Journal of Shoulder and Elbow Arthroplasty (Mar 2023)

The Reverse Shoulder Arthroplasty Angle in MRI: Impact of the Articular Cartilage in the Estimated Inclination of the Inferior Glenoid

  • Rodrigo de Marinis MD,
  • Julio J. Contreras MD,
  • Catalina Vidal PT,
  • Cristóbal Palma MD,
  • Manuela Angulo MD,
  • Alfonso Valenzuela MD,
  • Ricardo Jaña MD,
  • Claudio Calvo MD,
  • Rodrigo Liendo MD,
  • Francisco Soza MD

DOI
https://doi.org/10.1177/24715492231167110
Journal volume & issue
Vol. 7

Abstract

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Purpose To describe the reverse shoulder arthroplasty angle (RSA angle) in magnetic resonance imaging (MRI) and compare the angle formed using bony landmarks (Bony RSA angle or B-RSA angle) with another angle formed using the cartilage margin as reference (Cartilage RSA angle or C-RSA angle). Methods Adult patients with a shoulder MRI obtained in our hospital between July 2020 and July 2021 were included. The C-RSA angle and B-RSA angle were measured. All images were independently assessed by 4 evaluators. Intraclass correlation coefficient (ICC) was determined for the B-RSA and C-RSA to evaluate interobserver agreement. Results A total of 61 patients were included with a median age of 59 years (17-77). C-RSA angle was significantly higher than B-RSA (25.4° ± 0.7 vs 19.5° ± 0.7, respectively) with a P-value <.001 . The overall agreement was considered “good” for C-RSA (ICC = 0.74 [95% CI 0.61-0.83]) and “excellent” for B-RSA angle (ICC = 0.76 [95% CI 0.65-0.85]). Conclusions C-RSA angle is significantly higher than B-RSA angle. In cases without significant glenoid wear neglecting to account for the remaining articular cartilage at the inferior glenoid margin may result in superior inclination of standard surgical guides.