Ideal angle of upper and lower syndesmotic fixation based on weightbearing computed tomographic imaging in uninjured ankles
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Syndesmotic fixation remains a controversial topic, however most authors recommend fixation of the disrupted syndesmotic complex in unstable ankle fractures. There is no clear reference for the angle of syndesmotic fixation, historically 30° has been cited but recently refuted, with new and current literature. It is common practice to place 2 points of transyndesmotic fixation one with fixation placed at around 2 cm above the ankle joint and the second point approximately 3.5 cm above the plafond. Our hypothesis is that the ideal angle of transyndesmotic fixation is less than 30° and that the ideal angle changes when you move proximal from the 2-cm level to 3.5-cm level. This is based on cross-sectional anatomy as seen on weightbearing computerized tomography imaging. It is imperative to achieve adequate reduction of the syndesmosis to prevent instability and a malaligned ankle joint, as this can result in refractory pain and early onset of degenerative changes. We reviewed 50 weightbearing computerized tomography scans of the foot and ankle to identify what we call the adjusted syndesmotic fixation angle. Our review found adjusted syndesmotic fixation angle to be 19.7° with ranges of (8°-31°) at 2 cm and 24.8° with ranges of (14°-38°) at 3.5 cm above the tibial plafond. These values were statistically significant when compared to historically cited 30°. Our research concludes that the historically cited 30° angle is frequently not the ideal angle for syndesmotic fixation and actually is less.
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