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. [1, 2, 3] It is the most common closed tendon injury seen in athletes, though it is also common in nonathletes after "innocent" trauma. Mallet finger has also been referred to as drop, hammer, or baseball finger (though baseball accounts for only a small percentage of such injuries). (See Etiology and Epidemiology.)
The terminal portion of the extensor mechanism that crosses the DIP joint in the midline dorsally is responsible for active extension of the distal joint. A flexion force on the tip of the extended finger jolts the DIP joint into flexion. This may result in a stretching or tearing of the tendon substance or an avulsion of the tendon's insertion on the dorsal lip of the distal phalanx base. In either instance, active extension power of the DIP joint is lost, and the joint rests in an abnormally flexed position. (See Etiology and Presentation.)
Although athletes and coaches often believe mallet injuries to be minor, with many cases going 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 a delay in or lack of treatment may produce permanent disability. (See Prognosis, Workup, and Treatment.)
Controversy exists as to whether the management of bony mallet injuries should be closed or open, especially when the dorsal avulsion fragment is large and the substance of the distal phalanx is subluxed anteriorly. The literature, however, supports the concept of nonoperative treatment even in these cases. (See Treatment.)
For patient education information, see the First Aid and Injuries Center, as well as Mallet Finger and Broken Finger.
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Despite active extension effort, the distal interphalangeal joint of the index finger rests in flexion, characteristic of a mallet finger.
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Typical mallet finger deformity.
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This radiograph depicts a large, dorsal-lip avulsion fracture from the distal phalanx, a bony mallet injury.
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Mallet fracture with volar subluxation of the distal phalanx.
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Stable mallet fracture that involves 40% of the joint surface.
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Dorsal aluminum foam splint for the treatment of a mallet finger.
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Stack splints are widely used for the treatment of mallet finger.
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Molded plastic stack splint for the treatment of mallet finger.
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A skin-tight plaster cast can effectively hold the distal interphalangeal joint extended and the proximal interphalangeal joint (PIP) flexed when a mallet deformity is accompanied by a hyperextensible PIP. Not immobilizing the PIP in partial flexion risks the development of a swan-neck deformity.
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Pressure-sore formation can result from a splint that is applied too tightly, especially if the joint is maintained in a hyperextended position rather than a position of neutral extension.
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This photo demonstrates a thermoplastic blank for a custom-molded mallet finger splint and an oblique view of the molded splint in place.
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Dorsal view of the custom-molded thermoplastic splint in place.
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Volar view of the thermoplastic splint in place.
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Application of the thermoplastic splint.
