As a prey animal in the wild, horses developed the ability to sleep standing up via a “stay apparatus” that allows them to relax their muscles and doze without collapsing. In the front legs, the apparatus automatically engages when their muscles relax. In the hind legs, the horse engages it by shifting its hip position to lock the patella in place.
Dr. Terri Clark, assistant professor of anatomy, needed a good way to show students how the stay apparatus works. So she ordered a box of bones and put Annamaria Tadlock (Class of 2015) to work on a model.
Tadlock started with nothing but the bones from the left front leg of a horse. She went to a hardware store for screws and a specialty store for some leather. Clark provided epoxy and wire. Tadlock had to figure out where to go from there.
Most of the models in the CVM anatomy classroom have been glued together but that wouldn’t work here. Clark wanted a moveable model that would demonstrate how the ligaments and tendons prevent the fetlock from overextending. “The goal is for students to better understand the stay apparatus of the front limb of the horse,” she says.
Tadlock cut strips of leather to represent the ligaments and tendons and she used rubber tubing to represent the muscle bellies. “I watched a video of a similar stay apparatus that a professor built. It was a grainy old video that Dr. Clark had. I also used pictures from Dr. Clark’s lectures. I sized the leather strips by cutting them longer than I needed, placing them on the bones and then gradually cutting them down until it was right.”
The hardest part for Tadlock was working on all the small bones in the carpus. “It’s a double joint that needs to flex. The way I originally wired it together, it kept breaking so I had to change from two single loops to making a system of moveable wire chain that took the pressure off. I also used a heavier wire.”
In addition to the carpentry skills needed for this project, Tadlock’s leather-working experience came in handy. “The leather is not new to me because my husband and I make leather journals and bags.”
Having taken Clark’s class, Tadlock understands personally how useful this model will be.” I think it will be really helpful for students to be able to see some of the smaller ligaments and where they go because when you are dissecting, it’s hard to separate them out. With this you can unhook each individual “ligament” to see the ones underneath.”
Despite the challenge of constructing the carpus, Tadlock enjoyed this project. “It was really neat when I finally had it all together and it actually stood on its own,” she says.
