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 (such as a fall or pull) or at the

tendon A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...

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-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as ...

s. Highly trained athletes 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, t ...

from its socket in

alveolar bone The alveolar process () or alveolar bone is the thickened ridge of bone that contains the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The structures are covered by gums as part of the oral cavity. The synonymous t ...

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

Tuberosity avulsion of the 5th metatarsal

left, Proximal fractures of 5th metatarsa The

tuberosity In the skeleton of humans and other animals, a tubercle, tuberosity or apophysis is a protrusion or eminence that serves as an attachment for skeletal muscles. The muscles attach by tendons, where the enthesis is the connective tissue between the ...

avulsion fracture (also known as pseudo-Jones fracture or dancer's fracture is a common fracture of the

fifth metatarsal The fifth metatarsal bone is a long bone in the foot, and is palpable along the distal outer edges of the feet. It is the second smallest of the five metatarsal bones. The fifth metatarsal is analogous to the fifth metacarpal bone in the hand. As ...

(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

$Avulsion fracture of tibial tuberosity, annotated$ A tibial tuberosity avulsion fracture is an incomplete or complete separation of the tibial tuberosity from the

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

. This occurs as a result of a violent contraction of the

quadriceps muscles The quadriceps femoris muscle (, also called the quadriceps extensor, quadriceps or quads) is a large muscle group that includes the four prevailing muscles on the front of the thigh. It is the sole extensor muscle of the knee, forming a large ...

, 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

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 operation in orthopedics that involves the surgical implementation of implants for the purpose of repairing a bone, a concept that dates to the mid-nineteenth century and was made applicable for routine treatment in the m ...

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 Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

published a study examining evidence for tendon avulsions in

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

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

Tyrannosaurus ''Tyrannosaurus'' is a genus of large theropod dinosaur. The species ''Tyrannosaurus rex'' (''rex'' meaning "king" in Latin), often called ''T. rex'' or colloquially ''T-Rex'', is one of the best represented theropods. ''Tyrannosaurus'' live ...

'' and ''

Allosaurus ''Allosaurus'' () is a genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic epoch ( Kimmeridgian to late Tithonian). The name "''Allosaurus''" means "different lizard" alludin ...

''.

Scars A scar (or scar tissue) is an area of fibrous tissue that replaces normal skin after an injury. Scars result from the biological process of wound repair in the skin, as well as in other organs, and tissues of the body. Thus, scarring is a natu ...

from these sorts of injuries were limited to the humerus and

scapula The scapula (plural 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 eith ...

. 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 The teres major muscle is a muscle of the upper limb. It attaches to the scapula and the humerus and is one of the seven scapulohumeral muscles. It is a thick but somewhat flattened muscle. The teres major muscle (from Latin ''teres'', meaning ...

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