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Year |
2001 |
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Question Number |
56 |
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Category |
Select |
Question
Which of the following is considered the most rigid fixation technique for the fracture shown in Figures 11a and 11b?
1- Tension band
2- Syndesmosis screw
3- Lag screw
4- Lateral plate
5- Posterior plate
Figures
Answer (click for answer)
Preferred Response : 5
The two most widely used ankle fracture classification guides are Weber-AO and the Lauge-Hansen guides. For simplicity sake we’ll stick to Weber. Weber A fractures are lat. Malleolar tip avulsions or transverse fractures below the joint. They are treated non-surgically. Weber B fractures occur at the level of the joint and their treatment is controversial. Studies cited in Trauma 2 OKU report that 3mm displacement of the lateral malleolus creates no changes in the loading characteristics of the ankle. The studies also show that ORIF had similar results as nonsurgical treatment of lat.malleolar fractures with 3mm of displacement. The indication for surgical management of lat. Malleoelar fractures is the presence of >1mm talar displacement in any x-ray view. The study quoted in the OKU showed 42% reduction in tibio-talar contact area with only a 1mm lateral shift. The Deltoid ligament acts as the primary restraint to anteriolateral displacement of the talus. Any talar displacement infers an injury to the deltoid ligament(when there is no medial malleolar fracture). Even with a bimalleolar fracture, studies have shown that the deltoid ligament was incompetent in 27% after ORIF. The take home message is that, with a lateral malleolar fracture, any talar displacement is an indication for anatomic fixation of the lateral malleolus.
Fixation of the fracture is dictated by fracture configuration. However in a spiral oblique fracture can be fixed with a lag screw and a posterior antiglide plate. The posterior positioning of the plate reduces plate prominence and has been shown to result in greater screw purchase, especially in osteoporotic bone. When the situation allows it, placing the lag screw through the plate greatly reduces the need for screws in the distal fragment.
Reference: Kellam JF, Fischer TH, Tornetta P III, Bosse MJ, Harris MB (eds): Orthopaedic Knowledge Update: Trauma 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 203-225.
Schaffer JJ, Manoli A II: The antiglide plate for distal fibular fixation. A biomechanical comparison with fixation with a lateral plate. J Bone Joint Surg Am 1987; 69:596-604,