An injury to the flexor digitorum profundus (FDP) tendon, also known as a jersey finger.
**Detailed Explanation:**
Jersey finger is a type of tendon injury that occurs when the DIPJ is forcibly hyperextended while the FDP muscle contracts, leading to tendon rupture at its weakest point, the insertion on the distal phalanx. It is commonly seen in American football players when a tackler grabs hold of an opponent's jersey, leading to a sudden and forceful extension of the finger.
2. How would you examine the patient to confirm the diagnosis and what would the radiographs likely show?
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Examination involves testing FDP function by fixing the middle phalanx in extension and asking the patient to attempt to actively flex the finger at the DIPJ. The radiograph may show an avulsion fracture from the base of the distal phalanx.
Show Explanation
Inability to flex the DIPJ is suggestive of a ruptured FDP tendon. On inspection, the injured finger may lie in slight extension compared to the other fingers in the resting posture, with tenderness on the volar side of the finger and the retracted tendon may be palpable over the proximal phalanx or in the palm. Radiographs are often normal, but in some cases may reveal an avulsion fracture from the base of the distal phalanx.
3. Which finger is most commonly affected and why?
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The ring finger is most commonly affected, thought to be due to its prominence compared to other digits in flexion that may expose it to greater forces during grip.
Show Explanation
The ring finger is restricted to passive extension due to intertendinous connections, which prevents it from being fully extended when the middle and small finger MCPJs are flexed to 90 degrees. The predominance of ring finger injuries may also be due to its prominence compared to other digits in flexion during grip, which may expose it to greater forces and therefore greater risk of injury.
4. How are these injuries classified?
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FDP tendon avulsion injuries are classified on the basis of the extent of proximal retraction of the tendon and the type of avulsion.
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Leddy and Packer classified FDP tendon avulsion injuries into three types based on the extent of proximal retraction of the tendon and the type of avulsion. Smith later added a fourth type that includes a combination of a bony avulsion from the distal phalanx and tendon avulsion from the fragment into the palm.
5. How should this injury be managed?
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Prompt diagnosis and surgical repair of FDP avulsions is recommended in order to preserve any residual blood supply and also because clinical assessment of the level of injury is inexact.
Show Explanation
Non-operative management is rare and only reserved for cases where surgery is contraindicated because of patient co-morbidities. The treatment approach depends on the severity and type of the injury. Two incisions are required to repair type I injuries, and bone anchors may be used. Type II injuries are repaired with similar approaches, while type III injuries may not require proximal tendon repair. Type IV injuries require a combination of techniques used for types I-III injuries. Hand therapy is essential for a good outcome, and early active mobilization preferrered.
