Answer: Refer the cheerleader to a hand surgeon (B).
This patient has a rupture of the central extensor tendon of the pinky finger at the PIP joint. The mechanism of injury and her inability to completely extend the injured finger at the PIP joint alert you to this type of injury. An x-ray may sometimes be normal but in this case, it shows the flexion of the PIP joint. Surgical repair of the rupture should be scheduled without delay.3
Most injuries at this joint occur from forced extension, not flexion, and result in a volar plate rupture.4 If swelling and pain make evaluation of an acute dislocation injury difficult, splinting in the “safe hand” position for 72 hours while icing the injured finger will make it possible to do a more detailed follow-up exam.3
Extended periods of splinting can make the PIP joint very stiff, however—and harder to treat than the original injury.5 If the rupture of the central extensor tendon is undetected or simply not treated, a Boutonniere deformity, in which the PIP joint is flexed and the DIP joint is hyperextended, is the likely result.3
CASE 3 A 24-year-old man “jammed” his right ring finger while trying to catch a ball that was passed to him during a pick-up basketball game. He has rested and iced the finger for a couple of days, but it’s still painful and hard to move. He has no significant medical history and has been taking only acetaminophen for the pain.
Examination reveals that the injured finger has good capillary refill, 2-point discrimination is intact at 5 mm, and the other fingers on his right hand have no deformities and a normal range of motion. On the injured finger, however, the DIP joint is swollen and tender; it cannot be fully extended (FiGURE 3).
WHAT'S YOUR DIAGNOSIS?
A. Jersey finger.
B. Distal tuft fracture.
C. Mallet finger.
D. Finger sprain.
E. Trigger finger.
B. Distal tuft fracture.
C. Mallet finger.
D. Finger sprain.
E. Trigger finger.
Answer: The basketball player has mallet finger (C).
Mallet finger typically occurs on the dominant hand. The key physical finding is that the joint is “stuck” in flexion, which is evident during an exam and on x-ray. Although the DIP joint may be passively fully extended, the patient with mallet finger is unable to actively extend it.
Mallet injuries, which are common in sports and associated with minor trauma, are typically caused by sudden forced flexion of the DIP joint during active extension of the finger. This can either stretch or tear the extensor tendon or lead to avulsion of the tendon insertion from the dorsum of the distal phalanx, with or without a fragment of bone. The injury is called a “soft” mallet finger when there is no bone involvement and a “bony” mallet finger when an avulsion is present, like the one that is evident on the FIGURE 3 x-ray (see arrow).
On clinical examination, the finger may or may not have an obvious deformity; similarly, you won’t always see bruising, swelling, or tenderness over the DIP joint.6 The work-up should include posterior/anterior, oblique, and lateral x-rays, followed by an examination of the soft tissue and a range-of-motion evaluation of the metacarpophalangeal and PIP joints. In acute injuries, tenderness is elicited with palpation over the dorsal aspect of the DIP joint. Although most patients develop an extensor lag at the DIP joint immediately after injury, the deformity may be delayed by a few hours or even days.6,7
Nonsurgical management is the standard of care for most mallet injuries, including mallet fractures involving less than one-third of the articular surface with no associated DIP joint subluxation.7
If there is no displacement, round-the-clock splinting to keep the joint in extension for a minimum of 6 weeks is indicated, followed by 2 to 3 weeks of nighttime splinting. It is important that the splinting allow for complete extension of the DIP joint but flexion of the PIP joint. Keeping the PIP in extension for prolonged periods can lead to permanent stiffness of the joint, while failure to provide any immobilization may lead to permanent deformity.
Surgery is indicated for a fracture fragment involving >30% of the joint surface (as demonstrated in the radiograph), volar subluxation, or a swan neck deformity—and when conservative therapy fails.7
CASE 4 An 18-year-old high school football player presents with pain and swelling at the tip of his right ring finger from an injury that occurred a week ago. When the player he was trying to tackle broke away, the patient says, he immediately felt pain and a “pop” in the finger.