Thursday, January 12, 2012

Mirels Classification for Risk of Pathological Fracture

The Mirels system classifies the risk of pathologic fracture based on scoring four variables on a scale of 1-3: location of lesion, radiographic appearance, size, and pain. An overall score is calculated, and a recommendation for or against prophylactic fixation is made.

  1 2 3
Location Upper extremity Lower extremity Intertrochanteric
Radiographic appearance Blastic Mixed Lytic
Sizea < 1/3 1/3 - 2/3 >2/3
Pain Mild Moderate Functionalb
a  Size is determined as a fraction of the cortical thickness.
b  Functional pain is defined as severe pain or pain aggravated by limb function.

Score Fracture Risk Recommendation
≥9 33%-100% Prophylactic fixation is recommended
=8 15% Clinical judgment should be used
≤7 <4% Observation and radiation therapy can be used

As an example, the lytic, intertrochanteric lesion shown above takes up >2/3 of the cortical thickness, getting an overall score of 9 in the absence of any clinical information about the degree of pain.


Mirels H. Metastatic disease in long bones. A proposed scoring system for diagnosing impending pathologic fractures. Clin Orthop Relat Res. 1989 Dec;(249):256-64.

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