Subcutaneous fat index: a reliable tool for lumbar spine studies.

• The subcutaneous fat tissue thickness at L1-L2 level (subcutaneous fat index [SFI]) was superior to BMI in predicting LBP and spine degeneration. However, a reliable cutoff value has not been previously defined. • The subcutaneous fat index had reliable cutoff values of 8.45 mm and 9.4 mm for females and males, respectively. • Females with an SFI of > 8.45 mm and males with > 9.4 mm had significantly higher rates of severe IVDD, Modic changes, and fatty infiltration in their paraspinal muscles.