Suture-Button Versus Screw Fixation of the Syndesmosis: A Biomechanical Analysis

Abstract

Background: The treatment of ankle fractures with syndesmotic injuries associated with disruption of the deltoid ligament complex is controversial. The purpose of this study was to compare both the biomechanical and physiologic properties of suture-button fixation to the intact syndesmosis and screw fixation. Materials and Methods: Eight fresh frozen human cadaveric ankles were used in three different groups. One group had an intact syndesmosis and deltoid ligamentous complex and two groups had fixation of the syndesmosis after its disruption along with disruption of the deltoid ligaments. One fixation group used a suture-button and the other used a 3.5-mm tricortical syndesmotic screw. The syndesmotic gap after cycling at submaximal loads, laxity due to cycling, and fibular movement allowed in the sagittal plane were all measured and analyzed for statistical significance. Results: The syndesmotic gap after cycling was not significantly different between the intact group (9.1 mm) and the suture-button group (8.8 mm) ( p = 0.1509). The screw fixation group had a significantly smaller gap (7.9 mm) as compared to the other two groups (screw versus intact, p = 0.00004; screw versus suture-button, p = 0.0004). The intact group did not demonstrate a significant difference in laxity before (9.0 mm) and after (9.1 mm) cycling ( p = 0.0670), whereas the suture-button group did have a significant difference (before, 8.01 mm; after, 8.28 mm) ( p = 0.000251). The movement of the fibula in the sagittal plane was significantly greater in the suture-button group (3.17 mm) as compared to the intact group (2.77 mm) ( p = 0.00554). Screw fixation allowed significantly less fibular movement in the sagittal plane (1.16 mm) as compared to the intact ( p = 0.00014) and suturebutton ( p = 0.0000012) groups. Conclusion: Suture-button fixation maintained reduction after cycling with submaximal loads that compared favorably to the intact syndesmosis. It also allowed more physiologic movement of the fibula in the sagittal plane when compared to tricortical screw fixation. Clinical Relevance: Syndesmotic injury fixation has traditionally used screws to provide a rigid construct in which healing can take place. We believe a less rigid fixation method, such as suture-button fixation, provides a more physiologic type of healing of the syndesmosis.