Correlation of Tibial Tubercle Overgrowth With Increased Posterior Tibial Slope: A Novel Radiographic Assessment

Background: An elevated posterior tibial slope (PTS) is associated with an increased risk for anterior cruciate ligament and meniscal injury. Recent evidence suggests that the PTS is elevated in patients with Osgood-Schlatter disease.

Purpose: To determine whether there is an association between objective measures of anterior tibial tubercle growth and PTS.

Study design: Cross-sectional study; Level of evidence, 3.

Methods: A total of 100 radiographs were randomly selected from a sample of patients who had received a lateral knee radiograph that captured at least 15 cm of the tibia distal to the knee joint line at a single institution between December 2020 and March 2022. The PTS was measured, and tibial tubercle growth was quantified with 2 novel measurements. For these measurements, a line was drawn on the radiograph from the most anterosuperior point on the tibia to the point on the anterior cortex of the tibia 10 cm distal from the starting point. The tibial tubercle height (TTH) was measured as the perpendicular distance from this line to the most prominent portion of the anterior tibia. The anterior tibial tubercle angle (TTA) was measured as the angle between the endpoints of the line made previously and the most prominent portion of the tibial tubercle, with a more acute angle indicating a more prominent tibial tubercle. The relationship between TTA, TTH, and PTS was evaluated using a univariate linear regression model.

Results: The mean patient age was 33.1 ± 14.1 years. The mean TTA was 158.6°± 4.7°, the mean TTH was 8.8 ± 2.0 mm, and the mean PTS was 9.7°± 2.6°. A significant correlation was found between PTS and TTA (r = -0.46; β = -0.46; P < .001) as well as TTH (r = 0.43; β = 0.43; P < .001).

Conclusion: Objective measures of anterior tibial tubercle overgrowth correlated with an elevated PTS. Every 2.2° of anterior TTA deviation from the mean and every 2.3 mm in TTH deviation from the mean correlated with a 1° difference in the PTS. This suggests a link between the development of the tibial tubercle and PTS, and it potentially helps to explain why the PTS is elevated in certain patients.