Mirels classification is a system used to predict the highest risk of pathological fracture among long bones affected by metastases. For a long bone metastasis, a score is assigned for each of:
site
location
matrix
presence of pain
Classification
-
1 point
upper limb
involving <1/3 of bone diameter
blastic/sclerotic lesion
mild pain
-
2 points
lower limb
involving 1/3-2/3 of bone diameter
mixed sclerotic/lytic lesion
moderate pain
-
3 points
trochanteric region
involves >2/3 of bone diameter
lytic lesion
functional pain
This will give a minimum score of four and a maximum score of 12. A score of ≥9 suggests that prophylactic fixation should be performed 1,2. For score 8 lesions, treatment is based on clinical judgment and for lower scores clinical management and radiotherapy is suggested. The overall sensitivity of the Mirel classification predicting fracture is ~90% but specificity is only 35% (meaning there will be unnecessary fixations) leading to debate about its usefulness 1,4.
History and etymology
Hilton Mirels (fl. 2024), a South African-born, American orthopedic surgeon, practising in New York State, described his proposed scoring system in an article published in 1989 6.
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