The effect of ankle distraction on arthroscopic evaluation of syndesmotic instability: A cadaveric study

Background: To assist with visualization, orthopaedic surgeons often apply ankle distraction during arthroscopic procedures. The study aimed to investigate whether ankle distraction suppresses fibular motion in cadaveric specimens with an unstable syndesmotic injury. Methods: Fourteen fresh-frozen above knee specimens underwent arthroscopic assessment with 1) intact ligaments, 2) after sectioning of the anterior inferior tibiofibular ligament, the interosseous ligament, and the posterior inferior tibiofibular ligament, and 3) after sectioning of the deep and superficial deltoid ligament. In all scenarios, the lateral hook test, anterior-posterior hook test, and posterior-anterior hook test were applied. Each test was performed with and without ankle distraction. Coronal plane anterior and posterior tibiofibular diastasis as well as sagittal plane tibiofibular translation due to the applied load were arthroscopically measured. Findings: Tibiofibular diastasis in the coronal plane, as measured at both the anterior and posterior third of the incisura, was found to be significantly less when ankle distraction was applied, as compared to arthroscopic evaluation in the absence of distraction. In contrast, measurement of sagittal plane tibiofibular translation was not affected by ankle distraction. Interpretation: Since arthroscopic findings of syndesmotic instability are subtle the differential values of the syndesmotic measurements taken on and off distraction are clinically relevant. To optimally assess syndesmotic instability one should evaluate the syndesmosis without distraction or focus on fibular motion in the sagittal plane when distraction is required.