Jersey finger is an injury to the terminal flexor mechanism at the level of the distal interphalangeal (DIP) joint. This can be due to either rupture of the flexor digitorum profundus (FDP) tendon in Zone 1 or an avulsion fracture of the distal phalanx with a fragment of bone that remains attached to the tendon (Figure 35.1). The degree of retraction of the tendon ranges from minimal displacement to retraction into the palm.

Mechanism of injury—Injury occurs when a flexed DIP joint is forcefully hyperextended and the FDP tendon ruptures at its weakest point, which is the insertion site (Figure 35.2). The term “jersey finger” is derived from the classic scenario in which an athlete grabs an opponent’s jersey and the DIP joint is hyperextended. Rupture most often occurs at the bony insertion and less often at the musculotendinous junction.

Epidemiology—The injury commonly occurs in athletes who are involved in contact sports, most notably rugby and football, but can occur in nonathletes as well. Musculotendinous rupture is rare and occurs most often in a traumatic distal phalanx amputation injury or in patients with underlying inflammatory conditions. The ring finger is
involved in 75% of FDP avulsions. The higher susceptibility of the ring finger to this injury is related to several anatomic differences. It has been demonstrated that the ring finger has the least independent motion of all the digits. Also the insertion of the ring finger FDP is weaker than the FDP insertion of the long finger. Finally, the ring finger extends farther than the other digits during full grip and absorbs the most force during pull-away testing, making it prone to avulsion.

Presentation—Patients often present with acute pain and swelling over the volar surface of the distal finger. The point of maximal tenderness may indicate the location of the avulsed tendon.

Physical Examination—On examination, the affected finger lies in extension relative to other fingers in resting position (Figure 35.3). Patients are unable to actively flex the DIP joint when asked to make a fist. Often
patients will resist flexion of the entire finger as a result of pain, which can obscure the diagnosis. In the acute setting, an FDP avulsion can be misdiagnosed as a “sprained finger.” It is essential that the clinician isolates DIP and proximal interphalangeal (PIP) joint motion to prevent a delay in diagnosis. In some cases, the physician may be able to palpate the flexor tendon retracted proximally along the flexor sheath.

Imaging—Anteroposterior, lateral, and oblique radiographs should be obtained to assess for avulsion fractures or articular injuries. A bony avulsion fragment of the volar lip of the distal phalanx articular surface may be present (Figure 35.4). Approximately 50% of FDP avulsions are associated with an osseous fragment. If the injury is purely tendinous, the only radiographic finding will be slight extension of the DIP in resting position. MRI can be used if the diagnosis is unclear or the location of the retracted tendon is unknown.

Classification—The Leddy and Packer classification system is used most commonly (Table 35.1). Type I, II, and III injuries are most common.