History
In mallet finger, the patient’s history involves a forced distal interphalangeal (DIP) joint flexion injury, after which he or she notices an inability to actively extend the distal joint (though full passive extension remains intact). The dorsum of the joint may be slightly tender and swollen, but often the injury is painless or nearly painless. Patients may think that the joint is only sprained and continue playing sports, with 1 or more days passing before they notice a loss of active extension.
Typically, the athlete with a mallet fracture has a history of a direct blow to the finger, followed by pain and swelling at the DIP joint and an inability to actively fully extend the joint.
Physical Examination
The physical examination findings of mallet finger include localized swelling and tenderness to palpation at the affected DIP joint, as well as an inability to actively extend the injured joint. (See the images below.)
Despite active extension effort, the distal interphalangeal joint of the index finger rests in flexion, characteristic of a mallet finger.
In some individuals, the swan-neck deformity, with hyperextension of the proximal interphalangeal (PIP) joint, may be found, owing to imbalance of the extensor mechanism. However, this is more often a late finding in untreated injuries.
Mallet finger injuries have often been described in terms of Doyle's classification, which comprises the following four main types [1] :
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Type I - Closed injury with or without small avulsion fracture
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Type II - Open injury; laceration
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Type III - Open injury; abrasions with loss of skin or tendon
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Type IV - (A) Physeal injury to distal phalanx (children); (B) fracture fragment involving 20-50% of the articular surface; (C) fracture fragment involving more than 50% of the articular surface
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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.
