REVERSE HILL-SACHS LESIONS

A reverse Hill-Sachs lesion is an impaction fracture of the anteromedial humeral head, made when the anterior head impacts against the posterior glenoid rim during a posterior dislocation. Its glenoid-side partner is the reverse Bankart lesion, an injury to the posterior glenoid labrum. Both occur in posterior shoulder instability and dislocation.

The missed dislocation. Posterior dislocations are the most commonly missed major joint dislocation, with over 50% missed at first presentation. Many are found late as a locked posterior dislocation, in which the head is impacted on the rim and cannot be reduced closed. Always check the axillary view.

Acute or chronic. Under 3 weeks is acute; over 3 weeks is chronic. The distinction affects whether the head can be reduced and whether it is still viable.

Mechanism. Axial loading of the adducted, internally rotated arm, or violent muscle contraction. The internal rotators (latissimus dorsi, pectoralis major, subscapularis) are stronger than the external rotators, and during a seizure or electrocution their massive contraction overpowers the external rotators and drives the head posteriorly.

The mirror image. The defect is a reflected image of the standard Hill-Sachs lesion, which is posterolateral:

Associated injuries. Look for these alongside the humeral defect:

• Reverse Bankart, a posterior labral tear
• Posterior glenoid rim fracture, the "reverse bony Bankart"
• Lesser tuberosity fracture, which can be avulsed by subscapularis
• Posterior capsular stretch, typically present in chronic cases

The glenoid track. The concept was developed for anterior instability. Through the range of motion the glenoid keeps a contact zone that sweeps across the humeral head, the glenoid track, classically about 83% of the glenoid width. A defect that stays within that zone throughout motion is on-track: the rim never drops into it and the shoulder is stable. A defect that extends beyond the medial margin of the track is off-track: the rim falls into it and the head dislocates, or engages.

The posterior analogue. Applied to the reverse Hill-Sachs, the same logic runs against the posterior rim. Posterior glenoid bone loss and an anteromedial humeral-head defect are opposing lesions, and they combine to narrow the contact track that remains (see the clockface maps below):

Why it matters. An off-track reverse Hill-Sachs is exactly the lesion in which an isolated soft-tissue (reverse Bankart) repair fails. The bony defect must be filled or bypassed, by reverse remplissage, modified McLaughlin or allograft, or the track effectively widened. A small on-track defect can be stabilised by soft-tissue or non-operative means, and this is the biomechanical justification for the size-based algorithm and for the engaging-lesion warning.

The caveat. The glenoid-track and gamma-angle numbers are extrapolated from anterior instability. They are biomechanically plausible but not yet validated in robust posterior cohorts, so use them as a framework rather than a hard cut-off (see Controversies). The fully validated anterior glenoid track is developed in the Hill-Sachs and glenoid-bone-loss topics.

View larger

View larger

Defect size. The percentage of the articular surface involved is the most clinically useful classification for decision making. The critical size is put at 20-25% depending on the source: larger defects are unstable and engage with the posterior glenoid rim.

Gamma angle. The angle between the axis of the defect and the anatomical neck, used to predict instability. An angle greater than 90 degrees suggests a higher risk of engaging.

Chronic dislocations. One classification separates 20-50% humeral-head deficiency, over 50% deficiency and fracture-dislocation patterns, because each demands a different reconstructive ceiling.

View larger

History. A seizure, an electric shock, or a fall on the flexed, adducted arm, followed by pain, a "locked" shoulder and inability to externally rotate. In the missed case the patient has been treating it as a "frozen shoulder" for months.

Examination. The arm is held in adduction and internal rotation. The anterior shoulder is flattened and the coracoid prominent, with fullness posteriorly. A block to external rotation is pathognomonic of a locked posterior dislocation.

Tests for posterior instability. Always compare with the contralateral side:

1. Posterior drawer test - supine; axial load plus posterior force
2. Jerk test - seated; flexion to 90, adduction and axial load, with a "clunk" as the head subluxes posteriorly
3. Kim test - a variation of the jerk test for inferior-posterior labral pathology
4. Load and shift - grades translation (Grade I-III)

Neurovascular. Test the axillary nerve: sensation over the regimental badge area and deltoid function. It is less commonly injured in posterior than in anterior dislocation, but verify it.

View larger

Radiographs. The trauma series is an AP, an axillary lateral and a scapular Y. The axillary lateral is the gold standard, showing the head posterior to the glenoid; on the scapular Y the head lies posterior to the intersection of the Y. The AP carries its own signs:

• Lightbulb sign - the internally rotated head looks symmetrical (pearl below)
• Loss of the half-moon overlap
• Trough line sign - the impression fracture seen on the AP
• Rim sign - joint space widened to greater than 6mm

View larger

CT is mandatory for operative planning. It quantifies the defect as a percentage of the articular surface and assesses glenoid bone loss, the reverse bony Bankart.

MRI assesses the posterior labrum (reverse Bankart) and cuff integrity (subscapularis). It is often done if the diagnosis is unclear or for chronic pain.

View larger

Bilateral dislocations. When both shoulders are injured, pairing radiographs, CT, 3D reconstruction and MRI exposes side-to-side differences in defect size, head viability and cuff condition before reconstruction.

View larger

View larger

Every decision pivots on whether the humeral head is salvageable, so why it loses viability and how to judge it is the decisive assessment. A non-viable head sends an otherwise-reconstructable defect straight to arthroplasty.

The vascular insult. The impaction and capsular stripping of the dislocation can injure the posteromedial vessels and the arcuate (terminal) branch of the anterior humeral circumflex artery, which supplies most of the head, risking avascular necrosis.

Pressure necrosis. While the head sits locked on the posterior glenoid rim, the rim bores progressively into the soft anteromedial bone, enlarging the defect and causing articular collapse. The longer it stays dislocated and the bigger the defect, the more of the head dies. That is why the under-3-week acute window matters and why neglected cases do badly.

The second axis. The assessment is not defect size alone. A viable, congruent, non-collapsed head with a reconstructable defect is preserved by modified McLaughlin or allograft; a collapsed, fragmented or avascular head, or one with established arthrosis, goes to arthroplasty regardless of the percentage. CT defines the bone defect and collapse, and MRI assesses marrow viability and AVN.

Fracture-dislocations. The same fork applies. A reconstructible displaced proximal-humerus fracture-dislocation is reduced and internally fixed when head viability and fragment anatomy permit preservation. Severe humeral-head comminution with posterior instability is converted to reverse arthroplasty when reliable head reconstruction is not possible.

View larger

View larger

A patient with a painful, stiff, internally-rotated shoulder after a seizure or fall is easily mislabelled. The differentials below are the classic exam traps.

Acute (under 3 weeks). The goal is to reduce the head and keep it reduced. Closed reduction is done under conscious sedation or GA with traction and gentle anterior pressure; avoid force, which risks fracture. Early reduction minimises cartilage damage.

Small defects (under 20%) are stable after reduction and are treated by closed reduction or neglect.

After reduction. A stable shoulder is immobilised in external rotation (gunslinger brace) for 4-6 weeks. If it redislocates or engages in functional range of motion, it goes to surgery.

Chronic or unstable: operate by size. Once the head is judged salvageable, defect size chooses the procedure:

Modified McLaughlin. McLaughlin's original operation transfers the subscapularis tendon into the defect; the modified procedure transfers the lesser tuberosity with subscapularis attached. The bony plug fills the hole and the tightened subscapularis acts as a check-rein preventing internal rotation. Careful protection of the axillary nerve is required.

1. Deltopectoral approach
2. Identify the anteromedial impression fracture
3. Lesser tuberosity osteotomy, with subscapularis attached
4. Reduce the humeral head into the glenoid
5. Prepare the defect bed with curette or burr to encourage healing
6. Secure the lesser tuberosity bone block into the defect with screws or suture anchors

View larger

Disimpaction and grafting. In an intermediate defect the impacted articular surface is elevated, the void packed with cancellous graft and the subscapularis repaired anatomically (see Controversies for disimpaction against filling the defect).

View larger

Segmental allograft. Used when the defect is large but the joint is salvageable, in a young patient. Through a deltopectoral approach, a fresh femoral head or humeral head allograft is shaped to match the defect ("snowman" or wedge shape) and fixed with countersunk headless compression screws. It restores spherical head shape effectively, but allograft availability can be a limiting factor.

View larger

Arthroscopic reverse remplissage. The defect is filled with subscapularis via suture anchors: an anterior anchor is placed at the centre of the prepared defect and mattress sutures secure the subscapularis into it. In the case below the posterior labrum is repaired at the same time, addressing both humeral and glenoid-sided instability. The technique is good for small and medium defects, although the size algorithm above lists it for defects under 20% (see Controversies).

View larger

View larger

Combined bipolar defects. When a Hill-Sachs and a reverse Hill-Sachs lesion coexist, posterior anchors capture capsule and infraspinatus while the anterior subscapularis transfer fills the reverse defect.

View larger

Arthroplasty. Reserved for defects over 45-50% or older low-demand patients. The choice follows the glenoid and the cuff:

• Hemiarthroplasty if the glenoid is intact, though it is less commonly used now due to glenoid erosion risk
• Anatomic total shoulder if the glenoid is arthritic but the cuff intact
• Reverse total shoulder if the cuff is deficient or in the very elderly

Modified McLaughlin. Good to excellent results in 75-85% of patients, with a low recurrence rate if sized correctly.

Allograft. A technical procedure, but it shows good survival at 10 years. The risks are graft resorption and necrosis.

Neglected cases. Associated with poor functional outcomes and rapid progression to osteoarthritis if left unreduced.

View larger

Related pages: Posterior Shoulder Instability is the parent condition and the page that matters most here - a reverse Hill-Sachs is one structural cause of it, and the recurrent instability Robinson quantified is managed there; Hill-Sachs Lesions for the anterior mirror image, whose glenoid-track and remplissage concepts are borrowed by this page but were derived for the opposite direction and the opposite bone loss; Proximal Humerus Fractures because a fifth of Hawkins' locked dislocations carried an undisplaced proximal humeral fracture and the fracture-dislocation is a different operation; Avascular Necrosis of the Shoulder for the head-viability question that overrides defect size in the algorithm above; and Reverse Total Shoulder Arthroplasty and Total Shoulder Arthroplasty for the salvage end of the ladder once the head is unreconstructable.