0
Research Papers

Experimental Evidence of Impingement Induced Strains at the Interface and the Periphery of an Embedded Acetabular Cup Implant

[+] Author and Article Information
Christoph Arndt1

 University of Leipzig, Medical Faculty,Department of Orthopaedic Surgery,Laboratory for Biomechanics, Liebigstr. 20, 04103 Leipzig, Germany

Christian Voigt1 n2

 University of Leipzig, Medical Faculty,Department of Orthopaedic Surgery,Laboratory for Biomechanics, Liebigstr. 20, 04103 Leipzig, Germanychristian.voigt@medizin.uni-leipzig.de

Hanno Steinke

 University of Leipzig, Medical Faculty,  Institute of Anatomy, Liebigstr. 13, 04103 Leipzig, Germanyhanno.steinke@medizin.uni-leipzig.de

Georg v. Salis-Soglio, Roger Scholz

 University of Leipzig, Medical Faculty,Department of Orthopaedic Surgery,Laboratory for Biomechanics, Liebigstr. 20, 04103 Leipzig, Germany

1

Authors contributed equally.

2

Corresponding author.

J Biomech Eng 134(1), 011007 (Feb 09, 2012) (8 pages) doi:10.1115/1.4005686 History: Received September 13, 2011; Revised January 03, 2012; Posted January 24, 2012; Published February 08, 2012; Online February 09, 2012

After total hip arthroplasty, impingement of implant components may occur during every-day patient activities causing increased shear stresses at the acetabular implant–bone interface. In the literature, impingement related lever-out moments were noted for a number of acetabular components. But there is little information about pelvic load transfer. The aim of the current study was to measure the three-dimensional strain distribution at the macrostructured hemispherical interface and in the periphery of a standard acetabular press-fit cup in an experimental implant-bone substitute model. An experimental setup was developed to simulate impingement loading via a lever arm representing the femoral component and the lower limb. In one experimental setup 12 strain gauges were embedded at predefined positions in the periphery of the acetabular cup implant inside a tray, using polyurethane composite resin as a bone substitute material. By incremental rotation of the implant tray in steps of 10 and 30 deg, respectively, the strains were measured at evenly distributed positions. With the described method 288 genuine strain values were measured in the periphery of an embedded acetabular cup implant in one experimental setup. In two additional setups the strains were evaluated at different distances from the implant interface. Both in radial and meridional interface directions strain magnitudes reach their peak near the rim of the cup below the impingement site. Values of equatorial strains vary near zero and reach their peaks near the rim of the cup on either side and in some distance from the impingement site. Interestingly, the maximum of averaged radial strains does not occur, as expected, close to the interface but at an interface offset of 5.6 mm. With the described experimental setup it is now possible to measure and display the three-dimensional strain distribution in the interface and the periphery of an embedded acetabular cup implant. The current study provides the first experimental proof of the high local stresses gradients in the direct vicinity of the impingement site. The results of the current study help for a better understanding of the impingement mechanism and its impact on acetabular cup stability.

FIGURES IN THIS ARTICLE
<>
Copyright © 2012 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 5

Measurements of radial strains at different latitude angles (10 deg, 20 deg, 30 deg, and 40 deg) at an interface offset of 3.6 mm

Grahic Jump Location
Figure 1

Experimental setup; (a) ground plate; (b) rotatable implant tray; (c) self-restraining hand winch mounted to a sled; (d) lever arm (femoral component); (e) plunger mounted to a sled

Grahic Jump Location
Figure 2

Modular hip implant system (ESKA Implants GmbH & Co, Lübeck, Germany); hemispherical cup composed of a metal socket (type 2000, size 7, OD 68 mm, material CoCrMo, TiNb coat.) and a custom made metal insert (size 7, ID 32 mm); metal head (OD 32 mm, cone 12/14 mm, material CoCrMo)

Grahic Jump Location
Figure 3

Polar coordinate system; describes the location of the measurement points at the hemispherical interface by latitude and meridian angles; a local coordinate system at the interface is used to define the strain gauge orientation in radial, meridional, and equatorial directions; the meridional and equatorial directions are tangential to the hemispherical interface

Grahic Jump Location
Figure 4

X-rays of all three experimental setups; show the positions of the strain gauges at different latitude angles of 10 deg, 20 deg, 30 deg, and 40 deg in the periphery of an embedded acetabular cup implant, respectively; because of the small size of the strain gauges only the connecting wires can be seen; (a) First experimental setup; double stack strain gauges were applied directly to the interface (0 mm); single strain gauges were placed at a radial offset of 3.6 mm to the interface; (b) Second experimental setup; double stack strain gauges were applied at a radial offset of 2 mm to the interface; single strain gauges were placed at a radial offset of 5.6 mm to the interface; (c) Third experimental setup; double stack strain gauges were applied at a radial offset of 3.6 mm to the interface; single strain gauges were placed at a radial offset of 7.2 mm to the interface

Grahic Jump Location
Figure 10

Meridional strains measured at the impingement site at different latitude angles (10 deg, 20 deg, 30 deg, and 40 deg) at different interface offsets of 0, 2, and 3.6 mm; the horizontal lines show the average values for each interface offset

Grahic Jump Location
Figure 6

Distribution of radial strains; range of latitude angles 10 deg – 40 deg; interface offset 3.6 mm

Grahic Jump Location
Figure 7

Radial strains measured at the impingement site at different latitude angles (10 deg, 20 deg, 30 deg, and 40 deg) at different interface offsets of 3.6, 5.6, and 7.2 mm; the horizontal lines show the average values for each interface offset

Grahic Jump Location
Figure 8

Measurement of meridional strains at different latitude angles (10 deg, 20 deg, 30 deg, and 40 deg) at an interface offset of 3.6 mm

Grahic Jump Location
Figure 9

Distribution of meridional strains; range of latitude angles 10 deg – 40 deg; interface offset 3.6 mm

Grahic Jump Location
Figure 11

Measurement of equatorial strains at different latitude angles (10 deg, 20 deg, 30 deg, and 40 deg) at an interface offset of 3.6 mm

Grahic Jump Location
Figure 12

Distribution of equatorial strains; range of latitude angles 10 deg – 40 deg; interface offset 3.6 mm

Grahic Jump Location
Figure 13

Equatorial strains measured at the impingement site at different latitude angles (10 deg, 20 deg, 30 deg, and 40 deg) at different interface offsets of 0, 2, and 3.6 mm

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In