The Effect of Flexible Suture Button Fixation on the Reduction of the Syndesmosis: A Cadaver Study.

BACKGROUND: To evaluate the reduction ability of a suture button device on the syndesmosis and determine whether quadricortical or tricortical placement of the cortical button affects syndesmotic reduction; prior studies have not quantified the degree of improvement or determined whether button position or drill hole aperture accounts for the reduction benefit.

METHODS: Seven cadaveric lower extremity specimens were used. Syndesmotic ligaments were sectioned. To evaluate the reduction ability, the fibula was intentionally malreduced either anterior or posterior. A 3.5-mm screw was placed followed by a TightRope (Arthrex Inc) placed quadricortical and tricortical, all placed through the same drill path and trajectory. Axial CT scans using a 3D fluoroscopic spin (Siemens Cios Spin; Simens Healthineers) were obtained after each implant: screw (S), quadricortical (Q) TightRope, and tricortical (T) TightRope. Translation and rotation were calculated. Reduction improvement from S was calculated for Q and T and analyzed using 1-sample t tests. A paired t test was used to compare the average improvement between Q and T.

RESULTS: The average intentional malreduction in S was 5.10 ± 2.8 mm. The average rotational difference from baseline was 12.7° ± 4.0°, with 5 of 7 having internal rotation. In comparison, the reduction improved by 2.50 ± 1.6 mm (P = .005) in Q and 3.2 ± 1.5 mm in T (P = .001). With the numbers available, no significant difference could be detected between Q and T (P = .27). In both Q and T, 3 specimens returned to within 1 mm of baseline reduction. Q improved an average of 8.9° ± 6.1° (P = .008) and within 3.9° ± 5.2° of baseline fibular rotation. T improved by an average of 11.6° ± 4.5° (P = .0004) and within 1.3° ± 1.1° of baseline fibular rotation. With the numbers available, no significant difference in rotational improvement between Q and T could be detected (P = .227).

CONCLUSION: Placement of a suture button device appears to aid in syndesmotic reduction at the time of fixation toward anatomic, with an average improvement of approximately 3 mm of translation and approximately 10° of rotation. Quadricortical and tricortical placement does not seem to play a major role in the improvement of reduction; the degree of correction appears related to the 3.7-mm drill aperture permitting suture movement rather than button position.

CLINICAL RELEVANCE: Surgeons can expect a flexible suture button device to improve a suboptimal provisional syndesmotic reduction at the time of fixation by approximately 3 mm of translation and 10° of rotation. This improvement does not appear to depend on whether the construct is quadricortical or tricortical, suggesting that button position need not drive device selection for this purpose. As new flexible fixation devices enter the market, surgeons should be aware that the degree of initial corrective movement is related to the cortical drill aperture size rather than button position.