SLR - January 2015 - Steven R. Smith

The Effect of Suture-Button Fixation on Simulated Syndesmotic Malreduction: A Cadaveric Study

Reference: Westermann RW, Rungprai C, Goetz JE, Femino J, Amendola A, Phisitkul P. The Effect of Suture-Button Fixation on Simulated Syndesmotic Malreduction: A Cadaveric Study. J Bone Joint Surg Am. 2014 Oct 15;96(20):1732-8.

Scientific Literature Review

Reviewed By: Steven R. Smith, DPM
Residency Program: HealthPartners, INC at Regions Hospital, St. Paul, Minnesota

Podiatric Relevance: The purpose of this paper was to discuss the current treatment for disruption of the distal tibio-fibular syndesmosis. The paper discussed that injuries to the ankle syndesmosis are fairly common. The incident of syndesmotic disruption with an ankle sprain is 5-18 percent and with 11-20 percent of these injuries being treated operatively. When treated operatively, malreduction with screw fixation is 22-52 percent. Malreduction of the syndesmosis is one of the main concerns when performing this procedure and can lead to poor outcomes including post-traumatic arthritis. This article was aimed at determining whether malreduction with syndesmotic fixation is better tolerated with screw fixation versus suture button technique. They hypothesized that with similar degrees of malreduction in cadaveric specimens, there will be decreased amounts of malreduction in the suture button fixation when compared to the screw fixation groups after repeated testing through ROM.

Methods: Initially, a pilot study was performed to identify the number of specimens needed to achieve a significant power of 0.8 and alpha of 0.05. CT images were obtained of the 12 fresh frozen cadaveric specimens to determine the control position of the syndesmosis. Disruption of the distal tibio-fibular syndesmosis was performed by sectioning of the ligaments including sectioning of the deltoid ligament. There was both an anterior and posterior malreduction group measured on CT images. Each cadaver had both the 4.5 mm screw fixation as well as suture button fixation with variation in which fixation method was performed first. The same drill holes were used for both the 4.5 mm screw and suture button technique. The 4.5 mm screw and suture button were placed were placed 20 mm proximal to the tibio-talar joint and 30° from posterior to anterior in the coronal plane with four cortices purchased. The ankles then went through a 40° arc range of motion for 15 cycles after each fixation. A CT image was obtained to evaluate the syndesmotic fixation using the standardized Phisitikul technique. A technique previously described to measure the syndesmotic malreduction based on the anterior-posterior and medial-lateral displacement on CT. The blinded observers performed of the measurements.

Results: They found less post fixation malreduction with the use of the suture button fixation. With anterior pattern malreduction, the suture button technique allowed 62 percent greater correction with a p-value of 0.02. They found 93 percent greater improvement in alignment in the suture button fixation group compared to the screw fixation, with a p-value of <0.0001. There was not a significant difference in the coronal plane with a p-value set at 0.05. The order of fixation was varied to assess for bias, and there was no significant difference based on the order of fixation.

Conclusions: The goal of the study was to determine that malreduction via off-axis clamping of the syndesmosis is better tolerated with suture-button fixation. It was internally controlled with using the cadaver specimens’ preoperative CT images. Selection bias was controlled by altering the order of fixation and comparing it to find no significant difference. It was a cadaveric study and therefore unknown whether this degree of malreduction difference is of clinical importance, further clinical studies will need to evaluate this issue. Commentary on the article stated, “Biggest problem with syndesmotic fixation is not in the a-p direction but in the coronal plane” by Dr. Thomas DeCoster, MD. No significant difference was found in the medial-lateral measurements in the coronal plane. No measurement of fibular overlap, medial clear space, tibia-fibular clear space, intra-operative hook test or stress imaging was mentioned in this article, which are the standard to which foot and ankle surgeons determine the syndesmosis alignment. As the commentary within the journal touched on, it’s unknown whether loose fixation to allow reduction of malreduced syndesmosis is clinically better than the standard screw fixation, and allowing the ligaments to heal or form fibrosis prior to screw breakage or removal.  

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