The exact causes of avascular necrosis are often a mystery. Much the same as the lives of dinosaurs. That’s right. Dinosaurs. Keep reading to learn more about this unlikely connection, or find out about the original story here.
Avascular necrosis is a rare condition that causes bone tissue death. It can affect a wide variety of patients. What’s tricky about it is that in early stages it presents no symptoms. Down the line, symptoms are somewhat similar to arthritis. It’s hard to imagine that any time you feel joint pain you should be seeing a doctor, but that’s basically the only good advice. The key is that when the pain is persistent, something is really wrong. Patients suffering avascular necrosis can have joint pain even when lying down.
In about a quarter of all patients, the cause of avascular necrosis is unknown. We know that it is caused when bones are cut off from blood flow. But absent of trauma, and preexisting disease, not much is known about the root of avascular necrosis. To read more about our current knowledge on avascular necrosis, click here.
One known trauma that can lead to blocked blood supply is the bends. Formally known as decompression sickness, the bends is a result of poorly managed diving. Divers must take great care when returning to the surface to prevent bubbles from forming in the body. The effects of these bubbles can range from uncomfortable to lethal.
What we didn’t know about either condition until recently is that it also impacted the lives of dinosaurs.
Bruce Rothschild is a physician by day. In his off time, he studies the pathology of paleolithic creatures. In other words, he takes great interest in the disease of prehistoric animals. While studying the Platecarpus, a lengthy, aquatic reptile of the mosasaur family, Rothschild and his colleagues discovered an unusual length of dead tissue in otherwise healthy bone. The surprising diagnosis was avascular necrosis. Even more surprising was that after ruling out other causes, they determined that decompression sickness, or the bends, had been responsible.
After this initial finding, Rothschild began finding this form of necrosis in many other species. Advancing further along the fossil record shows a decrease in occurrence. It’s been suggested, therefore, that it merely took time for early reptiles to evolve and adapt for these conditions. Even if that’s the case, the bends still has been documented to effect modern aquatic species today. A study in 2014 documented the first known example of the bends in loggerhead turtles. While ancient and modern reptiles have been highly susceptible to this condition, few cases of mammals have been found to study.
The design of the reptilian heart causes increased susceptibility to the bends. Unlike mammals, reptiles, like the loggerhead turtle, have connected left and right heart chambers. The transfer of blood between these chambers is greatly increased in comparison to species without the connection. The danger, however, is that this increases exposure of arteries to air bubbles.
In some rare cases, humans can be born with a similar opening between their heart chambers. This rarely causes illness on land, but raises the likelihood of decompression sickness significantly. Perhaps further study of this unusual connection, or the fossil record will continue to shed light on the histories and causes of avascular necrosis.