Abstract
BackgroundThe tibial slope plays an important role in knee surgery. However, standard radiographic measurement techniques have a low reproducibility and do not allow differentiation between medial and lateral articular surfaces. Despite availability of three-dimensional imaging, so far, no real 3D measurement technique was introduced and compared to radiographic measurement, which were the purposes of this study.MethodsComputed tomography scans of 54 knees in 51 patients (41 males and 10 females) with a mean age of 46 years (range 22–67 years) were included. A novel 3D measurement technique was applied by two readers to measure the tibial slope of medial and lateral tibial plateau and rim. A statistical analysis was conducted to determine the intraclass correlation coefficient (ICC) for the new technique and compare it to a standard radiographic measurement.ResultsThe mean 3D tibial slope for the medial plateau and rim was 7.4° and 7.6°, for the lateral plateau and rim 7.5° and 8.1°, respectively. The mean radiographic slope was 6.0°. Statistical analysis showed an ICC between both readers of 0.909, 0.987, 0.918, 0.893, for the 3D measurement of medial plateau, medial rim, lateral plateau and lateral rim, respectively, whereas the radiographic technique showed an ICC of 0.733.ConclusionsThe proposed novel measurement technique shows a high intraclass agreement and offers an applicable opportunity to assess the tibial slope three-dimensionally. Furthermore, the medial and lateral articular surfaces can be measured separately and one can differentiate the slope from the plateau and from the rim. As three-dimensional planning becomes successively more important, our measurement technique might deliver a useful supplement to the standard radiographic assessment in slope related knee surgery.Level of evidenceLevel III, diagnostic study.
Highlights
The tibial slope plays an important role in knee surgery planning
An increased tibial slope was recognized as a risk factor for anterior cruciate ligament (ACL) rupture in native knees [11,12,13,14], whereas a decreased tibial slope could be identified as a risk factor for posterior cruciate ligament (PCL) injury [15]
There is lack of clarity regarding the accuracy of these measurements: On the one hand the anatomical tibial axis cannot reliably be determined on most lateral knee radiographs and, on the other hand, one cannot differentiate between the medial and the lateral articular surface
Summary
The tibial slope plays an important role in knee surgery. standard radiographic measurement techniques have a low reproducibility and do not allow differentiation between medial and lateral articular surfaces. There is lack of clarity regarding the accuracy of these measurements: On the one hand the anatomical tibial axis cannot reliably be determined on most lateral knee radiographs and, on the other hand, one cannot differentiate between the medial and the lateral articular surface. These factors lead to an unsatisfying intraclass correlation [23,24,25,26]. There is no measurement technique which considers the three-dimensional anatomical tibial axis and the volumetric constitution of the proximal tibia to differentiate between medial and lateral plateau and rim in a three-dimensional model
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