An avulsion fracture is a

bone fracture A bone fracture (abbreviated FRX or Fx, Fx, or #) is a medical condition in which there is a partial or complete break in the continuity of any bone in the body. In more severe cases, the bone may be broken into several fragments, known as a ''c ...

which occurs when a fragment of bone tears away from the main mass of bone as a result of

physical trauma Injury is physiology, physiological damage to the living tissue of any organism, whether Injury in humans, in humans, Injury in animals, in other animals, or Injury in plants, in plants. Injuries can be caused in many ways, including mechanic ...

. This can occur at the

ligament A ligament is a type of fibrous connective tissue in the body that connects bones to other bones. It also connects flight feathers to bones, in dinosaurs and birds. All 30,000 species of amniotes (land animals with internal bones) have liga ...

by the application of forces external to the body (such as a fall or pull) or at the

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

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 contraction Muscle contraction is the activation of Tension (physics), tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in musc ...

s. Highly trained

athletes An athlete is most commonly a person who competes in one or more sports involving physical strength, speed, power, or endurance. Sometimes, the word "athlete" is used to refer specifically to sport of athletics competitors, i.e. including trac ...

can overcome this neurological inhibition of strength and produce a much greater force output capable of breaking or avulsing a bone.

Types

Dental avulsion

Traumatic complete displacement of a

tooth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tea ...

from its socket in

alveolar bone The alveolar process () is the portion of bone containing the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The alveolar process is covered by gums within the mouth, terminating roughly along the line of the mandibu ...

. It is a serious dental emergency in which prompt management (within 20–40 minutes of injury) affects the

prognosis Prognosis ( Greek: πρόγνωσις "fore-knowing, foreseeing"; : prognoses) is a medical term for predicting the likelihood or expected development of a disease, including whether the signs and symptoms will improve or worsen (and how quickly) ...

of the tooth.

Tuberosity avulsion of the 5th metatarsal

left, Proximal fractures of 5th metatarsal 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 The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

. 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.

Treatment

$Avulsion fracture of the left first metacarpal$ If the fracture is small, it is usually sufficient to treat with rest and support bandage, but in more severe cases, surgery may be required. Ice may be used to relieve swelling. Displaced avulsion fractures are best managed by either open reduction and internal fixation or closed reduction and pinning. Open reduction (using surgical incision) and

internal fixation Internal fixation is an Surgery, operation in orthopedics that involves the surgical implementation of Implant (medicine), implants for the purpose of repairing a bone, a concept that dates to the mid-nineteenth century and was made applicable fo ...

is used when pins, screws, or similar hardware is needed to fix the bone fragment.

Other animals

Dinosaurs

In 2001, Bruce Rothschild and other paleontologists published a study examining evidence for tendon avulsions in

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

dinosaurs. Among the dinosaurs studied, avulsion injuries were only noted among ''

Tyrannosaurus ''Tyrannosaurus'' () is a genus of large theropod dinosaur. The type species ''Tyrannosaurus rex'' ( meaning 'king' in Latin), often shortened to ''T. rex'' or colloquially t-rex, is one of the best represented theropods. It lived througho ...

'' and ''

Allosaurus ''Allosaurus'' ( ) is an extinct genus of theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period ( Kimmeridgian to late Tithonian ages). The first fossil remains that could definitively be ascribed to th ...

''. Scars from these sorts of injuries were limited to the

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

and

scapula The scapula (: scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side ...

. 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.Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331-336.

References

{{DEFAULTSORT:Avulsion Fracture Bone fractures