Explorative study of the sensitivity and specificity of the pronator quadratus fat pad sign as a predictor of subtle wrist fractures.
OBJECTIVE
To investigate the value of post-traumatic pronator quadratus (PQ) fat pad sign as a reliable predictor of subtle wrist fractures.


METHODS
This was a prospective study of 68 patients undergoing X-ray for traumatic wrist injuries and subsequent MRI. The reliability of a positive PQ fat pad sign on X-ray, defined as either raised, interrupted or obliterated, was evaluated in detection of subtle wrist fractures.


RESULTS
Out of 68 patients, 28 had a positive PQ sign without any obvious bony injuries on plain radiographs; of these, the PQ fat pad was obliterated in 11, disrupted in 12, and raised in five cases. Fractures defined as cortical interruption or trabecular fractures were revealed in 13/28 (46 %) patients with a positive PQ sign but only in 7/40 (18 %) patients with a negative sign. With regards to different types of abnormal PQ fat planes, fractures were present in 7/12 patients with a disrupted plane (58 %), 6/11 patients with an obliterated plane (54 %), and none of the patients with a raised plane. The overall sensitivity and specificity of a positive PQ sign in the prediction of occult wrist fractures were 65 and 69 %, respectively.


CONCLUSIONS
Our findings indicate that a positive pronator quadratus (PQ) fat pad sign is not a reliable predictor of subtle fractures of the wrist, although we believe that it is a useful radiographic sign in justifying MRI for further clarification of possible joint abnormalities including occult fracture and cortex interruption.
Department of Radiology, North Cumbria University Hospitals NHS Trust, Carlisle, UK. farshid.fallahi@ncuh.nhs.uk
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F
Fallahi
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Jafari
Gail
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Jefferson
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P
Jennings
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Read
D000273:Adipose Tissue / Q000000981:diagnostic imaging / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000473:pathology*; D011859:Radiography; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014954:Wrist Injuries / Q000000981:diagnostic imaging / Q000473:pathology*; D014962:X-Ray Film; D055815:Young Adult