Executive Editor: Chris Colton

Authors: Renato Fricker, Matej Kastelec, Fiesky Nuñez, Terry Axelrod

Metacarpals - Base fracture

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Glossary

1 Introduction top

A typical site for metacarpal base fractures is the fifth metacarpal. enlarge

A typical site for metacarpal base fractures is the fifth metacarpal. Most of these fractures are comminuted and impacted, and are often associated with carpo-metacarpal fracture dislocations. Additional dorsal shearing fractures of the hamate may be present. These fractures are usually fixed with plates, or K-wires in the case of small fragments, and may need bone grafting.


These fractures are usually fixed with plates, or K-wires in the case of small fragments, and may need bone grafting. enlarge

CT scans are very helpful to determine the number, size and position of the fragments.


Depending on the fracture geometry, simpler fractures can be treated with lag screws ... enlarge

Simple fractures

Depending on the fracture geometry, simpler fractures can be treated with lag screws (e.g. extensor carpi ulnaris tendon avulsion fractures), or with T-, Y- or L-shaped plates.


Fractures of the fifth metacarpal base may be associated with a carpo-metacarpal dislocation of the ... enlarge

Dislocation of the 4th metacarpal

Fractures of the fifth metacarpal base may be associated with a carpo-metacarpal dislocation of the fourth ray. In that case, the fourth metacarpal is reduced first and usually stabilized with transfixion K-wires.
Occasionally, there is a subluxation of the 3rd metacarpal, or even the 2nd metacarpal, and any combination of additional fractures can be seen.

2 Reduction top

Apply axial traction on the finger, either manually or with a finger trap. enlarge

Restore length

Apply axial traction on the finger, either manually or with a finger trap. A small external fixator can be used, with K-wires inserted into the hamate and the distal metacarpal, preliminarily to fix the reduction.
Capsulotomy is needed to check the reduction of the articular fragments if the joint capsule is not already ruptured.


Use a dental, pick, a periosteal elevator, or small K-wires to reduce the fragments. Insert small K-wires for preliminary... enlarge

Reduce fragments

Use a dental, pick, a periosteal elevator, or small K-wires to reduce the fragments. Insert small K-wires for preliminary fixation of these articular fragments. Occasionally, these K-wires are inserted percutaneously; make sure not to injure the dorsal sensory branch of the ulnar nerve.
In case of a bone defect, bone graft from the distal radius is used to fill the void.
Check reduction using image intensification.
If the hamate is uninjured, its articular surface can be used as a template for restoring the articular surface of the metacarpal base.


Turn the hand over and flex the fingers passively to check for correct rotational alignment. enlarge

Check rotational alignment

Turn the hand over and flex the fingers passively to check for correct rotational alignment.
The image on the right shows rotational malalignment of the middle finger (“scissoring”).


In the case of a shearing fracture of the hamate, reduce this fragment first and fix it with a lag screw. enlarge

Accompanying hamate fracture

In the case of a shearing fracture of the hamate, reduce this fragment first and fix it with a lag screw.

3 Plate preparation top

Depending on fragment size, a 2.0 mm, or, more frequently, a 1.5 mm plate is used. enlarge

Plate selection

Depending on fragment size, a 2.0 mm, or, more frequently, a 1.5 mm plate is used.
T-, L- or Y-shaped plates can be used and the choice depends on the geometry of the fracture.
At least 2 screws should be inserted into the diaphyseal fragment.


The plate must be contoured exactly to fit the surface of the metacarpal, including any necessary twisting. enlarge

Contouring of the plate

The plate must be contoured exactly to fit the surface of the metacarpal, including any necessary twisting.

4 Fixation top

Be careful to ensure that the screws do not perforate the joint surface. enlarge

Apply the plate

Position the plate exactly so that the articular fragments can be fixed using screws through the proximal plate holes. Often, it is not possible to insert a screw into each fragment. Small fragments should be supported by adjacent large fragments, or bone graft.
Be careful to ensure that the screws do not perforate the joint surface.


If necessary, small K-wires can be inserted transversely just deep to the subchondral cortical bone, in order to buttress ... enlarge

Buttress small fragments

If necessary, small K-wires can be inserted transversely just deep to the subchondral cortical bone, in order to buttress these small fragments.


Drill carefully in order not to displace the fragments. enlarge

Drill for first screw

Begin fixation with the most critical articular fragment.
Drill carefully in order not to displace the fragments.
Measure for the length of the screw.


Insert the first screw without completely tightening it. Confirm the reduction and correct screw position. enlarge

Insert first screw

Insert the first screw without completely tightening it.
Confirm the reduction and correct screw position using image intensification.


With the first screw in place, align the plate along the shaft. enlarge

Fix plate to diaphysis

With the first screw in place, align the plate along the shaft. Usually, the plate is now fixed to the diaphyseal fragment with one screw through its most distal hole. Tighten this screw.


Drill the second main articular fragment. enlarge

Insert second proximal screw

Drill the second main articular fragment. Avoid penetration of the joint surface and interference with the first screw. Measure screw length with a depth gauge.
Insert the screw and alternately tighten the two screws in the articular fragments


If additional large metaphyseal fragments need fixation, insert screws through the plate, or insert an independent lag screw. enlarge

Further fragments

If additional large metaphyseal fragments need fixation, insert screws through the plate, or insert an independent lag screw.
If needed, use additional bone graft to fill any defect.


Insert the second and, if possible, a third screw into the diaphyseal fragment and tighten them. enlarge

Insert second diaphyseal screw

Insert the second and, if possible, a third screw into the diaphyseal fragment and tighten them.


When the fixation is completed, remove the external fixator and K-wires, other than those needed to buttress small articular ... enlarge

Complete osteosynthesis

When the fixation is completed, remove the external fixator and K-wires, other than those needed to buttress small articular fragments.

5 Complex fragmentation top

If fixation can not be performed with screws and plates, stabilization can be achieved with an external fixator bridging ... enlarge

Bridging fixation with ExFix

If fixation can not be performed with screws and plates, stabilization can be achieved with an external fixator bridging the fracture zone from the hamate to the metacarpal.
This allows for the restoration of correct length and rotational alignment.


This can also be performed using a bridging plate as an internal fixator with screws inserted into the hamate and the ... enlarge

Bridging fixation with internal fixator

This can also be performed using a bridging plate as an internal fixator with screws inserted into the hamate and the diaphysis of the metacarpal.
The plate is removed when the fracture has completely healed after about 4 months.

v1.0 2008-11-08