Posterior Dislocation of Shoulder: Lightbulb Sign & Reduction

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A 45-year-old man with epilepsy is brought to the emergency department following a sei- zure. He complains of right shoulder pain and these radiographs are taken. 1. Describe the appearances in these radiographs. These radiographs are an AP view of the shoulder and a scapular ‘Y’ view of the right shoulder. The images and the history are suggestive of a posterior dislocation of the shoulder. On these views, the humeral head has a ‘lightbulb’ appearance on the AP view due to its internally rotated position. The distance between the anterior rim of the glenoid and the humeral head is increased, there is a suggestion of a vertical line where there has been impaction on the humeral head from the posterior glenoid and the anterior glenoid appears empty. 2. How would you investigate and assess this patient? I would undertake a careful history and examination of this patient, trying to elu- cidate the age of the injury and any current neurovascular symptoms or deficit. I would expect to find the shoulder in fixed internal rotation or with very limited external rotation. I would be suspicious of an impaction fracture or defect in the humeral head from the posterior glenoid and a CT scan would help to define this. This would usually be in the anteromedial aspect of the humeral head, a reverse Hill–Sachs lesion, and so may contribute to ongoing posterior instability of the shoulder. 3. How would you manage this patient? In the acute situation, it may be possible to reduce this dislocation closed with good anaesthesia and formal muscle relaxation. I would have one careful attempt in the emergency department in the acute situation using sedation and with anaesthetic support. I would attempt reduction using a forward flexion, adduction and axial traction manouvre. I would attempt to unlock the humeral head from the posterior glenoid rim using direct lateral pressure on the humeral head followed by external rotation of the shoulder once unlocked. Should this fail then I would be prepared to take the patient to theatre for full general anaesthesia, muscle relaxation and the potential for an open reduction via a deltopectoral approach.
I would be wary if there was any suggestion that this was a neglected injury older than 2 or 3 weeks, especially in an elderly osteoporotic patient. Chronic dislocations are more difficult to reduce closed and more likely to need open intervention. In addition, there is significant potential to make the situation worse in an osteoporotic patient where a soft humeral head impacted on the glenoid rim can be converted into a head-splitting fracture by overzealous manipulation.
Once reduced, I would assess the stability of the shoulder through a range of movement, arrange further imaging with CT if not already done to assess any defect in the humeral head and place the patient in a sling. 4. What reconstructive options might be available to this patient?
If the shoulder is stable then nothing further may be required. If the shoul- der is unstable then surgical options might include transfer of the supraspinatus attachment/lesser tuberosity into the humeral head defect for a small to moderate- sized defect (up to 25% of the surface area). Instability with a larger defect could be addressed with an allograft fixation with or without a rotational osteotomy or joint arthroplasty surgery.
Posterior Dislocation of Shoulder