Lumbar multifidus thickness changes during active leg raising with ultrasound imaging can detect patients with chronic non-specific low back pain

Background: Altered lumbar multifidus (LM) activation has been found in populations with non-specific chronic low back pain (NSCLBP).Objective: To detect differences in LM muscle thickness at rest and during active manoeuvres between patients with NSCLBP and pain-free controls and to analyze the ability of LM thickness change during the active straight leg raise (ASLR) with rehabilitative ultrasound imaging to detect patients with NSCLBP. Design: Cross-sectional observational study.Methods: Seventy volunteers (50% patients NSCLBP) were recruited. 18 B-mode images of LM at L4-L5 or L5-S1 level selecting the most symptomatic level (both sides, six at rest and three during ASLR) were collected by a blinded assessor. Differences between patients and controls in LM muscle thickness at rest, during ASLR (holding 3sec), and 5 s after ASLR were calculated. In addition, discriminant validity was evaluated by calculating the area under the receiver operating characteristic curve (ROC), sensitivity, specificity and positive and negative like-lihood ratio.Results: Significant LM thickness change differences during ASLR were found within and between groups: bilaterally, LM thickness change during ASLR was significantly higher in healthy controls than in NSCLBP pa-tients. Ipsilateral LM muscle thickness change was sensitive to detect individuals with NSCLBP (ROC = 0.79-0.80). Conclusion: Pain-free individuals exhibited significantly greater LM thickness changes bilaterally during the ASLR compared to patients with NSCLBP. LM thickness change during the ASLR has good validity for discriminating patients with NSCLBP. Further studies should assess benefits of LM training programs in the management of these patients.