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 due to the application forces external to the body (such as a fall or pull) or at the tendon due to a muscular contraction that is stronger than the forces holding the bone together. Generally muscular avulsion is prevented due to 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.
For displaced avulsion fractures, they are best managed by either open reduction and internal fixation or closed reduction and pinning. Open reduction (cutting open the joint) and internal fixation is used when pins, screws, or similar hardware is needed to fix the bone fragment.
Traumatic complete displacement of a tooth from its socket in alveolar bone. It is a serious dental emergency in which prompt management (within 20–40 minutes of injury) affects the prognosis of the tooth.
The tuberosity avulsion fracture (also known as pseudo-Jones fracture or dancer's fracture is a common fracture of the fifth metatarsal (the bone on the outside edge of the foot extending to the little toe). This fracture is likely caused by the lateral band of the plantar aponeurosis (tendon). 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.
Tibial tuberosity avulsion
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 (rest, ice, compression, elevation) 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.
Occurrence in non-humans
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.
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