Mirel’s Criteria or Score – Mnemonic

Mirel’s scoring system rates 4 criteria from 1 to 3 with maximum possible score of 12 to assess the risk of pathological fracture due to metastases and also serves as a guide for considering prophylactic fixation. The parameters of the criteria can be remembered using the mnemonic MIREL’S.

mirel's criteria
  1. MMorphology of metastases
  2. IIntensity of pain
  3. RRatio of lesion size to bone diameter (as seen on plain radiograph)
  4. EEight (cut-off value)
  5. LLocation of metastases
  6. ‘S – Looks like 15 (score 8 = 15% risk of pathological fracture)
ScoreSite of lesionSize of lesionNature of lesionPain
1Upper limb< 1/3 of cortexBlasticMild
2Lower limb1/3–2/3 of cortexMixedModerate
3Trochanteric region> 2/3 of cortexLyticFunctional

He recommended prophylactic fixation with a patient scoring more than 8 or more. With this scoring system, patient with functional pain (severe pain at rest or pain with use of limb) and lytic lesion automatically scores 8 or more. However, it was created before the bisphosphonates were used. With a score of 8, clinical judgement is necessary for decision making.

Mirels’ scoreClinical recommendation
≤ 7Radiotherapy and observation
8Use clinical judgment
≥ 9Prophylactic fixation

Risk of pathological fracture according to Mirel’s score:

  1. <6: 0%
  2. 8: 15%
  3. 12: 100%

Harrington (preceded Mirel’s criteria and is not validated) defined an impending fracture as:

  1. ‘Lytic’ bony lesion
  2. Involving > ½ the diameter of the bone (>2.5 cm in greatest diameter)
  3. Associated with persistent pain
  4. Radiographic progression after radiation.

Example: A lytic metastasis in the proximal diaphysis of right femur which encompasses half of the diameter of bone producing severe limb pain at rest would score: 3 (lytic) + 2 (lower limb) + 2 (1/2 diameter) + 3 (functional pain) = 10. This is an impending fracture according to Harrington’s criteria as well. Fracture is likely to occur without operative intervention and hence, prophylactic fixation with intramedullary nail should be considered in this case.

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