• Jeremy M LaMothe, Josh R Baxter, Sydney C Karnovsky, Conor I Murphy, Susannah Gilbert, and Mark C Drakos.
• 1 Hospital for Special Surgery, New York, NY, USA.
• Foot Ankle Int. 2018 Apr 1; 39 (4): 479-484.

BackgroundExternal rotation, lateral, and sagittal stress tests are commonly used to diagnose syndesmotic injuries, but their efficacy remains unclear. The purpose of this study was to characterize applied stresses with fibular motion throughout the syndesmotic injury spectrum. We hypothesized that sagittal fibular motion would have greater fidelity in detecting changes in syndesmotic status compared to mortise imaging.MethodsSyndesmotic instability was characterized using motion analysis during external rotation, lateral, and sagittal stress tests on cadaveric specimens (n = 9). A progressive syndesmotic injury was created by sectioning the tibiofibular and deltoid ligaments. Applied loads and fibular motion were synchronously measured using a force transducer and motion capture, respectively, while mortise and lateral radiographs were acquired to quantify clinical measurements. Fibular motion in response to these 3 stress tests was compared between the intact, complete lateral syndesmotic injury and lateral injury plus a completely sectioned deltoid condition.ResultsStress tests performed under lateral imaging detected syndesmotic injuries with greater sensitivity than the clinical-standard mortise view. Lateral imaging was twice as sensitive to applied loads as mortise view imaging. Specifically, half as much linear force generated 2 mm of detectable syndesmotic motion. In addition, fibular motion increased linearly in response to sagittal stresses (Pearson's r [ρ] = 0.91 ± 0.1) but not lateral stresses (ρ = 0.29 ± 0.66).ConclusionStress tests using lateral imaging detected syndesmotic injuries with greater sensitivity than a typical mortise view. In addition to greater diagnostic sensitivity, reduced loads were required to detect injuries.Clinical RelevanceSyndesmotic injuries may be better diagnosed using stress tests that are assessed using lateral imaging than standard mortise view imaging.

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