Presentation
Day 3 post left hip hemiarthroplasty. Found to have left hemiparesis on morning ward round.
Patient Data
Initial xrays show an intra-capsular left femoral neck fracture. This was treated with a cemented hemiarthoplasty.
CT head shows hypodensity involving the right insula, putamen, frontal, temporal and parietal operculum, extending into the centrum semiovale. This is associated with sulcal swelling. Appearances are consistent with an acute right MCA infarct.
The thin slices and region of interest show fat density (-35 HU) embolus in the right MCA M1 and M2 segments. The appearances are consistent with fat embolism, likely from the arthroplasty.
Case Discussion
This case illustrates the importance of reviewing fine slices on CT, if available. MCA bifurcation emboli are much easier to see on thin slices, whether of high or low density (as in this case).
Reaming of the intra-medullary canal and the use of cemented techniques (as occurred with our patient) are known to be risk factors for the development of fat embolism 1. Fat embolism mainly occurs in the setting of long bone fractures, and can happen whether the fracture is treated operatively or non-operatively. Less common traumatic causes include massive soft tissue injury, severe burns, bone marrow biopsy and transplant, cardiopulmonary resuscitation (CPR), liposuction, and median sternotomy. Non-traumatic causes are uncommon but have been reported, and include acute pancreatitis, fatty liver, steroid therapy, lymphography, fat emulsion infusion, and hemoglobinopathies 2.
The treatment of fat embolism syndrome is mainly supportive 3. Thrombolytic therapy is not likely to be effective as the lesion is not composed of thrombus. In this case, the unknown time of onset and extensive involvement of the MCA territory (more than one-third) were further contra-indications.
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