Answer

See the answer in page 52.

Answers

1. The anterior–posterior X-ray of the erect shoulder shows subtle fracture of greater tuberosity and a fat–fluid level.
2. The final diagnosis is lipohemarthrosis.

Discussion

Lipohemarthrosis results from an intracapsular fracture in which fat from the bone marrow is released into the joint space and mixes with the blood (hemorrhage).^[1],[2] Lipohemarthrosis is most commonly observed in traumatic knee injuries including distal femoral fracture and tibial plateau fracture. In fact, lipohemarthrosis is observed in about 40% of all intracapsular fractures of the knee.^[2],[3],[4] However, it is not only limited to the knee and can also be seen in the shoulder, hip and elbow joints.^[5]

Because fat has a lower density than blood, they separate and form a fat–fluid level, with the blood layer lying inferiorly and the fat layer superiorly.^[2] This fat–fluid level can usually be identified on any horizontal beam radiographs, provided that the beam is tangential to the fat–blood interface.^[3] However, in the glenohumeral joint, it is unusual to detect lipohemarthrosis on plain radiographs, and the fat–fluid level can only be detected in an erect view. In case of simple hemarthrosis, the fat–fluid level can be seen on an MRI. However, to confirm the diagnosis of lipohemarthrosis, the fat layer should demonstrate its respective characteristics (e.g., drop signal on fat–sat sequences).^[6]

Management

In patients with undisplaced fracture and lipohemarthrosis, the area is first immobilized with a sling for 4–6 weeks to manage the fracture. There is no specific treatment required for lipohemarthrosis as the fat–fluid interface would resolve itself in due course.

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Conflicts of interest

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