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Three‐dimensional study of the musculotendinous architecture of lumbar multifidus and its functional implications

Lumbar multifidus (LMT) is a key muscle, which provides stability to the lumbar spine, and has been shown to have altered neuromuscular recruitment following acute episodes of low back pain. Architectural parameters are important determinants of function, but have not been well documented for LMT. Therefore, the purpose of this study is to model and quantify the architecture of LMT throughout its volume. Nine male and one female formalin‐embalmed cadaveric specimens (average age 80 ± 11 years) without any evidence of spinal deformity/pathology were used. The musculotendinous components of LMT were serially dissected and digitized. Next, the data were imported into MAYA™ to create a three‐dimensional model of each segment of LMT from which architectural parameters including fiber bundle length (FBL), fiber bundle angle (FBA), and tendon length were quantified. Water displacement was used to determine volume. The data were analyzed using paired t‐tests and ANOVA followed by Tukey's post‐hoc test (P ≤ 0.05). LMT (L1–L4) has three architecturally distinct regions: superficial, intermediate, and deep. Intermediate LMT was absent in all specimens at L5. Mean FBL decreased significantly (P ≤ 0.05) from superficial (5.8 ± 1.6 cm) to deep (2.9 ± 1.1 cm) as did volume (superficial, 5.6 ± 2.3 ml; deep, 0.7 ± 0.3 ml) measured at each region. By contrast, mean FBA increased from superficial to deep. The current study lends further evidence to support the role of different regions within LMT to serve distinct functions particularly to produce movement and/or control stability. Clin. Anat. 21:539–546, 2008. © 2008 Wiley‐Liss, Inc.