The Effect of Varying Tension of a Suture Button Construct in Fixation of the Tibiofibular Syndesmosis - Evaluation Using Stress Computed Tomography.

BACKGROUND/PURPOSE: There have been no studies assessing the optimal biomechanical tension of suture button constructs. The purpose of this study was to assess optimal tensioning of suture button fixation and its ability to maintain reduction under loaded conditions using a stress computed tomography (CT) model.

METHODS: Ten cadaveric lower limbs disarticulated at the knee were used. The limbs were placed in a modified ankle load frame that allowed for the application of sustained torsional axial, or combined torsional/axial loads. The syndesmosis and the deltoid ligament complex were sectioned and the limbs were randomized to receive a suture button construct tightened at 4kg, 8kg, or 12kg. The specimens were loaded under the 3 loading scenarios with CT scans performed after each as well as at the conclusion of testing. Multiple measurements of translation and rotation were compared to baseline CT scan taken prior to sectioning.

RESULTS: Significant lateral (maximum 5.26mm) and posterior translation (maximum 6.42mm) as well as external rotation (maximum 11.71°) was noted with the 4kg repair. Significant translation was also seen with the both the 8kg and 12 kg repairs however the incidence was less than with the 4kg repair.Significant overcompression (ML=1.69mm, B=2.69mm) was noted with the 12kg repair and also with the 8kg repair (B=2.01mm).

CONCLUSION: Suture button constructs must be appropriately tensioned to maintain reduction and re-approximate the degree of physiological motion at the distal tibiofibular joint. These constructs also demonstrate overcompression of the syndesmosis however the clinical effect of this remains to be determined.