A Radiological Study for Assessing Syndesmosis Malreduction: Its Validity and Limitation

Cortices of Fibula and Tibia Can Provide Landmarks for Accurate Syndesmosis Fixation Angle: Computed Tomography Validation of Angle Bisector Method

Anatomic syndesmosis reduction is necessary to restore ankle biomechanics and prevent poor clinical outcomes, but malreduction can be encountered frequently since the ideal fixation angle varies between patients and fixation levels. This study aimed to validate the angle bisector method to reveal whether it provides an accurate syndesmotic fixation angle that is patient- and level-specific. Lower extremity CT angiography of 50 consecutive patients (25 male, 25 female) without evident ankle pathology were evaluated. The average age was 52.8 (±18, range: 18-75). Lines tangent to anterior and posterior cortices of tibia and fibula were drawn in the axial plane at both 2 cm and 3.5 cm above the ankle joint line. Bisection of the angle formed between these lines was drawn and its relationship with the centroidal axis, which is proposed to be the ideal syndesmotic axis, was evaluated. The angle between the bisector line & the centroidal axis and the distance between their most lateral intersections with the fibula were calculated. The measurements were made by 3 blinded observers. Intra- and interobserver reliability analyses were conducted. The average centroidal axis-bisector angle was 2.1° ± 2.1° at 2 cm and 0.6° ± 1.3° at 3.5 cm level. The average distance to the actual syndesmosis entry point was 1.0 ± 0.9 mm at 2 cm and 0.4 ± 0.4 mm at 3.5 cm level. The values didn't show any significant difference according to gender. Intra- and interobserver reliability analysis showed excellent correlation in all parameters (interclass correlation coefficient > 0.90). Angle bisector method was found strongly reliable providing accurate direction for syndesmotic axis. It can provide a patient- and level-specific angle for the application of syndesmotic implants without increasing the fluoroscopy exposure. Its use can have a broad impact on functional outcomes of ankle injuries by decreasing the malreduction rates. Further cadaveric validation and safety studies should be conducted for possible clinical usage.

Instability of the distal tibiofibular syndesmosis

The distal tibiofibular syndesmosis (DTFS) is more frequently injured than previously thought. Early diagnosis and appropriate treatment is essential to avoid long term complications like chronic instability, early osteoarthritis and residual pain. Management of these injuries require a complete understanding of the anatomy of DTFS, and the role played by the ligaments stabilizing the DTFS and ankle. High index of suspicion, appreciating the areas of focal tenderness and utilizing the provocative maneuvers help in early diagnosis. In pure ligamentous injuries radiographs with stress of weight bearing help to detect subtle instability. If these images are inconclusive, then further imaging with MRI, CT scan, stress examination under anesthesia, and arthroscopic examination facilitate diagnosis. An injury to syndesmosis frequently accompanies rotational fractures and all ankle fractures need to be stressed intra-operatively under fluoroscopy after fixation of the osseous components to detect syndesmotic instability. Non-operative treatment is appropriate for stable injuries. Unstable injuries should be treated operatively. Anatomic reduction of the syndesmosis is critical, and currently both trans-syndesmotic screws and suture button fixation are commonly used for syndesmotic stabilization. Chronic syndesmotic instability (CSI) requires debridement of syndesmosis, restoration of ankle mortise with or without syndesmotic stabilization. Arthrodesis of ankle is used a last resort in the presence of significant ankle arthritis. This article reviews anatomy and biomechanics of the syndesmosis, the mechanism of pure ligamentous injury and injury associated with ankle fractures, clinical, radiological and arthroscopic diagnosis and surgical treatment.

Investigating the Radiological Outcomes of Syndesmosis Injuries in Ankle Fracture Patients After Suture Button Fixation

Concomitant syndesmotic injury occurs in 10% of ankle fractures. Anatomic reduction and maintenance of this reduction is critical in ensuring ankle stability and preventing long-term complications. This is a retrospective cohort study aimed at evaluating the mid-term radiological outcomes of syndesmotic injuries in ankle fracture patients after surgical fixation with suture button device. The study group included 33 patients. Plain radiographs including anteroposterior, lateral and mortise views of the affected ankle were performed preoperatively, postoperatively and at 3-month follow-up. Anteroposterior views were used to measure the amount of tibiofibular overlap and tibiofibular clear space. Paired Student's t test and linear model regression were performed. Between the immediate postoperative and 3-month follow-up period, there was a mean decrease in tibiofibular overlap of 0.841 (±2.07) mm (p = .0259). There was a mean increase in tibiofibular clear space of 0.621 (±1.46) mm (p = .0201). In addition, we found significant correlation between fracture type and change in tibiofibular clear space (p = .047). Our study showed that there is statistically significant widening of the syndesmosis after suture button fixation at 3-month follow-up as evidenced by reduced tibiofibular overlap and increase in tibiofibular clear space. However, they remain within the maximum threshold for acceptable syndesmotic widening of 1.5 mm. Further correlation between radiological outcomes and patient function is needed to determine clinical significance of these changes.