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Mirels’ Criteria for Prophylactic Fixation

Calculators  Oncology
Mirels criteria for prophylactic fixation is used to determine metastatic lesion in a long bone.
Lesion Site
Upper limb 1
Lower limb 2
Trochanteric region 3
Lesion Size
Less than 1/3 of cortex 1
1/3 to 2/3 of cortex 2
More than 2/3 of cortex 3
Nature of lesion
Blastic 1
Mixed 2
Lytic 3
Pain Level
Mild 1
Moderate 2
Functional 3
Result:

Background

Measured Factor
Mirels scoring system
Measured Factor Disease
  • Long bone lesion
  • Metastatic lesion in a long bone
Measured Factor Detail
Mirels scoring system is used to diagnose impending pathologic fractures in long bone. this method is based on four charactersticts like site of lesion, nature of lesion, size of lesion and pain.
Speciality
Orthopedic Surgeon
Body System
Oncology
Measured Factor Low Impact
  • Score of ≤7 showed 0-4% chances of risk of fracture which is safe to irradiate.
Measured Factor High Impact
  • Score 8 showed 15% of risk of fracture which is consider as prophylactic fixation
  • Score of ≥9 showed >33% of fracture risk and is an indication of prophylactic fixation

Result Interpretation

Ranges Ranges
  • Critical High: ≥9
  • Normal: ≤7
Result High Conditions
  • Long bone lesions
False Positive
  • Sensitivity or specificity for Mirels’ classification increases the chances of false positives results.
References: 4
Test Limitations
Specific criteria is needed to predict impending fracture at borderline scores | Mirels’ classification is applicable only to metastatic lesions in long bones. It cannot be applied to the vertebral column like spine which is most common site for metastatic breast cancer
References: 4

Studies

Study Validation 1
The aim of this study was to validate the Mirels' rating system for predicting the pathologic fractures in 53 patients with femoral metastatic lesions. Mirels score was calculated for each patient and side by side independent clinical judgment was determined for impending fracture by examiners. Results showed highly significant agreement between both the approaches measured by overall Kappa and concordance for individual and overall scores. Overall sensitivity was founded 91% and specificity was 35%. Mirels' score seems to be a valid, effective and more sensitive tool than clinical judgment However, more specific parameters are needed to be found to make improvements
References: 5
Study Validation 2
This study aimed to validate the Mirels score in impending pathological fractures in metastatic disease of the lower limb. 62 patients with mean age of 65 years and with various types of metastatic carcinoma were recruited in the study. During initial presentation pain radiographs were assigned scored using Mirels system. Anatomical site, size, and radiographic appearance were some of the component of the score measured. Fleiss' kappa test was used to calculate inter- and intraobserver reliability. Kappa values for the interobserver variability and intra-observer reliability of the Mirels score were k = 0.554 and k = 0.608 respectively. This study concluded that Mirels score need more validation studies to prove its reproducibility in predicting the risk of pathological fracture
References: 6
Study Validation 3
The objective of the study was to validate the Mirels' rating system in patients with in humeral bone lesions. A total of 17 case histories and plain radiographs of 16 subjects with humeral metastases were analyzed through a web-based survey. Mirels' criteria were calculated by physicians to provide a impended fracture in patients. This outcome was then compared with the original results of cohort of 12 patients. The sensitivity and specificity of Mirels score was found to be 14.5% and 82.9%, respectively when Mirels score of 9 points or greater was used as definition and when 7 or more points was used as the definition of impending pathologic humeral fracture sensitivity increased to 81% but specificity was decreased to 32%.This study concluded that Mirels rating system was less reproducible and valid, so it needs to be validated with further prospective studies.
References: 7
Study Additional 1
The aim of this study was to analyze a scoring system combined of four clinical risk factors. A retrospective analysis was done on 78 lesions that had been irradiated without prophylactic surgical fixation. Score were assigned to the radiographic images and were analyzed for any impended fracture. Results showed 51 lesions that did not fracture during the subsequent six months and 27 lesions that fractured within six months. A mean score of 7 was seen in the nonfracture group while in fracture group had a 10 mean score. With increasing score the risk of fracture also increased. This study concluded that lesions scores of ≤ 7 can be considered for irradiation without risk of fracture while lesions with scores of ≥ 8 required  prophylactic internal repair before irradiation therapy
References: 8

References

  1. Mirels H. Metastatic disease in long bones: A proposed scoring system for diagnosing impending pathologic fractures. 1989. Clin Orthop Relat Res. 2003;(415 Suppl):S4-13.
  2. 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):S201-7.
  3. 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.
  4. 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.
  5. 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):S201-7.
  6. 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
  7. 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):1279-84.
  8. Mirels H. Metastatic disease in long bones. A proposed scoring system for diagnosing impending pathologic fractures. Clin Orthop Relat Res. 1989;(249):256-64.