Reduced scapular neck impingement in 145° neck-shaft angle semi-inlay compared with 155° neck-shaft angle inlay reverse total shoulder arthroplasty during active external rotation

Background: The purpose of this study was to measure the distance between the scapular neck and the humeral polyethylene insert in shoulders with a 145° neck-shaft-angle (NSA) semi-inlay reverse total shoulder arthroplasty (rTSA) during active external rotation and to compare it with the distance in...

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Main Authors: Itaru Kawashima, MD, PhD, Norimasa Takahashi, MD, PhD, Keisuke Matsuki, MD, PhD, Ryo Haraguchi, MD, Hayato Ryoki, MD, Thomas W. Wright, MD, Scott A. Banks, PhD
Format: Article
Language:English
Published: Elsevier 2025-07-01
Series:JSES International
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Online Access:http://www.sciencedirect.com/science/article/pii/S2666638325000829
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author Itaru Kawashima, MD, PhD
Norimasa Takahashi, MD, PhD
Keisuke Matsuki, MD, PhD
Ryo Haraguchi, MD
Hayato Ryoki, MD
Thomas W. Wright, MD
Scott A. Banks, PhD
author_facet Itaru Kawashima, MD, PhD
Norimasa Takahashi, MD, PhD
Keisuke Matsuki, MD, PhD
Ryo Haraguchi, MD
Hayato Ryoki, MD
Thomas W. Wright, MD
Scott A. Banks, PhD
author_sort Itaru Kawashima, MD, PhD
collection DOAJ
description Background: The purpose of this study was to measure the distance between the scapular neck and the humeral polyethylene insert in shoulders with a 145° neck-shaft-angle (NSA) semi-inlay reverse total shoulder arthroplasty (rTSA) during active external rotation and to compare it with the distance in shoulders with a 155° NSA inlay rTSA. Methods: Twenty shoulders with 145° NSA semi-inlay rTSA and 18 shoulders with 155° NSA inlay rTSA were analyzed. Each shoulder underwent computed tomography and fluoroscopy. Fluoroscopic images were acquired during the activity, starting from internal rotation at the side and progressing to maximum external rotation, while keeping the shoulder adducted. Using model-image registration techniques, the poses of 3-dimensional models were iteratively adjusted to match their silhouettes with those in the fluoroscopic images. Based on the 3-dimensional kinematics of the implants, the closest distance between the scapular neck and polyethylene insert was computed. The data from 10° internal rotation to 50° external rotation were used for analysis. It was also evaluated whether the distance approached within 1 mm, as it was considered that impingement occurred between the scapular neck and polyethylene insert at this proximity. Results: The distance between the scapular neck and the polyethylene insert significantly decreased as the shoulder externally rotated (P < .001). This distance was significantly larger in shoulders with semi-inlay rTSA compared to those with inlay rTSA (P < .001). The rate of shoulders that approached within 1 mm of distance during activity was significantly lower in the semi-inlay rTSA group than in the inlay rTSA group [20.0% (4/20) vs. 83.3% (15/18), respectively, P < .001]. Conclusions: The distance between the scapular neck and the polyethylene insert during active external rotation was greater in a 145° NSA semi-inlay rTSA compared to a 155° NSA inlay rTSA. This study supports the notion that a 145° NSA semi-inlay rTSA significantly reduces scapular notching compared to a 155° NSA inlay rTSA. However, scapular notching, especially caused by maximum external rotation, should still be considered in shoulders with a 145° NSA semi-inlay rTSA as well, as the distance significantly decreases during external rotation.
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spelling doaj-art-e70b98ff12a1477791a27186225fefeb2025-08-20T03:50:22ZengElsevierJSES International2666-63832025-07-01941244125010.1016/j.jseint.2025.03.001Reduced scapular neck impingement in 145° neck-shaft angle semi-inlay compared with 155° neck-shaft angle inlay reverse total shoulder arthroplasty during active external rotationItaru Kawashima, MD, PhD0Norimasa Takahashi, MD, PhD1Keisuke Matsuki, MD, PhD2Ryo Haraguchi, MD3Hayato Ryoki, MD4Thomas W. Wright, MD5Scott A. Banks, PhD6Department of Orthopaedics Surgery and Sports Medicine, University of Florida, Gainesville, FL, USA; Department of Orthopaedic Surgery, Yachiyo Hospital, Anjo, Japan; Corresponding author: Itaru Kawashima, MD, PhD, Department of Orthopaedics Surgery and Sports Medicine, University of Florida, 3450 Hull Road, Gainesville, FL 32611, USA.Sports Medicine and Joint Center, Funabashi Orthopaedic Hospital, Chiba, JapanSports Medicine and Joint Center, Funabashi Orthopaedic Hospital, Chiba, JapanSports Medicine and Joint Center, Funabashi Orthopaedic Hospital, Chiba, JapanSports Medicine and Joint Center, Funabashi Orthopaedic Hospital, Chiba, JapanDepartment of Orthopaedics Surgery and Sports Medicine, University of Florida, Gainesville, FL, USADepartment of Mechanical &amp; Aerospace Engineering, University of Florida, Gainesville, FL, USABackground: The purpose of this study was to measure the distance between the scapular neck and the humeral polyethylene insert in shoulders with a 145° neck-shaft-angle (NSA) semi-inlay reverse total shoulder arthroplasty (rTSA) during active external rotation and to compare it with the distance in shoulders with a 155° NSA inlay rTSA. Methods: Twenty shoulders with 145° NSA semi-inlay rTSA and 18 shoulders with 155° NSA inlay rTSA were analyzed. Each shoulder underwent computed tomography and fluoroscopy. Fluoroscopic images were acquired during the activity, starting from internal rotation at the side and progressing to maximum external rotation, while keeping the shoulder adducted. Using model-image registration techniques, the poses of 3-dimensional models were iteratively adjusted to match their silhouettes with those in the fluoroscopic images. Based on the 3-dimensional kinematics of the implants, the closest distance between the scapular neck and polyethylene insert was computed. The data from 10° internal rotation to 50° external rotation were used for analysis. It was also evaluated whether the distance approached within 1 mm, as it was considered that impingement occurred between the scapular neck and polyethylene insert at this proximity. Results: The distance between the scapular neck and the polyethylene insert significantly decreased as the shoulder externally rotated (P < .001). This distance was significantly larger in shoulders with semi-inlay rTSA compared to those with inlay rTSA (P < .001). The rate of shoulders that approached within 1 mm of distance during activity was significantly lower in the semi-inlay rTSA group than in the inlay rTSA group [20.0% (4/20) vs. 83.3% (15/18), respectively, P < .001]. Conclusions: The distance between the scapular neck and the polyethylene insert during active external rotation was greater in a 145° NSA semi-inlay rTSA compared to a 155° NSA inlay rTSA. This study supports the notion that a 145° NSA semi-inlay rTSA significantly reduces scapular notching compared to a 155° NSA inlay rTSA. However, scapular notching, especially caused by maximum external rotation, should still be considered in shoulders with a 145° NSA semi-inlay rTSA as well, as the distance significantly decreases during external rotation.http://www.sciencedirect.com/science/article/pii/S2666638325000829Rotator cuff tearReverse total shoulder arthroplastyArthroplastyShoulderScapular notchingImpingement
spellingShingle Itaru Kawashima, MD, PhD
Norimasa Takahashi, MD, PhD
Keisuke Matsuki, MD, PhD
Ryo Haraguchi, MD
Hayato Ryoki, MD
Thomas W. Wright, MD
Scott A. Banks, PhD
Reduced scapular neck impingement in 145° neck-shaft angle semi-inlay compared with 155° neck-shaft angle inlay reverse total shoulder arthroplasty during active external rotation
JSES International
Rotator cuff tear
Reverse total shoulder arthroplasty
Arthroplasty
Shoulder
Scapular notching
Impingement
title Reduced scapular neck impingement in 145° neck-shaft angle semi-inlay compared with 155° neck-shaft angle inlay reverse total shoulder arthroplasty during active external rotation
title_full Reduced scapular neck impingement in 145° neck-shaft angle semi-inlay compared with 155° neck-shaft angle inlay reverse total shoulder arthroplasty during active external rotation
title_fullStr Reduced scapular neck impingement in 145° neck-shaft angle semi-inlay compared with 155° neck-shaft angle inlay reverse total shoulder arthroplasty during active external rotation
title_full_unstemmed Reduced scapular neck impingement in 145° neck-shaft angle semi-inlay compared with 155° neck-shaft angle inlay reverse total shoulder arthroplasty during active external rotation
title_short Reduced scapular neck impingement in 145° neck-shaft angle semi-inlay compared with 155° neck-shaft angle inlay reverse total shoulder arthroplasty during active external rotation
title_sort reduced scapular neck impingement in 145° neck shaft angle semi inlay compared with 155° neck shaft angle inlay reverse total shoulder arthroplasty during active external rotation
topic Rotator cuff tear
Reverse total shoulder arthroplasty
Arthroplasty
Shoulder
Scapular notching
Impingement
url http://www.sciencedirect.com/science/article/pii/S2666638325000829
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