In medicine, an avulsion is an injury in which a body structure is forcibly detached. It most commonly refers to a surface trauma where all layers of the skin have been torn away, exposing the underlying structures (e.g. subcutaneous tissue, muscle, tendons). This is similar to an abrasion but more severe, as body parts such as an eyelid or an ear can be partially or fully detached from the body. The term comes from the Latin word avellere, "to tear off".

[edit] Types of avulsions

• Ear
• Eyelid
• Nail
• Nerve (brachial plexus)
• Skin
• Tooth
• Surgical

[edit] Ear avulsions

The ear is particularly vulnerable to avulsion injuries due to its exposed position on the side of the head.^[1] The most common cause of these injuries is human bites, followed by falls, motor vehicle accidents, and dog bites.^[1] A partially avulsed ear can be reattached through suturing or microvascular surgery, depending on the severity of the injury.^[2][3] Microvascular surgery can also be used to reattach a completely avulsed ear,^[4][5][6] but its success rate is lower because of the need for venous drainage.^[7][8] The ear can also be reconstructed with cartilage and skin grafts.^[7]

[edit] Eyelid avulsions

This is an uncommon injury^[9] that can be caused by motor vehicle accidents,^[10] dog bites,^[11][12] or human bites.^[11] Eyelid avulsions are repaired by suturing after a CT scan is performed to determine where damage to the muscles, nerves, and blood vessels of the eyelid has occurred.^[10] More severe injuries require reconstruction, however, this usually results in some loss of function and subsequent surgeries may be necessary to improve structure and function.^[13] Microvascular surgery is another method of repair but used rarely.^[12] Sometimes botulinum toxin is injected into the eyelid to paralyse the muscles while the eyelid heals.^[10]

[edit] Traumatic nail avulsions

Trauma to the nail can cause the nail plate to be torn from the nail bed.^[14] Unlike other types of avulsion, when a nail is lost, it is not reattached. Following the loss of the nail, the nail bed forms a germinal layer which hardens as the cells acquire keratin and becomes a new nail.^[15] Until this layer has formed, the exposed nail bed is highly sensitive and should be covered with a non-adherent dressing, as an ordinary dressing will stick to the nail bed and cause extreme pain upon removal.^[16] In the average person, fingernails require 3 to 6 months to regrow completely, while toenails require 12 to 18 months.

[edit] Brachial plexus avulsions

In this type of injury, the brachial plexus (a bundle of nerves that sends signals from the spine to the arms, shoulders, and hands) is torn from its attachment to the spine. One common cause of this injury is when a baby's shoulders rotate in the birth canal during delivery and cause the brachial plexus to stretch and tear.^[17] It occurs in 1-2 out of every 1,000 births.^[18] Shoulder trauma during motor vehicle accidents is another common cause.^[19] Detachment of the nerves causes pain and loss of function in the arms, shoulders, and hands. Neuropathic pain can be treated with medication, but function can only be restored through surgical reattachment or nerve grafts.^[19] For intractable pain, a procedure called dorsal root entry zone (DREZ) lesioning is effective.^[19]

[edit] Skin avulsions

The most common avulsion injury, skin avulsions usually occur during motor vehicle accidents. The severity ranges from skin flaps (minor) to degloving (moderate) and amputation of a finger or limb (severe). Suprafascial avulsions are those in which the depth of the removed skin reaches the subcutaneous tissue layer.^[20] Subfascial avulsions are those deeper than the subcutaneous layer.^[20] Small suprafascial avulsions can be repaired by suturing, but most avulsions require skin grafts or reconstructive surgery.

[edit] Tooth avulsions

A tooth completely or partially (such that the dental pulp is exposed) detached from its socket is avulsed. Secondary (permanent) teeth can be replaced and stabilised by a dentist.^[21] Primary (baby) teeth are not replaced because they tend to become infected and to interfere with the growth of the secondary teeth.^[21] A completely avulsed tooth that is replaced within one hour of the injury can be permanently retained.^[21] The long-term retention rate decreases as the time that the tooth is detached increases, and eventually root resorption makes replacement of the tooth impossible.^[21] To minimise damage to the root, the tooth should be kept in milk or sterile saline while it is outside of the mouth.^[21][22]

[edit] Surgical avulsions

An avulsion is sometimes performed surgically to relieve symptoms of a disorder or prevent a chronic condition from recurring. Small incision avulsion (also called ambulatory phlebectomy) is used to remove varicose veins from the legs in disorders such as Chronic venous insufficiency.^[23] A nail avulsion is performed to remove all or part of a chronic ingrown nail.^[24] Facial nerve avulsion is used to treat the involuntary twitching in Benign Essential Blepharospasm.^[25][26] However, it often requires additional surgeries to retain function^[25] and botulinum toxin injections have proved to be a more effective treatment with fewer complications.^[26]

[edit] See also

• Physical trauma
• Plastic surgery
• Skin grafting

[edit] References