Location and thickness of delaminated rotator cuff tears: cross- sectional analysis with surgery record review Motoki Tanaka, MD a , Akimoto Nimura, MD, PhD b, *, Norimasa Takahashi, MD, PhD c , Tomoyuki Mochizuki, MD, PhD d , Ryuichi Kato, MD, PhD b,e , Hiroyuki Sugaya, MD, PhD c , Keiichi Akita, MD, PhD a a Department of Clinical Anatomy, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan b Department of Functional Joint Anatomy, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan c Shoulder and Elbow Center, Funabashi Orthopaedic Hospital, Chiba, Japan d Department of Orthopaedic Surgery, Nissan Tamagawa Hospital, Tokyo, Japan e JA Kyosai Research Institute, Tokyo, Japan ARTICLE INFO Keywords: Rotator cuff tear Delamination Arthroscopic image Superficial layer Deep layer Joint capsule Level of evidence: Anatomy Study, In Vivo Background: To facilitate better treatment, we analyzed morphologic features of delamination from the viewpoint of the location of delamination and the thickness of each layer. Materials and Methods: Of 270 shoulders that consecutively underwent arthroscopic rotator cuff repair, 210 were included. During the operation, the surgeon assessed the size of the rotator cuff tear, deter- mined the presence and location of delamination, and compared the thickness between superficial and deep layers if delamination was present. Immediately after the operation, the surgeon wrote down the data in the record form. The authors retrospectively referred to these surgical records to investigate those items. Results: Delamination was found in 111 of 210 shoulders. The overall preoperative Constant score did not significantly differ between the 2 groups. In terms of the location, 7.2% cases had delamination in the anterior part, 74.8% in the posterior part, and 18.0% in both parts (Fleiss κ = 0.9). The larger the rotator cuff tear, the more frequently the delamination was limited to the posterior part (trend P = .001). As for layer thickness comparison, 40.0% of the shoulders with small tears, 38.8% with medium tears, 66.0% with large tears, and 80.0% with massive tears had a thicker deep layer than superficial layer (Fleiss κ = 0.9). The larger the size of the rotator cuff tear, the more frequently the deep layer was thicker than the su- perficial layer (trend P = .001). Conclusions: The larger the rotator cuff tear, the more carefully shoulder surgeons should observe and treat the posterior and deep part of delamination. © 2017 The Author(s). Published by Elsevier Inc. on behalf of American Shoulder and Elbow Surgeons. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/). In terms of treatment of rotator cuff tears, precise perception of the anatomy of the rotator cuff insertion is an important element and facilitates correct repair, according to the shape of the torn site, thereby improving the prognosis. Although delamination, defined as “distal layer separation and normal horizontal retraction of the deep layer” (Fig. 1), is one of the negative prognostic factors, 2,7,8,18 its pathologic process remains unclear. In various approaches to di- agnosis of delamination, the prevalence of delamination has been reported to vary among studies from 5.2% (magnetic resonance imaging by Walz et al 24 ) to 92.0% (arthroscopic surgery by Han et al 9 ). 3,7,12,20 To date, clinical features of delamination are still unclear because of the paucity of previous reports. Clark and Harryman 4 noted that the deepest layer of the normal rotator cuff consisted not only of musculotendinous units but also of the capsule of the shoul- der joint. Nimura et al previously reported that the width of the capsular attachment on the humerus varies according to the location. 17 Based on these facts, the deep layer of delamination should consist of both the musculotendinous and capsular structures, and the histologic composition of the deep layer should differ from that of the superficial layer. Thus, we hypothesized that the occur- rence of delamination varies according to the anteroposterior location, and the thickness of each layer is changed in relation to the expansion of the torn site of the rotator cuff tendon. The ob- jective of this study was to analyze the morphologic features of delamination by retrospectively reviewing surgical records from the viewpoint of the location of the delamination and the thickness of This study was approved by the Institutional Review Board of Funabashi Ortho- paedic Hospital (No. 2015038), and all of the patients provided informed written consent. * Corresponding author: Akimoto Nimura, MD, PhD, Department of Functional Joint Anatomy, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan. E-mail address: nimura.orj@tmd.ac.jp (A. Nimura). https://doi.org/10.1016/j.jses.2017.11.004 2468-6026/© 2017 The Author(s). Published by Elsevier Inc. on behalf of American Shoulder and Elbow Surgeons. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). JSES Open Access 2 (2018) 84–90 Contents lists available at ScienceDirect JSES Open Access journal homepage: www.elsevier.com/locate/jses