Pelvic fractures (Malgaigne fracture)

Case contributed by Dr Andrew Dixon

Presentation

Motorbike accident.

Patient Data

Age: 55
Gender: Male

This case featured in our 2016 Trauma Radiology Course which is now available to view online.

X-ray

Trauma Series

Fracture of the right superior and inferior pubic rami and the right sacral ala. The pubic symphysis and sacroiliac joints remain normally aligned. 

CT

Pelvic CT

CT confirms fractures of the right superior and inferior pubic rami with associated haematoma within the right pelvic side wall / obturator internus muscle. There is also buckling of the anterior cortex of the right sacral ala lateral to the sacral foramina consistent with a sacral fracture in Dennis zone 1. Combination of the pubic rami and sacral ala fracture is consistent with a vertical shear mechanism also known as Malgaigne fracture. There is a small volume of pre-sacral haemorrhage seen in association with the sacral fracture. Presence of pre-sacral fluid on a trauma CT is a reliable sign that there will be a sacral fracture and should always prompt close investigation of the bones. 

Annotated image

On the x-ray image the white arrow indicates abrupt loss of the normal sacral foraminal margin on the right consistent with fracture. The yellow arrows indicate the superior and inferior pubic rami fractures. The CT image shows small volume pre-sacral haemorrhage which is a finding that is almost always a sign of sacral fracture in trauma patients. 

Case Discussion

This case demonstrates a combination of right pubic rami and sacral ala fractures consistent with a vertical shear mechanism of injury (Malgaigne fracture). Nicely seen on the plain film is subtle loss of the normal sacral foraminal margin indicating sacral ala fracture. On the CT, there is a good example of small volume pre-sacral haemorrhage.     

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Case information

rID: 31610
Case created: 18th Oct 2014
Last edited: 28th Jul 2016
Inclusion in quiz mode: Included

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