Ethics approval was acquired from the Anti-Doping Lab Qatar Review Board (IRB No. F2016000153). Written informed consent was obtained from all athletes at time of inclusion. Between September 2016 and July 2019, athletes with acute ankle injuries were recruited for this prospective cohort study. All athletes presenting to the outpatient department of Aspetar Orthopaedic and Sports Medicine Hospital within 7 days after an acute ankle injury were assessed for eligibility. Inclusion criteria were: acute ankle injuries in adult athletes (≥ 18 yrs), participating in sports at a professional or recreational level. Ankle injuries were excluded if imaging demonstrated a frank fracture or if the 3 T MRI study could not be acquired within 10 days post-injury.
A daily clinic for athletes with acute sports injuries is organized by Aspetar Orthopaedic and Sports Medicine Hospital. Patients can be seen by an Orthopaedic Surgeon or Sports Medicine Physician without the requirement of a referral. This results in a high volume of patients of which the majority presents within 24 h post-injury. The main language spoken by the medical staff at our institution is English; therefore, during consultation a nurse is present to provide Arabic translation.
Injury history and physical examination
An Orthopaedic Surgeon or Sports Medicine Physician recorded injury history and performed physical examination. Findings were recorded on a standardized reporting form. Injury history included: (1) Injury [new/recurrent] (2) Occasion [game/training/non-sports injury], (3) Contact [contact/non-contact], (4) Mechanism of injury [inversion/eversion/external-rotation/internal-rotation], (5) Perceived presence of swelling [yes/no], (6) Perceived ankle instability [yes/no], (7) Sensation of pain radiating up the leg [yes/no]. Physical examination included; (1) Presence of hematoma [yes/no] (2) Tenderness to palpation [lateral/medial/anterior/posterior] (3) Tenderness length over the syndesmosis [in cm], (4) Ability to walk normally [yes/no], (5) Ability to walk on toes [yes/no], Ability to walk on heels [yes/no], (6) Passive range of motion in dorsal flexion, plantar flexion, inversion and eversion [full/restricted/painful], (7) Presence of swelling [yes/no], (8) Swelling site [laterally/medially/anterior/posterior/syndesmosis].
The physicians performing the syndesmosis tests were provided with a short description of the clinical tests. No calibration session was organized prior to initiation of this study, to reflect a true clinical setting. The standardized clinical examination included a total of six syndesmosis tests: palpation of the AITFL ; squeeze test [10, 23], weight-bearing dorsiflexion external rotation (WB DF ER) test, non-weight-bearing dorsiflexion external rotation (NWB DF ER) test [16, 23], fibular translation test  and the Cotton test  (Supplementary appendix). Tests were considered positive if they provoked pain over the distal tibiofibular joint or if the examiner noticed instability of the ankle syndesmosis (Cotton test) [3, 10, 16, 17]. If the patient was unable to weight-bear (WB DF ER) or if a clinical test was too painful to be completed fully (Squeeze test, NWB DF ER test, Fibular translation test) they were considered positive (Cotton test excluded).
Overall clinical suspicion of syndesmosis injury
Clinical suspicion was based on the physicians’ overall interpretation of injury history, physical examination, and syndesmosis tests. Clinical suspicion was recorded using the modified West Point grading system: partial rupture of the Anterior Inferior Tibiofibular Ligament (AITFL) with a stable syndesmosis (Grade I); complete rupture of the AITFL and injury to the Interosseous Ligament (IOL) with a stable syndesmosis (Grade IIa); complete rupture of the AITFL, IOL and the Posterior Inferior Tibiofibular Ligament (PITFL) or Deltoid ligaments with dynamic instability of the syndesmosis (Grade IIb) and complete disruption of the syndesmosis with frank diastasis (Grade III). Overall clinical suspicion for syndesmosis injury was considered positive when the modified West Point grading system was scored grade I or higher.
In this study, MRI was used as reference standard. With a sensitivity of 100% and specificity of 93% for injury of the AITFL, MRI has demonstrated to be a valuable alternative to arthroscopy . Patients underwent MRI scans using a wide-bore 3.0-T MRI system (GE Discovery, GE Healthcare, Chicago, Illinois, United States) with an 8-channel receive only Foot & Ankle array (Invivo, Philips Healthcare, Best, The Netherlands). In the sagittal plane T1-weighted and Proton-Density Fat-Saturated [PD-FS] sequences were obtained, axial T2-weighted and PD-FS sequences were acquired and in the coronal plane PD-FS sequences were obtained .
Grading of syndesmosis ligaments
The obtained MR scans were graded by two musculoskeletal radiologists (J.A. & M.A.) with 11 and 3 years of experience in MSK-imaging, respectively.
Acute injuries of the AITFL, IOL and PITFL were graded according the four grade Schneck grading system: normal (Grade 0); low-grade sprain (Grade 1: peri-ligamentous high signal/edema on proton density-weighted sequences and no discontinuity of fibers); partial discontinuity (Grade 2: partial discontinuity but preserved remnant fibers) and complete discontinuity (Grade 3).
Due to limited interrater and intrarater reliability for grading of the individual syndesmosis ligaments according the Schneck grading system (K 0.37–0.89), diagnostic disagreements between the radiologists were resolved in a consensus meeting .
Evaluation of MRI-findings
In this study, we evaluated the diagnostic value of injury history, physical examination, syndesmosis tests and clinical suspicion for partial or complete discontinuity of the AITFL and/or IOL and/or PITFL. The individual syndesmosis ligament (AITFL/IOL/PITFL) with the highest grade of injury was used as reference standard. For this analysis, grading was dichotomized as: (1) No discontinuity (normal ligament or peri-ligamentous edema) (2) Discontinuity (partial or complete discontinuity).
The diagnostic value of injury history, clinical findings, syndesmosis tests and clinical suspicion were evaluated using the MRI findings. The results of injury history and physical examination were dichotomized if needed; Occasion was dichotomized to (1) game (2) other; Each mechanism of injury was dichotomized to i.e. (1) inversion (2) other mechanism of injury. Tenderness to palpation and presence of swelling were dichotomized per location to i.e. (1) tenderness to palpation laterally (2) no palpation to tenderness laterally and range of motion was dichotomized per direction to i.e. (1) dorsal flexion painful (2) dorsal flexion not painful.
For each variable, a contingency table was created. From the 2 × 2 tables prevalence of positive test results, sensitivity, specificity, positive and negative likelihood ratio’s (LR+ and LR-), positive predictive value (PPV) and negative predictive value (NPV) were calculated, including confidence intervals (CI 95%). For tenderness length an optimal cut-off (Youden’s index = maximal value) was calculated using a ROC curve. For each variable the area under the curve (AUC) was calculated.
To test if a combination of variables could predict the presence of syndesmosis injury, we performed a logistic regression analysis. First, we analyzed the association between each variable and the presence of syndesmosis injury in a univariate logistic regression analysis. Variables with a p value < 0.15 were included in a multivariate logistic regression model. Regression analysis was performed using the forward method. Odds ratios for each variable were presented with their corresponding confidence intervals (CI 95%) and statistical significance was set at p value < 0.05. Statistical analysis was performed using SPSS software (V.21; IBM Corp). No a priori power analysis was performed for the outcome of this study.