Background
The term mallet finger has long been used to describe the deformity produced by disruption of the terminal extensor mechanism at the distal interphalangeal (DIP) joint (see image below).[1, 2, 3, 4] Mallet finger is the most common closed tendon injury that is seen in athletes; this injury is also common in nonathletes after "innocent" trauma. Mallet finger has also been referred to as drop, hammer, or baseball finger (although baseball accounts for only a small percentage of such injuries).
Typical mallet finger deformity. Athletes and coaches often believe mallet injuries to be minor, and many cases go untreated. All individuals with finger injuries, including suspected mallet finger, should have a systematic evaluation performed. Good results can usually be obtained with early treatment of such injuries, whereas delay or lack of treatment may produce permanent disability.
For excellent patient education resources, visit eMedicine's Hand, Wrist, Elbow, and Shoulder Center and Sports Injury Center. Also, see eMedicine's patient education articles Mallet Finger and Broken Finger.
Related eMedicine topics:
Hand, Finger Nail and Tip Injuries
Hand, Fracture and Dislocations: Phalangeal
Related Medscape topics:
Resource Center Adolescent Medicine
Resource Center Exercise and Sports Medicine
Specialty Site Orthopaedics
Functional Anatomy
The tendinous mallet injury represents a disruption of the terminal extensor tendon at its insertion on the distal phalanx. Mallet injury is most commonly caused by forced flexion against an actively extended digit (eg, when a ball strikes the end of a finger); a direct blow over the dorsum of the DIP joint may also produce a mallet finger. The resultant deformity occurs by unopposed flexion of the distal phalanx.
Mallet deformity can also be associated with a fracture of the dorsal articular surface of the distal phalanx. Radiographically, these bony avulsions can be characterized into 3 common patterns, as follows:
- A tiny fleck of bone that involves less than 25% of the articular surface
- A large bony fragment that involves 30% or more of the articular surface
- An avulsion of any size that is associated with palmar subluxation of the distal phalanx
Generally, fleck fractures and nondisplaced avulsions that involve up to 40% of the joint surface are believed to be stable injuries.[2] Individuals with stable injuries are candidates for conservative treatment.
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