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:

  • Adductor policis - adduction and supination

  • Abductor policis longus (APL) - radial and proximal displacement

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

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


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:

  • Extraarticular fractures

  • Intaarticular fractures (controversial tend to advocate closed reduction and percutaneous fixation)

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:

  • Intraarticular fractures

  • Unstable extraarticular fractures (long oblique)

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