Background: Ankle syndesmotic ligament injury is an important factor affecting clinical outcome after lower extremity injury with as little as 2 mm of syndesmotic displacement leading to worse clinical outcome. One important factor is the appropriate placement of clamps and fixation across the syndesmosis. When not ideally aligned, these can result in malalignment of the fibula in the incisura. This study sought to provide computer validation of using the center-center technique to identify an ideal centroid axis for placement of syndesmotic implants. Methods: Thirty computed tomography (CT) scans of patients from July 1, 2016, to June 30, 2018, with normal syndesmoses were evaluated. Center-center and centroid measurements were drawn and compared on the axial CT images at 10, 20, and 30 mm superior to the tibial plafond. Three observers recorded measurements for the same 50 patients in order to compare interobserver reliability. Results: The difference between the centroid and center-center axis at each height level was a mean 0.4 degrees (range, 0.3-0.5 degrees). The center-center and centroid axis change by externally rotating as the height increases away from the tibial plafond with mean, 3 degrees (range, 0-6.1 degrees). Intraclass correlation coefficients (ICCs) were measured at 0.98, thus demonstrating excellent intraobserver and interobserver reliability on these measurements. Conclusion: The center-center technique can be used to identify the centroid axis within an acceptable degree of rotation at heights above the tibial plafond that are relevant to an operating surgeon placing syndesmotic fixation. Clinical Relevance: Theoretically, this aligns the centroids of the fibula and tibia, which achieves the same ideal patient-specific alignment and raises the question as to the extent to which the centroid and center-center axes correlate in the general population. If present, a strong correlation has potentially high clinical importance when planning syndesmotic fixation.

Category: Ankle Introduction/Purpose: When necessary, surgical treatment of ankle syndesmosis disruption typically yields excellent functional outcomes. That is, when the syndesmosis is correctly reduced. However, accurate reduction of the ankle syndesmosis is difficult to achieve reproducibly. A clinically important step would be to translate the precision of a computed tomography (CT)-based technique for syndesmosis reduction accuracy assessment into a validated clinical approach. Reb et al. previously demonstrated the clinical feasibility of translating the CT tibiofibular line (CT-TFL) to a clinical technique. However, this study raised questions regarding several potentially significant confounding effects. These included the effects of fibula morphology. The present study evaluated the validity and reliability of the CT-TFL technique, particularly with regard to variations in fibula morphology. Methods: An IRB approved, retrospective cross sectional study of consecutive foot and ankle CT scans obtained for non-ankle complaints and without radiographic evidence of ankle injury or prior surgery. 3 trained observers repeatedly performed measurements on the 52 patients meeting criteria. Anterolateral fibula shape was categorized in the axial plane 10 mm superior to the plafond. The CT-TFL was drawn contacting the longest section of straight anterolateral cortical surface of fibula with this length recorded. The CT-TFL distance measurement was made connecting the CT-TFL to the closest point of tibial surface (Figure 1). Means, standard deviations, and 95% confidence intervals were calculated for continuous variables and frequencies were calculated for categorical variables. Intraobserver and interobserver consistency were assessed using intraclass correlation for continuous variables and Fleiss’ kappa for categorical variables. The optimal range of straight anterolateral fibula cortical length was determined by plotting CT-TFL contact length versus observer consistency of CT-TFL distances. Results: Mean fibula cortical contact length ranged from 3.74 mm (95% CI 3.24 to 4.24 mm) to 11.45 mm (95% CI 11.21 to 11.69mm). Mean TFL distance ranged from -2.83 mm (95% CI -3.65 to -2.00) to 5.03 mm (95% CI 4.48 to 5.57 mm). Intraobserver and interobserver consistencies were excellent (minimum ICC, 0.87) for these measurements. For fibula shape categorization, intraobserver consistency ranged from substantial to almost perfect (Fleiss’ Kappa range, 0.73 to 0.97). However, interobserver consistency was moderate (Fleiss’ Kappa, 0.55). 6 mm to 10 mm of fibula contact length corresponded to a minimum of excellent observer consistency for CT-TFL distance (ICC 0.80 to 0.98). Conclusion: The study refines and expands upon the initial description of the CT-TFL technique. Among uninjured syndesmoses, a broader range of CT-TFL values were observed than previously reported, including negative values of which some were relatively large. Instead of fibula shape, anterolateral fibula cortical contact length was more useful in discerning which subjects were best suited for this technique. Excellent observer consistency occurred when 6 mm to 10 mm of fibula contact length was present. These results support the validity of the TFL technique and further characterize its role in the clinical setting.

Category: Ankle Introduction/Purpose: Distal tibiofibular syndesmosis sprain has been reported among 13% to 23% of all ankle fractures, often requiring surgery. However, post-operative malreduction rates have been reported to range from 0 to 54%. Optimal reduction is a significant predictor of overall functional outcome. The centroids of the tibia and fibula align the theoretically ideal axis of syndesmosis fixation alignment. The “Center-Center” method for syndesmosis fixation is a recently described intraoperative technique for aligning the central axes of the tibia and fibula on the ankle lateral fluoroscopic view, seemingly aligning the centroids. There is a lack of validation and outcomes data to support this technique. This study was performed in order to determine how reliably the ”center-center” technique aligns with the centroid axis of the fibula and tibia. Methods: This was a quantitative descriptive study utilizing 30 axial computed tomography scans from July 1, 2016 to June 30, 2018. Eighteen males and 12 females were included with an average age of 44-years-old. CT measurements were made using Visage 7. Three observers measured the maximum difference in degrees between the Center-Center and Centroid measurements at 10 mm, 20 mm, and 30 mm proximal to the tibial plafond for each patient. The Center-Center axis was established by internally rotating the CT image until the fibula aligned within the center of the tibia. The centroid measurement was established using a tool that calculated the centroid of each bone. Finally, the difference in external rotation required to obtain the Center-Center measurements were observed at levels 10 mm versus 20 mm, 20 mm versus 30 mm, and 10 mm versus 30 mm. Results: The Center-Center and Centroid axes were highly consistent within and between subjects and levels, differing on average by a mean 0.39 degrees (95% CI 0.29 to 0.49 degrees) across all comparisons. These axes externally rotated a mean 3.10 degrees (95% CI 2.56 to 3.64 degrees) from 10 mm to 20 mm and a mean 2.72 degrees (95% CI 2.35 to 3.09 degrees) from 20 mm to 30 mm. There were no statistically significant differences in the mean values obtained between observers for any axis at any height (p-value range 0.4 to 1.0) and intraclass correlation indicated excellent to near perfect interobserver agreement (ICC range, 0.876 to 0.988). Conclusion: The Center-Center technique consistently and closely aligns the fibula and tibia along the Centroid axis. These two axes externally rotate approximately 3 degrees for each 10 mm above the plafond. The Center-Center technique may offer the highly accurate means sought for achieving accurate and consistent intraoperative syndesmosis fixation alignment due to its highly consistent relationship to the Centroid axis. Surgeons should be aware of the external rotation of these axes between heights as the axes externally rotated a mean 3 degrees for each 10 mm height increase. Failure to correct limb rotation for each height could result in iatrogenic malreduction.