Avulsion fracture

Schematic diagram of an avulsion fracture

Avulsion fracture off lunate bone

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.

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.^[1]

For displaced avulsion fractures, they are best managed by either open reduction and internal fixation or closed reduction and pinning.^[2]

Dental avulsion

Main article: Dental avulsion

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.^[3]

Tuberosity avulsion

fifth metatarsal with tuberosity shown

The tuberosity avulsion fracture (also known as pseduo-Jones fracture or dancer's fracture^[4] is a common fracture of the fifth metatarsal (little toe).^[5] This fracture is likely caused by the lateral band of the plantar aponeurosis (tendon).^[6] 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.^[5] Healing is usually completed within eight weeks.^[7]

Occurrence in non-humans

Dinosaurs

A 2001 study found evidence of a tendon avulsion on the arm of Sue the T. rex.

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 than those of their descendants, the birds.^[8]

See also

• Segond fracture
• Dental trauma

References

1. ^ "Avulsion fracture: How is it treated?". Mayo Clinic. April 8, 2010. http://www.mayoclinic.com/health/avulsion-fracture/AN00200. Retrieved April 22, 2010. 
2. ^ "5th Metatarsal Fractures". Musculoskeletal Consumer Review. December 3, 2008. http://mcr.coreconcepts.com.sg/5th-metatarsal-fractures/. Retrieved May 8, 2010. 
3. ^ Zadik Y (December 2008). "Algorithm of first-aid management of dental trauma for medics and corpsmen". Dent Traumatol 24 (6): 698–701. doi:10.1111/j.1600-9657.2008.00649.x. PMID 19021668. 
4. ^ Robert Silbergleit. "Foot Fracture". Medscape.com. http://emedicine.medscape.com/article/825060-overview. Retrieved 19 October 2011. 
5. ^ ^{a b} Gary A. Rosenberg and James J. Sferra (September/October 2000). "Treatment Strategies for Acute Fractures and Nonunions of the Proximal Fifth Metatarsal". Journal of the American Academy of Orthopaedic Surgeons 8 (5): 332–338. 
6. ^ Richli WR, Rosenthal DI (1984 Oct). "Avulsion fracture of the fifth metatarsal: experimental study of pathomechanics". American Journal of Roentgenology 143 (4): 889–91. 
7. ^ JC DeLee (1993). RA Mann and MJ Coughlin. ed. Surgery of the Foot and Ankle, 6th ed.. 2. St Louis: Mosby-Year Book. pp. 1627–1640. 
8. ^ 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.