1 Principles topenlarge
If nailing and MIPO are contraindicated, ORIF should be performed. If the fracture configuration does not allow axial compression, a lag screw should be used to achieve interfragmentary compression.
Depending on plate position and fracture configuration, the lag screw will be introduced either through a plate hole or outside the plate. If possible, insert the lag screw outside the planned plate. If not, the lag screw is introduced through one of the plate holes after application of the plate with one screw in each main fragment. This technique requires a fracture configuration and plate placement that permit insertion of screws perpendicular to the fracture plane.
The remaining shearing and rotational forces have to be eliminated by a so called protection plate.
Plate selection and preparation
The chosen plate (usually a narrow, 4.5 mm DCP) should allow
1. A hole near the middle of the fracture, for the first lag screw to be inserted as perpendicularly as possible to the fracture plane.
2. Sufficient length for at least 3 screws proximal and distal to the fracture zone.
Usually a 10-12 hole straight 4.5 mm DCP is used. The plate has to be twisted and bent to fit perfectly on the surface of the tibia where it will lie.
The bend of the plate is usually a 20 cm radius, and the twist is approximately 20 degrees.
2 Direct reduction topenlarge
Reduce and preliminarily hold the fracture and the plate with two reduction clamps. This can be difficult, because of the need to maintain both fracture reduction and plate position. Be careful to protect soft-tissue attachments which provide bone vascularity.
1. Reduce fracture and fix temporarily with small screws, or predrilled K-wires - to be removed before lag screws are tightened.
2. Plan plate position carefully. Fix one side of fracture definitively, then reduce the opposite side before its definitive fixation.
3 Drilling and tapping topenlarge
Drilling the gliding hole for the first lag screw
Using a 4.5 mm drill guide and a 4.5 mm drill bit, drill a gliding hole in the near cortex, with the plate properly positioned.
Ensure that the direction of the drill is as perpendicular to the fracture plane as possible.
Drilling the thread hole for the first screw
Insert the 4.5 mm / 3.2 mm drill through the gliding hole. Use a 3.2 mm drill bit to drill a thread hole just through the far cortex.
Measure for screw length
Use a depth gauge through the plate to measure for screw length.
Measure the longer side of an oblique drill hole, as shown, to ensure sufficient screw length.
A screw should protrude 1-2 mm through the opposite cortex to ensure thread purchase. However, too long a screw may be tender, or injure soft tissues.
Tap the thread hole
Use a 4.5 mm cortical tap with the corresponding drill sleeve to tap the thread hole.
4 Lag screw insertion topenlarge
Insertion of first lag screw
Carefully insert the first lag screw and tighten it.
Insertion of the second lag screw
Repeat the process described above for the second lag screw. Drill the
gliding and thread holes, measure and tap the thread hole.
Insert the second lag screw and tighten it.
After each screw is inserted and tightened, confirm satisfactory reduction and compression.
5 Plate fixation topenlarge
Insertion of diaphyseal fixation screws
The screws closest to the fracture zone are inserted first. Alternately insert the following screws, working your way outwards.
In the diaphysis, use cortical screws, observing the following steps:
- Drill both cortices using the appropriate drill guide to ensure a central drill hole with the 3.2 mm drill bit.
- Measure for screw length.
- Tap both cortices using the 4.5 mm tap and appropriate drill sleeve.
- Insert the screw.
Insertion of metaphyseal plate screws
If the plate extends over the metaphysis, use 6.5 mm cancellous screws, observing the following steps:
- Drill using the appropriate drill guide to ensure a central drill hole with the 3.2 mm drill bit. Do not penetrate the joint.
- Measure for screw length.
- Tap just the near cortex using the 6.5 mm tap and appropriate sleeve.
- Insert cancellous screws and carefully tighten them, checking fracture and plate.
Metaphyseal screws should be as long as possible. They must avoid the ankle joint. Slight penetration of the thin metaphyseal cortex is permissible, with pre-drilling.