Quantifying thoracolumbar fascia deformation to discriminate acute low back pain patients and healthy individuals using ultrasound

Reduced shear strain and deformability of the thoracolumbar fascia has been linked to low back pain. A number of ultrasound examination methods have been developed for laboratory rather than clinical practice. The aim of this study was to examine the reliability and discriminative validity (patients vs. healthy individuals) of an ultrasound (US) measurement method for the quantification of thoracolumbar fascia deformation (TLFD). A cross-sectional study with US assessment and rater blinding was conducted in a manual therapy clinic and a university laboratory. 16 acute low back pain (aLBP) patients and 15 healthy individuals performed a standardized trunk extension task. US measurements of TLFD were carried out independently by two raters by imaging the TLF in the starting and ending positions of the movement. Intra-rater and inter-rater reliability were calculated using intraclass correlation coefficients (ICCs) and minimal detectable changes (MDC) were calculated. Receiver operating characteristic (ROC) curve analysis was used to determine the cut-off for TLFD to discriminate the study groups. Kappa statistics were performed to assess rater agreement in discrimination. Intra-rater reliability was excellent (ICC: .92, MDC: 5.54 mm, p < .001) and inter-rater reliability was good (ICC: .78, MDC: 8.70 mm, p < .001). The cut-off for TLFD was 6 mm with a sensitivity of 100% and a specificity of 93.75% and the raters agreed moderately (κ = 0.74, p < .001) when distinguishing patients and controls. The reliability of the US method for assessing TLFD is moderate to excellent, and the ability to discriminate aLBP patients from healthy individuals is moderate. The method could be used to capture an additional parameter in morphological aLBP screenings.