Entwicklung eines 3-dimensionalen messverfahrens zur bestimmung des tibialen gefälles im spiral-CT

Aim: The measurement or, respectively, the correction of the tibial slope is an important subject in the field of knee arthroplasty and in the procedure of cruciate ligament reconstruction. However, a valid value of the tibial slope cannot be obtained from the conventional plain X-rays in a reproducible way. The aim of this study was to evaluate the proximal tibial slope with a new CT measurement system and to compare the values with the X-ray method. Method: Using 6 cadaver tibiae, the antero-posterior slope of the proximal tibia was measured at 0°, 2.5°, 5°, 10°, 15°, 20°, 30° internal rotation using the plain X-ray and spiral CT (3D-MPR reconstruction). Both methods were compared. Results: The variation of the measurement of the tibial slope with the X-ray method was > 5° even if the optimal 0° rotation in the lateral view was applied. Moreover, the measurement error increased to 14° while increasing the rotation of the tibia. Using the new CT system, the error was less than 3° in all measurements. Conclusion: The measurement of the tibial slope in the conventional X-ray technique showed a high variation of the values depending on the rotation of the tibia in the lateral view. In contrast, the measurements with the new CT system represented a precise method with a small variation of the tibial slope values. For this reason detailed questions regarding the precise anatomy of the proximal tibia cannot be answered precisely with plain X-rays.