Jersey Finger

Overview & Mechanism

Jersey finger is an avulsion injury of the flexor digitorum profundus (FDP) tendon from its insertion at the base of the distal phalanx, caused by forced extension of an actively flexed DIP joint. It is the mirror image of mallet finger (which avulses the extensor tendon at the same location). The injury classically occurs when a player`s finger catches in another player`s jersey while attempting to tackle — the finger is forcefully extended while the FDP is contracting, avulsing the tendon from the distal phalanx. The ring finger is the most commonly affected digit (due to its anatomical characteristics — it has the longest excursion and the weakest insertion).

Epidemiology: predominantly affects young male athletes (rugby, American football); the ring finger accounts for approximately 75% of cases; the patient often presents late — the injury is frequently missed or misidentified as a `sprain` at initial presentation; delayed diagnosis worsens outcome due to tendon retraction and adhesion formation
Mechanism: active FDP contraction against a sudden forced DIP extension; the FDP tendon tears from the base of the distal phalanx — with or without a bony fragment; the degree of tendon retraction depends on the presence of the vinculae (the blood-supply structures that tether the tendon) and whether a bony fragment is still attached
Why the ring finger? The ring finger FDP has independent excursion (unlike the middle and little fingers whose FDPs share a common muscle belly and therefore limit each other`s retraction); the ring finger insertion is the weakest of all FDP insertions; and the ring finger has the greatest tendon excursion — these factors combine to make the ring finger most vulnerable to avulsion and most prone to significant retraction

Classification — Leddy & Packer

Type	Description	Vascularity	Timing of Surgery
Type I	Tendon retracts into the palm; both vinculae brevis and longus are disrupted; no bony fragment; the tendon is in the palm (proximal to A1 pulley)	AVASUCLAR — both vinculae disrupted; tendon vulnerable to ischaemic necrosis; most urgent	Repair within 7–10 days (before tendon becomes non-viable and shortened beyond reach); the most urgent type
Type II	Tendon retracts to the level of the PIP joint; vinculum longus intact (this tethers the tendon at the PIP level); ± small bony fragment	Partial — vinculum longus maintains some blood supply; less urgent than Type I	Repair within 3–4 weeks (most common type; greatest flexibility in timing)
Type III	Large bony avulsion fragment that is too large to retract through the A4 pulley; tendon remains attached to the fragment at the DIP level; the bony fragment holds the tendon in place	Intact vascularity — tendon remains at the DIP level; both vinculae intact	ORIF of the bony fragment; can be performed up to 6 weeks; the bony fragment prevents retraction; least urgent type
Type IV (Robins modification)	Large bony fragment (Type III) AND simultaneous avulsion of the tendon from the fragment (double avulsion — the tendon avulses from the fragment AND the fragment from the bone)	Most complex; both injuries present simultaneously	ORIF of fragment + tendon repair; most challenging type; urgent

Clinical Assessment & Investigations

History: often the injury is missed initially — the patient may present days to weeks later with inability to flex the DIP joint; tenderness in the finger and palm; swelling; may have been told it was `just a sprain`; ask specifically about the mechanism — forced extension of the flexed finger
Clinical diagnosis: inability to actively flex the DIP joint while the PIP joint is held in extension (blocking FDS); the patient can flex the PIP joint (FDS is intact) but cannot flex the DIP joint (FDP avulsed); palpation may reveal a tender mass in the palm (Type I) or at the PIP level (Type II) representing the retracted tendon; loss of the normal resting finger cascade (the affected finger lies in relatively more extension than its neighbours)
Plain X-ray (AP, lateral, oblique of the finger): identifies bony avulsion fragment at the DIP joint (Type III/IV); the size of the fragment guides management; X-ray is mandatory in all suspected jersey finger injuries to exclude a bony avulsion — this determines the Leddy-Packer type and urgency of surgery
MRI or USS: may locate the retracted tendon (particularly Type I — tendon in the palm) and assess tendon integrity; rarely required if clinical diagnosis is clear and X-ray available; useful in late-presenting or atypical cases

Surgical Management

Surgical repair — the standard treatment for all types: the FDP tendon must be repaired or the bony fragment fixed for any functional DIP flexion to be restored; non-operative management results in a permanently flail DIP joint (the patient can only flex the finger with FDS); a flail DIP that is troublesome functionally can be addressed by DIP arthrodesis but this is a secondary salvage procedure — primary repair is always preferred
Approach: Brunner (zigzag) incisions or a lateral approach to the finger; the A4 pulley at the DIP level must be preserved during tendon passage; venting A2 only if necessary and repairing it after; careful retrieval of the retracted tendon from the palm (Type I) or PIP level (Type II) using a tendon passer
Repair technique for Types I and II: the tendon is advanced to the distal phalanx; a core suture (4-strand repair — Modified Kessler or Adelaide technique) is placed in the tendon; the tendon is reattached to the bone using a suture anchor or bone tunnels (pull-through suture tied over a button on the dorsum of the distal phalanx — the `button` technique)
Type III management: the bony fragment is reduced and fixed with a mini-screw (Herbert screw) or K-wire; the fragment is at the DIP level and carries the tendon with it — reattachment of the fragment restores FDP function
Post-operative: DIP joint held in slight flexion in a dorsal splint; early active mobilisation protocol (Belfast / Duran) commences at 2–5 days under hand therapy supervision; the 4-strand repair allows early active mobilisation; return to contact sport at 3–4 months

Delayed Presentation

Late-presenting jersey finger (>4–6 weeks): direct repair is usually impossible due to tendon shortening, retraction, and adhesion formation; the FDP muscle-tendon unit shortens and loses compliance; options — FDP tendon graft (if the pulleys and FDS are intact; staged procedure — Stage 1 inserts a silicone Hunter rod to create a tendon sheath; Stage 2 places a tendon graft 3 months later); DIP arthrodesis (if the patient has a poorly functional or hyperextending DIP joint causing nuisance — simple, reliable, acceptable functional outcome); a late unrepairable Type I jersey finger usually results in permanent DIP flexion weakness and a hyperextended DIP posture (pseudo-mallet appearance)

Consultant-Level Considerations

Two-stage tendon reconstruction (Hunter rod technique): for delayed jersey finger requiring reconstruction; Stage 1 — the scarred tendon bed is excised and a silicone rod (Hunter rod) is placed from the distal phalanx to the palm, passing through the intact pulleys; the rod induces formation of a pseudosheath; the patient regains passive digital motion during this stage; Stage 2 (3 months later) — the rod is exchanged for a tendon graft (palmaris longus or plantaris); the graft is woven through the pseudosheath and secured distally to the bone and proximally to the FDP muscle; this staged approach allows a reliable tendon sheath to form before graft insertion, improving gliding and reducing adhesion formation
A4 pulley preservation: the A4 pulley overlies the middle of the distal phalanx; it is the critical pulley for FDP function at the DIP joint; section of the A4 pulley during jersey finger repair to facilitate tendon passage causes bowstringing and significantly impairs DIP flexion mechanics; the A4 pulley must be preserved; if the FDP tendon cannot pass through the A4 pulley (due to swelling or bulk of the repair), the repair site should be made as smooth and slim as possible before passage; A4 pulley reconstruction is technically demanding and should be avoided if possible

Exam Pearls

Jersey finger: FDP avulsion from distal phalanx; forced extension of actively flexed DIP; ring finger 75% of cases (weakest insertion, greatest excursion); often missed initially
Diagnosis: inability to actively flex DIP joint (hold PIP extended, ask patient to flex DIP — no movement); FDS intact (PIP flexion preserved); palpable mass in palm (Type I) or at PIP level (Type II)
Leddy-Packer Type I: retracted to palm; both vinculae torn; avascular; MOST URGENT — repair within 7–10 days; tendon becomes non-viable and non-retrievable
Type II: retracted to PIP; vinculum longus intact; ± small bony fragment; repair within 3–4 weeks; most common type
Type III: large bony fragment prevents retraction through A4 pulley; tendon at DIP level; both vinculae intact; ORIF of fragment; least urgent (up to 6 weeks)
Type IV: Type III fragment + tendon also avulsed from fragment; most complex; ORIF + tendon repair
X-ray mandatory: identifies bony avulsion (Type III/IV); determines Leddy-Packer type and urgency
A4 pulley: MUST be preserved during repair; critical for DIP joint FDP mechanics; section = bowstringing + loss of DIP flexion power
Delayed presentation (>4–6 weeks): direct repair impossible; options — staged tendon graft (Hunter rod technique × 2 stages) or DIP arthrodesis
Hunter rod: Stage 1 — silicone rod forms pseudosheath (3 months); Stage 2 — tendon graft through pseudosheath; used for delayed/complex FDP reconstruction

References

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