Hill-Sachs Lesion

A Hill-Sachs lesion is a compression fracture of the posterosuperolateral humeral head, produced when the head impacts the anterior glenoid rim during anterior dislocation. It is found in about 65 to 70% of first time anterior dislocations and in nearly all recurrent cases. Size and orientation decide significance.

An engaging lesion lies parallel to the glenoid edge when the arm is abducted and externally rotated, so the head catches on the glenoid rim and dislocates. The glenoid track concept defines this: the glenoid track width is about 83% of the glenoid width minus any anterior glenoid bone loss. A lesion that extends beyond the medial edge of the track (the defect plus the distance from the cuff footprint exceeds the track) is off track and engages. Combined humeral and glenoid loss (bipolar) increases risk.

The reverse Hill-Sachs lesion is an anteromedial impaction after posterior dislocation, seen with seizures and electric shock. Size is graded as under 20% of the articular surface (small), 20 to 40% (moderate) and over 40% (large). Complications are recurrent dislocation, a locked dislocation, instability arthropathy and, in neglected cases, humeral head collapse.

• Anterior: pain and deformity after dislocation, then recurrent apprehension, catching and slipping at the end range of abduction and external rotation
• Chronic locking in a position the patient cannot escape
• Reverse lesion: a fixed internally rotated arm with inability to externally rotate, after a seizure or electric injury
• Red flags: delayed presentation of a locked dislocation, a fracture, neurovascular injury, and recurrent dislocation with small trauma

• Radiographs: anteroposterior in internal rotation shows the defect. Axillary and West Point views show the glenoid. For a reverse lesion, the trough line sign and a fixed internally rotated humeral head.
• CT with three dimensional reconstruction: defect depth, width, orientation and percentage of the head, and glenoid bone loss. Calculate on track versus off track status.
• MRI or MR arthrography: marrow oedema when acute, plus labrum, capsule and cuff.
• Dynamic arthroscopic assessment under anaesthesia: engagement of the defect on the glenoid rim in abduction and external rotation.

Differentials: normal humeral head variation (bare area), humeral head osteonecrosis, cuff tear, labral tear, proximal humerus fracture, multidirectional instability.

Acute dislocation: reduce as soon as possible (within 24 hours), since delay enlarges the defect and makes reduction harder. Use intra articular lidocaine 1% 10 to 20 mL or procedural sedation (propofol 1 mg/kg IV then 0.5 mg/kg boluses with monitoring), with gentle traction and rotation and no forceful leverage. Sling for 1 to 3 weeks, paracetamol 1 g orally every 6 hours, ibuprofen 400 mg orally every 8 hours with food for up to 7 days, and cuff strengthening for 3 months.

Anterior lesions:

• Small, on track lesions: treat the associated labral tear with arthroscopic repair (3 or more anchors) when surgery is indicated.
• Moderate off track lesions with an acceptable glenoid: arthroscopic remplissage, in which the infraspinatus tendon and posterior capsule are fixed into the defect with 1 or 2 anchors, combined with labral repair. External rotation loss is about 5 to 10 degrees.
• Large defects (over 25 to 40% of the head), bipolar loss, or recurrence after repair: Latarjet (coracoid fixed with two 3.5 to 4.0 mm screws) or osteochondral allograft of the head.
• Large chronic defects with arthritis: humeral head resurfacing or arthroplasty.

Reverse lesions:

• Under 20% in an acute dislocation: closed reduction, then immobilise in slight external rotation for 4 weeks.
• 20 to 40%: transfer of the subscapularis tendon or lesser tuberosity into the defect.
• Over 40%, or chronic with arthritis: hemiarthroplasty or total shoulder arthroplasty.
• Treat seizures and exclude other causes.

Cefazolin 2 g IV before incision (3 g if over 120 kg).

Complications: stiffness, recurrence, graft resorption, nerve injury, infection and arthritis.

Follow up at 2 and 6 weeks, 3 and 6 months. Counsel on avoiding forced abduction and external rotation until healed.