1 Principles top
A1.2 fractures comprise transverse and short oblique fractures (< 30°) of the ulna with the radius and the proximal radioulnar joint (PRUJ) intact.
Absolute fracture stability, achieved by interfragmentary compression, results in direct bone healing.
Using self-compressing plates (DCP, LC-DCP, LCP, etc.), axial compression results from eccentric screw (load screw) insertion.
Prebending the plate
If the plate which will exert axial compression is exactly contoured to the anatomically reduced fracture surface, there will be some gapping of the opposite cortex, when the plate is tensioned by tightening the load screw.
The solution to this problem is to “over-bend” the plate so that its centre stands off 1-2 mm from the anatomically reduced fracture surface.
When the neutral side of the plate is applied to the bone, slight gapping of the cortex will occur directly underneath the plate.
As the load screw is tightened, the tension generated in the plate compresses the fracture evenly across the full diameter of the bone.
The plate on the ulna can be positioned under the extensor carpi ulnaris muscle (A), under the flexor carpi ulnaris muscle (B), or in the interval between extensor and flexor carpi ulnaris muscles (C). With a more proximal fracture it can be more difficult to place the plate underneath the extensor muscle. With more distal fractures, plates should be placed in the interval between the extensor and flexor carpi ulnaris muscles (C).
While plate position on the tensile (subcutaneous) aspect of the ulna (C) is biomechanically preferable, plate prominence can be a problem and cause irritation. In order to avoid too superficial a position of the plate, it can be placed towards positions (A) or (B) where it will be covered by the muscle compartment.
In the following procedure, we demonstrate the plate positioned deep to the extensor carpi ulnaris muscle (A).
2 Reduction topenlarge
Open and anatomical reduction
Reduce the fracture anatomically, using a reduction forceps on each main fragment. The use of blunt, as opposed to pointed, reduction forceps can be helpful, particularly if greater forces are required.
Pearl: leverage technique for transverse, or especially short oblique, fractures
A small bone lever can be used to reduce transverse, or short oblique, fractures as illustrated.
Pearl: lengthening by twisting of reduction forceps
Reduction of overlapping short oblique fractures can sometimes be achieved by twisting a reduction forceps, thereby lengthening the fracture.
Maintain fracture reduction
A reduced transverse fracture can not be maintained with reduction forceps alone. However, transverse fractures are usually dentate and are intrinsically stable after anatomical reduction.
If not, fix the plate to one fragment and then reduce the other fragment onto the plate.
A bone spreader, placed between the end of a plate and an independent screw, can be used to distract the fracture for reduction.
In order to maintain the reduction, using the same independent screw, preliminary axial compression can then be obtained by pulling the plate end towards the screw with a small Verbrugge clamp.
3 Plate length and number of screws topenlarge
In the forearm, three bicortical screws are required in each main fracture fragment due to the high torsional stresses. For biological reasons, not every plate hole needs to be occupied by a screw. Therefore, plates with at least 8 or 9 holes are usually chosen.
In short oblique forearm shaft fractures an empty plate hole may be necessary at the level of the fracture, but only if the fracture configuration demands.
4 Fixation topenlarge
Dynamic compression principle
The holes of the plate are shaped like an angled cylinder. The spherical undersurface of the screw head slides down the inclined cylinder as the screw is tightened.
The horizontal movement of the head, as it impacts against the angled side of the hole, results in movement of the bone fragment relative to the plate, and leads to compression of the fracture.
Prebend the plate
After the plate has been contoured anatomically to the reduced bone surface, prebend it with the handheld bending pliers, or a pair of bending irons, as explained in the principles section.
Insert 1st screw
The prebent plate is fixed to one of the main fragments with a screw in neutral mode. A reduction forceps is placed on the opposite fragment to hold it in the reduced position against the plate.
Note: Because of the design of the LC-DCP holes, the neutral drill guides for the LC-DCP have a very slightly eccentric hole and an arrow, which needs always to point towards the fracture line.
Insert 2nd screw eccentrically
A second screw is inserted eccentrically (yellow drill sleeve) into the opposite fragment.
Note: the arrow on the drill sleeve has to point towards the fracture line.
By tightening the eccentrically-inserted screw, axial compression is achieved.
Insert additional screws
Normally, additional screws in each fragment will be inserted in a neutral position.
However, should it be necessary to increase the axial compression, a second screw can be inserted eccentrically into either fragment.
As the second eccentric screw is tightened, the first screw in the same fragment needs to be loosened slightly to allow the plate to slide on the bone.
Pearl: alternative drill sleeve
For inserting screws into the limited contact dynamic compression plate (LC-DCP), the Universal Drill Guide can be used as well. When this drill guide is pressed into the plate hole, the screw position will be neutral (A). When it is held against the end of the plate hole, without exerting downward pressure, the screw position will be eccentric (B).
All other screws are inserted in a neutral position (green drill sleeve) and do not serve further to increase compression.
5 Check of osteosynthesis topenlarge
Check the completed osteosynthesis by image intensification. Make sure that the plate is at a proper location, the screws are of appropriate length and a desired reduction was achieved.
The elbow should be stabilized at the epicondyles and the forearm rotation should be checked between the radial and ulnar styloids.
6 Assessment of Distal Radioulnar Joint (DRUJ) top
Before starting the operation the uninjured side should be tested as a reference for the injured side.
After fixation, the distal radioulnar joint should be assessed for forearm rotation, as well as for stability. The forearm should be rotated completely to make certain there is no anatomical block.
The elbow is flexed 90° on the arm table and displacement in dorsal palmar direction is tested in a neutral rotation of the forearm with the wrist in neutral position.
This is repeated with the wrist in radial deviation, which stabilizes the DRUJ, if the ulnar collateral complex (TFCC) is not disrupted.
This is repeated with the wrist in full supination and full pronation.
In order to test the stability of the distal radioulnar joint, the ulna is compressed against the radius...
...while the forearm is passively put through full supination...
If there is a palpable “clunk”, then instability of the distal radioulnar joint should be considered. This would be an indication for internal fixation of an ulnar styloid fracture at its base. If the fracture is at the tip of the ulnar styloid consider TFCC stabilization.