Reliability of Plain Radiographs Versus Magnetic Resonance Imaging to Measure Tibial Slope in Sports Medicine Patients: Can They Be Used Interchangeably?

Abstract

Background: The slope of the tibial plateau has been proposed as a reason for failure of anterior cruciate ligament reconstruction. Purpose: To evaluate the interobserver reliability of measurements of tibial slope on radiographs versus magnetic resonance imaging (MRI) scans and to assess whether the modalities can be used interchangeably for this purpose. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: This retrospective study included 81 patients aged 18 to 30 years who were evaluated in a sports medicine setting for knee pain and who had lateral knee radiographs as well as knee MRI scans on file. Medial and lateral tibial plateau slope measurements were made by 3 blinded reviewers from the radiographs and MRI scans using graphic overlay software. The paired t test was used to compare measurements of the medial tibial plateau slope (MTPS) and lateral tibial plateau slope (LTPS) from radiographs and MRI scans. Intraclass correlation coefficients (ICCs) were calculated to determine intra- and interobserver reliability of measurements within each imaging modality, and Pearson correlation coefficients were calculated to determine the relationship between measurements on radiographs versus MRI scans. Results: Imaging from 81 patients were included. The average MTPS was significantly larger on radiographs compared with MRI scans (8.7° ± 3.6° vs 3.7° ± 3.4°; P < .001), and the average LTPS was also significantly larger on radiographs compared with MRI scans (7.9° ± 3.4° vs 5.7° ± 3.7°; P < .001). ICC values indicated good to excellent intraobserver agreement for all imaging modalities (ICC, 0.81-0.97; P ≤ .009). The ICCs for interobserver reliability of MTPS and LTPS measurements were 0.92 and 0.85 for radiographs, 0.87 and 0.83 for MRI based off the subchondral bone, and 0.86 and 0.71 for MRI based off the cartilage, respectively ( P < .001). Medium correlation was noted between radiographic and MRI measurements; Pearson correlation coefficients for radiographic versus subchondral MRI measurements were 0.30 and 0.37 for MTPS and LTPS, respectively. Conclusion: The average MTPS and LTPS were significantly larger on radiographs compared with MRI scans. Although tibial slope measurements using radiography and those using MRI are reliable between individuals, the measurements from radiographs and MRI scans cannot be used interchangeably, and caution should be used when interpreting and comparing studies using measurements of the tibial slope.

Posterior Tibial Slope in Patients Undergoing Bilateral Versus Unilateral ACL Reconstruction: MRI and Radiographic Analyses

“…The variability in tibial slope measurements among different methods and imaging modalities has been investigated by several studies. 15,19,23,29 Naendrup et al 29 found that PTS measurements have a high degree of variability between measurement methods and imaging modalities, reporting a difference of up to 5° between methods. Jahn et al 23 recently found that the MPTS was larger by approximately 5° on radiography compared with MRI, with the LPTS being 2° greater on radiography.…”

“…13,30,38 Furthermore, these comparisons have been limited to either lateral radiography or magnetic resonance imaging (MRI), 13,17,30,38 although it has been shown that PTS values derived from radiography versus MRI may differ by up to 5°. 23…”

Increased lateral femoral condyle ratio measured by MRI is associated with higher risk of noncontact anterior cruciate ligament injury

“…The primary limitation of this study is that only conventional MRI was used to measure the morphological parameters of this study, instead of 3D-MRI examination. When morphological parameters are measured, the ideal sagittal section should be perpendicular to the line connecting the posterior condyle of the femur [ 25 ], which is difficult to ensure with conventional MRI [ 26 ]. Conventional MRI with excessive section thickness will make it difficult to accurately identify the sections and points of interest, resulting in errors [ 27 ].…”

Morphological Analysis of the Tibial Slope in 720 Adult Knee Joints

“…The difference was 0.4° for each TSK and TSH. Jahn et al retrospectively examined images of 81 patients to compare measurements of medial and lateral TS between radiographs and MRI [ 42 ]. The authors pointed out that in an exactly lateral radiograph, the medial and lateral TS can obtain reproducible measurements.…”