Reliability of Ultrasound Imaging for the Assessment of Lumbar Multifidi Thickness in Older Adults With Chronic Low Back Pain

Background and Purpose: Ultrasound imaging (USI) has been shown to be a reliable measure for direct assessment of the lumbar multifidi among younger adults. However, given age- and chronic low back pain (CLBP)-related spinal changes, similar studies are needed before clinical use of USI among older adults with CLBP. The goals of this study were to evaluate intra-and interexaminer reliability for USI assessment of multifidi thickness at rest and during a contraction and to determine standard error of measurement values (SEMs) and minimal detectable change values (MDCs) among older adults with CLBP. Methods: Thirty-one adults, aged 60 to 85 years, with CLBP were recruited. Two examiners performed USI assessments of multifidus thickness at rest and during a contralateral lower extremity lift. Intraclass correlation coefficients (ICCs) were used to estimate inter-and intraexaminer reliability. Additionally, SEMs and MDCs were calculated. Results: All USI measurement techniques demonstrated excellent within-day, interexaminer procedural reliability (ICCs: 0.82-0.85) and good-to-excellent between-day, interexaminer procedural reliability (ICCs: 0.72-0.79). The SEMs ranged from 0.36 to 0.46 cm; MDCs ranged from 1.01 to 1.26 cm. Regardless of the measurement technique, examiner 1, the more experienced examiner, demonstrated lower SEMs and MDCs than examiner 2. Discussion: Lower ICCs, greater SEMs, and greater MDCs for USI multifidus thickness assessment in older adults with CLBP, when compared with previously published, procedural reliability results for younger adults with and without low back pain, may indicate that imaging is more challenging in this patient population. Factors, such as examiner training and participant anthropometrics, may impact reliability. Conclusions: Good-to-excellent intra-and interexaminer USI procedural reliability may provide clinicians a direct assessment technique for clinical evaluation of the lumbar multifidi in older adults with CLBP. SEMs and MDCs may allow for accurate interpretation of USI assessments in this population.