The evaluation of lumbar multifidus muscle function via palpation: reliability and validity of a new clinical test

Background contextThe lumbar multifidus muscle provides an important contribution to lumbar spine stability, and the restoration of lumbar multifidus function is a frequent goal of rehabilitation. Currently, there are no reliable and valid physical examination procedures available to assess lumbar multifidus function among patients with low back pain.PurposeTo examine the inter-rater reliability and concurrent validity of the multifidus lift test (MLT) to identify lumbar multifidus dysfunction among patients with low back pain.Study design/settingA cross-sectional analysis of reliability and concurrent validity performed in a university outpatient research facility.Patient sampleThirty-two persons aged 18 to 60 years with current low back pain and a minimum modified Oswestry disability score of 20%. Study participants were excluded if they reported a history of lumbar spine surgery, lumbar radiculopathy, medical red flags, osteoporosis, or had recently been treated with spinal manipulation or trunk stabilization exercises.Outcome measuresConcurrent measures of lumbar multifidus muscle function at the L4-L5 and L5-S1 levels were obtained with the MLT (index test) and real-time ultrasound imaging (reference standard).MethodsThe inter-rater reliability of the MLT was examined by measuring the level of agreement between two blinded examiners. Concurrent validity of the MLT was investigated by comparing clinicians' judgments with real-time ultrasound imaging measures of lumbar multifidus function.ResultsInter-rater reliability of the MLT was substantial to excellent (κ=0.75 to 0.81, p≤.01) and free from errors of bias and prevalence. When performed at L4-L5 or L5-S1, the MLT demonstrated evidence of concurrent validity through its relationship with the reference standard results at L4-L5 (rbis=0.59-0.73, p≤.01). The MLT generally failed to demonstrate a relationship with the reference standard results from the L5-S1 level.ConclusionsOur results provide preliminary evidence supporting the reliability and validity of the MLT to assess lumbar multifidus function at the L4-L5 spinal level. Additional research examining the measurement properties and utility of this test should be undertaken before confident implementation with patients.