1 General considerations topenlarge
In Monteggia lesions two points are crucial for successful reduction of the radial head:
- Restoration of ulnar length
- Stable reduction of the radiocapitellar joint
An anatomical reduction of the ulna may not be sufficient to anatomically reduce and stabilize the radiocapitellar joint. An overcorrection of the ulna may be necessary, and this can make plating technically difficult.
2 Order of reduction and fixation top
The usual strategy to deal with a Monteggia lesion is:
- Perform a stable anatomical reduction or overcorrection of the ulna.
- Assess the radial head position and stability using image intensification.
- If necessary, revise the position of the ulna.
- If necessary, perform an open reduction of the radial head.
3 Patient preparation top
4 Choice of approach top
The ulna is exposed through a posterior approach.
If the radiocapitellar relationship is not perfect and stable, then the joint can be explored through a lateral approach.
An alternative is the posterolateral approach, which provides access to both the proximal ulna and the radial head. A disadvantage of this approach is the potential for cross-union.
5 Reduction and fixation of the ulnar fracture top
Reduction of the ulna
The alignment of the ulna is addressed first.
The ulna needs to be fully out to length and stable. If this is not achieved the radial head can redislocate or sublux leading to permanent loss of forearm function.
Prebending the plate for a Monteggia lesion
A plate can be contoured to overcorrect the proximal ulna and improve the stability of the radiocapitellar joint.
The overcorrected ulnar shaft will hold the radius reduced through tension in the interosseous membrane.
This may result in greater stability of the radiocapitellar joint than with an anatomically reduced ulna.
Ulnar osteotomy for plastic deformity
There is a strong tendency for the radial head to redislocate in a Monteggia lesion with plastic deformity of the ulna as the ulna rebounds to the original position.
An osteotomy of the proximal ulnar shaft with overreduction can be held with an appropriately contoured plate.
In the illustrated example an apex dorsal angulation of the ulna prevents anterior redislocation of the radial head.
6 Assessing the radial head position topenlarge
Reduction of radial head
The radial head will usually reduce closed and remain stable once the ulna has been aligned.
Rotation of the forearm may be necessary to complete the reduction of the radial head.
After fixation of the ulna, use an image intensifier to carefully evaluate the position of the radial head relative to the capitellum.
This must be confirmed through a full range of flexion, extension, pronation and supination.
Revision of ulnar reduction and fixation
At this stage the ulnar reduction can be revised if required, often to an overcorrected position, which usually results in stable anatomic reduction of the radial head.
If there is residual subluxation or instability in any position after optimization of the ulnar correction, there may be interposed tissue (usually annular ligament) in the radiocapitellar joint and an open reduction of this joint should be performed.
7 Open reduction of radial head topenlarge
Approach to radial head
Perform a lateral approach and manually reduce the radial head.
Removal of blocks to reduction
The annular ligament is the most common intraarticular block to reduction. In rare cases the ligament can be gently repositioned around the radial head.
More often the ligament must be incised or excised to allow reduction of the radial head.
Reassessment of radial head position
Reassess the position and stability of the radial head by direct visual inspection and image intensification.
8 Final assessment topenlarge
Check the completed osteosynthesis with image intensification. These images should be retained for documentation.
If an image intensifier is not available an x-ray should be obtained before discharge.
Make sure that the plate is at the correct location, the screws are of appropriate length, the desired reduction has been achieved and the radial head remains in the appropriate position.
Check the forearm rotation.