The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Tribology of Prosthetic Joints - Validation of Wear Simulation Methods

Olof Calonius

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Mechanical Engineering, for public examination and debate in Auditorium K216 at Helsinki University of Technology (Espoo, Finland) on the 4th of October, 2002, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-6084-0)   [2564 KB]
Dissertation is also available in print (ISBN 951-666-603-5)

Abstract

In hip and knee arthroplasty, loosening of prosthetic components is the principal reason for expensive and complicated reoperations. Loosening is believed to be caused mainly by tissue reactions to wear particles removed from ultrahigh molecular weight polyethylene bearing surfaces. The tissue reactions, leading to bone loss, depend on the size and amount of the particles. Wear simulators are important in the evaluation of prosthetic joints and their materials. The validation of a simulation is based on the comparison of wear rates and wear mechanisms with clinical findings. Polyethylene wear particles from two different hip simulators, a pin-on-disk hip wear device, and a knee wear simulator, were examined using digital image analysis. The average equivalent circle diameter of the particles was 0.10-0.69 μm, which corresponded well with published clinical studies. The particle size distribution was influenced by crosslinking, counterface roughness, and type of simulation (hip or knee). The kinematics of the hip joint in walking, and of ten contemporary hip simulators was analyzed. To this end, software for computing tracks drawn on the counterface by arbitrary points of the bearing surface, the so-called slide tracks, was developed and experimentally verified. The slide track pattern, produced by many points, illustrated the relative motion. Walking was shown to result in open slide tracks on the center of contact, implying continually changing direction of sliding. This phenomenon, known to be crucial for valid wear simulation, was reproduced by simulators having abduction-adduction motion in addition to flexion-extension motion. The most widely used hip simulator, commonly referred to as biaxial, was found to be actually three-axial. The new method can be further utilized, e.g., for computing an improved wear factor involving the variation of relative motion and contact pressure with location.

This thesis consists of an overview and of the following 6 publications:

  1. Saikko, V., Ahlroos, T. and Calonius, O., A three-axis knee wear simulator with ball-on-flat contact. Wear Vol. 249 (2001), p. 310-315. © 2001 Elsevier Science. By permission.
  2. Saikko, V., Ahlroos, T., Calonius, O. and Keränen, J., Wear simulation of total hip prostheses with polyethylene against CoCr, alumina and diamond-like carbon. Biomaterials Vol. 22 (2001), p. 1507-1514. © 2001 Elsevier Science. By permission.
  3. Saikko, V., Calonius, O. and Keränen, J., Effect of counterface roughness on the wear of conventional and crosslinked ultrahigh molecular weight polyethylene studied with a multidirectional motion pin-on-disk device. J Biomed Mater Res, Vol. 57 (2001), p. 506-512. © 2001 Wiley Periodicals, Inc. By permission.
  4. Calonius, O. and Saikko, V., Analysis of polyethylene particles produced in different wear conditions in vitro. Clin Orthop, Vol. 399 (2002), p. 219-230. © 2002 Lippincott Williams & Wilkins. By permission.
  5. Saikko, V. and Calonius, O., Slide track analysis of the relative motion between femoral head and acetabular cup in walking and in hip simulators. J Biomech Vol. 35 (2002), p. 455-464. © 2002 Elsevier Science. By permission.
  6. Calonius, O. and Saikko, V., Slide track analysis of eight contemporary hip simulator designs. J Biomech Vol. 35 (2002), p. 1439-1450. © 2002 Elsevier Science. By permission.

Keywords: prosthetic joint, polyethylene, wear particles, slide track

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© 2002 Helsinki University of Technology

Last update 2011-05-26