1 Principles topenlarge
With good bone quality, large infrasyndesmotic fragments of the lateral malleolus with a transverse fracture line can be fixed with a well-contoured plate under slight compression, functioning as a tension band.
Tension band principles
The tension band converts tensile forces into compression forces. The following criteria must be fulfilled for a plate to act as a tension band:
- The fractured bone must be eccentrically loaded
- The plate must be placed on the tension side
- The plate must be able to withstand the tensile forces
- The bone must be able to withstand the compressive force which results from the conversion of distraction forces by the plate.
There must be a bony buttress opposite to the plate to prevent cyclic bending. The opposite cortex needs to have contact.
2 Reduction topenlarge
Do not strip the periosteum other than minimally, on either side of the fracture site, in order to control anatomical reduction of the fragments.
Reduce and temporarily hold the fracture with small pointed reduction forceps.
3 Plate preparation topenlarge
Choosing length and contouring the plate
Choose the length of a one-third tubular plate as determined by preoperative planning. At least two screws must find a secure hold in each of the distal and the proximal fragments. Usually a five- or six-hole plate is used.
Before the plate is applied, it must be contoured.
Contouring is best done with the help of an appropriate aluminum template. The plate should fit the contour of the bone surface perfectly throughout its entire length.
Place the contoured plate firmly onto the bone, and determine the position of the first proximal screw near the fracture site.
Remove the plate.
4 Pearl topenlarge
A one-third tubular plate molded as a hook plate can be used to fix a small lateral fragment (where there is space for only one screw), or a severely osteoporotic bone.
The sequence of the application of the hook plate differs from the procedure described above.
First, place the tip of the hook through the ligament into the tip of the lateral malleolus.
Use an impactor for anchoring the hook tip in the bone.
Insert a screw into the hole immediately above the hook to secure the plate onto the distal fragment.
Insert a proximal cortical screw in an eccentric position to obtain compression.
Complete the fixation by inserting the other screws in the planned sequence.