Seymour fracture

The Seymour fracture is a clinically important subtype of mallet finger type injury. The Seymour fracture is comprised of a distal phalanx physeal fracture that has an associated nail bed injury commonly with ungual subluxation.

Clinical presentation

The skeletally-immature patient presents with what clinically appears to be a mallet finger deformity with associated soft tissue trauma at the proximal nail fold. The nail plate may demonstrate obvious signs of avulsion or subluxation, lying superficial to the nail fold or in a more occult situation the nail bed injury may be hidden more proximally and deep to the nail fold. 

Pathology

The injury pattern can result from a number of mechanisms, the most common of which include crush injuries, sporting injuries (often hyperflexion) and falls. The injury typically occurs when the distal phalanx of a fully extended digit undergoes forceful flexion or the distal phalanx experiences a crush injury for example in a closing door. 

Radiographic features

Plain radiograph

In skeletally-immature individuals, a fracture demonstrating a Salter-Harris type I or Salter-Harris type II pattern through the physis of the distal phalanx or a fracture involving the proximal metaphysis 1-2 mm distal to the epiphyseal plate is seen in conjunction with volar angulation of the diaphysis.

Widening of the physis can be appreciated on AP projections while lateral and oblique projections better demonstrate the aberrant volar angulation. 

In many cases, disruption of the overlying soft tissue envelope can be appreciated along with some subcutaneous emphysema. In the absence of nail fold and soft tissue envelope changes, clinical correlation should be recommended to exclude a Seymour fracture. 

Since a large number of Seymour fractures are the result of crush injuries, care should be taken to assess for retained radiopaque foreign bodies at the site of the fracture. 

Serial imaging studies should consider delayed union, malunion and non-union, in addition to assessment for radiographic changes of osteomyelitis. Growth disturbance of the distal phalanx has also been reported in some cases.

Treatment and prognosis

Early review and treatment by a specialist hand (plastic/orthopaedic) surgeon are recommended as delayed treatment has been associated with a high risk of infection. 

Open injuries are more prone to soft tissue infection and development of osteomyelitis and thus warrant operative intervention. 

Principles of operative management:

• antibiotic therapy 
• early debridement and washout
• accurate reduction
• rigid fixation 
• nail bed repair 

Principles of conservative management:

• antibiotic therapy 
• closed reduction 
• splinting 

Complications

• osteomyelitis
• delayed union, malunion, non-union 
• disturbance of distal phalanx bone growth 

History and etymology

The importance of the pattern of injury was first highlighted by the Scottish orthopaedic surgeon N Seymour in 1966 ⁵. The seminal article titled "Juxta-epiphyseal fracture of the terminal phalanx of the finger" was published in the Journal of Bone and Joint Surgery ⁵ and the pattern of injury has subsequently carried the eponymous name 'Seymour fracture'. The pattern of injury is less commonly also called a juxta-epiphyseal fracture of the distal phalanx. 

Differential diagnosis

• mallet finger injury (various subtypes)