Seymour Fracture and Paediatric Nail-bed Injuries

A Seymour fracture is a paediatric distal phalanx physeal or juxta-epiphyseal fracture with associated nail-bed injury. In practical terms, it is an open fracture until proven otherwise. The injury usually follows a fingertip crush, door injury, ball strike, fall, forced flexion injury or great-toe stubbing mechanism. The X-ray may look small, but the open nail-bed wound makes the injury high risk.

The classic clinical trap is that Seymour fractures resemble mallet finger, but the treatment is different.

The consultation should answer four questions:

1. Is this a nail-bed wound communicating with bone?
2. Is the fracture through or near the open distal phalanx physis?
3. Is germinal matrix or nail bed interposed in the fracture?
4. Is the reduction stable after the soft-tissue block is cleared?

The great toe has an equivalent injury after axial load or stubbing trauma. It is less commonly discussed than finger Seymour fracture, but the logic is the same: nail-bed injury plus distal phalangeal physis involvement requires open-fracture thinking.

The distal phalanx physis lies near the base of the distal phalanx, close to the nail-bed complex. In a Seymour fracture, the distal phalanx is forced into a flexed posture through the weak physeal or juxta-epiphyseal region.

The important soft-tissue structure is the germinal matrix. It produces most of the nail and sits deep to the proximal nail plate. When the nail plate is avulsed or displaced, the germinal matrix can fold into the fracture gap. This creates two problems: it blocks reduction and it leaves devitalised or contaminated soft tissue inside an open physeal fracture.

The nail plate position is therefore diagnostic. A normal nail plate tucks beneath the eponychial fold. In Seymour fracture, the proximal edge of the nail plate may sit on top of the eponychial fold, making the nail look too long. This subtle sign may be more obvious than the X-ray.

The injury behaves differently from a simple tuft fracture or mallet finger because the open physis and nail-bed laceration connect the outside environment with the growth plate and distal phalanx. That is why early antibiotics, debridement, reduction and nail-bed repair matter.

The usual mechanism is a crush or forced-flexion load to the fingertip. Door-crush injuries are common, but ball sports, falls, machinery, direct blows and toe-stubbing injuries can produce the same pattern. The child often presents with pain, swelling, bleeding at the nail fold and a fingertip that appears flexed at the DIP joint.

Mechanistically, the injury sits between two familiar patterns:

• Like mallet finger, the distal phalanx appears flexed.
• Like an open fracture, there is communication through the nail bed.
• Like a physeal fracture, growth disturbance is possible.
• Like a nail-bed laceration, final nail appearance depends on precise soft-tissue repair.

This combination is why the diagnosis is easy to underestimate. The wound may be tiny, the child may move the finger, and the X-ray may show only subtle physeal widening. The red flag is the combination of distal phalanx posture and proximal nail-fold injury.

History

The history should quickly determine mechanism, contamination, delay and infection risk.

• Mechanism: door crush, ball injury, fall, forced flexion, direct blow, machinery injury or toe stubbing.
• Time from injury: delayed presentation changes infection risk and debridement planning.
• Nail symptoms: bleeding at the proximal nail fold, nail plate avulsion, nail plate sitting high, subungual haematoma or visible nail-bed wound.
• Contamination: soil, farm injury, water exposure, bite, dirty sports field or foreign material.
• Previous treatment: antibiotics, splinting, trephination, nail removal or attempted reduction.
• Infection symptoms: increasing pain, redness, discharge, fever, odour or progressive swelling.
• Functional context: digit involved, hand dominance, school or sport needs, and associated fingertip injuries.

Examination

Inspection is the most important part of the examination. A Seymour fracture may look like a minor nail injury unless the proximal nail fold is examined carefully.

Active motion can be misleading. A child may still flex through the FDP and may have pain-limited extension. Preserved motion does not exclude an open physeal injury.

Obtain dedicated radiographs of the affected digit, not just a hand X-ray. The AP view helps with alignment and associated fractures, but the true lateral view is the key image. The lateral view shows the relationship between the distal phalanx epiphysis, physis, metaphysis and nail plate.

Look for:

• Widening of the distal phalanx physis.
• Salter-Harris I or II fracture pattern.
• Juxta-epiphyseal fracture just distal to the physis.
• Flexion deformity or volar angulation of the distal fragment.
• Nail plate displacement or soft-tissue swelling.
• Subtle physeal asymmetry compared with the contralateral digit if uncertain.

Imaging cannot replace the nail-fold examination. A tiny radiographic abnormality with proximal nail-fold bleeding is still clinically important. Conversely, an apparent mallet posture in a skeletally immature patient should not be accepted as simple tendinous mallet injury until the nail bed and lateral film are reassuring.

The differential diagnosis matters because each injury has a different treatment pathway.

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Management is built around a simple principle: if the nail bed is violated and the distal phalanx physis is injured, this is an open fracture. The aim is to prevent infection, remove the soft-tissue block, restore distal phalanx alignment, repair the nail bed and protect the reduction until union.

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Preparation

Confirm the diagnosis clinically and radiographically. Consent should cover open fracture care, nail-bed repair, possible K-wire fixation, infection, nail deformity, stiffness, malunion, non-union, physeal disturbance and possible further surgery. Give antibiotics according to local open-fracture and paediatric hand protocols. Check tetanus status.

Exposure and debridement

Clearing the reduction block

The germinal matrix or nail bed is often folded into the fracture. This is the reason closed reduction may repeatedly fail. Extract the interposed tissue gently with fine instruments. Do not keep forcefully manipulating the distal phalanx against a soft-tissue block.

Reduction and fixation

Reduce the distal phalanx anatomically and confirm alignment clinically and with AP and lateral imaging.

The wire often crosses the DIP joint to hold the distal phalanx, but fixation should follow fracture stability, child factors and local hand-surgery practice.

Nail-bed repair and stenting

Repair the germinal or sterile matrix precisely with fine absorbable sutures. The aim is smooth nail-bed continuity without inversion, overlap or excessive tension. Replace a clean nail plate, or use a sterile substitute, beneath the eponychial fold to prevent fold adhesion and support nail regrowth. Apply a non-adherent dressing and protective splint.

Antibiotic choice and duration should follow local paediatric open-fracture and hand-injury protocols. A typical clean acute injury is usually covered for skin flora. Broaden the discussion with senior clinicians for bites, farm injuries, water exposure, immunocompromise, gross contamination, delayed presentation or established infection.

The follow-up question is not only "has the fracture united?" It is also "has infection declared itself, is the nail growing normally, and is distal phalanx growth staying acceptable?"

Early

• Missed open fracture and delayed antibiotics.
• Pin-site infection when fixation is used.
• Loss of reduction from unrecognised matrix interposition or inadequate fixation.
• Soft-tissue necrosis from crush injury or tight dressings.
• Persistent pain, swelling and stiffness.

Late

• Osteomyelitis, especially after delayed diagnosis.
• Non-union or malunion of the distal phalanx.
• Persistent mallet deformity or extensor lag.
• Nail deformity including ridging, split nail, hook nail or absent nail growth.
• Premature physeal arrest and distal phalanx growth disturbance.
• DIP stiffness and hypersensitive fingertip.

A Seymour fracture is small in size but high in consequence. The decision-making sequence is: recognise the open physeal injury, protect against infection, remove the soft-tissue block, restore nail-bed anatomy, stabilise the fracture if needed and follow the nail and physis.

The nail plate is a diagnostic structure. If it is perched on top of the eponychial fold, the germinal matrix is likely disrupted. Simply pushing the distal phalanx straight and applying a mallet splint can trap matrix in the fracture and leave contamination behind.

Operative care should be meticulous but not aggressive. Irrigate, debride devitalised tissue, remove interposed matrix, reduce anatomically, repair the nail bed with fine absorbable suture, stent the eponychial fold with the nail or substitute when appropriate, and stabilise if the fracture is unstable. Avoid repeated physeal trauma during wire placement.

The strongest answer starts by naming the injury correctly: an open distal phalanx physeal or juxta-epiphyseal fracture with nail-bed injury. That opening phrase immediately separates it from a simple mallet finger.

The next step is to explain why the clinical appearance is deceptive. The distal phalanx is flexed, but the nail fold is the dangerous clue. If the proximal nail plate sits superficial to the eponychial fold, the germinal matrix has probably been disrupted. If germinal matrix is trapped in the fracture, reduction fails until the tissue is cleared.

Nail-bed repair is not cosmetic trivia. It is part of fracture management because the nail bed and fracture communicate. Poor matrix alignment causes nail deformity. Missed contamination causes infection. Persistent soft-tissue interposition causes malunion, non-union or redisplacement.

A safe family explanation is:

"This is a small bone injury at the end of the finger, but because the nail bed is torn it behaves like an open fracture. We need to clean it properly, put the nail bed and bone back in the right position, give antibiotics, and then watch for infection, healing and nail growth."

Common pitfalls

• Calling it a mallet finger and treating with extension splint alone.
• Ordering only a hand X-ray and missing the true lateral digit view.
• Not looking under or around the proximal nail fold.
• Trying repeated closed reductions despite a soft-tissue block.
• Forgetting antibiotics and tetanus assessment.
• Repairing skin but leaving the nail bed and physis untreated.