Reliability of ultrasonography for the cervical multifidus muscle in asymptomatic and symptomatic subjects.

A test-retest and inter-tester study was designed to assess the reliability of ultrasonography to depict the size of the cervical multifidus muscle in asymptomatic and symptomatic subjects. Ten asymptomatic women (range 19-48 years) and 10 women with chronic whiplash associated disorder (WAD), grade II, (range 19-49 years), matched for height and weight participated. The women were imaged by ultrasonography on two separate occasions by two different testers. On each occasion the cross-sectional area (CSA), and the transverse versus the anterior-posterior dimensions (shape ratio) at the C4 level were measured. The repeated measurements of the CSA were plotted against their means to reveal the limit of agreement. Good agreement was found for the asymptomatic group measurements and the intra-tester agreement for the symptomatic group. The inter-tester agreement for the symptomatic group was questionable. The size of the multifidus muscle was significantly reduced in the symptomatic group ( P<0.05 ). The results indicate that loss of clarity of the fascial layer between the semispinalis cervicis muscle and the cervical multifidus muscle may be a diagnostic sign of muscle atrophy. Ultrasonography can be used to precisely measure the size of the cervical multifidus muscle at the C4-level in asymptomatic young female subjects; it is also reliable for symptomatic subjects if the same tester performs the measurements. Additional criteria are recommended to improve the inter-tester agreement for symptomatic subjects.