1. Virtual assessment of internal rotation in reverse shoulder arthroplasty based on statistical shape models of scapular size
- Author
-
Lisa A. Galasso, MD, Alexandre Lädermann, MD, Brian C. Werner, MD, Stefan Greiner, MD, Nick Metcalfe, BS, Patrick J. Denard, MD, Albert Lin, MD, Anthony Romeo, MD, Anup Shah, MD, Asheesh Bedi, MD, Benjamin W. Sears, MD, Bradford Parsons, MD, Brandon Erickson, MD, Bruce Miller, MD, Christopher O’Grady, MD, Daniel Davis, MD, David Lutton, MD, Dirk Petre, MD, Evan Lederman, MD, Joern Steinbeck, MD, John Tokish, MD, Julia Lee, MD, Justin Griffin, MD, Kevin Farmer, MD, Matthew Provencher, MD, Michael Bercik, MD, Michael Kissenberth, MD, Patric Raiss, MD, Peter Habermeyer, MD, Philipp Moroder, MD, Robert Creighton, MD, Russell Huffman, MD, Sam Harmsen, MD, Sven Lichtenberg, MD, Tim Lenters, MD, Tyrrell Burrus, MD, and Tyler Brolin, MD
- Subjects
Shoulder arthroplasty ,Virtual ,Preoperative planning ,Internal rotation ,Range of motion ,Lateralization ,Orthopedic surgery ,RD701-811 ,Diseases of the musculoskeletal system ,RC925-935 - Abstract
Background: The purpose of this study was to assess impingement-free internal rotation (IR) in a virtual reverse shoulder arthroplasty simulation using a Statistical Shape Model based on scapula size. Methods: A database of over 10,000 scapulae utilized for preoperative planning for shoulder arthroplasty was analyzed with a Statistical Shape Model to obtain 5 scapula sizes including the mean and 2 standard deviations. For each scapula model, one glenosphere size (33-42 mm) was selected as the best fit based on consensus among 3 shoulder surgeons. Virtual implantation variables included 1) lateral offset (0-12 mm in 2-mm increments), 2) inferior eccentricity (0, 2.5, 5, and 7.5 mm), and 3) posterior eccentricity (0, 2.5, and 5 mm). The neck shaft angle was fixed at 135° with an inlay design humeral prosthesis. IR at the side (IR0) and in abduction (IRABD) were then simulated. Results: Maximum impingement-free IR0 was reached with increasing inferior offset in combination with increasing lateralization. Lateralization was the most important variable in increasing impingement-free IRABD. Maximum IRABD was reached at 4-6 mm of lateralization with smaller scapula (−2 to 0 standard deviation). Increasing lateralization up to 12 mm continues to increase IRABD for larger-sized scapula (+1 to +2 standard deviation). Optimal inferior offset and lateralization to maximize IR did have a small loss of external rotation in neutral abduction. There was no loss of external rotation in 60° of abduction. Conclusion: In a virtual model, the glenosphere position required to maximize IR varied by scapula size. For smaller scapulae, maximum IR0 was reached with a combination of 2.5-mm inferior offset and 0- 4 mm of lateralization. For larger scapulae, maximum IR0 was reached with a combination of 2.5 mm of inferior offset and 4 mm of lateralization. The amount of lateralization required to maximize IRABD also varies by scapula size. Maximum IRABD was reached in smaller scapula with 4-6 mm of lateralization and at least 12 mm of lateralization in larger scapula. These findings may be applied in the clinical decision-making process knowing that impingement-free IR and IRABD can be maximized with combinations of inferior offset and lateralization based on scapula size with minimal effect on external rotation and external rotation in 60° of abduction.
- Published
- 2024
- Full Text
- View/download PDF