The effect of hemiarthroplasty implant modulus on contact mechanics: an experimental investigation

Carolyn J Berkmortel; Jakub Szmit; G Daniel Langohr; Graham J W King; James A Johnson

doi:10.1016/j.jse.2021.06.009

The effect of hemiarthroplasty implant modulus on contact mechanics: an experimental investigation

J Shoulder Elbow Surg. 2021 Dec;30(12):2845-2851. doi: 10.1016/j.jse.2021.06.009. Epub 2021 Jul 20.

Authors

Carolyn J Berkmortel¹, Jakub Szmit², G Daniel Langohr³, Graham J W King², James A Johnson⁴

Affiliations

¹ Department of Mechanical and Materials Engineering, Western University, London, ON, Canada.
² Bioengineering Laboratory, Roth McFarlane Hand and Upper Limb Centre, Lawson Health Research Institute, St Joseph's Health Care, London, ON, Canada; Department of Surgery, Western University, London, ON, Canada.
³ Department of Mechanical and Materials Engineering, Western University, London, ON, Canada; Bioengineering Laboratory, Roth McFarlane Hand and Upper Limb Centre, Lawson Health Research Institute, St Joseph's Health Care, London, ON, Canada.
⁴ Department of Mechanical and Materials Engineering, Western University, London, ON, Canada; Bioengineering Laboratory, Roth McFarlane Hand and Upper Limb Centre, Lawson Health Research Institute, St Joseph's Health Care, London, ON, Canada; Department of Surgery, Western University, London, ON, Canada. Electronic address: jajohnso@uwo.ca.

PMID: 34293420
DOI: 10.1016/j.jse.2021.06.009

Abstract

Background: Hemiarthroplasties cause damage to the cartilage that they articulate against, which is a major limitation to their use. This study investigated the use of lower-stiffness materials to determine whether they improve hemiarthroplasty contact mechanics and thus reduce the risk of cartilage damage.

Methods: Eleven fresh-frozen cadaveric upper extremities were disarticulated and fixed in a custom-built jig that applied a static load of 50 N to the radiocapitellar joint. Flexion angles of 0°, 45°, 90°, and 135° were tested with radial head implants made of cobalt-chrome (CoCr) and ultrahigh-molecular-weight polyethylene (UHMWPE) compared with the native radial head. A Tekscan thin-film sensor was used to measure the contact area and contact pressure between the radius and capitellum.

Results: UHMWPE and CoCr were too stiff in the application of hemiarthroplasty, resulting in lower contact areas and higher contact pressures relative to the native joint. The native contact area was, on average, 42 ± 20 mm² larger than that of UHMWPE (P < .001) and 55 ± 24 mm² larger than that of CoCr (P < .001). UHMWPE had a contact area 13 ± 10 mm² greater than that of CoCr (P = .014).

Discussion and conclusion: This study shows that even though UHMWPE has a stiffness several times lower than CoCr, the use of this material in hemiarthroplasty led to only a minor improvement in contact mechanics. Neither implant restored contact similar to the native articulation. Investigations into new materials to improve the contact mechanics of hemiarthroplasty should focus on materials with a lower stiffness than UHMWPE.

Keywords: Radial head; cadaveric; cartilage; contact area; contact pressure; hemiarthroplasty; material; stiffness.

MeSH terms

Biomechanical Phenomena
Cadaver
Elbow Joint* / surgery
Elbow Prosthesis*
Hemiarthroplasty*
Humans
Prosthesis Design
Radius / surgery