A systematic review of studies on the diagnostics and classification system used in surgically treated, acute, isolated, unstable syndesmotic injury: a plea for uniform definition of syndesmotic injuries.

Objective: To this day, diagnostic standards and uniform definition for acute, isolated syndesmotic injuries are missing. The aim of the current study was to conduct a systematic review of the classification systems and diagnostics currently applied and to propose a best evidence diagnostic approach. Methods: Medline (PubMed), Scopus, Cochrane Central Register of Controlled Trials, and Embase were searched from inception to June 5, 2022, for studies reporting the outcome of surgically treated acute, isolated syndesmotic injuries. First, all classifications used in the eligible studies were identified and illustrated according to the individual syndesmotic structures injured. Second, the indication for surgery and stabilization, based on the diagnostics applied and the time point assessed (pre- or intra-operatively), was analyzed, including the applied cutoff criteria. Results: Ten out of 4190 studies, comprising 317 acute ligamentous syndesmotic injuries, met the inclusion criteria. Seven studies facilitated one of the three different classification systems (Calder, West Point, or Sikka classification). Eight studies based their indication for surgery on a combination of clinical and radiographic examinations and two on radiographs only. The most applied clinical tests were the external rotation stress test and squeeze test. The most common radiologic diagnostics were plain radiographs and MRI. Intraoperatively, instability was verified most commonly using arthroscopy. Conclusion: Current classifications and diagnostics for syndesmotic injuries are heterogeneous, often cannot be attributed to the ligaments injured. An evidence-based diagnostic algorithm based on noninvasive diagnostics and an anatomy-based classification for acute syndesmotic instability is presented.