Remove one K-wire and drill a hole through the fragment parallel to the other K-wire, using a 2.5 mm drill bit and protection sleeve.
Measure the depth of the hole and tap the near tibial cortex with the 4.0 mm cancellous tap and protection sleeve. Insert a 4.0 mm partially threaded cancellous screw, with a washer if needed.
Replace the second K-wire with the second lag screw.
Confirm satisfactory reduction and screw placement with X-ray control.