What is This?

After 30 years of using dual X-ray absorptiometry (DXA) to examine bone, muscle, and fat in clinical, as well as, athletic populations I have come across some interesting cases.  Periodically, I would like to share some of those cases with you, and will provide scans when able. I hope that you enjoy seeing some of these scans and, ultimately, you are able to learn from these cases and they help you in your own practice.

Since the NFL Football Combine just concluded a few weeks ago, I thought I would start with a scan that pertains to football.  If you look at the scan below, you will notice on the subject’s right leg a little ghost (red circle) of an image on the femur.  When I first saw this scan, I initially thought it was an artifact of some kind and did not pay any attention to it.  However, on future scans of this individual, the artifact remained in exactly the same spot on every scan. Clearly, it was not an artifact, but something with the bone itself.  In conversations with this individual, I found out that during his career he was on the kickoff team and he went downfield to tackle an individual who was running at full speed. The ball carrier lowered his head and his helmet struck this individual squarely in his thigh pad.  The force that the ball carrier delivered with his helmet was enough to crack this individual’s thigh pad. Of course, he got a new thigh pad, but he also had a lot of pain in the area following the game. The team’s medical staff examined the leg and determined that this individual had suffered a bone contusion.  The result of that bone contusion was that, over time, the spot on the femur that suffered the impact from the helmet calcified enough to create a visible “bump” on the DXA scan.  

In examining the bone mineral content (BMC) between the right and left leg there was a small difference between the two legs (977 g vs. 974 g).  However, this is not surprising being that the right leg was this individual’s dominant leg and there is often a little asymmetry between the two legs. The bone mineral density (BMD) for these two legs also demonstrated a similar result, with the BMD for these two legs being only slightly different (1.98 g/cm2) vs. 1.97 g/cm2).  

Two things stick out for me regarding this scan.  The first is that the DXA was able to pick up this small area of calcification.  The second is how the force of one blow was enough to not just crack a thigh pad, but also, to alter the bone structure itself.

About the Author

Donald Dengel, Ph.D., is a Professor in the School of Kinesiology at the University of Minnesota and is a co-founder of Dexalytics. He serves as the Director of the Laboratory of Integrative Human Physiology, which provides clinical vascular, metabolic, exercise and body composition testing for researchers across the University of Minnesota.

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