importance. In particular, the complex, yet biomechanically realistic non-cyclic motion, represented by the random track, resulted in a wear factor significantly higher than that produced by a fixed slide track shape.

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Section: Discussionmentioning

confidence: 99%

Performance analysis of the RandomPOD wear test system

Saikko

Kostamo

2013

Wear

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“…15,21 Analysis of the wear paths produced by different simulators has shown a wide variation, ranging from simple linear paths with infinite aspect ratios to open circular paths with low aspect ratios. 22 The potential importance of variations in individual THA patient's wear paths on wear rates has recently been recognized, with altered gait cycle inputs used to predict wear rate in a finite element model. 9 This study is the first to test the relationship between individual patient kinematics and clinical wear rates for a large group of patients at long-term follow-up.…”

Section: Discussionmentioning

confidence: 99%

“…The apparent lack of association between factors that are known to directly affect wear rate in vitro 10,22 underlines the multifactorial nature of wear in vivo. The poor adjusted r 2 values suggest the presence of other factors that influence wear rate.…”

Section: Discussionmentioning

confidence: 99%

The influence of wear paths produced by hip replacement patients during normal walking on wear rates

Bennett¹,

Humphreys²,

O’Brien³

et al. 2008

Journal Orthopaedic Research

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Variation in wear paths is known to greatly affect wear rates in vitro, with multidirectional paths producing much greater wear than unidirectional paths. This study investigated the relationship between multidirectional motion at the hip joint, as measured by aspect ratio, sliding distance, and wear rate for 164 hip replacements. Kinematic input from three-dimensional gait analysis was used to determine the wear paths. Activity cycles were determined for a subgroup of 100 patients using a pedometer study, and the relationship between annual sliding distance and wear rate was analyzed. Poor correlations were found between both aspect ratio and sliding distance and wear rate for the larger group and between annual sliding distance and wear rate for the subgroup. However, patients who experienced a wear rate <0.08 mm/year showed a strong positive correlation between the combination of sliding distance, activity levels, and aspect ratio and wear rate (adjusted r 2 ¼ 55.4%). This group may represent those patients who experience conditions that most closely match those that prevail in simulator and laboratory tests. Although the shape of wear paths, their sliding distance, and the number of articulation cycles at the hip joint affect wear rates in simulator studies, this relationship was not seen in this clinical study. Other factors such as lubrication, loading conditions and roughness of the femoral head may influence the wear rate. ß

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“…In earlier studies, Saikko and Calonius presented the first verified computations of the kinematics of the prosthetic hip joint illustrated as so-called slide track patterns [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Effect of contact pressure on wear and friction of ultra-high molecular weight polyethylene in multidirectional sliding

Saikko¹

2006

Proc Inst Mech Eng H

123

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Please cite the original version: Saikko, Vesa. 2006 All material supplied via Aaltodoc is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user. ABSTRACTComputational wear models need input data from valid tribological tests. For the wear model of total hip prosthesis, the contact pressure dependence of wear and friction of ultra-high molecular weight polyethylene (UHMWPE) against polished CoCr in diluted calf serum lubricant was studied, and useful input data produced. Two test devices were designed and built, heavy load circularly translating pin-on-disk (HL-CTPOD) wear test device and HL-CTPOD friction measurement device. Both can be used with a wide range of loads. The wear surface diameter of the test pin was kept constant, 9 mm, whereas the load was varied so that the nominal contact pressure ranged from 0.1 MPa to 20 MPa. The wear factor decreased with increasing contact pressure, whereas the coefficient of friction first increased with increasing contact pressure with low pressure values, and then decreased. Up to the pressure of 2.0 MPa, the wear mechanisms and wear factors were in good agreement with clinical findings. In the critical range of 2.0-3.5 MPa, the wear mechanisms and wear factors started to differ from clinical ones, and the decrease of the wear factor steepened. The discrepancy became more and more evident as the pressure was gradually increased beyond 3.5 MPa. It appears that the pressure value of 2.0 MPa should not be exceeded in pin-on-disk wear tests that are to reproduce the clinical wear of UHMWPE acetabular cups.

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Force track analysis of contemporary hip simulators

Cited by 32 publications

References 13 publications

Performance analysis of the RandomPOD wear test system

Performance analysis of the RandomPOD wear test system

The influence of wear paths produced by hip replacement patients during normal walking on wear rates

Effect of contact pressure on wear and friction of ultra-high molecular weight polyethylene in multidirectional sliding

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