Symmetry and reliability of the anterior distal tibial angle and plafond radius of curvature

Abstract

Introduction: Using the radiographs of uninjured extremities as a template for reduction of articular fractures may be beneficial. While there is a significant amount of radiographic data about the relationship of bony landmarks in the hip and knee, there is minimal data investigating the symmetry of lateral measurements in ankles side to side. The aim of this study was to determine if radiographic anatomic differences were evident when comparing bilateral lateral radiographs of uninjured patient ankles.

Patients and methods: A retrospective review of patients with bilateral lateral ankle radiographs for mid- or fore-foot related complaints was performed. Patient demographics and radiographic measurements relating to the anterior distal tibial angle (ADTA) and plafond radius of curvature (ROC) were collected. Paired student's t-test was used to determine similarities.

Results: 478 patient radiographs were evaluated and 215 met inclusion criteria. The average ADTA was 84.0° (76°-92°, σ=3.03°) and plafond ROC was 20.4 mm (11.3-37.1 mm, σ=4.01 mm). There was no significant difference between left and right ankles in ADTA (p = 0.08) and ROC (p = 0.06). Females had a significantly smaller ROC and larger ADTA (p<0.001,p = 0.03). Inter-observer and intra-observer reliability were excellent for the ADTA (>0.9) and good for the ROC (>0.75).

Conclusion: This study demonstrates that the ADTA and plafond ROC measurements are reliable and symmetrical in patients. Furthermore, females are more like to have a flatter ADTA (closer to 90°) and a smaller ROC of their plafond. These findings confirm that the lateral radiograph of the uninjured ankle may be used as a template for reduction when treating articular injuries of the distal tibia.

Keywords: Ankle Joint / diagnostic imaging; Ankle joint / anatomy & histology; Radiography / methods; Reproducibility of results; Tibia / anatomy & histology.