Biomechanik der Sagittalebene des Kniegelenks

[The correct tibial slope? Comparison of measuring methods]

INTRODUCTION

From a biomechanical point of view, the tibial slope plays a significant role in relation to the loading of the ligament structures in the knee joint. Currently, there are various methods of measurement for the tibial slope, which makes it difficult to compare the measurement results obtained. These differences can be decisive factors for the indication and the extent respectively of the correction of the tibial slope. The aim of this work is to present the differences in results between the measurement methods, and to compare these with the posterior tibial slope (PTS).

METHODS

By means of a comparative analysis, six measurement techniques for the tibial slope were examined. Using six parameters (correlation coefficient, range, deviation of the average slope value, correction coefficient, difference in the corrected measurements, range of the corrected measurements), these results were compared with the PTS. In this prospective study, the PTS was measured in 107 (49 male, 58 female, age 42.6 ± 23.4 years) strictly lateral plain radiological projections of the tibia with the talocrural joint in comparison with the measurement methods according to Han, Brazier, Moore and Harvey, Pietrini and LaPrade and a supratuberosity measurement.

RESULTS

The posterior slope was observed at a mean value of 6.9° (± 8.6°). Compared with the PTS, tibial slope values were increased in 55.5 % of all measurements examined and decreased in 42.4 %. In 2 % the values were identical to those of PTS. The deviations observed were significant at up to +2.9° (± 1.7°) and -2.3° (± 1.5°) respectively in comparison with the measured PTS (p < 0.001). 25.9 % of the results showed a slope value more than 2°too high and 17.6 % one less than -2° too low. Thus, in 43 % of the results clinically relevant results that were too high or too low were observed for the tibial slope compared with the PTS (p < 0.001). The correlation analyses showed very high linear connections with PTS (p < 0.001) for all methods, from r2 = 0.88 (in Moore and Harvey) up to r2 = 0.98 (in Han). The ranges varied between 13.90° (Moore and Harvey) and 18.30° (Han).

CONCLUSION

Depending on the measurement method, the slope values obtained should be individually evaluated, in order to draw the correct clinical conclusions. In principle, the radiological assessment of the whole lower leg is essential, so that concomitant pathologies in the area of the entire tibia can be detected. In everyday clinical practice, the measurement according to Han et al., and thus a shorter X‑ray projection, makes it possible to draw optimal conclusions about the PTS. LOE: Prospective diagnostic study, Level II.

Morphological Analysis of the Tibial Slope in 720 Adult Knee Joints

Background: The tibial slope (TS) defines the posterior inclination of the tibial plateau (TP). The “individual physiological” TS plays a crucial role in knee-joint stability and should be taken into account in knee-joint surgery. The aim of this study was to analyse the specific morphology of the TS for the medial (med) and lateral (lat) TP in relation to patient characteristics and the measurement method. Methods: In this retrospective study, MRI images of knee joints from 720 patients (mean age: 49.9 years [±17.14]) were analysed. The TS was assessed using two established methods according to Hudek (TSH) and Karimi (TSK) for the med and lat TP and gender/side specificity was analysed. Results: TSH for the med and lat TP showed significantly (p < 0.001) different values compared to TSK (TSKmed: 2.6° (±3.7), TSHmed: 4.8° (±3.5); TSKlat: 3.0° (±4.0), TSHlat: 5.2° (±3.9)). The angles of the lat TP were significantly higher than those of the med TP (TSK: p < 0.001; TSH: p = 0.002). Females showed a higher med and lat TS compared to males (p < 0.001). Conclusions: The measurement method has an influence on the values of the TS in knee-joint MRIs. The TS is significantly different for the med and lat TP regardless of the measurement method. There are gender-specific differences for the TS.