Description
Objectives: To compare tibial slope in healthy patients versus patients with knee osteoarthritis and patients with anterior cruciate ligament reconstruction (ACLR) failure, as well as to compare the different methods of radiographic measurement of tibial slope.
Methods: In this case-control study, 85 Chilean patients were included, who were evaluated with lateral knee and lateral leg X-rays. 35 of them were healthy patients with a mean age of 52 years (range 39-72 years). The second group was 35 patients with knee osteoarthritis with a mean age of 66 years (range 53-82 years) and a third group of 15 patients with ACLR tears with a mean age of 28 years (range 19-37 years). Tibial slope was measured in all cases using the mechanical and anatomical axis in lateral leg radiography associated with measurement of the anterior curvature of the tibia and anatomical axis according to the Dejour method in lateral knee radiography. Analysis by group was performed between each measurement method using the t test and Pearson's correlation was used to relate the anterior curvature of the tibia to the differences in tibial slope value between lateral leg radiography and lateral knee radiography in each group. P≤0.01 was considered statistically significant for each test.
Results: In the first group of healthy patients, there were 19 men and 16 women. The values are described in table 1:
lateral leg x-ray
Posterior tibial slope, mechanical axis Posterior tibial slope, anatomical axis
Anterior tibial bowing angle 1,3° (0,9° - 1,5°)
lateral knee x-ray
Posterior tibial slope, Dejour's Method 8,5° (7,2° - 9,2°)
lateral knee x-ray
Posterior tibial slope, Dejour's Method 9,2° (8,1° - 11,5°)
lateral knee x-ray
Posterior tibial slope, Dejour's Method 8,7° (7,8° - 11,2°)
7,9° (7,7° - 8,4°) 8,3° (7,1° - 9.0°)
In the group of patients with knee osteoarthritis, there were 17 men and 18 women. The values are described in table 2:
lateral leg x-ray
Posterior tibial slope, mechanical axis Posterior tibial slope, anatomical axis
10,4° (8,5° - 12,1°) 9,1° (8,1° - 11,4°)
Anterior tibial bowing angle 2,8° (1,7° - 6,4°)
In the group of patients with ACLR failure, there were 11 men and 4 women. The values are described in table 3: lateral leg x-ray
Posterior tibial slope, mechanical axis Posterior tibial slope, anatomical axis 9,9° (8,7° - 12,0°) 8,7° (7,8 °- 11,2°)
Anterior tibial bowing angle 2,5° (1,6° - 5,1°)
There was a significantly difference between tibial slope measurement by mechanical axis, and by anatomical axis in lateral knee radiographs and lateral leg radiographs (paired-samples t test, p<0.01). Also there was a positive and signifcant correlation (Spearman correlation, R=0.371, p>0.01) between the tibial anterior bowing angle and the diference of tibial posterior slope measurement of the mechanic axis and the anatomical tibial axis.
Conclusions: Based on our results, there is an increased tibial slope in patients with knee osteoarthritis and in those with ACLR failure compared to healthy patients. In accordance with the literature, the values of our study confirm that in the presence of an increased anterior curvature of the tibia, the measurement of tibial slope is underestimated when calculated using the anatomical axis technique, especially when measured only with lateral knee radiography. We therefore suggest routine evaluation of anterior curvature of the tibia in patients who require evaluation of tibial slope for more accurate results.
