Acromioclavicular Joint and Scapular Ligaments

  • Alberto Costantini


The acromioclavicular (AC) joint is a diarthrodial joint ostensibly connecting the acromion and the distal clavicle, but in reality suspending the entire arm, via the clavicle and sternoclavicular joint, from the axial skeleton. Using the AC joint as a pivot point, the scapula (acromion) can protract and retract. The AC joint, which is approximately 9 mm by 19 mm, is formed by the distal clavicle and the acromion process of the scapula (Fig. 2.1). The articular surface of the acromion is concave (relative to the subacromial space) and has an anterior and medial orientation toward the convex, distal, end of the clavicle. The joint allows gliding, shearing and rotational motion. The articular surface of the acromial end of the clavicle is hyaline cartilage until 17 years of age, at which time it acquires the structure of fibrocartilage. Similarly, the articular surface of the clavicular side of the acromion becomes fibrocartilage at approximately 23 years of age [1]. The angle of the AC joint on AP view is variable. Urist found it was inclined from superolateral to inferomedial in 49% of cases, vertically oriented in 27%, incongruous in 21% and laterally oriented in 3% [2]. The joint is also inclined a few degrees from anterolateral to posterior medial on the axillary view. Viewed anteriorly, the inclination of the joint may be almost vertical or downward medially, the clavicle overriding the acromion by an angle of as much as 50°.


Suprascapular Nerve Acromioclavicular Joint Distal Clavicle Scapular Notch Coracoclavicular Ligament 
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Copyright information

© Springer-Verlag Italia 2008

Authors and Affiliations

  • Alberto Costantini
    • 1
  1. 1.Arthroscopic Surgery DepartmentConcordia Hospital for Special SurgeryRomeItaly

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