Superficial and deep lumbar multifidus layers of asymptomatic individuals: intraday and interday reliability of the echo intensity measurement.

Abstract

Ultrasonography has been used to understand the functional and biomechanical aspects of the lumbar multifidus muscle in vivo. To characterize the multifidus echogenicity, the peculiarities of their superficial and deep layers must be considered. The present paper aimed to characterize the lumbar multifidus echo intensity (EI), in both superficial and deep layers, in ultrasonography images acquired in longitudinal and transversal orientations. Evaluator obtained two images in each side of the lumbar of the volunteer, who was lying on prone position. Ultrasonography images were taken with probe in transversal and longitudinal orientations. EI was estimated by means average value of the grayscale distribution histogram, by extracting from region of interest of the superficial and deep layer. All participants returned for a second test day. Two-way MANOVA test was applied to compare EI measurements, considering layers and side factors. The reliability and variability were analyzed by the intraclass correlation coefficient and standard error measurements (SEM), respectively. Two-way MANOVA found significant difference between the layers in the transversal and longitudinal images, but not between the sides. Interdays reliability ranged of reasonable to excellent, and SEM values were lower than 17.08%. The superficial layer of the multifidus muscle showed higher EI values than the deeper one. These analyses can serve as a basis for future studies approaching multifidus of the people with low back pain.