The mechanical and inflammatory low back pain (MIL) index: development and validation

Area of Science:

• Orthopedics
• Physical Therapy
• Pain Management

Background:

• Non-specific low back pain (NSLBP) presents diagnostic challenges.
• Differentiating mechanical and inflammatory LBP is crucial for effective treatment.
• Existing assessment tools may lack specificity for LBP subtypes.

Purpose of the Study:

• To develop and validate the Mechanical and Inflammatory Low Back Pain Index (MIL).
• To create a concise, reliable 7-item tool for assessing NSLBP.
• To aid clinicians in distinguishing between mechanical and inflammatory LBP symptoms.

Main Methods:

• 170 participants with NSLBP completed the MIL, Roland Morris Questionnaire (RMQ), SF-12, and Backache Index (BAI).
• Test-retest reliability was assessed in 37 patients over three days without treatment.
• Factor analysis, internal consistency, and validity (face, content, discriminant, convergent) were evaluated.

Main Results:

• Confirmatory factor analysis supported a two-factor model for the MIL.
• Internal consistency was moderate (α = 0.68–0.72), and test-retest reliability was high (ICC = 0.91).
• The MIL demonstrated good discriminant validity for both mechanical (AUC = 0.74) and inflammatory (AUC = 0.92) LBP.

Conclusions:

• The Mechanical and Inflammatory Low Back Pain Index (MIL) is a valid and reliable clinical instrument.
• The MIL effectively discriminates between mechanical and inflammatory LBP in patients with NSLBP.
• This tool can improve the accuracy of low back pain assessment and guide targeted interventions.