Metacarpal fractures are common accounting for 10% of all fractures and 40% of all hand fractures.
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Terminology
Specific names are given to fractures of the base of the first metacarpal (see: fractures of the thumb):
gamekeeper thumb (not always includes a fracture)
Specific names are given to fractures of the fifth metacarpal:
fracture dislocation of the base of the 5th metacarpal: reverse Bennett fracture dislocation
fracture of 5th metacarpal neck: Boxer fracture
Epidemiology
The lifetime incidence of a metacarpal fracture is 2.5% ref. Fractures of the 5th metacarpal make up 25% of all metacarpal fractures (which equates to 10% of all hand fractures) ref.
Pathology
They are a result of direct or indirect trauma with the nature and direction of the force being directly related to the type of injury. Specific injury patterns include ref:
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carpometacarpal (CMC) joint injury
metacarpal base fractures and dislocation of the CMC joint
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metacarpal shaft and neck fractures
these are usually a result of axial loading or direct trauma (clenched fist and solid surface); torsional force may also result in this type of injury
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metacarpal head injury
these are intra-articular fractures that result from axial loading or direct trauma; collateral ligament avulsion fractures are caused by forced deviation of the flexed metacarpophalangeal joint (MCPJ).
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metacarpophalangeal joint dislocations
dorsal MCPJ dislocations are the most frequent and a result of forced hyperextension of the digit
Differential diagnosis
in children, consider pseudoepiphysis at the base 2