1 General considerations topenlarge
Plating is the standard technique for treating forearm fractures in adults and is therefore best considered for skeletally mature or nearly mature children.
Children with open physes have thick active periosteum favoring stability and rapid healing with the ESIN method. Where such techniques are unavailable plating may be used in younger children.
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 Principles top
Order of reduction and fixation
The usual strategy to deal with a Monteggia lesion is:
- 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.
Choice of approach
The ulna is exposed by the direct approach between the flexor and extensor muscle compartments.
If the radiocapitellar relationship is not perfect and stable, then the radiocapitellar joint can be explored.
A lateral (Kocher) approach to the elbow is usually performed.
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.
3 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.
Fixation of the ulna
Plating of pediatric forearm shaft fractures follows the technique for plate fixation in adults.
The steps for ulnar fracture fixation are described in the relevant plating procedure for each fracture type:
- Plating for simple transverse fracture
- Plate and screw fixation for oblique or spiral fracture
- Bridge plating for unstable multifragmentary fracture
Prebending the plate for a Monteggia lesion
Overcorrecting the ulna can be necessary to improve the stability of the radiocapitellar joint.
The ulnar shaft will hold the radius reduced through the interosseous membrane.
In children with Monteggia lesions and proximal ulnar shaft fractures, a plate can be contoured to produce an overcorrected position.
This may result in greater stability of the radiocapitellar joint than anatomically reducing the ulna.
Ulnar osteotomy for plastic deformity
A Monteggia lesion with plastic deformity of the ulna has a strong tendency for the radial head to redislocate 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.
4 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.
Rotational movements 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 anatomical 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.
5 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.
6 Final assessment topenlarge
Check the completed osteosynthesis with image intensification. These images should be retained for documentation or alternatively 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.
Stabilize the elbow at the epicondyles and check the forearm rotation.