An active 81-year-old woman was evaluated 3 days after injuring her right hand while playing pickleball. After hitting the ball with extra force, she had immediately felt pain over the dorsum of her right hand. She then noticed progressive swelling of the affected area over the next 2 days.

Examination revealed swelling over the metacarpal of her right fourth finger, and she had difficulty extending that finger (Figure 1).

QUESTION

Based on the patient's history and physical examination, which one of the following is the most likely diagnosis?

• A. Central extensor tendon injury with boutonnière deformity.

• B. Distal extensor tendon rupture with dorsal avulsion fracture (mallet finger).

• C. Dupuytren contracture.

• D. Extensor digitorum tendon rupture.

• E. Flexor digitorum profundus avulsion fracture.

DISCUSSION

The correct answer is D: extensor digitorum tendon rupture, which is characterized by a reduced ability to extend the affected finger at the metacarpophalangeal joint. Extensor tendon injuries of the hand are common, with an incidence of 14 per 100,000 person-years. They occur twice as often as flexor injuries of the fingers. Extensor tendon injuries are categorized into eight zones, with odd-numbered zones over joints and even-numbered zones between them.¹ This patient's injury occurred in zone six, over the metacarpal bone of the fourth finger. Extensor tendon injuries most commonly involve the index finger or thumb; injuries in zone six are less common, accounting for only 5% of hand tendon injuries.²