Pathological fracture risk (Mirels classification)

Last revised by Dr Daniel J Bell on 10 Mar 2022

Mirels classification is a system used to predict the highest risk of pathological fracture among long bones affected by metastases, and is based on site, location, matrix and/or 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. 2022), 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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