The mechanism of this fracture is a combination of compression and shearing forces. The patient usually presents with angular deviation and malrotation.
Use of lag screw
Be sure to insert the screw as a lag screw, with a gliding hole in the near (cis) cortex, and a threaded hole in the far (trans) cortex. Inserting a screw, across a fracture plane, that is threaded in both cortices (position screw) will hold the fragments apart and apply no interfragmentary compression.
Often, the fracture can be reduced by applying traction via finger traps.
For more accurate reduction, a small pointed reduction forceps is used gently to manipulate the fracture. Application of excessive force can result in fragmentation. Check reduction using image intensification. Note Anatomical reduction is important to prevent chronic instability, or posttraumatic degenerative joint disease.
Preliminary fixation by K-wire
Preliminarily fix the fragments by inserting a K-wire. Be careful to place it in such a way that it will not conflict with later screw placement.
Do not insert screws too close to the fracture apex or the subchondral bone. A minimal distance from the fracture line, equal to the screw head diameter, must be observed. Screw length needs to be adequate for the screw to penetrate and purchase in the opposite (trans) cortex.
Drilling and alternative preliminary fixation
Leaving the reduction forceps in place, drill a gliding hole as perpendicular to the fracture plane as possible, using a 1.5 (or 1.3) mm drill bit for a 1.5 (1.3) mm screw. Insert a 1.5 (1.3) mm drill sleeve into the gliding hole. Use a 1.3 (or 1.0) mm drill bit to drill a threaded hole in the opposite fragment, just through the far (trans) cortex.
Leave the drill bit in the drill hole preliminarily to hold the reduction, if no K-wire has already been used for this purpose.
Drill for distal screw
Drill a gliding hole for a second lag screw close to the distal apex of the fracture line. This screw, too, should be placed as perpendicularly to the fracture plane as possible, using a 1.3 (or 1.0) mm drill bit for a 1.3 (1.0) mm screw. Insert a 1.3 (1.0) mm drill sleeve into the gliding hole. Use a 1.0 (0.8) mm drill bit to drill a threaded hole in the opposite fragment, just through the far (trans) cortex.
Insert proximal screw
Leaving the second drill bit in situ, insert the proximal lag screw. Do not completely tighten it at this time. The screw should just penetrate the opposite (trans) cortex.
Insert distal lag screw
Now insert the distal lag screw. This screw, too, should just penetrate the opposite cortex. Alternate tightening of the two lag screws helps to avoid tilting of the fragment, and applies even compression forces across the whole fracture surface.
Check using image intensification. Reduction must be anatomical.
Immobilize the hand in a safe position for at least 3 weeks. This may not be necessary in the case of large fragments when the lag screw fixation is judged at operation to be absolutely stable. In that case, buddy strapping is applied immediately postoperatively.
See patient 5 days after surgery to check the wound, clean and change the dressing. After 10 days, remove the sutures. Check x-rays.
Remove the splint at 3 weeks, and apply buddy strapping.