Anatomy
There are three bones in the shoulder: the humerus (the bone of the upper arm), the scapula (shoulder blade) and the clavicle (collarbone). Articulations between these bones make up the shoulder joints. The main joint, commonly referred to as “the shoulder joint”, is the joint between the head of the humerus and glenoid cavity of the scapula and is called the humeroscapular or glenohumeral joint. The second joint of the shoulder is formed by the articulation between the clavicle and the acromion (extension of the scapula that forms the top of the shoulder) and is called acromioclavicular joint or AC joint. The two joints are stabilized by associated muscles and ligaments.
Fig.1: Main components of the shoulder joint. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Shoulder dislocation
Shoulder dislocation occurs when the humeral head slips out of the pocket made by glenoid cavity of the scapula (Fig. 2). This usually happens as a result of trauma (fall, sport injury,..). Dislocation can be anterior where the humerus slips to the front or posterior where it dislocates behind the normal position. Anterior dislocation is more common.
Fig.2 : Types of shoulder dislocation. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Below is a narrated animation about shoulder dislocation, bankart lesion and repair. Click here to license this video and/or other orthopaedic videos on Alila Medical Media website.
Bankart lesion and shoulder instability
The glenoid cavity has a ring of fibrocartilage tissue called the labrum around it. The labrum makes the cavity deeper and helps to keep the humeral head in place (Fig.3). During anterior shoulder dislocation, the head of the humerus may be pressed against and damages the anterior portion of the labrum. This type of labral tear is called bankart. Damaged labrum makes it easier for the humeral head to slip out of place again. This vicious cycle leads to repeated shoulder dislocation and severely damaged labrum. The condition is called shoulder instability as it feels like slipping out anytime. Treatment includes physical therapy and, in some cases, surgery for bankart repair (see below).
Click here to see an animation of bankart lesion and arthroscopic repair on Alila Medical Media website where the video is also available for licensing.
Fig. 3: Anatomy of the shoulder joint with the humerus slightly abducted to show the glenoid cavity and labrum. Types of labral lesions are shown on the right. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Bankart repair
During surgery the damaged cartilage is removed, area is cleaned, small holes are then drilled into the bone of glenoid fossa to hold small suture anchors with threads. The threads are attached to the labrum and pulled tightly to hold the labrum to the glenoid (Fig.4). Over time, the labrum will reattach to the glenoid naturally. Physical therapy will be needed to regain the shoulder range of motions and strength.
Fig.4: Steps of bankart repair surgery. See text for details. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Bankart repair can be done with arthroscopic or open surgery. While arthroscopy is minimal invasive, open surgery maybe recommended for larger tears. In arthroscopic surgery only two or three small incisions are made, an arthroscope is inserted through one of the incision. Arthroscope is an instrument equipped with light and camera which transmits image of the joint to a computer screen. Other small tools are inserted to carry out the repair (Fig.5).
Click here to see an animation of arthroscopic bankart repair.
Fig. 5 : Arthroscopic surgery for bankart repair. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
