Anterior Shoulder Instability
HAGL Lesion Repair
The avulsion of the capsular ligaments from the humerus was first noted in 1942 by DePalma in four of five acute dislocations that were surgically explored. This type of shoulder pathology was overlooked for the next 50 years while the Bankart lesion was established as the “essential lesion” responsible for glenohumeral instability. In open surgical procedures for shoulder instability, the humeral avulsion of glenohumeral ligaments (HAGL) is easily unnoticed. It can be mistaken for an iatrogenic breach of the capsule when attempting to dissect the subscapularis tendon from the anterior capsule. It was 1988 that this pathology was again noted when Bach et al described two cases of “lateral capsular avulsion” as a cause for shoulder instability. The HAGL was first noted arthroscopically, and an arthroscopic technique for repair described in 1995. Bokor et al reported on 41 cases of HAGL lesions in a retrospective review of the pathology of 547 cases of shoulder instability, an incidence of 7.5%. The incidence of the HAGL went up to 29.6% in the group of patients with instability without a Bankart lesion, and the incidence rose to 39% when the patient group was limited to traumatic instability without a Bankart lesion. The HAGL lesion has been established as a cause for shoulder instability and must be sought out in all patients with shoulder instability, especially those where the Bankart lesion is absent.
Mechanism of Injury
The mechanism of injury is the same as that for any traumatic dislocation, although DePalma demonstrated in the cadaver model that the HAGL tended to be produced by external rotation, while the Bankart lesion was produced by external rotation with simultaneous compression.
The patient with shoulder instability and a HAGL lesion will have the same physical findings as any patient with traumatic shoulder instability. The apprehension sign is the most commonly used of all tests for anterior instability and will be positive in patients with a HAGL lesion.
The HAGL has been demonstrated on magnetic resonance images (MRIs) and should be suspected in patients with traumatic instability and normal labral findings. Gadolinium would be useful in the MRI diagnosis, but is not routinely used in MRI for shoulder instability.
In open shoulder surgery the difficult dissection of the subscapularis must be carried out carefully to identify the HAGL lesion (Fig. 27–1). The surgeon must be on the lookout for scarring and irregularities of the capsule as the tendon-muscle unit is dissected from the inferior glenohumeral ligament (IGL). Open techniques that split the subscapularis in line with its fibers and perform a capsulotomy or capsuloplasty on the glenoid side will have difficulty identifying the scarred edge of ligaments avulsed from the humerus.
Arthroscopy greatly facilitates the diagnosis of this lesion, but even with the help of the arthroscope the surgeon must be aware of the lesion and look for the signs of the HAGL. The lesion is usually located in the anterior-inferior quadrant of the humeral origin of the IGL. The arthroscope must be directed into the axillary pouch and the lens oriented cephalad toward the humeral attachment of the inferior glenohumeral ligament.
The lesion is usually centered at the humeral attachment of the anterior band of the IGL and can extend into the middle glenohumeral ligament. Direct visualization of the fibers of the subscapularis muscle through the defect is the sina qua non of the lesion, but these muscle fibers can be covered by a thin film of scar tissue that obscures the lesion. A probe in the anterior portal is used to identify the retracted edge of capsule and dissect it from the subscapularis and any overlying scar.
Identification and preparation of the lesion:
1. Initial visualization from the posterior-inferior portal in axillary pouch
2. Anterior-superior and anterior-inferior portals created using spinal needle for precise localization
3. Trans-subscapularis portal enters joint at humeral margin in midpoint of lesion
4. Probe and shaver from various portals mobilizes and freshens the lesion at its bony and soft tissue margins