Thumb Metacarpal
Anatomy
Anatomical
snuff box at base of thumb metacarpal, bounded by - Abductor policis longus
(APL) and Extensor policis brevis (EPB) anteriorly and Extensor policis
longus (EPL) posteriorly. In base consider, superficial branch radial nerve and
radial artery.
Displacement of
fracture at base occurs due to pull of:
Radiographs
Ask for Ap and lat of thumb not AP and lat of hand.
Classification
Seperate intra articular from extra articular.
They are not all Bennett's fractures. A Bennett's farcture is an intraarticular
fracture dislocation of the base of the thumb metacarpal
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Base of Thumb fractures
- 1. Extra-articular -
Transverse and oblique
- 2. Bennett's fracture - Fracture
dislocation base of thumb metacarpal
- 3. Rolando fracture- Multifragmentary fracture base of thumb
metacarpal (like pilon fracture)
- 4. Physeal injuries
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Extraarticular fractures
Oblique
fractures are harder to hold reduced closed than transverse. (see anatomy and
displacement forces)
Can accept 20
degrees of angulation.
Closed
treatment still suggested 4 weeks in a thumb spica cast.
Intraarticular
fractures
Treatment can
be controversial. Rockwood suggests erring on operative management as it is hard
to control the fragments with casting alone.
Some studies
have shown satisfactory results following closed treatment. However the problem
of a painful malunion is very difficult to salvage.
Treatment
Closed
reduction and plaster cast application
Charnley
emphasizes the importance of feel and precision in reduction and cast
application.
The fracture is
reduced by Hyperextending the thumb metacarpal (note metacarpal not IP joint)
A Bennett's
cast can be technically difficult. It is important to mould the cast
counteracting all the deforming forces and moulding at the base of the thumb
metaccarpal.
Indicated for:
Closed
reduction and K wire fixation
Consider
anatomy, one or two pins into trapezium or index metacarpal. In Rolando
fractures the aim is to distract the metaphysis and allow the comminuted area to
heal. k - wire into the index metacarpal. Protect with cast, remove pins 4-5
weeks.
Indicated for:
Open Reduction
and Internal Fixation
Is an option if
the fragments are large enough. Beware of comminuted fractures (Rolando)
Not for the
part time hand surgeon. Beware cutaneous nerves.
External
Fixation
External
fixation in rolando fractures (comminuted ) can allow for distraction and
metaphyseal healing.
Closed treatment of common fractures, John Charnley
pg 143-149
Last updated
11/09/15
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