Jersey Finger

Jersey finger is avulsion of the flexor digitorum profundus tendon from its insertion on the distal phalanx. It happens when a finger flexed in grip is forced into extension, for example when a player grabs an opponent's jersey in football or rugby. The ring finger is involved in about 75% of cases, because it is the most prominent and least protected finger in the grasp, and the profundus tendon to the ring finger is anchored least firmly.

Classification by level of retraction and fracture:

• Type I: tendon retracts into the palm, with rupture of both vincula and loss of blood supply (repair is needed within 7 to 10 days)
• Type II: tendon retracts to the proximal interphalangeal joint, with the long vinculum intact (repair is possible up to 6 weeks)
• Type III: a large bony fragment catches at the A4 pulley, which limits retraction
• Type IV: fracture with the tendon avulsed from the bone fragment and retracted into the palm
• Type V: bony avulsion with comminution of the distal phalanx

The injury is often dismissed as a sprain, and delay beyond 6 weeks makes primary repair difficult. Complications are loss of distal joint flexion, adhesions, flexion contracture, rupture of the repair, bowstringing, and the quadriga effect (a tight repair that limits flexion of the neighbouring fingers).

• Pain and swelling in the volar finger after a forced extension injury, with a snap sometimes felt
• Inability to actively flex the distal interphalangeal joint (when the other joints are held extended to test profundus function), with passive flexion preserved
• A palpable tender mass in the palm (type I) or at the proximal interphalangeal joint (type II), and the injured finger lying in slight extension in the finger cascade
• Bruising along the volar finger
• Red flags: open wound, neurovascular compromise, a missed injury beyond 1 week, and a bony fragment that is locked in the A4 pulley

• Clinical diagnosis by testing the profundus (the examiner holds the proximal and middle joints extended while the patient tries to flex the distal joint) and the superficialis function.
• Lateral and anteroposterior radiographs: avulsion fragment, its position and the type.
• Ultrasound: locates the retracted tendon stump and shows the gap.
• MRI when the level of retraction or the diagnosis is uncertain.

Differentials: flexor digitorum superficialis injury, flexor tendon laceration, distal interphalangeal dislocation, mallet finger, proximal interphalangeal dislocation, trigger finger, distal phalanx fracture.

This is an operative injury, and timing depends on the type.

• Surgical repair through a Bruner volar zigzag incision:
  • Retrieve the tendon, avoiding forced advancement. Do not shorten or advance the tendon over 1 cm, to avoid the quadriga effect.
  • Reattach to the distal phalanx with a suture anchor or a pull out suture tied over a button on the nail, using 3-0 or 4-0 braided non-absorbable suture.
  • Fix a large bony fragment with a 1.1 mm Kirschner wire or a 1.5 mm mini screw (types III to V).
  • Type I: repair within 7 to 10 days. Type II: within 6 weeks. Types III and IV: fixation promptly.
  • Cefazolin 2 g IV before incision (3 g if over 120 kg). Give tetanus toxoid 0.5 mL IM if immunity is not current.
• Postoperative rehabilitation: a dorsal blocking splint with the wrist flexed to about 30 degrees, metacarpophalangeal joints in 70 degrees of flexion and interphalangeal joints in extension. Begin early protected active or passive motion (modified Duran or Kleinert protocols) at day 2 to 5. Splint for 6 weeks, begin light strengthening at 8 weeks, and return to contact sport at 12 to 14 weeks.
• Analgesia: paracetamol 1 g orally every 6 hours, ibuprofen 400 mg orally every 8 hours with food for up to 7 days.
• Delayed presentation (over 6 weeks) or an unusable tendon:
  • If the superficialis tendon is intact and the patient has no functional loss, accept the deficit.
  • Distal interphalangeal arthrodesis or tenodesis for an unstable painful joint.
  • Staged tendon reconstruction with a silicone rod (first stage) and a palmaris longus graft (second stage) for a motivated patient with supple joints.
• Complications: repair rupture (about 5 to 10%), flexion contracture, adhesions needing tenolysis after 3 to 6 months of therapy, infection, nail deformity from the button and hardware problems.

Follow up at 2 days to 1 week, then at 2, 6 and 12 weeks. Counsel on early return for any sudden loss of flexion during the first 8 weeks.