XROMM…for dead things!

To understand how an animal moves, there’s no better way then to take a look inside the animal itself! XROMM, (X-Ray Reconstruction of Moving Morphology), is a 3D imaging technology created at Brown University, that allows its users to watch highly accurate animations of animal bones moving in 3D space. To do this, researchers combine CT-scan data with high-speed X-ray movies to produce stunning animations. This method has become increasingly popular in the field of animal and human kinematics and biomechanics– and has been used to understand how pigs chew (see video below), how fish feed, why you may tear your ACL, and even how moles destroy your lawn (mole forelimb kinematics).

Pig Mastication movie from: https://www.xromm.org/movies/

One of the benefits of this method is that you are collecting data in real time- you are observing the fish swallow its prey or the lizard scurrying across the ground as it actually does these movements. This helps researchers to really understand the movements of these bones, and to paint an accurate and reliable picture for what is really going on.

However, working with live animals is very challenging and requires special permits, precautions, and a whole lot of patience. Therefore, XROMM has also recently been used to study ex-vivo joint mobility, using cadavers or dead specimens. This opens up a whole new repertoire of animal taxa to be used for this type of analysis. In a new methods paper by Armita Manafzadeh, she outlines the benefits and challenges of using this method in a practical but exhaustive step-by-step guide.

Figure taken from Manafzadeh, 2020.

The paper outlines the qualifications for obtaining and preparing a good cadaver specimen, how to implant markers and position manipulators (see image below), how to collect X-ray data, track and manipulate it, and even the technical aspects of calculating six degree-of-freedom joint mobility. As ex-vivo XROMM studies continue to increase, Manafzadeh’s paper will provide a helpful and much needed workflow.

Figure taken from Manafzadeh, 2020.

This post was written by Kelsi Rutledge, a 3rd year Ph.D. student at UCLA studying the functional morphology and fluid dynamics of olfaction in batoid fishes. Check out her website here or follow her on Twitter here.

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