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Radiologic Comparison of Humeral Position according to the Implant Designs Following Reverse Shoulder Arthroplasty: Analysis between Medial Glenoid/Medial Humerus, Lateral Glenoid/Medial Humerus, and Medial Glenoid/Lateral Humerus Designs
Clinics in Shoulder and Elbow 2018;21:192-199
Published online December 1, 2018
© 2018 Korean Shoulder and Elbow Society.

Nam Su Cho, Ju Hyun Nam, Se Jung Hong, Tae Wook Kim, Myeong Gu Lee, Jung Tae Ahn, Yong Girl Rhee

Shoulder & Elbow Clinic, Department of Orthopaedic Surgery, College of Medicine, Kyung Hee University, Seoul, Korea
Correspondence to: Nam Su Cho
Department of Orthopaedic Surgery, Kyung Hee University Hospital at Gangdong, College of Medicine, Kyung Hee University, 892 Dongnam-ro, Gangdong-gu, Seoul 05278, Korea
Tel: +82-2-440-6154, Fax: +82-2-440-7498, E-mail: nscos1212@empas.com, ORCID: http://orcid.org/0000-0003-1643-1641
IRB approval: Kyung Hee University Hospital at Gangdong (KHNMC 2018-06-010).
Received June 10, 2018; Revised July 27, 2018; Accepted July 30, 2018.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
 Abstract
Background: The currently available reverse shoulder arthroplasty (RSA) designs can be classified into medial glenoid/medial humerus (MGMH), lateral glenoid/medial humerus (LGMH), and medial glenoid/lateral humerus (MGLH) prosthesis designs. The purpose of this study was to radiologically analyze the effect of different RSA designs on humeral position following RSA.
Methods: A total of 50 patients who underwent primary RSA were retrospectively analyzed. Among 50 patients, 33 patients (group A: MGMH) underwent RSA with Aequalis system (Wright, Inc, Bloomington, MN, USA), 6 (group B: LGMH) with Aequalis system using bony increased offset, and 11 (group C: MGLH) with Aequalis Ascend Flex system. The acromiohumeral distance, acromioepiphyseal distance (AED), lateral humeral offset (LHO), LHO from the center of rotation (LHOCOR), and deltoid length were radiologically measured to quantify the distalization and lateralization of the humerus.
Results: The increment in postoperative AED was 19.92 짹 3.93 mm in group A, 24.52 짹 5.25 mm in group B, and 25.97 짹 5.29 mm in group C, respectively (p=0.001). The increment in postoperative LHO was 0.13 짹 6.30 mm, 8.00 짹 12.14 mm, and 7.42 짹 6.88 mm, respectively (p=0.005). The increment in postoperative LHOCOR was 20.76 짹 6.06 mm, 22.04 짹 5.15 mm, and 28.11 짹 4.14 mm, respectively (p=0.002).
Conclusions: The radiologic analysis of the effect of different RSA designs on humeral position following RSA showed significant differences in the increment in postoperative AED, LHO, and LHOCOR between the 3 groups. Therefore, MGLH design seems to be more effective for humeral distalization and lateralization compared to original Grammont design.
Keywords : Shoulder; Cuff tear arthropathy; Massive rotator cuff tear; Reverse shoulder arthroplasty; Implant design