Mirels Score - Criteria for Prophylactic Fixation

Mirels Score Explained

The Mirel score consists of four criteria that determines patients with long bone metastasis who present a high fracture risk and that would benefit from prophylactic fixation. These criteria were first described in 1989, have been validated and the score has better properties than the previous Harrington criteria.

This is a weighted scoring system that helps clinicians quantify the risk of sustaining a pathologic fracture through a metastatic lesion in a long bone, by objectively analysing and combining the below four roentgenographic and clinical risk factors into a single score.

The score predicts fracture risk in the 6 months after radiotherapy

In the original study by Mirels, retrospective analysis of metastatic long bone lesions was completed in the case of 78 lesions that had been irradiated without prophylactic surgical fixation. Data on the four criteria had been collected before. In 51 of cases there were no fractures during the subsequent 6 months whilst in the remaining 27 cases, fractures occurred.

The mean score was 7 in the non-fracture group and 10 in the fracture group. Lesions with scores of 7 or lower can be safely irradiated whilst lesions with scores of 8 or higher require prophylactic internal fixation prior to irradiation.

References

Original reference

Mirels H. Metastatic disease in long bones. A proposed scoring system for diagnosing impending pathologic fractures. Clin Orthop Relat Res. 1989; (249):256-264.

Other references

Howard EL, Shepherd KL, Cribb G, Cool P. The validity of the Mirels score for predicting impending pathological fractures of the lower limb. Bone Joint J. 2018; 100-B(8):1100-1105.

Evans AR, Bottros J, Grant W, Chen BY, Damron TA. Mirels' rating for humerus lesions is both reproducible and valid. Clin Orthop Relat Res. 2008; 466(6):1279-1284.

Damron TA, Morgan H, Prakash D, Grant W, Aronowitz J, Heiner J. Critical evaluation of Mirels' rating system for impending pathologic fractures. Clin Orthop Relat Res. 2003; (415 Suppl):S201-S207.

Jawad MU, Scully SP. In brief: classifications in brief: Mirels' classification: metastatic disease in long bones and impending pathologic fracture. Clin Orthop Relat Res. 2010; 468(10):2825-7.