2025 ISAKOS Biennial Congress ePoster
The Flexion Angle and the Intra-Articular Version in Different MRI Recording Techniques Influence the Tibial Tuberosity - Trochlea Groove Distance
Ole Grunenberg, MD GERMANY
Lucas K. Palma Kries, MD, Münster GERMANY
Michael J. Raschke, MD, Prof., Münster GERMANY
Christian Peez, MD, Münster, NRW GERMANY
Luise M. Hägerich, MD, Münster GERMANY
Elmar Herbst, MD, PhD, Muenster GERMANY
Christoph Kittl, MD, MD(res), Muenster GERMANY
Adrian Deichsel, MD, Münster, NRW GERMANY
Department of Trauma, Hand and Reconstructive Surgery, University Hospital Muenster, Münster, NRW, GERMANY
FDA Status Not Applicable
Summary
Extension of the knee with a simultaneous higher knee version in the rotatory MRI technique, suggests increased TT-TG close to extension, due to the screw-home mechanism.
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Abstract
Purpose
The tibial tuberosity - trochlea groove distance (TT-TG) is one of the most frequently used parameters to evaluate the risk of recurrent patellar dislocation. However, clinical practice showed different measurements of the TT-TG in conventional knee magnetic resonance imaging (MRI) and rotatory MRI. The purpose of this study was to compare the TT-TG and the tibial tuberosity – posterior cruciate distance (TT-PCL) between the investigated techniques. It was hypothesized that the TT-TG varies due to differences in knee flexion angle.
Methods
25 patients with both a conventional knee MRI and a rotatory MRI were retrospectively included to this study. The main difference between the rotatory MRI and the conventional MRI is that the lower extremity coil in rotatory MRI allows full knee extension and includes both legs from the hips to the ankle, while the knee MRI coil in conventional MRI places the knee in slight flexion. Patients were excluded if surgery was performed, or an injury occurred between the two MRI scans. TT-TG and TT-PCL were measured in each of the MRI scans. Furthermore, knee flexion angle as well as intra-articular knee version were determined. A two-tailed Wilcoxon matched-pairs signed-rank test was used to compare the parameters between rotatory and conventional MRI. Spearman’s correlation coefficient was used to detect correlations between the TT-TG and TT-PCL with the assessed parameters. All parameters were evaluated by two raters. The inter-rater reliability of the measurements was assessed by using the intraclass correlation coefficient (ICC).
Results
The TT-TG was significantly (P < 0.05) higher in rotatory MRI (median 18.4 mm, IQR 7.3 mm), in comparison to conventional MRI (median 12 mm, IQR 5.7 mm). The TT-PCL did not differ significantly between the groups (P = n.s.). Knee flexion angle was significantly higher in the conventional MRI (median 21.4°, IQR 8.6°) compared to rotatory MRI (median 3.1°, IQR 3.4°, P < 0.0001). The knee version was significantly lower in the conventional MRI (median 2°, IQR 6.3°) compared to the rotatory MRI (median 9°, IQR 7.3°, P < 0.0001). Significant correlations were found between the knee version and the knee flexion angle (r = -0.69, 95%-CI = -0.82 to -0.49, P < 0.0001), between the TT-TG and the knee version (r = 0.67, 95%-CI = 0.46 to 0.8, P < 0.0001) and between the TT-TG and the knee flexion angle (r = -0.56, 95%-CI = -0.74 to -0.31, P < 0.0001). All measurements showed excellent interrater agreement (ICC 0.87 - 0.94).
Conclusion
TT-TG measurements are dependent on flexion angle in intra-articular version, which vary with differing MRI techniques, with clinically relevant differences. The TT-PCL is not influenced by these factors. Extension of the knee with a simultaneous higher knee version in the rotatory MRI technique, suggests increased TT-TG close to extension, due to the screw-home mechanism.