Slideshow
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Figure 1. Patient is unable to flex his distal interphalangeal (DIP) joint but can flex his interphalangeal (IP) joint.
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Figure 2. When holding his middle phalanx in extension, the patient is unable to flex the DIP joint.
A 13-year-old boy presents 1 week after a right ring finger injury. The patient reports he was playing basketball when he jumped up and grabbed the net and felt a pop in his finger, with accompanying sharp pain. Radiographs are negative for a fracture. On physical examination, the patient is unable to flex his distal interphalangeal (DIP) joint but can flex his interphalangeal (IP) joint (Figure 1). When holding his middle phalanx in extension, the patient is unable to flex the DIP joint (Figure 2).
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A careful physical examination and knowledge of finger anatomy are essential to prevent undiagnosed finger injuries. The main flexor tendons of the finger include the flexor digitorum superficialis (FDS) and the flexor digitorum profundus (FDP) tendons. The FDS tendon inserts at the volar aspect of the middle phalanx and acts to flex the proximal interphalangeal (PIP) joint. The FDP tendon inserts at the volar base of the distal phalanx and acts to flex the DIP joint.
A jersey finger is an avulsion of the FDP tendon off its insertion at the base of the distal phalanx. The mechanism of injury is a forced extension on a flexed finger such as when a football player grabs the jersey of a player who runs away.1 The middle finger is involved in 75% of cases as the increased length results in a more forceful DIP flexion when grasping.1
On physical examination, patients will be unable to make a full fist and flex the DIP joint. Radiographs of the finger are critical for identifying a bony avulsion compared with a pure tendon avulsion. Ultrasound may be useful in assessing tendon anatomy in cases without fracture.1 Tendon avulsion injuries require surgical repair, which includes reattaching the tendon back down to the distal phalanx. This should be performed within 3 weeks of injury or the tendon can retract and become irreparable.2,3 Avulsion fractures often require open reduction and internal fixation of the fracture fragment. Hand therapy is used postoperatively and return to sport is expected approximately 3 months after surgery.2,3
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants.
References
1. Abrego MO, Shamrock AG. Jersey finger. StatPearl [Internet]. StatPearl Publishing; August 8, 2022. https://www.ncbi.nlm.nih.gov/books/NBK545291/
2. Ruchelsman DE, Christoforou D, Wasserman B, Lee SK, Rettig ME. Avulsion injuries of the flexor digitorum profundus tendon. J Am Acad Orthop Surg. 2011;19(3):152-162. doi:10.5435/00124635-201103000-00004
3. Bachoura A, Ferikes AJ, Lubahn JD. A review of mallet finger and jersey finger injuries in the athlete. Curr Rev Musculoskelet Med. 2017;10(1):1-9. doi:10.1007/s12178-017-9395-6
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