Causes / typical injury mechanism:
- A reverse Hill-Sachs lesion (RHSL), also called a McLaughlin lesion, is an impaction fracture of the anteromedial humeral head resulting from a posterior shoulder dislocation.
- The most common cause of dislocation is trauma, such as falling on an outstretched hand from a bicycle. Other mechanisms of this injury include direct trauma to the shoulder or violent muscle contractions related to epileptic seizures and electrocution.
- Chronic posterior shoulder instability is more common than frank dislocation. Repetitive posterior-directed loads forcing the humeral head against the edge of the glenoid can also result in an RHSL.
- The patient typically presents with a history of chronic posterior shoulder instability, which may have begun at a young age after an acute posterior shoulder dislocation or as a result of high-impact pushing sports such as football or bench-pressing. Less commonly, the patient presents acutely with a first-time posterior shoulder dislocation or with a chronically stiff shoulder after a remote event when dislocation was missed.
- On examination, the patient has limited shoulder external rotation, flexion, and abduction. Pain is reproduced with a wall push-up.
- Posterior shoulder dislocation is a rare injury, comprising 2%-5% of all shoulder dislocations.
- RHSLs are observed in up to 90% of acute, first-time, traumatic posterior shoulder dislocations.
- The typical age of patients is between 35 and 67 years.
- Males are more commonly affected.
- History of posterior shoulder dislocation.
- Young age at the time of the first instability episode.
- Chronic posterior shoulder instability.
- Activities with a posteriorly directed force on the humeral head – bench-pressing, football, wrestling, gymnastics, swimming, etc.
- Osteonecrosis of the humeral head.
- Glenohumeral arthritis.
- Epilepsy and other seizure disorders.
- Glenoid retroversion.
Grade / classification system:
- Type 1 – Unlocked dislocations associated with small RHSLs.
- Type 2 – Locked dislocation associated with large RHSLs.
- Type 3 – Chronic locked dislocations associated with very large RHSLs.