Executive Editor: Chris Colton

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

Thumb - Base

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Glossary

1 Introduction top

Extraarticular fractures of the base of the thumb metacarpal are often displaced, with a flexion deformity and may show ... enlarge

Extraarticular fractures of the base of the thumb metacarpal are often displaced, with a flexion deformity and may show palmar comminution (Winterstein fracture).


The pull of the thenar muscles results in palmar flexion of the distal fragment. enlarge

Displacement due to muscle forces

The pull of the thenar muscles results in palmar flexion of the distal fragment.


If the flexion deformity exceeds 30 degrees, thumb function may be impaired due to muscle imbalance. Internal fixation ... enlarge

Flexion deformity

If the flexion deformity exceeds 30 degrees, thumb function may be impaired due to muscle imbalance. Internal fixation allows for anatomical reduction.


If standard plates are used, bone graft from the distal radius may be necessary to avoid delay in bone healing and ... enlarge

Instability due to palmar comminution

If standard plates are used, bone graft from the distal radius may be necessary to avoid delay in bone healing and consequent secondary displacement, or failure of fixation. Angularly stable plate fixation, using a locking compression plate (LCP), prevents secondary displacement without the need of bone grafting.

2 Reduction top

Angularly stable plate fixation in the proximal fragment allows for reduction using the plate as a lever. enlarge

Indirect reduction with the plate

Angularly stable plate fixation in the proximal fragment allows for reduction using the plate as a lever (as described below).

View animation


Alternatively, and especially when a conventional plate is used, reduction can be performed with axial traction on the ... enlarge

Reduction by traction

Alternatively, and especially when a conventional plate is used, reduction can be performed with axial traction on the thumb, either manually, or with help of a finger trap, and simultaneous pressure on the dorsal aspect of the diaphysis.


Preliminary stabilization can be achieved with an obliquely inserted K-wire. enlarge

Preliminary stabilization

Preliminary stabilization can be achieved with an obliquely inserted K-wire.
If anatomical reduction is demonstrated using image intensification, a 2 mm LCP T-plate is fixed to the dorsal aspect of the first metacarpal using standard locking techniques.

3 Plate preparation top

Cut the 2.0 mm LCP to length so that 2 screws can be fixed in the distal diaphyseal fragment. enlarge

Plate length

Cut the 2.0 mm LCP to length so that 2 screws can be fixed in the distal diaphyseal fragment.


The plate has to be adapted accurately to the contour of the proximal fragment. enlarge

Contouring of the plate

The plate has to be adapted accurately to the contour of the proximal fragment. Use bending pliers to contour the plate. Be careful to bend in between the holes by positioning the pliers over the plate holes. Alternatively, insert the threaded bolt into the plate holes to bend the plate.
The bend should never go through a hole as this may damage the locking mechanism.


Be careful not to overbend, as there is a comminuted zone at the opposite cortex, which can not withstand compression. enlarge

Adding a slight bend

In order to prevent the screw from penetrating the joint, a slight bend is necessary. Be careful not to overbend, as there is a comminuted zone at the opposite cortex, which can not withstand compression.

4 Plate fixation top

Put the plate on the dorsal aspect of the proximal fragment, with a threaded drill guide in one of the outer holes. enlarge

Insertion of first screw

Mark the plane of the first carpo-metacarpal joint with a thin K-wire or a hypodermic needle. Put the plate on the dorsal aspect of the proximal fragment, with a threaded drill guide in one of the outer holes. Drilling must be parallel to the marker wire (or needle) to ensure that the screw will not penetrate the joint. Confirm using image intensification.
Drill through the threaded drill guide. Remove the drill guide and measure the appropriate screw length with a depth gauge.
Insert the locking screw without completely tightening it.


Align the plate along the axis of the shaft. enlarge

Plate alignment

Align the plate along the axis of the shaft.


Insert a second screw using the same technique. Always use a threaded drill guide when preparing for locking screws. enlarge

Insertion of 2nd screw in the proximal fragment

Insert a second screw using the same technique. Always use a threaded drill guide when preparing for locking screws.


Pressing the plate down to the diaphyseal fragment with a periosteal elevator will automatically tilt the articular ... enlarge

Reduction by using the plate as a lever

Pressing the plate down to the diaphyseal fragment with a periosteal elevator will automatically tilt the articular fragment into its correct position. Check the reduction of the dorsal fracture line.
Confirm using image intensification.


Insert a screw through the most distal plate hole. This screw would normally be a standard screw, as it engages in thick ... enlarge

Insertion of distal screws

Insert a screw through the most distal plate hole. This screw would normally be a standard screw, as it engages in thick cortical bone. A locking screw, using a threaded drill guide when drilling, may be inserted in osteoporotic bone, or when otherwise indicated.
The second distal screw is inserted using the same technique.

v1.0 2008-11-08