Orthopedics and Orthopedics Surgery

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Mallet Finger (Extensor Injury—Zone 1)
Background
Avulsion of the extensor tendon from its distal insertion at the dorsum of the DIP joint produces an extensor lag at the DIP joint. The avulsion may occur with or without a bony fragment avulsion from the dorsum of the distal phalanx. This is termed a mallet finger of bony origin, or mallet finger of tendinous origin (Figs. 1–20 and 1–21). The hallmark finding of a mallet finger is a flexed or dropped posture of the DIP joint (Fig. 1–22) and an inability to actively extend or straighten the DIP joint. The mechanism is typically forced flexion of the fingertip, often from the impact of a thrown ball.

Classification of Mallet Finger
Doyle (1993) described four types of mallet injury:

Type I—extensor tendon avulsion from the distal phalanx.

Type II—laceration of the extensor tendon.

Type III—deep avulsion injuring the skin and tendon.

Type IV—fracture of the distal phalanx with three subtypes:

Type IV A—transepiphyseal fracture in a child.
Type IV B—less than half of the articular surface of the joint involved with no subluxation.
Type IV C—more than half of the articular surface involved and may involve volar subluxation.

Treatment
Abound and Brown (1968) found that several factors are likely to lead to a poor prognosis after mallet finger injury:

Age older than 60 years.

Delay in treatment of more than 4 weeks.

Initial extensor lag of more than 50 degrees.

Too short a period of immobilization (<4 wk).

Short, stubby fingers.

Peripheral vascular disease or associated arthritis.
The results of mallet finger treatment are not universally good by any method of treatment.

Continuous extension splinting of the DIP joint, leaving the PIP free for 6 to 10 weeks (with a plastic stack splint) is the typical treatment for mallet fingers of tendinous origin (Fig. 1–23). If no extensor lag exists at 6 weeks, night splinting for 3 weeks and splinting during sports activities for an additional 6 weeks are employed.

The patient must work on active ROM of the MCP and PIP joints to avoid stiffening of these uninvolved joints. At no point during the healing process is the DIP joint allowed to drop into flexion, or the treatment must be repeated from the beginning. During skin care or washing, the finger must be held continuously in extension with the other hand while the splint is off.

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