In three short pages, surgeons can obtain a quick, but thorough review of a condition known as mallet thumb. This evidence-based continuing education activity provides updated information on indications for the treatment of mallet thumb (both surgical and nonsurgical approaches), methods of splinting, and expected results from treatment. All information comes from the most current available literature on mallet thumb injuries.
A mallet injury affects the distal interphalangeal or DIP joint of the finger (or more rarely, the interphalangeal joint of the thumb). This joint is commonly injured during sporting activities such as baseball. If the tip of the finger or thumb is struck with the ball, the tendon that attaches to the small bone underneath can be injured. Untreated, this can cause the end of the finger to fail to straighten completely, a condition called mallet finger or mallet thumb.
Using the case of a 20-year-old woman with mallet thumb from a softball injury, the authors of this continuing education tool aid surgeons in providing best possible care for their patients with similar injuries. When faced with such a problem, the question is always, What is the preferred treatment?
The patient presented with a nontender but swollen thumb that she could no longer fully extend at the tip. The examiner could straighten the thumb fully (passively). X-rays were normal with no sign of fracture, dislocation, or other bony damage. The injury occurred three weeks before the surgeon evaluated the patient. The mechanism of injury was the typical failure to catch a speeding baseball that struck the end of the thumb instead.
A review of the literature and current evidence reveals no consensus on the most effective or recommended treatment. And the evidence presented is based on published case reports like this one. In general, closed injuries that do not require surgery are splinted. Open injuries are repaired surgically possibly using K-wire fixation of the interphalangeal joint of the thumb. When present, ruptured (avulsed) tendons of the thumb are reattached or reconstructed.
MRIs can be used to see how far an avulsed tendon has retracted (pulled away from the bone). The space between the end of the tendon and the place on the bone where it belongs is called a tendon gap. If the tendon hasn’t retracted too much, it can be stretched and pulled back to the insertion point and then reattached (repaired). If the tendon gap is too great, then a tendon graft may be needed (reconstruction). But there is no cut off point to determine when the gap requires repair versus reconstruction.
The type of splint to use for the nonoperative approach remains unknown as well. How long to use splinting (duration) for best results is also unknown. The most common time period for splint wear is four to six weeks when the injury is acute (occurred within the last two weeks). Results reported from different case series varied depending on whether the injury was open or closed and in the case of closed injuries — how much time had passed between injury and evaluation/treatment.
According to some studies, the earlier the treatment, the better the outcome. Closed injuries often results in better interphalangeal joint extension. Patients do not always get all of their normal motion (full thumb extension) back. In the case of this patient, a custom-made thumb spica splint was worn full-time for six weeks. Then she wore a nighttime splint for another four weeks. Four months after injury, she had full thumb motion and was satisfied with the results.
The authors note that evidence to support standardized treatment protocols are lacking because thumb mallet injuries are so rare. More multicenter studies are needed determine if and when nonsurgical treatment is best, what type of splinting to use, how long to use splinting, and when to attempt repair versus reconstruction based on tendon gapping. In addition, surgeons need evidence-based guidance to determine type of post-operative care and when to recommend formal hand therapy.