Capsular attachment of the subregions of rotator cuff muscles

Takuma Yuri,Hiromi Fujii,Saori Yoshida,Hiroto Kobayashi,Yuta Takano,Akira Naito,Yoshiro Kiyoshige

doi:10.1007/s00276-019-02288-7

Abstract

PurposeThis study aimed to morphologically and histologically investigate the relationship between deep subregions of the rotator cuff muscle and shoulder joint capsule as well as the relationship between the rotator cuff tendon or capsule and bony insertion.MethodsWe examined 13 shoulders of embalmed cadavers and measured the capsular attachments and footprints macroscopically. We also histologically examined the fibres in three shoulders.ResultsLoose attachment, which was less tight with spaced connective tissue, and firm attachment, which was tight with dense connective tissue, were found under the surface of the supraspinatus and infraspinatus. The anterior-deep and posterior-deep subregions of the supraspinatus and the middle partition and inferior partition of the infraspinatus formed firm attachments to the capsule. The mean areas of firm attachment for the anterior-deep subregion, posterior-deep subregion and middle partition were 118.8 mm2, 267.8 mm2 and 399.3 mm2, respectively, while the area of the inferior partition was small. The transverse fibres were located just lateral to the medial edge of the firm attachment area. The thick capsule had a substantial footprint. Both tendon fibres and the capsule inserted into the superior and middle facets through the attachment fibrocartilage.ConclusionsThe posterior-deep subregion of the supraspinatus and middle partition of the infraspinatus evenly occupied the capsular attachment area. The transverse fibres were located just lateral to the medial edge of the firm attachment area, and the thick capsule had a substantial footprint. Both tendon fibres and the capsule inserted into the superior and middle facets through the attachment fibrocartilage.

Highlights

Many investigators have mentioned the relationship between the rotator cuff tendon and gleno-humeral joint capsule [10, 12, 16] since Clark precisely studied it [5, 6]
We obtained coronal sections parallel to the tendons of the anterior region and posterior region of the supraspinatus according to Roh et al and Kim et al [10, 17] and sections of the superior, middle, and inferior partitions of the infraspinatus according to Fabrizio and Clemente as well as Bacle et al [1, 7]
To compare the areas of loose and firm attachments of the supraspinatus subregions and infraspinatus partitions, we performed a Kruskal–Wallis test followed by a Bonferroni post hoc test

Summary

Introduction

Many investigators have mentioned the relationship between the rotator cuff tendon and gleno-humeral joint capsule [10, 12, 16] since Clark precisely studied it [5, 6]. Fabrizio and Clemente as well as Bacle et al independently divided the infraspinatus muscle into three partitions: the superior, middle, and inferior partitions [1, 7]. Both supraspinatus subregions and infraspinatus partitions are supported by intra-muscular innervations [7, 9]. Yuri et al and Kuwahara et al demonstrated that these subregions are functionally distinct [11, 18] and that the posterior-deep subregion and middle partition have a similar function in external rotation [11] These observations suggest that the posterior-deep subregion and middle partition independently contribute to joint movement. We hypothesized that the posterior-deep subregion of the supraspinatus and the middle partition of the infraspinatus formed capsular attachment since the posterior-deep subregion and middle partition have similar functions [11]

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