Mallet Finger

It is commonly caused by a "jamming" injury (e.g., basketball hitting the tip of the extended finger). The force force-flexes the DIPJ against extensor resistance, snapping the tendon or avulsing bone.

The classic presentation is a patient who jammed the tip of an extended finger and now cannot straighten the last joint. The fingertip droops into flexion and will not actively lift, although it can be passively pushed straight.

• Typical patient: young athlete after a ball-sport injury, or an older adult after a trivial knock (e.g. tucking in a bedsheet).
• Hallmark sign: extension lag at the DIPJ with preserved passive extension.
• Acute features: dorsal swelling, tenderness and bruising over the DIPJ; in bony mallet a palpable step or fragment.
• Red flags: any skin breach (open/Type II-III), a flexed bleeding fingertip in a child (Seymour fracture), or a developing swan-neck posture at the PIPJ.

History Factors

• Mechanism: Jamming vs Laceration.
• Timing: Acute (less than 4 weeks) vs Chronic (greater than 4 weeks).
• Occupation: Surgeon/Musician (needs perfect glide) vs Labourer (needs stable union).

Late presentation (greater than 4 weeks) can still be treated with splinting.

Physical Exam

• Look: Drooping DIPJ. Erythema/Swelling (acute).
• Move:
  • Active: Loss of active extension (Lag).
  • Passive: Full passive extension (rules out locked joint/fracture block).
• Swan Neck: Check for PIPJ hyperextension.
• Open: Check for laceration (don't miss a Type II).

Always document the rotational alignment of the finger.

The thumb has its own, much rarer, version of the injury - mallet thumb - which examiners like to contrast with the finger lesion.

• The tendon is different: extension of the thumb IP joint is driven by the terminal insertion of the extensor pollicis longus (EPL). A mallet thumb is therefore an EPL terminal disruption (closed avulsion, laceration, or a bony avulsion of the dorsal distal phalanx) producing an IP-joint extension lag.
• Lower splinting success: unlike the finger's thin terminal slip, EPL has a strong, more proximal muscle belly with greater excursion that tends to retract a ruptured tendon, so closed extension splinting is less reliable and there is a lower threshold for primary repair - particularly for open injuries and displaced bony fragments.
• Same principles otherwise: a true lateral radiograph, attention to joint congruency/subluxation, and IP extension immobilisation for stable closed or undisplaced bony injuries.

The "drooped fingertip" is not always a terminal extensor injury. Distinguishing these saves a patient from being splinted for a problem a splint cannot fix.

Tenodermodesis is one option for the chronic symptomatic mallet, but examiners expect two further named procedures - especially once a swan-neck deformity has developed.

• Fowler central slip tenotomy: for the chronic mallet that has produced (or threatens) a swan-neck deformity with a supple PIP joint. The central slip is divided over the proximal part of the middle phalanx, releasing the proximal extensor tether so that more extensor force is transmitted distally to the terminal tendon - improving the DIP lag while letting the hyperextended PIP drop back. A small (around 10-15 degree) residual PIP extensor lag is accepted; a true boutonniere is the feared over-correction.
• Oblique retinacular ligament (Spinner-Choi) reconstruction: a tendon graft (a lateral band or free graft) routed from the volar proximal phalanx, volar to the PIP axis, to the dorsal distal phalanx. Acting as a dynamic tenodesis, it simultaneously extends the DIP and restrains PIP hyperextension - addressing both components of the mallet-driven swan neck at once.
• Joint-level salvage: a painful, arthritic or grossly unstable chronic DIP is often best treated by DIP arthrodesis rather than soft-tissue reconstruction.

• Skin Necrosis: From tight splint. Most common.
• Nail Deformity: Ridging from germinal matrix injury (by splint or fracture).
• Recurrence: If splint removed too early.
• Stiffness: Loss of flexion. Often worse than the original 10 degree lag.
• Septic Arthritis: From pin track infection.
• Functional Deficit: Most patients adapt well to a minor lag, but cannot adapt to a stiff, painful joint.
• Hypersensitivity: Common at the fingertip. Desensitization therapy is needed.

Key Rehabilitation Principles:

• Continuous splinting is essential - even brief flexion can undo weeks of healing
• Patient education is the single most important factor in outcome
• Monitor skin - dorsal skin necrosis is avoidable with proper splint fit
• PIPJ exercises prevent stiffness and Swan Neck progression

Global Epidemiology

• Mallet finger is among the most common closed tendon injuries of the hand, with a recognised peak in young men (sport-related forced flexion) and a second peak in older women (low-energy domestic injury, often involving thin dorsal skin).
• Typical mechanisms worldwide: ball-sports (basketball, volleyball, cricket, baseball, netball), bedmaking/tucking sheets, and catching a digit on clothing.
• The long, middle and ring fingers of the dominant hand are most often affected; bony mallet fractures account for a substantial minority of cases.

Side-by-Side Guideline Comparison

The striking feature is convergence: every major society recommends splint-first management and reserves surgery for volar subluxation, open injury, or selected large fragments. The genuine area of disagreement is the exact articular-percentage threshold (one-third versus one-half).

Registry and Outcome Notes

• There is no dedicated arthroplasty/implant registry for mallet finger, as the injury is rarely implant-based. Outcome evidence derives from RCTs, cohort series and the Cochrane review rather than national registries.
• Reported splinting success rates cluster around 80-90% acceptable outcome, with a residual extension lag of roughly 5-10 degrees that is usually functionally and cosmetically well tolerated.

High- vs Limited-Resource Practice

• Well-resourced settings: custom thermoplastic or perforated splints fabricated by hand therapists, structured education, and ready access to percutaneous pinning for subluxed fractures.
• Limited-resource or remote settings: off-the-shelf Stack splints, aluminium-foam splints, or simple thermoplastic; telehealth-supervised splinting protocols have been shown to be safe and effective where in-person therapy is scarce.
• Antibiotics for open injuries: open mallet injuries and Seymour fractures are treated as open fractures - urgent debridement plus a first-generation cephalosporin (e.g. cephalexin) with anti-staphylococcal cover, a recommendation consistent across guidelines and supported by the Seymour fracture literature.

• The articular-percentage threshold. The "one-third rule" for surgery is a teaching convention, not a validated cut-off. Reviews note that size alone has never reliably predicted who benefits from surgery; congruency (absence of volar subluxation) is the more defensible determinant.
• Surgery versus splinting for displaced bony mallet. The Cochrane review found no high-quality evidence that surgery outperforms splinting, even for larger fragments, while surgery adds infection and nail-deformity risk. Many surgeons still operate on subluxed joints, but the benefit is assumed rather than proven.
• Optimal splint type and duration. No splint design has been shown clearly superior; 6 versus 8 weeks and the weaning schedule are based on tradition and small trials, not robust RCTs.
• Persistent radiographic gap. A residual fracture gap or incomplete reduction frequently coexists with excellent function - a strong argument for treating the patient, not the X-ray.
• Extension block pinning patient selection. Long dorsal-cortex fragments and older patients do worse after extension block pinning, suggesting morphology-based selection rather than a one-technique-fits-all approach.