1. SPECTRUM OF MRI FINDINGS IN GLENOHUMERAL INSTABILITY
ABSTRACT ID NO: 50

2. INTRODUCTION
The shoulder joint is a ball and socket type of joint that has two main stabilizers:
the rotator cuff muscles (dynamic)
the labral-ligamentous complex (static).
The primary function of the rotator cuff muscles is to centralize the humeral head, limiting superior translation during abduction.
The glenohumeral joint is the most commonly dislocated joint. The normal glenoid labrum height and width are 3 mm and 4 mm.
The glenoid labrum is the ring of fibrocartilage that provides attachment to the glenohumeral ligaments and the capsule at the glenoid rim and deepens the glenoid fossa. The attachments of the glenohumeral ligaments and the long head biceps anchor to the labrum are stronger than the attachment of the labrum to the glenoid rim. Therefore, the glenoid labrum is commonly torn or avulsed when excessive force is applied to a glenohumeral ligament or the long head biceps

3. ANATOMY
LATERAL VIEW OF THE GLENOID FOSSA WITH ITS LIGAMENTS

4. The glenohumeral ligaments (inferior, middle, and superior) are thickened bands of the joint capsule that extend from the inferior and anterior glenoid and glenoid labrum, to the anatomic neck region of the humerus.
The inferior glenohumeral ligament (IGHL) is a hammock-like structure that attaches to the inferior glenoid, glenoid labrum, and the humeral neck. Thickened portions of the IGHL anteriorly and posteriorly are referred to as the anterior and posterior bands.

5. The middle glenohumeral ligament (MGHL) varies in thickness, shares a common origin with the SGHL & helps stabilize the shoulder anteriorly from 0-45 degrees of abduction and external rotation.
The superior glenohumeral ligament (SGHL) is the smallest ligament and acts with the coracohumeral ligament to stabilize the glenohumeral joint It prevents posterior and inferior translation of the humeral head.
MGHL
CHL
SGHL
LH –BICEPS TENDON GL

6. On MRI the normal labrum demonstrates low signal intensity on all pulse sequences, due to the lack of mobile protons in this dense fibrocartilage. On cross sectional imaging, the normal labrum is most commonly triangular, but can also be round, cleaved, notched, flat, or absent
DISCUSSION
For localization purposes, the labrum is divided into six zones includes: superior, anterosuperior, anteroinferior, inferior, posteroinferior, and posterosuperior.

7. MRI diagnosis of labral tears is based on abnormalities in the signal intensity, morphology, and location (displacement) of the labrum. The labrum may be frayed, crushed, avulsed, or torn.
Tears are classified by morphology, displaced or nondisplaced, and by location. Labral tears can extend into the biceps anchor as well as the glenohumeral ligaments.
MRI criteria for diagnosing labral tears include :
Surface irregularity,
Increased signal within the substance of the labrum that extends to the labral surface ,
Fluid or contrast imbibed into the substance of the labrum ,
Labral avulsions.
Secondary signs of labral tears include paralabral cysts , periosteal stripping and tearing, labral associated bone injuries .

8. Anterior Instability
Posterior Instability

10. A Bankart lesion is a tear of the anterioinferior glenoid labrum with an associated tear of the anterior scapular periosteum, with or without associated fracture of the anterior inferior glenoid rim
Classic Bankart lesion
Bony Bankart lesion

11. A Perthes lesion is a variant of the Bankart, where the anterioinferior labrum is avulsed from the glenoid and the scapular periosteum remains intact but is stripped medially.

12. A BHAGL is a bony HAGL, that involves a bone fragment.
A HAGL lesion is humeral avulsion of the glenohumeral ligament that occurs from shoulder dislocation, with avulsion of the inferior glenohumeral ligament from the anatomic neck of the humerus.
A BHAGL is a bony HAGL, that involves a bone fragment.
Reverse HAGL lesion: In posterior instability there is complete avulsion of the posterior attachment of the shoulder capsule and the glenohumeral ligament from the posterior humeral neck
HAGL
Reverse HAGL lesion

13. The GLAD lesion refers to glenolabral articular disruption, which involves a tear of the anterior inferior labrum with an associated glenoid chondral defect
Glenoid avulsion of the glenohumeral ligaments (GAGL) implies an avulsion of the IGHL from the inferior pole of the glenoid, without an associated inferior labral disruption
GLAD
GAGL
AVUL OF IGHL

14. The ALPSA lesion is characterized by a torn anteroinferior labrum with an intact but stripped periosteum and medial displacement of the labrum and inferior glenohumeral ligament
Inferior ALPSA or cul-de-sac lesion is medial displacement of both the anterior-inferior labrum and the IGHL under the inferior neck of the glenoid
ALPSA
TORN ANTR INF LABRUM
IGHL
Inferior ALPSA
AIL
IGHL

15. Hill-Sachs lesion consists of bony injury to the posterosuperior humeral head as a result of inferior displacement (which occurred when the humeral head struck the anterior inferior glenoid during anterior dislocation).
Reverse Hill-Sachs lesion consists of an anteromedial superior humeral head impaction fracture
Bennett lesion is an extra- articular crescentic posterior ossification associated with posterior labral injury and capsular avulsion
Hill-Sachs lesion
Reverse Hill-Sachs lesion
Bennett lesion

16. Rotator cuff interval tear do not appear as complete disruption of the fibers of its components but as thinning, irregularity, or focal discontinuity of the rotator interval capsule.
Posterosuperior labral tear in association with a paralabral cyst may be seen in patients with posterior instability
Rotator cuff interval tear
Paralabral cyst

17. The SLAP lesion is an injury involving the superior aspect of the glenoid labrum, which includes the biceps tendon anchor.
SLAP CLASSIFICATION
Type II
Type IV
BHL with extension into biceps tendon

18. SLAP CLASSIFICATION TYPE VII TYPE V
SLAP lesion with anteroinferior extension
Superior labral tear with MGHL extension
TYPE IX
Fraying of MGHL
global labral abnormality

19. CONCLUSION
Anterior instability is the most common type of shoulder instability.
It is associated with a Bankart lesion and its variants and abnormalities of the anterior band of the inferior glenohumeral ligament, whereas posterior instability is associated with reverse Bankart and reverse Hill- Sachs lesions.
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