The Relationship Between the Distal Tibial Fibular Syndesmosis and the Varus Deformity in Patients With Varus Ankle Osteoarthritis

Abstract

Background: The impact of varus ankle osteoarthritis (OA) on the distal tibial fibular syndesmosis is poorly described. This study aimed to investigate the possible relationship between the condition of the distal tibial fibular syndesmosis and the degree of the varus deformity using weightbearing simulated computed tomography (CT), in patients with varus ankle OA. Methods: This retrospective comparative study included 155 varus ankles, divided into 4 Takakura-Tanaka groups (stage 2, 3a, 3b, and 4). A control group comprised 35 ankles without prior ankle disorders. The angles between the tibial shaft and the articular surface of the tibial plafond on the anteroposterior view (TAS), and articular surfaces of the tibial plafond and talar dome (TTW) were measured from weightbearing ankle radiographs. The varus angle of the ankle (VA) was defined as 90 – TAS + TTW. On the CT axial view, 1 cm proximal to the tibial plafond, the area of the syndesmosis (“CT-area”) and the distance between the fibula and the tibia (CT-FCS) were measured. Results: The CT area in stages 2, 3a, 3b, 4, and control group were 99, 79, 77, 103, and 97 mm2, respectively. The CT-FCS were 3.5, 3.1, 2.9, 4.3, and 3.9 mm, respectively. In all 155 OA ankles, CT area and CT-FCS were negatively correlated with the VA (correlation coefficient r = –0.38, P