1 Preliminary remark on 21-A3 fractures top
Anatomical reduction and stable fixation of both fractures are desirable for 21-A3 fractures. Begin by exposing both fractures.
Usually, the ulnar fracture will be fixed first. Malreduction of the first of the fractures will usually impede reduction of the other. The specific fracture fixation is determined by the character of each fracture and is discussed below.
Rare type IV Monteggia fractures (complete dislocation of the radial head relative to capitellum) must be recognized, because both dislocation and fracture must be reduced.
2 Principles topenlarge
Lag screw principles
In oblique fractures of the radial neck, fixation is achieved by lag screws. Longer oblique fractures allow two screws. This is more secure, and should be preplanned.
The thread pulls the opposite bone fragment towards the head of the screw, placing the fracture ends under compression. The portion of the thread in the gliding hole does not purchase in the surrounding bone. Insert the lag screw(s) as perpendicularly to the fracture plane as possible.
Lag screw fixation may prove unsatisfactory for short oblique fractures of the radial neck. If so, plate fixation may be required.
Choice of implant
Mini fragment 1.5 mm, 2.0 mm, or 2.7 mm screws are used.
3 Reduction and provisional fixation topenlarge
Expose the fracture ends with minimal soft tissue dissection off the bone. Remove hematoma and irrigate.
Reduction is direct, aided by supination-pronation of the forearm. Reduce and provisionally fix the fracture with the help of small pointed reduction forceps.
Difficulty with reduction may be due to the ulna’s being malreduced, or because the radial head is dislocated from the capitellum, perhaps with interposed annular ligament.
4 Lag screw insertion topenlarge
Drill a gliding hole (sized according to chosen screw size, see fig.) for the lag screw into the proximal fragment.
Insert the appropriate drill sleeve into the gliding hole until it reaches the far cortical bone.
Now drill the far cortex with the appropriate drill bit.
Measure the depth of the hole with the hook of the depth gauge pointing distally. Tap the far cortex with the appropriate cortical tap, using the protection sleeve.
Always tap after measuring in order not to destroy the thread.
Lag screw insertion
Closely observe the compression effect on the fracture line while tightening the lag screw.
The reduction forceps should be removed just before the final tightening of the screw.
Second lag screw
If the fracture configuration allows the insertion of a second lag screw, it can be inserted now, using the same technique as described above.
5 Final assessment top
Finally, assess the range of motion in pronation, supination, flexion and extension. Fixation should be stable and crepitus or restricted motion should be absent. Radiocapitellar and ulnohumeral joints should remain located through a full range of motion.
Check fracture and screws with image intensifier or x-ray.