The anatomy of the coracohumeral ligament and its relation to the subscapularis muscle.
BACKGROUND
Only a few reports describe the extension of the coracohumeral ligament to the subscapularis muscle. The purposes of this study were to histo-anatomically examine the structure between the ligament and subscapularis and to discuss the function of the ligament.


METHODS
Nineteen intact embalmed shoulders were used. In 9 shoulders, the expansion of the ligament was anatomically observed, and in 6 of these 9, the muscular tissue of the supraspinatus and subscapularis was removed to carefully examine the attachments to the tendons of these muscles. Five shoulders were frozen and sagittally sectioned into 3-mm-thick slices. After observation, histologic analysis was performed on 3 of these shoulders. In the remaining 5 shoulders, the coracoid process was harvested to investigate the ligament origin.


RESULTS
The coracohumeral ligament originated from the horizontal limb and base of the coracoid process and enveloped the cranial part of the subscapularis muscle. The superficial layer of the ligament covered a broad area of the anterior surface of the muscle. Laterally, it protruded between the long head of the biceps tendon and subscapularis and attached to the tendinous floor, which extended from the subscapularis insertion. Histologically, the ligament consisted of irregular and sparse fibers abundant in type III collagen.


CONCLUSIONS
The coracohumeral ligament envelops the whole subscapularis muscle and insertion and seems to function as a kind of holder for the subscapularis and supraspinatus muscles. The ligament is composed of irregular and sparse fibers and contains relatively rich type III collagen, which would suggest flexibility.
Department of Orthopaedic Surgery, Kyoto University, Kyoto, Japan.
Ryuzo
R
Arai
Department of Clinical Anatomy, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Akimoto
A
Nimura
Department of Clinical Anatomy, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Kumiko
K
Yamaguchi
Department of Orthopaedic Surgery, Kawaguchi Kogyo General Hospital, Kawaguchi, Japan.
Hideya
H
Yoshimura
Shoulder and Elbow Service, Funabashi Orthopaedic Sports Medicine Center, Funabashi, Japan.
Hiroyuki
H
Sugaya
Department of Orthopaedic Surgery, Kyoto University, Kyoto, Japan.
Takahiko
T
Saji
Department of Orthopaedic Surgery, Kyoto University, Kyoto, Japan.
Shuichi
S
Matsuda
Department of Clinical Anatomy, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan. Electronic address: akita.fana@tmd.ac.jp.
Keiichi
K
Akita
D000368:Aged; D005260:Female; D006801:Humans; D008023:Ligaments, Articular / Q000033:anatomy & histology*; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D012782:Shoulder / Q000033:anatomy & histology*
Anatomy; collagen; coracohumeral ligament; histology; shoulder joint; subscapularis muscle