Trabecular bone density distribution in the scapula of patients undergoing reverse shoulder arthroplasty

Joshua H. Ehrlich, BHSc; Valeria Vendries, MSc; Timothy J. Bryant, PhD; Michael J. Rainbow, PhD; Heidi L. Ploeg, PhD; Ryan T. Bicknell, MD, MSc, FRCSC

JSES International (Jan 2022)

Trabecular bone density distribution in the scapula of patients undergoing reverse shoulder arthroplasty

Joshua H. Ehrlich, BHSc,
Valeria Vendries, MSc,
Timothy J. Bryant, PhD,
Michael J. Rainbow, PhD,
Heidi L. Ploeg, PhD,
Ryan T. Bicknell, MD, MSc, FRCSC

Affiliations

Joshua H. Ehrlich, BHSc: Human Mobility Research Centre, Queen’s University, Kingston, ON, Canada
Valeria Vendries, MSc: Human Mobility Research Centre, Queen’s University, Kingston, ON, Canada
Timothy J. Bryant, PhD: Human Mobility Research Centre, Queen’s University, Kingston, ON, Canada; Department of Mechanical and Materials Engineering, Queen’s University, Kingston, ON, Canada
Michael J. Rainbow, PhD: Human Mobility Research Centre, Queen’s University, Kingston, ON, Canada; Department of Mechanical and Materials Engineering, Queen’s University, Kingston, ON, Canada
Heidi L. Ploeg, PhD: Human Mobility Research Centre, Queen’s University, Kingston, ON, Canada; Department of Mechanical and Materials Engineering, Queen’s University, Kingston, ON, Canada
Ryan T. Bicknell, MD, MSc, FRCSC: Human Mobility Research Centre, Queen’s University, Kingston, ON, Canada; Department of Mechanical and Materials Engineering, Queen’s University, Kingston, ON, Canada; Division of Orthopaedic Surgery, Department of Surgery, Kingston General Hospital, Kingston, ON, Canada; Corresponding author: Ryan T. Bicknell, MD, MSc, FRCS(C), Kingston Health Sciences Centre Kingston General Hospital Site, Watkins 3 76 Stuart Street, Kingston, ON, Canada K7L 2V7.

Journal volume & issue: Vol. 6, no. 1
pp. 32 – 39

Abstract

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Background: To improve implant survival after reverse shoulder arthroplasty (RSA), surgeons need to maximize screw fixation. However, bone density variation and distribution within the scapula are not well understood as they relate to RSA. The three columns of bone in the scapula surrounding the glenoid fossa are the lateral border, the base of the coracoid process, and the spine of the scapula. In our previous study by Daalder et al on cadaveric specimens, the coracoid column was significantly less dense than the lateral border and spine. This study’s objective was to verify whether these results are consistent with computer tomography (CT) scan information from patients undergoing RSA. Methods: Two-dimensional axial CT images from twelve patients were segmented, and a three-dimensional digital model of the scapula was subsequently created using Mimics 17.0 Materialise Software (Leuven, Belgium). Hounsfield unit (HU) values representing cortical bone were filtered out to determine the distributions of trabecular bone density. An analysis of variance with post hoc Bonferroni tests determined the differences in bone density between the columns of bone in the scapula. Results: The coracoid superolateral (270 ± 45.6 HU) to the suprascapular notch was significantly less dense than the inferior (356 ± 63.6 HU, P = .03, ds = 1.54) and anterosuperior portion of the lateral border (353 ± 68.9 HU, P = .04, ds = 1.42) and the posterior (368 ± 70 HU, P = .007, ds = 1.65) and anterior spine (370 ± 78.9 HU, P = .006, ds = 1.54). Discussion/Conclusion: The higher-density bone in the spine and lateral border compared with the coracoid region may provide better bone purchase for screws when fixing the glenoid baseplate in RSA. This is in agreement with our previous study and indicates that the previous cadaveric results are applicable to clinical CT scan data. When these studies are taken together, they provide robust evidence for clinical applications, including having surgeons aim screws for higher-density regions to increase screw fixation, which may decrease micromotion and improve implant longevity.

Published in JSES International

ISSN: 2666-6383 (Online)
Publisher: Elsevier
Country of publisher: United States
LCC subjects: Medicine: Surgery: Orthopedic surgery; Medicine: Internal medicine: Specialties of internal medicine: Diseases of the musculoskeletal system
Website: https://www.journals.elsevier.com/jses-international

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