Reference Data for Modeling and Simulation of Layered Tissue Structures of Musculoskeletal Extremities

Ahmet Erdemir, PhD1, Tara Bonner, MS1, Robb Colbrunn, DEng1, J. Eric Jelovsek, MD, MMEd1, Joy P. Ku, PhD2, Mark Lobosky, BS1, Benjamin Landis, MS1, Erica Morrill, MS1, Tammy M. Owings, DEng1, Tyler Schimmoeller, BS1, Mike Wong, MS3

1 Cleveland Clinic, Cleveland, OH

2 Stanford University, Stanford, CA

3 Potrero Scientific, LLC, San Francisco, CA

Skin, fat, and muscle layers of the extremities are subject to high rates of injury during combat. Computational models of these tissue structures can provide the platform to understand injury mechanisms, support medical training, and guide the design of protective gear. Unfortunately, availability of comprehensive data, to enhance the quality and quantity of physiological representations of layered musculoskeletal tissues in virtual systems, is limited. The goal of this study is to acquire and disseminate anatomical and mechanical data collected on lower and upper extremities of the general population. An ultrasound system was instrumented with a load transducer for in vivo characterization of skin, fat, and muscle thicknesses in the upper and lower extremities in unloaded and loaded states. The unloaded state provided anatomic measures of the tissue layers for 48 regions (4 circumferential x 3 longitudinal x 4 segments). The loaded state utilized the ultrasound probe as an indenter to quantify the mechanical response of the layered tissue structures at eight locations (central regions, anteriorly and posteriorly). Participant information was collected including age, gender, height, mass, race, ethnicity, activity level (self-reported), and anthropometric data (3 circumferences and 1 length for each segment). The study was approved by the Cleveland Clinic IRB and the Human Research Protection Office of the U.S. Army. To date, 50 subjects have been tested (22 female, 28 male; 20 to 70 years old). The mean (±SD) for height, mass, and body mass index for these subjects were 1.70±0.09 m, 78±17.6 kg, and 26.8±5.6 kg/m2, respectively. The ranges of unloaded thicknesses of skin, fat and muscle were 0.46-4.15 mm, 0.04-52.76 mm, and 2.70-103.89 mm, respectively. Indentation forces reached up to 14.95 N (360 mm2 indenter area) at indentation depths of up to 42.1% of total tissue thickness. During indentation, deformations across all locations were 6.1±10.7%, 12.7±10.9%, and 19.2±8.1% for skin, fat, and muscle respectively. For the management and dissemination of data, a web-based system was developed. The system has an online interface for the team to upload raw (ultrasound images, probe forces) and derivative data (tissue thicknesses). It also provides a querying interface for the community to identify relevant data for download and prospective reuse. The data management and querying system is under evaluation and will be used to share the collected data publicly. The anatomy and mechanics of layered tissue structures will provide the foundation for authentic models for specific regions of the musculoskeletal extremity that represent diverse subjects across the general population. This comprehensive data set will allow the project team and others to capture realism in virtual reality systems for medical training, scientific research, and product design. This study has been supported by USAMRMC (W81XWH-15-1-0232). The views, opinions and/or findings contained in this document are those of the authors and do not necessarily reflect the views of the funding agency. Ultrasound imaging system and probes were loaned by Siemens Medical Solutions USA, Inc. See project site for more information; https://simtk.org/projects/multis.

Learning Objectives

Describe anatomical properties of skin, fat, and muscle layers of legs and arms.

Describe mechanical response of skin, fat, and muscle layers of legs and arms during indentation.

Learn how to find data sources for modeling and simulation of skin, fat, and muscle layers of legs and arms.