Executive Editor: Chris Colton

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

Thumb - Bennett fracture

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Glossary

1 Introduction top

Bennett’s injury is a fracture subluxation. The causative mechanism is axial overload along the first metacarpal with ... enlarge

Bennett’s injury is a fracture subluxation. The causative mechanism is axial overload along the first metacarpal with simultaneous flexion. The palmar oblique ligament holds the palmar marginal fragment in its anatomical position.


The distal part of the first metacarpal is adducted and supinated by adductor pollicis. The metacarpal as a whole is also ... enlarge

The distal part of the first metacarpal is adducted and supinated by adductor pollicis. The metacarpal as a whole is also displaced proximally by the abductor pollicis longus muscle.
The treatment goals are to reposition the first metacarpal in the carpo-metacarpal joint, and to restore the articular surface.


Depending on the size of the palmar marginal fragment, two treatment options are available. enlarge

Treatment options

Depending on the size of the palmar marginal fragment, two treatment options are available:


If the palmar marginal fragment comprises less than one third of the articular surface, one screw and a K-wire are used. enlarge

1) Screw and K-wire
If the palmar marginal fragment comprises less than one third of the articular surface, one screw and a K-wire are used.


If the fragment comprises more than one third of the articular surface, two screws are used. enlarge

2) Two screws
If the fragment comprises more than one third of the articular surface, two screws are used.


If the fragment comprises more than one third of the articular surface, two screws are used. enlarge

2 Small fragment: reduction top

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Inspection of the joint

To determine the exact geometry of the fracture and correct placement of the screws, it may be helpful to open the fracture plane by exerting traction and supination on the thumb.
The fracture surfaces must be irrigated for better visualization.


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Reduce the fracture by pronation of the metacarpal and hold the reduction with a pointed reduction forceps.
Under direct vision, check that the joint surface is anatomically reduced, and adjust as necessary.


Check the reduction and the position of the K-wire using image intensification. enlarge

K-wire

The fracture is stabilized with a 1.2 mm – 1.4 mm K-wire.

Check the reduction and the position of the K-wire using image intensification.

3 Small fragment: internal fixation top

Drill a thread hole through both fragments, using 1.5 mm drill. If a non-selftapping screw is used, tapping is necessary ... enlarge

Drilling for the lag screw

Drill a thread hole through both fragments, using 1.5 mm drill. If a non-selftapping screw is used, tapping is necessary at this stage.
Then use the larger 2.0 mm drill bit to overdrill the near fragment, creating the glide hole.
It is sufficient to overdrill only the first few millimeters of the near fragment. If the glide hole extends into the palmar marginal fragment, compression will not be achieved.
With smaller marginal fragments, it may be necessary to use a 1.5 mm screw (1.1 mm thread hole; 1.5 mm glide hole).


Insert the lag screw and carefully tighten it. enlarge

Insertion of the lag screw

Insert the lag screw and carefully tighten it.


The K-wire is now cut off below the skin, just above the cortex. Bending of the K-wire risks producing fragment displacement. enlarge

Confirm position and stability using image intensification.
Also assess the stability of the fixation under direct vision.
The K-wire is now cut off below the skin, just above the cortex. Bending of the K-wire risks producing fragment displacement.

4 Large fragment: open reduction top

In case of a large palmar marginal fragment, two screws are used. enlarge

Inside-out glide holes

In case of a large palmar marginal fragment, two screws are used.
Before reduction, supinate the metacarpal and drill two glide holes outwards from the fracture surface for more accurate positioning of the lag screws, perpendicular to the fracture plane, and evenly placed in the marginal fragment.


After drilling the glide holes, reduce the fracture by pronation of the metacarpal, and secure with pointed reduction forceps. enlarge

Reduce the fracture

After drilling the glide holes, reduce the fracture by pronation of the metacarpal, and secure with pointed reduction forceps.
Check the articular reduction under direct vision and using image intensification.

5 Large fragment: internal fixation top

Drill thread holes with a 1.5 mm drill bit through a drill sleeve inserted into the previously drilled glide holes. enlarge

Drill thread holes

Drill thread holes with a 1.5 mm drill bit through a drill sleeve inserted into the previously drilled glide holes.


Confirm position and stability using image intensification. Also assess the stability of the fixation under direct vision. enlarge

Insert screws

Insert two 2.0 mm self-tapping lag screws and alternately tighten them. Remove the reduction forceps.
Confirm position and stability using image intensification. Also assess the stability of the fixation under direct vision.

v1.0 2008-11-08