An avulsion fracture is a bone fracture which occurs when a fragment of bone tears away from the main mass of bone as a result of physical trauma. This can occur at the ligament by the application of forces external to the body or at the tendon by a muscular contraction that is stronger than the forces holding the bone together. Generally muscular avulsion is prevented by the neurological limitations placed on muscle contractions. Highly trained athletes can overcome this neurological inhibition of strength and produce a much greater force output capable of breaking or avulsing a bone.
The tuberosity avulsion fracture. This fracture is likely caused by the lateral band of the plantar aponeurosis. Most of these fractures are treated with a hard-soled shoe or walking cast. This is needed until the pain goes away and then the patient can return to normal activities. Healing is usually completed within eight weeks.
A tibial tuberosity avulsion fracture is an incomplete or complete separation of the tibial tuberosity from the tibia. This occurs as a result of a violent contraction of the quadriceps muscles, most often as a result of a high-power jump. Incomplete fractures are usually treatable with the traditional RICE method, but complete/displaced fractures will most often require surgery to pin the tuberosity back in place. Tibial tuberosity avulsions occur most often in teenagers that engage in a large amount of sporting activities, and many studies have shown a history with Osgood-Schlatter's disease to be linked to the fracture.
In 2001, Bruce Rothschild and other paleontologists published a study examining evidence for tendon avulsions in theropod dinosaurs. Among the dinosaurs studied, avulsion injuries were only noted among Tyrannosaurus and Allosaurus. Scars from these sorts of injuries were limited to the humerus and scapula. A divot on the humerus of Sue the T. rex was one such avulsion. The divot appears to be located at the origin of the deltoid or teres major muscles. The localization in theropod scapulae as evidenced by the tendon avulsion in Sue suggests that theropods may have had a musculature more complex and functionally different from those of their descendants, the birds.
