Mallet injuries, either tendinous or bony, are common. They are often studied together and typically treated in the same way with extension splintage for 6 to 8 weeks. Yet the evidence clearly shows there are different injuries that present in the same way. Tendinous mallet injuries present in older patients usually following a low energy injury; they are often painless. The commonly injured fingers are the middle and ring. The injuries are almost always single digit without concomitant injuries. There is an extensor lag of a mean of 310 (range 3°-590) in the patients treated in my unit. In contrast, bony mallet injuries occur at a younger age (mean 40 years) and are always due to high energy injuries. The injuries are always painful. The commonly injured fingers are the ring and little fingers. There are multiple injuries in 3% (range 2%-5%) and in 4% to 8% of cases, there are concomitant (nondigital) injuries according to data in my unit. Radiologically there is an appreciably smaller extensor lag; mean 130 (range 0°-400). In particular, bony mallet injuries are extension compression, not avulsion, fractures which should not logically be treated with an extension splint which will reproduce the direction of injury.
Keywords: Bony; Mallet; Mechanism of injury; Subluxation; Tendinous.
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