Humeral avulsion glenohumeral ligament (HAGL)

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Introduction

Humeral avulsion of the inferior glenohumeral ligament (HAGL) has been shown to be an infrequent cause of shoulder instability. This lesion occurs when the inferior glenohumeral ligament avulses from the inferior humeral neck. This is in contrast to the Bankart lesion in which the IGHL is disrupted from the glenoid.

As originally described by Nicola in 1942, this lesion appears to occur most commonly anteriorly. In two large series of anterior instability, anterior HAGL was found to occur in 7.5% to 9.4% of cases. Similar to its anterior counterpart, posterior avulsion of the inferior glenohumeral ligament has recently been described and appears to be an infrequent cause of posterior shoulder instability. Clinically, this posterior lesion has only been described in a limited number of case reports.

Anatomy

The IGHL complex plays a large role in buttressing anterior and inferior translation of the humeral head. The IGHL complex consists of an anterior band, posterior band, and an interposed axillary pouch. It is a major restraint to anterior and posterior translation at 90o of abduction.13 Failure of this ligament has been shown to occur at three sites: the glenoid insertion (40%), midsubstance (35%), and the humeral insertion (25%). In this cadaver study, the humeral insertion of the IGHL is the least common site of failure.

Classification

Recently, the HAGL lesion has been classified under the West Point Nomenclature. This system initially divides HAGL lesion as anterior (AHAGL) or posterior (PHAGL). Within these categories there are three subcategories listed below:

AHAGL- anterior HAGL with purely ligamentous avulsion
ABHAGL - anterior HAGL with boney avulsion
Floating AHAGL - AHAGL or ABHAGL with associated Bankart lesion

PHAGL- posterior HAGL with purely ligamentous avulsion
PBHAGL - posterior HAGL with boney avulsion
Floating PHAGL - PHAGL or PBHAGL with associated Bankart lesion

Presentation

There are no specific complaints unique to the HAGL lesion and symptoms may vary depending on the location (anterior or posterior). However, patients usually present after an episode of shoulder instability or dislocation. They may notice persistent pain or sense of instability after reduction or even Bankart repair.

Diagnosis

Physical exam and history are non-specific. MRI is often employed in the preoperative evaluation for patients with shoulder instability or suspected labral pathology for which HAGL would be included in the differential diagnosis. The MRI characteristics of HAGL that have been described in the literature include (1) increased signal intensity and thickening of the inferior capsule, (2) extravasation of contrast material or joint effusion along the medial humeral neck, and (3) a J-shaped axillary pouch ("J" sign) as opposed to the normal U-shaped structure.5, 12 However, the sensitivity and specificity of the MRI diagnosis of HAGL is currently unknown. There is a case series of 4 patients with false positive pre-operative MR diagnosis of HAGL that at arthroscopy were not found to have HAGL lesions. Ultimately, arthroscopy is gold standard for diagnosis. Thorough arthrosopic inspection of the shoulder is required in cases of instability to avoid a missed HAGL as 62% of patients with HAGL were found to have concomitant shoulder pathology at the time of arthroscopy.

Treatment

Both open and arthroscopic repair of this lesion has been described. The repair usually consists or reattachment of the torn IGHL to the humeral neck with suture anchors or bone tunnels. Rehabilitation is typically similar to Bankart repair.

Complcations

HAGL should be considered and search for in all patients with shoulder instability, even those with known Bankart lesions as this lesion may often be missed.

Other complications included failure of fixation, recurrent dislocation, continued pain and axillary nerve damage.

Red Flags and Controversies

The ability of MRI and MR arthrography to accurately diagnose this lesion has recently been called into question. MRI or MR arthrography may lack the resolution to definitively distinguish HAGL from other pathology of the IGHL.

Outcomes

There are no long term series evaluating the outcome of these patients, however, a limited number of case reports suggest that instability and pain may improve after surgical repair for those with significant symptoms.

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