The distance between the anterior and posterior edges of the fibula at a lateral internal rotation of 15° is associated with postoperative malreduction in patients with an ankle joint fracture combined with a lower tibiofibular syndesmosis injury.

Background: Malreduction remains a problem in patients with an ankle joint fracture combined with a lower tibiofibular syndesmosis injury. Current methods of malreduction evaluation have many limitations, and novel techniques are required.
Objectives: The aim of the study was to investigate the association between the distance between the anterior and posterior edges of the fibula at a 15° lateral internal rotation and postoperative malreduction in patients with an ankle joint fracture combined with a lower tibiofibular syndesmosis injury.
Material and Methods: This prospective observational cohort study enrolled 187 patients diagnosed with an ankle joint fracture combined with a lower tibiofibular syndesmosis injury between January 2020 and January 2022. The patients were divided into 2 groups according to their postoperative malreduction condition: the malreduction group and the non-malreduction group. After tibiofibular syndesmosis reduction, a computed tomography (CT) scan was used to measure the distance between the anterior and posterior edges of the fibula at a standard lateral position and a position with a lateral internal rotation of 15°. Demographic data and basic clinical characteristics were recorded for all patients.
Results: The mean distance between the anterior and posterior edges of the fibula was longer in malreduction patients than non-malreduction patients at the standard lateral and 15° lateral internal rotation positions. At a lateral internal rotation of 15°, the distance between the anterior and posterior edges correlated negatively with the postoperative Mazur and American Orthopaedic Foot and Ankle Society (AOFAS) scores, and correlated positively with the length of hospitalization and fracture healing time. Receiver operating characteristic (ROC) curves revealed the potential postoperative malreduction diagnostic value of fibular anterior-posterior edge distance using an internal rotation of 15°. Postoperative AOFAS score, length of hospitalization, fracture healing time, and the distance between the anterior and posterior edges of the fibula at a lateral internal rotation of 15° were independent risk factors of malreduction.
Conclusions: The fibular anterior-posterior edge distance at an internal rotation of 15° is associated with postoperative ankle joint function and the occurrence of malreduction.