Requested DocAlert: Picture Quiz Poll: A Rugby Player With a Finger Deformity

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BMJ 2016;353:i1911
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Endgames

Case Review

A rugby player’s finger injury

Thomas F M Yeoman, Philippa A Rust

Correspondence to: T F M Yeoman tyeoman@nhs.net

[EXCERPTS]

A 16 year old right hand dominant schoolboy presented to the emergency department with a painful, swollen right ring finger. Three days earlier he had injured his finger playing rugby and he thought the injury occurred while he was tackling an opponent. Although he was able to finish the game he has had discomfort and reduced movement in the finger since.

Ecchymosis and tenderness were noted over the distal phalanx on the palmar aspect of his hand, as well as some swelling and tenderness at the base of the ring finger. The finger had no neurovascular deficit and examination of the rest of the right hand was normal. No fracture was seen on a plain radiograph of the ring finger.
Fig 1 The patient’s right hand in a relaxed posture showing loss of normal cascade of the ring finger

Answers

1. What key aspect of the clinical examination would confirm the diagnosis?

Inability to actively flex the distal interphalangeal joint (DIPJ) is pathognomonic of rupture of the flexor digitorum profundus (FDP) tendon. To test the FDP tendon function, isolate the DIPJ by holding the proximal interphalangeal joint (PIPJ) in extension, thereby preventing the action of the flexor digitorum superficialis (FDS).
Fig 2 Testing the little finger FDP (flexor digitorum profundus) tendon function by isolating the DIPJ (distal interphalangeal joint), which required holding the PIPJ (proximal interphalangeal joint) in extension to prevent the action of FDS (flexor digitorum superficialis)
Fig 3 Testing the middle finger FDS (flexor digitorum superficialis) function by holding the neighbouring finger DIPJs (distal interphalangeal joints) in extension and thereby preventing the action of the common FDP (flexor digitorum profundus) muscle belly

Plain radiography can help identify a bone avulsion and its size, as well as an intra-articular fracture if present at the distal phalanx. The extent of tendon retraction may be estimated by the presence of a small bone fragment on a lateral radiograph of the hand. This fragment may be attached to the retracted tendon. Larger fracture fragments will normally prevent retraction of the avulsed tendon through the pulley system. Further imaging modalities, such as ultrasound and magnetic resonance imaging, can be useful adjuncts in the evaluation and diagnosis of these injuries, especially in delayed presentations and chronic injuries, but are generally not needed.

Awareness of this injury is important because these patients often present without serious pain or swelling, they have no open skin wound, and radiographs are often normal.

2. What is the name of this injury (the name provides a clue to the mechanism of injury)?

“Jersey finger” or “rugger jersey finger.” It classically occurs when a tackler has hold of an opponent’s jersey. The DIPJ is forcibly hyperextended when the FDP muscle is fully contracted, leading to tendon rupture at its insertion into the distal phalanx.

3. Which finger is most commonly affected?

The ring finger is affected in more than 75% of cases probably because of the ring finger’s prominence during flexion compared with the other fingers—it is longest in grip, which may subject it to greater forces.

4. How are these injuries classified?

The extent of tendon retraction proximally and the type of tendon avulsion. Tendon avulsion can affect the soft tissue only or a bone fragment as well.
Fig 4 Classification of FDP (flexor digitorum profundus) tendon avulsion injuries
Fig 5 Diagram of blood supply to the flexor digitorum profundus tendon through the vincular system

5. How are these injuries managed?

Most are treated surgically. Early intervention (by 7-10 days) is essential when the tendon is retracted as far as the palm. Delay can lead to FDP contraction and scarring of the pulley system, making primary repair impossible. Tendon avulsions require primary tendon to bone repair. Bone fragments can be fixed with small fragment screws.

Patient outcome

No abnormality was seen on radiography and our patient was diagnosed as having a type II FDP tendon avulsion. At the time of surgery, five days after the injury, the tendon was found to be retracted to the distal end of the A2 pulley. The tendon was reattached to the distal phalanx with two micro bone anchors. He was rehabilitated according to the local protocol of six weeks in a dorsal hood under the care of the hand therapists. He went on to make a full and uneventful recovery.
Fig 6 Intraoperative pictures. (A) Empty tendon sheath at the site of FDP (flexor digitorum profundus) insertion. Avulsed FDP retrieved distal to the A2 pulley; note the haematoma on the tendon as a result of vinculum avulsion. (B) The FDP tendon end is passed up the pulley system with the aid of a paediatric feeding catheter. (C) The tendon end is now distal to the A5 pulley. The blue prolene suture is in the distal end of the tendon and the white suture is from the Mitek anchor fixed to the distal phalanx
Fig 7 Hand in dorsal hood for flexor tendon rehabilitation, which involves early active mobilisation under the supervision of a hand therapist. (A) Lateral view of the dorsal hood showing the block to full extension. (B) Anterior view of dorsal hood
Fig 8 Clinical result three months after the operation showing a full active range of movement in extension (A, C) and flexion (B) and mature scar on the ring finger (C)

Patient consent obtained.

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