Figure 1
Diagram showing the passive stabilizers of the shoulder. The shoulder joint is intrinsically unstable due to the lack of osseous congruency between the humeral head and the glenoid. During the mid-range of motions, it is stabilized by the conjoint action of the rotator cuff and deltoid muscles. In the extremes of motion, it is stabilized by the capsulo-labro-ligamentous complex. The glenoid labrum (orange) increases the contact zone between the glenoid and the humeral head and serves as an anchor point for the glenohumeral ligaments (yellow). The latter are thickenings of the joint capsule and are attached to the glenoid in continuation with the periosteum (brown).
Figure 2
MR athrogram of a 50-year-old male, with no history of shoulder instability, showing absence of labrum at the antero-superior quadrant (long arrow) associated with thickened middle glenohumeral ligament (thick arrow), called the Buford complex. Note the slight detachment of the labrum (short arrow), which can frequently be seen in asymptomatic older patients, with varying locations (here at the postero-superior quadrant).
Figure 3
Sagittal MR arthrogram of the left shoulder, showing normal anatomy and method to localize labroligamentous lesions. Lesios are localized using a clockface projected on the glenoid cavity, with the three o’clock position being located at the anterior aspect by convention, no matter the shoulder side (the clockface is inverted for a left shoulder as shown here). The lesion can also be localized in quadrants (AS: antero-superior; PS: postero-superior; AI: antero-inferior; PI: postero-inferior). With the distention provided by the arthrographic procedure, there is good visibility of the glenohumeral ligaments. The MGHL (long arrows) is visible, characterized by its distal insertion on the deepest aspect of the subscapularis tendon. The anterior band of the IGHL is also visible (short arrowheads) (cp: coracoid process; ssp: supraspinatus tendon; isp: infraspinatus tendon; ssc: subscapularis tendon).
Figure 4
Sagittal MPR of CT arthrogram showing a quantification method for the antero-inferior glenoid bone loss in typical bony Bankart lesion (arrows). A best fit circle (red) is projected on the inferior rim of the glenoid. The width of the bone missing anteriorly (full yellow line) is divided by the diameter of the circle (dashed yellow line). A typical threshold of 20–30 percent typically indicates a glenoid augmentation procedure.
Figure 5
Axial (a) and sagittal oblique (b) reformats of MR arthrogram of patient with history of chronic antero-inferior dislocation, showing bony Bankart lesion at antero-inferior quadrant (arrows). Note that the fracture and bony avulsion may be difficult to visualize on axial images (a) and is more nicely depicted on sagittal oblique reformats (b).
Figure 6
Diagrams showing various patterns of injury of antero-inferior instability on the glenoid side. Various acronyms have been attributed to these patterns, but they can be broadly divided in two categories: those lesions with periosteum discontinuity, called Bankart lesions (a: bony Bankart; b: soft tissue Bankart), and those with capsulo-labro-ligamentous lesions with preserved continuity of the periosteum, called Bankart variants (c–f). The pattern of injury can involve detachment of the labrum (c) (called the Perthes lesion, best visible in ABER position as illustrated here); detachment of the labrum with periosteal sleeve avulsion (called the ALPSA lesion); and labral detachment associated with a chondral lesion (e) (called the GLAD lesion). Medial displacement of the labrum and the development of fibrous and scarry tissue is usually a sign of chronicity (f) (called the chronic ALPSA lesion).
Figure 7
MR arthrogram of a 54-year-old male with chronic shoulder instability, showing hypoplasia of posterior glenoid with labral and cartilaginous hypertrophy. There is posterior detachment of the posterior labrum (long arrow) and paralabral cysts formation (short arrow).
Figure 8
MR arthrogram of a 16-year-old male with history of chronic antero-inferior instability, showing detachment of antero-inferior labrum (black arrow) with torn periosteum (there is no more attachment of the labrum to the glenoid left), corresponding to a soft-tissue Bankart lesion. Note the Hill-Sachs lesion at the postero-superior aspect of humeral head.
Figure 9
MR arthrogram of 17-year-old male with history of antero-inferior shoulder dislocation, showing detachment of labrum at the antero-inferior quadrant (white arrow) with continuity of periosteum (black arrows).
Figure 10
MR arthrogram of 34-year-old male with history of chronic posterior shoulder instability, showing detached labrum with paralabral cyst at the postero-superior quadrant (arrow in a) and posterior Bankart lesion at the postero-inferior quadrant (black arrow in b). The bony fragment in b is difficult to visualize, but there is clear detachment of labrum and periosteal as well as the development of scarred tissue. The abrupt slope of the postero-inferior glenoid rim (white arrows in b) is indicative of bone loss (not to be confused with the physiological blunting of glenoid rim commonly seen at the postero-inferior quadrant).
Figure 11
MR arthrogram of 16-year-old male with history of chronic antero-inferior shoulder instability, showing detached labrum at the antero-inferior quadrant (arrow) with medial displacement and hypertrophic changes representing signs of chronicity.