1 Tension band principles top
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The tension band converts tensile forces into compression forces. There must be no comminution on the side opposite the plate. Note the contact of the articular surface in this fracture.
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The following criteria must be fulfilled for a plate to act as a tension band:
- The fractured bone must be eccentrically loaded.
- The plate must be placed on the tension side.
- The plate must be able to withstand the tensile forces.
- The bone must be able to withstand the compressive force which results from the conversion of distraction forces by the plate.
- There must be a bony buttress opposite to the plate to prevent cyclic bending. The articular surface needs to have contact, as illustrated here.
2 Reduction top
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Through a posterior incision, directly reduce the fracture with the help of pointed reduction forceps.
Temporarily hold the reduction with one or two K-wires. Insert the K-wires in a position where they do not interfere with the planned plate and screws.
Control reduction with direct visualization of the sigmoid notch and the posterior cortex of the olecranon and confirm with C-arm fluoroscopic control.
3 Plate preparation top
Implant choice
Use a 3.5 reconstruction plate, dynamic compression plate (DCP), limited contact dynamic compression plate (LC-DCP) or locking plate (LCP).
Choose the length of the plate so that at least two screws can be inserted in the most proximal fragment and three in the diaphysis.
If the fracture lies very proximal, or in osteoporotic bone, a preshaped olecranon LCP with locking head screws can be used to achieve better fixation.
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Plate contouring
Contour the plate to fit the proximal ulna, bending around the tip of the olecranon.
Contouring is achieved with bending irons and bending press. Thicker small fragment plates are difficult to bend so they fit around the proximal olecranon. Make sure the plate is bent enough.
4 Plate fixation top
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Proximal fixation
To achieve close bone plate contact, split the triceps attachment before positioning the plate.
Anchor the plate with two screws to the tip of the olecranon. Make sure that the screws do not protrude into the joint. Whenever possible, insert the screws bicortically, aiming the drill to the lateral or to the medial cortex.
Insert the third screw fixing the wedge fragment.
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Fracture compression
Compress the fracture with the help of a hook applied in the most distal plate hole and insert a screw just distal to the fracture line in neutral position. Alternatively, compression can be achieved by inserting the first distal screw in eccentric position.
Before compressing the fracture, remove the K-wires.
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Distal fixation
Insert the next two cortical screws in the distal fragment bicortically, through the anterior cortex and in a divergent pattern.
Make sure to maintain contour and width of the greater sigmoid notch.
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Pearl - fixation of a large wedge fragment
Depending on the fracture configuration, interfragmentary compression can be achieved by inserting a lag screw through the plate.
5 Possible fixation of a large coronoid fragment top
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Reduction of a large coronoid component of multifragmentary proximal ulna fractures can often be done through the fracture site. Provisional or definitive fixation can be placed at that time, but sometimes it helps to use a screw through a posterior plate for its fixation, as shown here. Insert this as a lag screw, as perpendicularly as possible to the fracture plane at the base of the coronoid. Smaller diameter screws may be better.
Further details of coronoid fixation
For further information on the fixation of coronoid fractures, see "Repair of coronoid fracture".
6 Alternative: Hook plate fixation top
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An alternative in very proximal ulna fractures can be the use of a one-third tubular hook plate.
Cut the screw hole on one end of the plate and bend it to form a bifid hook.
The hook engages in the proximal fragment, where it can be additionally fixed with one or two screws.
Apply the plate underneath the triceps brachii tendon and make sure that the tip does not impinge on the olecranon fossa.
Note
The one-third tubular plate is thin and may fail under bending
loads. Thus it should be used only as a tension band with good bone
support.
