Reliability of lumbar multifidus ultrasound assessment during the active straight leg raise test

Abstract

Background: Previous evidence showed altered lumbar multifidus (LM) activa-tion in populations with chronic nonspecific low back pain (LBP). We aimed toinvestigate the test–retest and inter-examiner reliability of ultrasound imaging(US) for assessing LM thickness at rest and activation during the active straightleg raise test (ASLR) and the association between thickness changes with clinicaloutcomes.Methods: Fifty- two patients with LBP and two examiners (one experienced andone novice) participated in this study. A total of 18 B- mode images at L4–L5 orL5–S1 level (both sides, 3 at rest and 6 during ASLR) were collected. For assess-ing test–retest reliability, the experienced examiner repeated the procedure after7 days. Intraclass correlation coefficients (ICC), standard error of measurements(SEM) and minimal detectable changes (MDC) were calculated.Results: Inter-examiner agreement was good to excellent (ICC3,2 = 0.71–0.92)and test–retest reliability was excellent (ICC3,1 = 0.91–0.98). Mean average ofmultiple measurements improved the agreement. Greater LM thickness at rest(p < .05) and greater thickness change after 3 s (p < .01) and 10 s (homolateralside, p < .01; contralateral side, p < .05) were associated with less pain intensity.Conclusions: US is a reliable method to assess the LM thickness at rest andcontracted during the ASLR in patients with LBP. The measurement at 3 s aftermaintaining ASLR, as well as the use of the mean of three measurements, hasbeen shown to be the most reliable method for measuring LM muscle thicknessduring ASLR.K E Y W O R D Slow back pain, lumbar multifidus, lumbar spine, reliability, stabilization, ultrasound imaging