In vivo reverse total shoulder arthroplasty contact mechanics

Madeleine L Van de Kleut; Chaithanya Nair; Jaques S Milner; David W Holdsworth; George S Athwal; Matthew G Teeter

doi:10.1016/j.jse.2020.05.036

In vivo reverse total shoulder arthroplasty contact mechanics

J Shoulder Elbow Surg. 2021 Feb;30(2):421-429. doi: 10.1016/j.jse.2020.05.036. Epub 2020 Jun 21.

Authors

Madeleine L Van de Kleut¹, Chaithanya Nair², Jaques S Milner³, David W Holdsworth⁴, George S Athwal⁵, Matthew G Teeter⁶

Affiliations

¹ Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada; School of Biomedical Engineering, Western University, London, ON, Canada; Lawson Health Research Institute, London, ON, Canada. Electronic address: mvandekl@uwo.ca.
² Faculty of Science, Western University, London, ON, Canada.
³ Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada.
⁴ Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada; Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada.
⁵ Lawson Health Research Institute, London, ON, Canada; Roth|McFarlane Hand and Upper Limb Center, Department of Surgery, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada.
⁶ Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada; Lawson Health Research Institute, London, ON, Canada; Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada; Roth|McFarlane Hand and Upper Limb Center, Department of Surgery, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada.

PMID: 32580021
DOI: 10.1016/j.jse.2020.05.036

Abstract

Background: Several in vitro studies have investigated the biomechanics of reverse total shoulder arthroplasty (RTSA); however, few in vivo studies exist. The purpose of this study was to examine in vivo RTSA contact mechanics in clinically relevant arm positions. Our hypothesis was that contact would preferentially occur in the inferior region of the polyethylene liner.

Methods: Forty patients receiving a primary RTSA were recruited for a prospective cohort study. All patients received the same implant design with a nonretentive liner. Stereo radiographs were taken at maximal active range of motion. Model-based radiostereometric analysis was used to identify implant position. Contact area between the polyethylene and glenosphere was measured as the geometric intersection of the 2 components and compared with respect to polyethylene liner size, arm position, and relative position within the liner.

Results: There were no differences in the proportion of contact area in any arm position between polyethylene liner sizes, ranging from 30% ± 17% to 38% ± 23% for 36-mm liners and 32% ± 21% to 41% ± 25% for 42-mm liners. Contact was equally distributed between the superior and inferior halves of the liner at each arm position (P = .06-.79); however, greater contact area was observed in the outer radius of the liner when the arm was flexed (P = .002).

Conclusion: This study highlights that contact mechanics are similar between 36- and 42-mm liners. Contact area is generally equally distributed throughout the liner across the range of motion and not preferentially in the inferior region as hypothesized.

Keywords: BIO-RSA; Reverse total shoulder arthroplasty; biomechanics; contact mechanics; glenosphere lateralization; radiostereometric analysis.

MeSH terms

Arthroplasty, Replacement, Shoulder*
Humans
Prospective Studies
Prosthesis Design
Range of Motion, Articular
Shoulder Joint* / diagnostic imaging
Shoulder Joint* / surgery