FRCS Oral: Abbreviated Jersey Finger Examination Prep
Key Takeaway
Your ultimate guide to FRCS Oral: Abbreviated Jersey Finger Examination Prep starts here. An examination abbreviated jersey finger primarily tests Flexor Digitorum Profundus (FDP) function. This involves fixing the middle phalanx in extension and asking the patient to actively flex the distal interphalangeal joint (DIPJ). Inability to flex the DIPJ confirms a ruptured FDP tendon. Radiographs may show an avulsion fracture.
A 24-year-old rugby player presents 48 hours post-injury. He reports forced extension of his ring finger while gripping a jersey. He cannot actively flex the DIP joint. Passive flexion is full. X-rays are negative for fracture. Explain your management plan, the classification of this injury, and the specific vascular considerations.
Candidate: "This is a clinical diagnosis of a Jersey finger. I would perform a thorough neurovascular exam and order a radiograph to rule out a bony avulsion. Given the history of forced extension and inability to flex the DIP, this is likely a Leddy and Packer Type I injury. Since it is acute, I would discuss surgical exploration and primary repair, ideally within 7-10 days, to preserve the vincula vascularity."
Failing to emphasize the urgency. Many candidates don't explicitly link the Type I classification to the disrupted vincula vascularity. A poor candidate might say, "I'll see him in a few weeks for a semi-elective repair," which is a catastrophic failure for Type I injuries, as the tendon will become necrotic.
A structured response is vital: 1. Classification: Identify it as a Leddy & Packer Type I (tendon retracted to palm, no bone, loss of vincula). 2. Vascular Pathology: Explain that the FDP avulses distal to the vincula, stripping the blood supply. 3. Urgency: Stress that repair must be prompt (7–10 days) to prevent irreversible tendon necrosis. 4. Surgical Plan: Mention Brunner incision, core suture technique (e.g., 4-strand), and a dorsal blocking splint for early active-motion rehab protocols.
During the clinical examination, you suspect a bony avulsion despite the initial plain film appearing relatively normal. What is your next step, and how does this change your classification?
Candidate: "I would order targeted views, such as a lateral radiograph of the specific digit, or consider cross-sectional imaging like an MRI or CT. If a bony fragment is identified at the level of the A4 pulley, it would reclassify the injury as a Leddy and Packer Type III."
Forgetting to mention the prognostic implications. A poor candidate identifies the fracture but ignores the fact that Type III injuries have a better blood supply (via the fragment's tether) than Type I, meaning the surgical urgency is lower.
Identify the "Bony Avulsion" (Type III). Note that: - Vascularity: The tethered bone fragment often maintains the vincula attachment, preserving blood supply. - Implication: This allows for a slightly more delayed surgical intervention (up to 3-4 weeks) compared to the "Type I" injury. - Fixation: Repair focuses on anatomical reduction and fixation of the bone fragment (using mini-screws or pull-out wire) to the distal phalanx base.
The patient returns 6 months later with an unsuccessful repair and chronic stiffness. He describes a 'paradoxical extension' of the DIP joint when he attempts to make a firm fist. What is this phenomenon called, and what is the underlying anatomical mechanism?
Candidate: "That sounds like the 'Lumbrical Plus' phenomenon. It occurs because the FDP tendon is either too short or scarred/advanced too proximally. When the patient attempts to flex, the lumbrical muscle is pulled proximally before the FDP can flex the DIP joint. Because the lumbrical inserts into the lateral bands, it causes paradoxical DIP extension."
Confusing "Lumbrical Plus" with the "Quadriga Effect." These are common traps. Quadriga = restricted flexion of adjacent fingers due to a common muscle belly. Lumbrical Plus = extension of the affected finger's DIP joint due to extrinsic muscle mechanics.
Demonstrate deep anatomical mastery: 1. Terminology: Correctly identify the "Lumbrical Plus" phenomenon. 2. Mechanism: The lumbrical origin (FDP) is displaced proximally. During attempted active flexion, the lumbrical is tensioned first. 3. Result: Since the lumbrical inserts into the extensor apparatus (lateral bands), it acts as an extensor of the DIP joint. 4. Management: This is a surgical complication requiring tenolysis or, in severe cases, release of the lumbrical muscle.
