Background: Whether the lower phase angle associated with worse physical function is a result of pain and muscle weakness in patients with lumbar spinal stenosis (LSS) is unclear.
Objective: To evaluate the association between phase angle and back pain-specific disabilities in patients with LSS.
Methods: In this single-center, cross-sectional study, 491 participants with LSS were enrolled. The phase angle and back pain-specific disability were measured using bioelectrical impedance analysis and the Oswestry Disability Index, respectively. General linear models were used to examine associations between phase angle and the Oswestry Disability Index with or without adjustment for age, sex, low back and lower limb pain, numbness in the lower extremities, total fat mass, and lower limb muscle mass.
Results: The mean (SD) phase angle was 4.4∘ (1.0∘), and the mean Oswestry Disability Index was 36.1 (14.1) points. Greater phase angles were associated with less Oswestry Disability Index points (p= 0.037) independent of fat mass, low back pain, and hip or lower limb pain.
Conclusions: A lower phase angle was associated with worse functional disability. Low phase angle may be an indicator of functional impairment due to low back pain associated with LSS.
Keywords: Oswestry Disability Index; Phase angle; bioelectrical impedance analysis; functional disability; lumbar spinal stenosis.