Learning objectives
To provide a basic understanding of how fat-fluid levels appear in bursae and tendon sheaths.
To describe this radiological finding in three different articular joint.
To consider differential diagnoses.
Background
Tendons are anatomic structures interposed between muscles and bones; they consist of dense fibrous connective tissue made up primarily of collagenous fibres embedded in a proteogycan-water matrix.
Synovial sheaths are serous envelopes formed by the parietal and visceral sheets,
that surround tendons at bone surfaces with peritendinous fluid for lubrication.
Their function is to contain the tendon allowing an easy glide.
Peritendinous fluid is normally less than 2 mm in thickness.1,2
A synovial sheath can be distinguished from the tendon only when the synovial fluid...
Findings and procedure details
We observed this finding in seven patients,
four cases in wrist,
two in ankle and one in hip,
studied with MRI (1.5T) and CT multislice.
In the wrist,
three patients presented fat-fluid level in the second and third extensor compartments associated with a Lister`s tubercle fracture.
Probably a cortical defect at the level of Lister`s tubercle injured almost one of the tendons that includes the second and third compartment,
due to their close proximity,
allowing fat bone marrow leakage into the tendon sheaths.11,12
The presence...
Conclusion
Free-floating fat sign within the tendon sheaths and bursae due to bone marrow fat extrusion after an intra-articular fracture,
is an important feature in the context of a traumatic injury.
In cases like our,
of known fractures,
this allows the radiologist to make an accurate report avoiding incorrect diagnoses and interpretations.
This is important to implement appropiate treatment and rehabilitation.
Although,
in cases without obvious fracture,
MRI or CT findings of fatty effusion in bursae or tendon sheaths,
as a secondary sign of intra-capsular fracture,...
References
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ECR.
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Le Corroller T,
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Floating fat in the wrist joint and in the tendon sheaths.
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Lugo-Olivieri CH,
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Fluid-fluid levels in injured knees: do they always represent lipohemarthrosis? Radiology.1996; 198: 499-502....