Is the Fibular Station on Lateral Ankle Radiographs Symmetric? A Retrospective Observational Radiographic Study.

Background: Precise reduction of a syndesmosis after disruption is critical to improve patient physical function. Intraoperative lateral radiographs of the unaffected ankle are often used in clinical practice as a template for anatomic syndesmotic reduction because sagittal plane malreduction is common. However, there is little data to suggest fibular station, or the position of the fibula in the AP plane on the lateral radiograph, is symmetric side-to-side in patients.

Questions/purposes: (1) Is the position of the fibula in the AP plane (fibular station) on lateral ankle radiographs symmetric in an individual? (2) Do the measurements used to judge the position of the fibula on lateral radiographs have good inter- and intraobserver reliability?

Methods: Over the period from August 2016 to October 2018, we identified 478 patients who presented to an orthopaedic clinic with forefoot and midfoot complaints. Skeletally mature patients with acceptable bilateral lateral ankle radiographs, which are common radiographs obtained for new patients to clinic for any complaint, were included. Based on that, 52% (247 of 478 patients) were included with most (22%, 107 patients) excluded for poor lateral radiographs. The most common diagnosis in the patient cohort was midfoot OA (14%, 35 patients). The median (range) age of the included patients was 54 years (15 to 88), and 65% (159 of 247) of the patients were female. Fibular station, defined as the position of the fibula in the AP plane, and fibular length were measured using a digital ruler and goniometer on lateral radiographs. A paired t-test was used to determine if no difference in fibular station existed between the left and right ankles. With 247 paired-samples, with 80% power and an alpha level of 0.05, we could detect a difference between sides of 0.008 for the posterior ratio, 0.010 for the anterior ratio, and 0.012 for fibular length. Two readers, one fellowship-trained orthopaedic traumatologist and one PGY-4, measured 40 patients to determine the inter- and intraobserver reliability by intraclass correlation coefficient (ICC).

Results: The posterior fibular station (mean right 0.147 [σ = 0.056], left 0.145 [σ = 0.054], difference = 0.03 [95% CI 0 to 0.06]; p = 0.59), anterior fibular station (right 0.294 [σ = 0.062], left 0.299 [σ = 0.061], difference = 0.04 [95% CI 0 to 0.08]; p = 0.20), and fibular length (right 0.521 [σ = 0.080], left 0.522 [σ = 0.078], difference = 0.05 [95% CI 0.01 to 0.09]; p = 0.87) ratios did not differ with the numbers available between ankles. Inter- and intraobserver reliability were excellent for the posterior ratio (ICC = 0.928 and ICC = 0.985, respectively) and the anterior ratio (ICC = 0.922 and ICC = 0.929, respectively) and moderate-to-good for the fibular length ratio (ICC = 0.732 and ICC = 0.887, respectively).

Conclusion: The use of lateral radiographs of the contralateral uninjured ankle appears to be a valid template for determining the position of the fibula in the sagittal plane. However, further prospective studies are required to determine the efficacy of this method in reducing the syndesmosis over other methods that exists.

Level Of Evidence: Level III, diagnostic study.