Syndesmotic injury is common in patients who sustain both ankle sprains and ankle fractures, occurring approximately 18 percent and 20 percent of the time respectively.1 A thorough history and physical examination are prudent for diagnosing these injuries. Missed or improperly treated syndesmotic injuries can result in lateral talar shift, chronic ankle instability and early degenerative changes to the ankle joint due to decreased surface contact.2 The tibiofibular squeeze test and external rotation maneuvers are two clinical maneuvers that can assist with diagnosis of syndesmotic injury.
For further evaluation, clinicians may utilize imaging such as X-ray, computed tomography (CT) or magnetic resonance imaging (MRI). Common parameters to assess on plain film radiographs include the tibiofibular overlap, tibiofibular clear space and medial clear space. Computed tomography can reportedly detect syndesmotic diastasis as small as two to three millimeters that is not as apparent with radiographic examination.3 Alternatively, one may obtain MRI for examination of syndesmotic injuries and researchers have shown that MRI diagnoses anterior inferior tibiofibular ligament injuries with 100 percent sensitivity and 96 percent specificity.4
Once one has determined that syndesmotic injury will require surgical intervention, the surgeon needs to decide the most appropriate method of fixation. Classically, syndesmotic screws have been the gold standard for syndesmotic fixation. There has been a significant amount of research into syndesmotic screws. This includes research looking at the utilization of either tricortical or quadcortical fixation, 3.5 mm or 4.5 mm screws, the number of syndesmotic screws, and the necessity of routine syndesmotic screw removal.
In relation to the number of cortices, there is much debate as to whether the syndesmotic screw should be tricortical or quadcortical. A tricortical screw can allow for greater physiologic motion, which can lead to hardware loosening rather than breaking. A quadcortical screw will theoretically result in an overall more stable construct in comparison to a tricortical screw. However, there has not been significant differences when evaluating pain, ankle dorsiflexion and function between tricortical and quadcortical constructs.5
Surgeons may use 3.5 mm and 4.5 mm screws for fixation of the syndesmosis. Some surgeons feel that a 3.5 mm screw may be more at risk for breakage due to the decreased diameter. On the other hand, concerns with a 4.5 mm screw include risk for discomfort due to increased head size. In a cadaveric study by Thompson and Gesink, they found no statistically significant difference between the biomechanical properties of each size screw.6
It is suggested that in cases requiring a more stable construct, such as Weber type C fracture, comminuted fracture, higher body mass index (BMI) or osteoporotic bone, patients may benefit from a second syndesmotic screw. In a study by Schepers and colleagues, they evaluated different parameters in relation to functional outcome after syndesmotic screw fixation.7 These parameters included the level of placement, number of cortices engaged, diameter of screw, use of second syndesmotic screw and timing of removal. They concluded that increasing BMI is an indication for loss of reduction regardless of the number of screws. Additionally, a second screw did not influence outcomes.
There is also disagreement regarding whether surgeons should routinely remove screw fixation. There are several studies that show high rates of screw removal due to soft tissue irritation, screw discomfort and screw loosening.8 This has led to discussion as to whether patients would benefit from regular removal of the implant prior to the occurrence of adverse effects. However, there has been no consensus regarding the optimal time for such removal. In addition, removal of hardware comes with its own risks and pitfalls such as increased costs, risk of infection, and recurrence of diastasis.
Emphasizing The Role Of Proper Syndesmotic Reduction In Patient Outcomes
Proper reduction of the syndesmosis is an important consideration. Studies show a high rate of malreduction with screw fixation.9,10 Utilizing unilateral CT scans to evaluate screw reduction of the syndesmosis, Gardner and colleagues found a 52 percent malreduction rate.10
In order to avoid malreduction, initial reduction of associated fibular fracture is recommended to help restore proper length to the fibula. Additionally, Phisitkul and coworkers found in a cadaveric study that surgeons can achieve the most consistent and accurate reduction of the syndesmosis by placing the reduction clamp at the lateral malleolar ridge and the anterior-to-posterior center of the tibia, 10 mm from the joint line.11
Another concern regarding proper reduction of the syndesmosis is the proper force necessary to achieve reduction and prevent overcorrection. There are several studies that document the incidence of overcompression of the syndesmosis.10 In the previously mentioned study by Phisitkul and coworkers, all the cadaveric specimens they examined had overcompression of the syndesmosis at an average of 0.9 millimeters on CT scan.11
Comparing Stabilization Techniques
In recent years, there has been development of the “suture button” technique for syndesmotic stabilization. These devices theoretically maintain physiologic motion of the syndesmosis without the need to remove the implant. This could help prevent recurrence of syndesmotic diastasis.
Comparing 21 patients with a suture button device and 19 patients with syndesmotic screw fixation, Kortekangas and colleagues used intraoperative bilateral CT and postoperative bilateral CT to evaluate accuracy and maintenance of syndesmotic reduction. They found that both groups had similar reduction and maintenance rates, and noted no significant difference in functional outcomes.9
A study by Laflamme and team compared 36 patients in a static fixation group with 34 patients in a dynamic fixation group. They found significant improvements to Olerud-Molander scores at three, six and 12 months post-op. Additionally, they noted a significantly lower implant failure in the dynamic fixation group (zero versus 36.1 percent) and greater loss of reduction in the static fixation group (11 percent versus 0 percent). They did not find a significant difference in American Orthopedic Foot and Ankle Society (AOFAS) scores at six and 12 months post-op. They concluded that the dynamic fixation device could offer better clinical and radiologic outcomes for patients over static fixation with syndesmotic screws.12
In a systematic review, Zhang and colleagues evaluated 10 studies that compared static versus dynamic fixation for syndesmotic injuries.13They found that static fixation and dynamic fixation had similar functional outcomes and postoperative complication rates. However, patients who had dynamic fixation had lower rates of implant removal, implant failure and malreduction.13
There are many considerations when planning for fixation of syndesmotic injuries. Not only must one consider whether to use dynamic versus static stabilization, but if the surgeon is planning to use static stabilization, he or she must consider screw diameter, the number of cortices purchased, and the number of screws. The surgeon must also decide if the patient will benefit from planned removal of screw fixation. It has been our experience that dynamic stabilization is best reserved for a younger patient population as well as active patients. Some surgeons may argue that the possible subtle malreduction that syndesmotic screws can cause is less tolerated in the young and active population.
Alternatively, those with more unstable syndesmotic injuries such as those associated with pronation, external rotation (PER-IV) and Weber type C fractures may benefit from utilization of either multiple dynamic stabilization implants, multiple syndesmotic screws or quadcortical syndesmotic screws to provide a more stable construct.
Dr. Hook is in private practice at Midland Orthopedic Associates and is affiliated with the residency program at Mercy Hospital and Medical Center in Chicago.
Dr. Narcisi is a third-year resident at Mercy Hospital and Medical Center in Chicago.
Dr. Martini is a second-year resident at Mercy Hospital and Medical Center in Chicago.
1. Inge SY, Pull Ter Gunne AF, Aarts CAM, Bemelman M. A systematic review on dynamic versus static distal tibiofibular fixation. Injury. 2016;47(12):2627-2634.
2. Ramsey PL, Hamilton W. Changes in tibiotalar contact caused by lateral talar shift. J Bone Join Surg Am. 1976;58(3):356-357.
3. Ebraheim NA, Lu J, Yang H, Mekhall AO, Yeasting RA. Radiographic and CT Evaluation of tibiofibular syndesmotic diastasis: a cadaver study. Foot Ankle Int. 1997;18(11):693-698.
4. Oae K, Takao M, Naito K, et al. Injury of the tibiofibular syndesmosis: value of MR imaging for diagnosis. Radiology. 2003;227(1):155-161.
5. Moore JA Jr, Shank JR, Morgan SJ, Smith WR. Syndesmosis fixation: a comparison of three and four cortices of screw fixation without hardware removal. Foot Ankle Int. 2006;27(8)567-572.
6. Thompson MC, Gesink DS. Biomechnical comparison or syndesmosis fixation with 3.5 and 4.5-millimeter stainless steel screws. Foot Ankle Int 2000;21(9):736-741.
7. Schepers T, van der Linden H, van Lieshout EM, Niesten DD, van der Elst M. Technical aspects of the syndesmotic screw and their effect on functional outcome following acute distal tibiofibular syndesmosis injury. Injury. 2014;45(4):775-779.
8. Zalavras C, Thordarson D. Ankle syndesmotic injury. J Am Acad Orthop Surg. 2007;15(6):330-339.
9. Kortekangas T, Savola O, Flinkkila T, et al. A prospective randomized study comparing TightRope and syndesmotic screw fixation for accuracy and maintenance of syndesmotic reduction assessed with bilateral computed tomography. Injury. 2015;46(6):1119-1126.
10. Gardner MJ, Demetrakopoulos D, Briggs SM, Helfet DL, Lorich DG. Malreduction of the tibiofibular syndesmosis in ankle fractures. Foot Ankle Int 2006;27(10):788-792.
11. Phisitkul P, Ebinger T, Goetz J, Vaseenon T, Marsh JL. Forceps reduction of the syndesmosis in rotational ankle fracture: a cadaveric study. J Bone Joint Surg Am. 2012;94(24):2256-2261.
12. Laflamme M, Belzile EL, Bedard L, van den Bekerom MP, Glazebrook M, Pelet S. A prospective randomized multicenter trial comparing clinical outcomes of patients treated surgically with a static or dynamic implant for acute ankle syndesmosis rupture. J Orthop Trauma. 2015;29(5):216-225.
13. Zhang P, Liang Y, Fang Y, Chen P, Wang J. A systematic review of suture-button versus syndesmotic screw in the treatment of distal tibiofibular syndesmosis injury. BMC Musculoskelet Disord. 2017;18(1):286.
14. Gardner MJ, Graves ML, Higgins TF, Nork SE. Technical considerations in the treatment of syndesmotic injuries associated with ankle fractures. J Am Acad Orthop Surg. 2015;23(8):510-518.