Objective: This study aimed to evaluate syndesmotic stability following anatomic reduction and fixation of the posterior malleolus (PM) of ankle fractures with syndesmotic instability, without utilizing a classical syndesmotic screw.

Methods: We have retrospectively evaluated patients with PM fracture and syndesmotic displacement between September 2012 and May 2017. The inclusion criteria were as follows: patients with (1) PM fracture, either isolated or a part of bi-/trimalleolar fracture with syndesmotic instability; (2) fractures fixed through a posterior approach; (3) fractures fixed with either screw or plate-screw combination; and (4) Bartonicek type 2-5 fractures. Among 145 patients, 41 (27 female, 14 male) met the inclusion criteria. The average age was 42.65 years, and the mean follow-up time was 19.41 months. Ankle fractures were classified according to the Weber classification, while PM fractures according to the Bartonicek classification. Perioperative reduction was evaluated by anteroposterior, lateral, and mortise views. Perioperative and postoperative stability was evaluated using Cotton and fibular translation tests. Postoperative syndemotic reduction was evaluated with computed tomography (CT) scan according to Dikos and Futamura.

Results: According to the Weber classification, 22 were type B, 17 type C, and 2 unclassified because they did not get lateral malleolus fracture. According to Bartonicek classification, 17 fractures (41.5%) were type 2, 14 (34.1%) type 3, 9 (22%) type 4, and 1 (2.4%) type 5. All patients had unilateral fractures. On postoperative CT scan evaluation, 38 (92.68%) patients got syndesmotic reduction, and 3 (7.32%) got syndesmotic malreduction.

Conclusion: This study demonstrated that if appropriate surgical principles are followed, and meticulous attention paid for reduction and fixation, fixing only the PM achieves syndesmotic stability for patients with PM fracture and syndesmotic diastasis. The indication for PM fixation should not be based on size alone. Not all, but PM fractures with syndesmotic displacement should be operated.