Is the posterior offset of femoral condyles related to the sagittal tibial slope?

Objectives: Aims of the study were to assess the sagittal tibial slope and posterior offset of femoral condyles and whether any correlation between the two is present. In particular, we hypothesized that the degree of posterior tibial slope is related to the posterior offset of femoral condyles to achieve adequate joint motion and stability during the flexion of the knee. Methods: We evaluated the magnetic resonance studies of the knees of 80 subjects, 45 males and 35 females, with an average age of 38.9 years, to assess the variability of posterior condylar offset and sagittal tibial slope and whether any correlation between the two is present. Measurements were performed by two independent observers using an imaging visualization software. The tibial slope was calculated on the medial and lateral side as the angle between the sagittal longitudinal axis and a line tangent to themedial and lateral plateau.The posterior condylar offset was calculated as the distance between the posterior femoral cortex and themost posterior point of the femoral condyle. Results: The tibial bone slope averaged 8 and 7.7, on the medial and lateral side, respectively, without significant difference between the two. The posterior offset of femoral condyles averaged 27.4 and 25.2 mm on the medial and lateral side, respectively (p = 0.001). The variation coefficient of posterior condylar offset and sagittal tibial slope was 11.5% and 38%, respectively. A significant relationship was found between the posterior condylar offset and sagittal tibial slope, but on the medial side only. Conclusions: In planning a cruciate retaining TKA, it may be helpful to take into account the posterior condylar offset and tibial slope concomitantly to achieve a satisfactory functional outcome.