Hamate fractures are rare and underreported. These injuries are usually misdiagnosed or confused with simple wrist sprains. Delayed diagnosis is not uncommon. The hamate is a triangular-shaped bone that forms part of the distal carpal row, articulating with the capitate (radially), triquetrum (proximally), and fifth and fourth metacarpals (distally).
Considering its unique anatomy (Figure 1), hamate fractures usually get subdivided into two broad groups: hook fractures and body fractures.[rx][rx]
Classification of hamate fractures:
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Type 1: Hook of the hamate fracture
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Type 2: Body of the hamate fracture
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2a: Coronal (may be dorsal oblique or splitting fracture)
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2b: Transverse fracture
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Associated hook fracture injuries:
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Ulnar artery injury
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Ulnar nerve injury
Associated body fracture Injuries:
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Fourth and fifth metacarpal fracture-dislocation
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Greater arc perilunate fracture-dislocation
Differential Diagnosis
Ulnar flexor carpi tendinitis and triangular fibrocartilage complex injuries are a common misdiagnosis.[rx] A hamate fracture accompanies a small percentage (1 to 2%) of distal radius fracture.[rx]
Other differential diagnoses include:
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Bipartite hamate
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Scaphoid fracture
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Capitate fracture
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Triquetrum fracture
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Pisiform fracture
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Ligamentous injuries (without fracture)
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Carpal bone dislocations
Treatment / Management
Surgical indications: displaced fractures, nonunion, ulnar nerve compression, median nerve compression, ulnar artery compression, tendon rupture and metacarpal subluxation.
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Hook fractures:
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Acute, nondisplaced: Immobilization, ulnar gutter cast for six weeks. There is still debate whether patients may profit from initial surgical treatment in this type of fractures. Sport players will usually benefit from early surgical management, returning to sports activities in three months.
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Acute, displaced: Excision of a bony fragment is the gold standard procedure. Open reduction and internal fixation (screws or Kirschner wires) is another proven treatment. Both alternatives showed similar clinical results.[23]
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Chronic pain, nonunion: These signs require fracture pinning with bone grafting.
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Surgical tech tips:
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The motor branch of the ulnar nerve must be clearly spotted and retracted before hook excision or drilling.
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After fractured fragment excision, periosteum closure should be over the base of the remaining body to protect the ulnar nerve and tendons
Complications
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Nonunion
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Posttraumatic arthritis
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Avascular necrosis in proximal pole (body fractures)
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Ulnar nerve compression (Guyon´s canal)
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Carpal tunnel syndrome
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Flexor digitorum profundus tendon rupture
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Ulnar artery thrombosis (hypothenar hammer syndrome)
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Ulnar artery compression
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Residual instability of fourth and/or fifth metacarpals
- 1 – Radioscaphoid arthritis
- 2 – Scaphocapitate arthritis
- 3 – Lunocapitate arthritis
Scaphoid nonunion advanced collapse (SNAC) is the end-stage and is managed with wrist fusion or proximal row corpectomy.
- Avascular necrosis – The incidence of this is approximately 30-40%. This is most likely to affect the proximal pole
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Scapholunate dissociation
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Delayed union – typically 90-95% if operatively managed fracture unites, but if there is doubt, CT scan may be needed to confirm union.