Tibial tuberosity-trochlea groove distance is dependent on flexion angle and intra-articular version in different magnetic resonance imaging recording techniques.

Purpose: The purpose of this study was to compare the tibial tuberosity-trochlea groove distance (TT-TG) and the tibial tuberosity-posterior cruciate distance (TT-PCL) between conventional and rotatory magnetic resonance imaging (MRI). It was hypothesised that the TT-TG varies between the investigated techniques, due to differences in knee flexion angle and intra-articular version. Variations in TT-TG could lead to misdiagnoses and consequently result in inappropriate surgical indications. Methods: Twenty-five patients with both a conventional knee MRI and a rotatory MRI (which allows full knee extension) due to recurrent patellar dislocation were included. TT-TG and TT-PCL, knee flexion angle and intra-articular version (external rotation) were determined in each scan. Inter-rater reliability was assessed using the intraclass correlation coefficient (ICC). Between-group differences were assessed using the Wilcoxon matched-pairs signed-rank test. Spearman's correlation coefficient was used to detect correlations between the TT-TG and TT-PCL with flexion angle and intra-articular version. Results: The TT-TG was significantly ( Conclusion: TT-TG measurements are dependent on flexion angle and intra-articular version, which vary with differing MRI techniques. Extension of the knee with a simultaneous higher intra-articular version in the rotatory MRI technique, suggests increased TT-TG close to extension, due to the screw-home mechanism. This should be considered to avoid misdiagnosis due to the TT-TG. Level of Evidence: Level III.