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Humeral Insertion of the Supraspinatus and InfraspinatusNew Anatomical Findings Regarding the Footprint of the Rotator Cuff
Tomoyuki Mochizuki, MD1; Hiroyuki Sugaya, MD2; Mari Uomizu, MD3; Kazuhiko Maeda, MD2; Keisuke Matsuki, MD4; Ichiro Sekiya, MD1; Takeshi Muneta, MD5; Keiichi Akita, MD3
1 Section of Orthopaedic Surgery, Division of Cartilage Regeneration, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
2 Funabashi Orthopaedic Sports Medicine Center, 1-833 Hazama, Funabashi, Chiba 274-0822, Japan
3 Unit of Clinical Anatomy, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan. E-mail address for K. Akita: akita.fana@tmd.ac.jp
4 Department of Orthopedic Surgery, Teikyo University Chiba Medical Center, 3426-3 Anegasaki Ichihara, Chiba 299-0111, Japan
5 Section of Orthopaedic Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
View Disclosures and Other Information
Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.
Investigation performed at the Unit of Clinical Anatomy, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan

The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2008 May 01;90(5):962-969. doi: 10.2106/JBJS.G.00427
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Abstract

Background: It is generally believed that the supraspinatus is the most commonly involved tendon in rotator cuff tears. Clinically, however, atrophy of the infraspinatus muscle is frequently observed in patients with even small to medium-size rotator cuff tears. This fact cannot be fully explained by our current understanding of the anatomical insertions of the supraspinatus and infraspinatus. The purpose of this study was to reinvestigate the humeral insertions of these tendons.

Methods: The study included 113 shoulders from sixty-four cadavers. The humeral insertion areas of the supraspinatus and infraspinatus were investigated in ninety-seven specimens. In sixteen specimens, all muscular portions of the supraspinatus and infraspinatus were removed, leaving the tendinous portions intact, in order to define the specific characteristics of the tendinous portion of the muscles. Another twenty-six shoulders were used to obtain precise measurements of the footprints of the supraspinatus and infraspinatus.

Results: The supraspinatus had a long tendinous portion in the anterior half of the muscle, which always inserted into the anteriormost area of the highest impression on the greater tuberosity and which inserted into the superiormost area of the lesser tuberosity in 21% of the specimens. The footprint of the supraspinatus was triangular in shape, with an average maximum medial-to-lateral length of 6.9 mm and an average maximum anteroposterior width of 12.6 mm. The infraspinatus had a long tendinous portion in the superior half of the muscle, which curved anteriorly and extended to the anterolateral area of the highest impression of the greater tuberosity. The footprint of the infraspinatus was trapezoidal in shape, with an average maximum medial-to-lateral length of 10.2 mm and an average maximum anteroposterior width of 32.7 mm.

Conclusions: The footprint of the supraspinatus on the greater tuberosity is much smaller than previously believed, and this area of the greater tuberosity is actually occupied by a substantial amount of the infraspinatus.

Clinical Relevance: The present study suggests that rotator cuff tears that were previously thought to involve only the supraspinatus tendon may in fact have had a substantial infraspinatus component as well.

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    References

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Tomoyuki Mochizuki, MD
    Posted on November 04, 2008
    Dr. Mochizuki and colleagues respond to Dr. Park
    Section of Orthopaedic Surgery, Division of Cartilage Regeneration, Tokyo Med. and Dent. Univ.

    We thank Dr. Park for his letter and comments and we appreciate the opportunity to clarify a number of facts described in our paper.

    Regarding the border between the supraspinatus and infraspinatus muscles, Dr. Park states that several studies have observed that the oblique fibers of both the supraspinatus and infraspinatus fuse or interdigitate as they converge onto the greater tuberosity (1-4). In our study, we removed the overlying coracohumeral ligament and the loose connective tissues, which enabled us to detect a distinct border between the supraspinatus and infraspinatus and to separate them by precisely tracing the anterior margin of the superior tendinous portion of the infraspinatus. We did not observe interdigitated fibers between the supraspinatus and infraspinatus. We discussed in our paper that these observations which differ from previous reports were attributable to the differences in dissection methods. Recently,we have reconfirmed the validity of our findings by examining histological sections around the insertion of the supraspinatus and infraspinatus. We will report these histological findings in another paper.

    Regarding the insertion area of the supraspinatus, Dr. Park proposed that the insertion area of the supraspinatus designated by us represents an anterior supraspinatus-"only" insertion area. This is not correct. We represented the entire area of the supraspinatus insertion. Roh et al reported that the supraspinatus muscle is composed of anterior and posterior muscle bellies (4). We also recognized and described these two separable structures of the supraspinatus in our paper as follows: the supraspinatus tendon was composed of two portions-- the anterior half was long and thick, and the posterior half was short and thin (Fig. 3, C); most of the muscle fibers of the supraspinatus, especially those of its superficial layer, ran anterolaterally toward the anterior tendinous portion, while the rest of the fibers from the deep layer ran laterally toward the medial margin of the highest impression margin on the greater tuberosity (Figs. 1; 2, A; and 3, A).

    Most of the supraspinatus muscle fibers which run anterolaterally and converge at the anterior tendinous portion [which correspond to the anterior supraspinatus described by Roh et al.(4)] were inserted into the anterior part of the triangular footprint of the supraspinatus, and the rest of the muscle fibers corresponding to the posterior infraspinatus by Roh et al.(4) were inserted into the medial margin of the triangular shaped footprint of the supraspinatus.

    References

    1. Clark JM, Harryman II DT. Tendons, ligaments, and capsule of the rotator cuff. Gross and microscopic anatomy. J Bone Joint Surg 1992;74A:713-25.

    2. Miller SL, Gladstone JN, Cleeman E, et al. Anatomy of the posterior rotator interval: implications for cuff mobilization. Clin Orthop 2003;408:152-6.

    3. Minagawa H, Itoi E, Konno N, et al. Humeral Attachment of the Supraspinatus and Infraspinatus Tendons: An Anatomic Study. Arthroscopy 1998;14:302-6.

    4. Roh MS, Wang VM, April EW, et al. Anterior and posterior musculotendinous anatomy of the supraspinatus. J Shoulder Elbow Surg 2000;9:436-40.

    Maxwell C Park
    Posted on July 25, 2008
    Humeral Insertion of the Supraspinatus and Infraspinatus
    Southern California Permanente Medical Group, Woodland Hills, CA

    To the Editor;

    I read with interest the study by Mochizuki et al, “Humeral Insertion of the Supraspinatus and Infraspinatus: New Anatomical Findings Regarding the Footprint of the Rotator Cuff”.This study attempts to redefine the characterization of how the supraspinatus and infraspinatus insert onto the greater tuberosity. This has obvious implications when attempting to repair a torn rotator cuff tendon involving these muscles.

    Several studies have observed how the oblique fibers from both supraspinatus and infraspinatus “fuse” or “interdigitate” as they converge onto the greater tuberosity(1-4). I agree that Figures 5 and 6 may show the supraspinatus insertion area, but perhaps this should be qualified as an anterior supraspinatus-"only" insertion area; this does not account for the fact that the supraspinatus and infraspinatus interdigitate and obligatorily share insertion site area on the greater tuberosity. At a minimum, this is what is clinically observed; to characterize the insertions as discrete and separate may not be helpful.

    The authors should be commended for delineating the supraspinatus anatomy. The qualification described above should be pointed out, however, as the description of a discrete triangular insertion area for the supraspinatus does not account for the aspect of the tendon that is shared with the infraspinatus on the greater tuberosity. This has been observed in the references cited(1-4), and should be a reminder to surgeons as they attempt to restore normal anatomy during rotator cuff repair.

    The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.

    1. Clark JM, Harryman II DT. Tendons, ligaments, and capsule of the rotator cuff. Gross and microscopic anatomy. J Bone Joint Surg 1992;74A:713-25. 2. Miller SL, Gladstone JN, Cleeman E, et al. Anatomy of the posterior rotator interval: implications for cuff mobilization. Clin Orthop 2003;408:152-6. 3. Minagawa H, Itoi E, Konno N, et al. Humeral Attachment of the Supraspinatus and Infraspinatus Tendons: An Anatomic Study. Arthroscopy 1998;14:302-6. 4. Roh MS, Wang VM, April EW, et al. Anterior and posterior musculotendinous anatomy of the supraspinatus. J Shoulder Elbow Surg 2000;9:436-40.

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