Non‐Destructive Determination of Muscle Architectural Variables Through the Use of DiceCT

Abstract

The fascicular architecture of skeletal muscle dictates functional parameters such as force production and contractile velocity. Muscle microarchitecture is typically determined by means of manual dissection, a technique that is inherently destructive to specimens. Furthermore, fascicle lengths and pennation angles are commonly assessed at only a limited number of sampling sites per muscle. We present the results of a digital technique to non-destructively assess muscle architectural variables for three jaw-adductor muscles within a specimen of the cercopithecine primate Macaca fascicularis (crab-eating macaque). The specimen is first subjected to a contrast-enhanced staining protocol to increase the density of internal soft tissues. High-resolution µCT scans are then collected and segmented to isolate individual muscles. A textural orientation algorithm is then applied to each muscle volume to reconstruct constituent muscle fascicles in three dimensions. Using this technique, we report muscle volume, fascicle length, angle of pennation, and physiological cross-sectional area (PCSA) for each muscle. These data are compared to results collected using traditional dissection of the contralateral muscles. Reconstructions of muscle volume and pennation angle closely correspond to the dissection results. The degree of similarity between measurements of fascicle length and PCSA varies between muscles, with temporalis demonstrating the greatest disparity between techniques; likely reflecting the complex geometry and fascicular arrangement of this muscle. The described technique samples a much larger number of fascicles than had previously been possible and non-destructively investigates the internal architecture of preserved specimens. We conclude that this approach demonstrates great potential for quantifying muscle internal architecture. Anat Rec, 301:363-377, 2018. © 2018 Wiley Periodicals, Inc.

Dynamic Musculoskeletal Functional Morphology: Integrating diceCT and XROMM

“…Not only does diceCT have the potential to improve our ability to measure musculo-tendon morphology, but it also enables data collection from museum specimens that were previously inaccessible to destructive techniques. Applications of diceCT and other staining methods include the digital dissection of muscles too small or complex for traditional dissection (Metscher, 2009;Jeffery et al, 2011;Holliday et al, 2013;Porro and Richards, 2017), determining muscle orientation in models of bite force (Gignac and Erickson, 2017;Sellers et al, 2017), reconstructing threedimensional muscle architecture (Kupczik et al, 2015;Dickinson et al, 2018), and improving the accuracy of inverse dynamic modeling of joint moments (Charles et al, 2016a,b). One of diceCT's key strengths in muscle functional morphology is its potential to measure muscle architecture in situ, which may generate more accurate measures of joint moment if architecture varies along the length of the muscle's attachment site.…”

“…One of diceCT's key strengths in muscle functional morphology is its potential to measure muscle architecture in situ, which may generate more accurate measures of joint moment if architecture varies along the length of the muscle's attachment site. Meanwhile, methods of digitally determining muscle architecture are promising and continue to improve (Kupczik et al, 2015;Dickinson et al, 2018).…”

“…Continued advances in semi-and fullyautomated marker tracking (Kn€ orlein et al, 2016) are necessary for these methods to be practically applied to orders of magnitude more trials, as has been done for skeletal kinematics and whole muscle length change with Vicon (Reed and Ross et al, 2012;Iriarte-Diaz et al, 2017). Using more automated methods to segment fascicles from diceCT data sets may reduce post-scanning processing time and would make the segmentation step of this method more replicable (Kupczik et al, 2015;Dickinson et al, 2018). Such temporal challenges must be surmounted before these methods are a practical and efficient means of testing functional hypotheses in more depth, such as comparing muscle function across multiple behaviors and conditions, as well as with the taxonomic breadth necessary to robustly argue that a structure has emerged through natural selection to endow an organism with a functional adaptation.…”

Behavioral Correlates of Cranial Muscle Functional Morphology

“…The final two papers in this first issue of our two-part series by Dickinson et al (2018), Orsbon et al (2018), and their colleagues are more examples of the technological leading-edge of muscle analysis. In the paper led by Dickinson, they employ diceCT but use an algorithmic approach to calculate fascicle lengths and pennation angles across a much larger number of fibers than implemented in previous techniques.…”

Functional Morphology and Behavioral Correlates to Postcranial Musculature

“…Traditional approaches to muscle functional morphology research focus mainly on the gross anatomy of muscles and their attachment to bones, while recently researchers are exploring muscle functional morphology using new approaches, in particular, analyses of fiber architecture—more elaborate analyses of the arrangements and dimensions of the fascicles and fibers present in a muscle. A growing body of studies is coupling traditional gross anatomical dissections with chemical dissection (Perry et al, ; Hartstone‐Rose et al, ), Diffusible iodine‐based contrast‐enhanced computed tomography (diceCT) and virtual dissection (Gignac et al, ; Dickinson et al, ; Santana, ) providing deeper information on muscle fiber architecture.…”