Varying Distance Between Suture-Endobuttons Does Not Improve Stability of the Transected Syndesmosis in a Motion Tracking Cadaveric Model

Category: Ankle; Sports Introduction/Purpose: A growing body of evidence favors the use of dynamic fixation techniques such as suture endo button over rigid screw fixation for syndesmotic injuries. However, specific dynamic fixation techniques have been poorly evaluated. The purpose of this study was to compare single suture-endobutton fixation (single) to double fixation with suture-endobuttons placed one centimeter (cm) apart (double 1 cm) and double fixation with suture-endobuttons placed three cm apart (double 3 cm). Methods: Twenty-four lower leg specimens from twelve cadavers were tested using a custom biaxial apparatus. Internal rotation, external rotation, and anterior and posterior translation of the tibia and fibula were examined using motion tracking systems after transection of deltoid and syndesmotic ligaments to compare three syndesmotic repair techniques: 1) a single suture-endobutton placed 1 cm above the joint line, 2) two suture suture-endobuttons placed 2 and 3 cm above the joint line, and 3) two suture- endobuttons placed 1 and 4 cm above the joint line. Results: All three endobutton constructs improved the stability of the syndesmosis by reducing aberrant motion after transection. There was no clear superiority of either single suture-endobutton (SEB), double suture-endobuttons placed 2 and 3 cm above the joint line (DSEB 1), or double suture-endobuttons placed 1 and 4 cm above the joint line (DSEB 3). DSEB 3 and DSEB 1 showed equal median laxity for tibia internal rotation (2.7 degrees, DSEB 1 (2.0 – 3.2) degrees, DSEB 3 (2.3 – 2.8) degrees), tibia external rotation (-0.2 degrees, DSEB 1 (-0.4 - 0.4) degrees, DSEB 3 (-0.4 - 0.3) degrees), and fibula external rotation (-0.3 degrees, DSEB 1 (-0.7 - 0.3) degrees, DSEB 3 (-0.7 - 0.7) degrees). Conclusion: Cadaveric biomechanical studies are critical to evaluate various suture-endobutton constructs prior to widespread use in patients. Our results demonstrate that the added cost of a second suture-endobutton may not confer substantial additional stability to the syndesmosis. Likewise, increased spread between suture-endobuttons appears to have minimal impact of syndesmotic stability