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

Background Previous evidence showed altered lumbar multifidus (LM) activation in populations with chronic nonspecific low back pain (LBP). We aimed to investigate the test-retest and inter-examiner reliability of ultrasound imaging (US) for assessing LM thickness at rest and activation during the active straight leg raise test (ASLR) and the association between thickness changes with clinical outcomes. Methods Fifty-two patients with LBP and two examiners (one experienced and one novice) participated in this study. A total of 18 B-mode images at L4-L5 or L5-S1 level (both sides, 3 at rest and 6 during ASLR) were collected. For assessing test-retest reliability, the experienced examiner repeated the procedure after 7 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 of multiple measurements improved the agreement. Greater LM thickness at rest (p < .05) and greater thickness change after 3 s (p < .01) and 10 s (homolateral side, 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 and contracted during the ASLR in patients with LBP. The measurement at 3 s after maintaining ASLR, as well as the use of the mean of three measurements, has been shown to be the most reliable method for measuring LM muscle thickness during ASLR.

Automated summary

The study found that ultrasound imaging is a reliable method for assessing lumbar multifidus thickness at rest and during contraction in patients with low back pain. Results indicated that measuring LM thickness at 3 seconds after maintaining ASLR, as well as using the mean of three measurements, is the most reliable method for assessing LM muscle thickness during ASLR.