The distal tibiofibular syndesmosis is a reliable landmark for 3° varus tibial resection in total knee arthroplasty: a radiological evaluation on 1296 cases

Purpose The purpose of this study was to evaluate the reproducibility and the accuracy of distal tibiofibular syndesmosis (DTFS) as landmark to perform controlled varus tibial resections during total knee arthroplasty (TKA). The hypothesis was that DTFS can be used to perform an accurate 3° varus tibial cut. Methods A retrospective analysis on a consecutive series of standard weightbearing full-length anteroposterior views of the lower limbs radiographic images was conducted. For each radiograph, the hip–knee–ankle (HKA) angle, the angle between the tibial mechanical axis and the line connecting the centre of the tibial spines and the DTFS (tibiofibular angle, TFA) and the medial proximal tibial angle (MPTA) were calculated. Each measurement was carried out twice by three independent observers, and intra- and inter-observer measurement reliability were assessed using the intraclass correlation coefficient (ICC) analysis. Results A total of 1296 lower limbs were analysed from a series of 648 weightbearing full-length anteroposterior radiographs. The ICC were > 90% for all measurements. The mean TFA value was 2.94 ± 0.68 (range 2.38–3.51). No differences were detected comparing the mean TFA value on the right and left limb ( p = 0.795) as well as comparing the values in male and female patients ( p = 0.691). Linear regression analysis did not find statistically significant correlation between TFA and MPTA, or TFA and HKA angles, respectively. Conclusion The distal tibiofibular syndesmosis is a reliable and easy reproducible radiographic landmark that can be used when planning a 3° varus tibial cut. Future studies are needed to confirm the validity of this method also in clinical settings. Level of evidence IV, retrospective case series.