Medial and lateral posterior tibial slope in the skeletally immature: Variability across pediatric ages without a consistent trend

Introduction: Increased knee posterior tibial slope (PTS) angle elevates anterior cruciate ligament (ACL) strain and ACL injury risk. Adult biomechanical research indicates that decreasing the PTS may reduce ACL injuries. Younger patients have much higher risk of ACL injury than adults, with limited anatomic research on tibial slope. The purpose of this study is to evaluate the pediatric medial and lateral PTS in a larger cohort group than prior research. Methods: Eighty-three computed tomography (CT) scans of the knee from children aged <2 to 11 years were evaluated using OsiriX imaging software. The PTS was evaluated at two distinct points on sagittal CT sections: (1) At the medial and 2) lateral tibial plateaus, both aligned with the central part of the coronal view of the femoral condyles. Results: The medial and lateral PTS demonstrated variability across ages <2 to 11 years, with mean values ranging from 3.6° ​± ​1.8°–8.7° ​± ​5.3° for medial slopes and 5.1° ​± ​3.3°–12.4° ​± ​3.6° for lateral slopes. The proportion of patients with at least one slope >10° peaked at age 8 (100 ​%) and age 6 (67 ​%). Simple linear regression revealed no statistically significant relationship between age and tibial slope for medial (coefficient of −0.07, p ​= ​0.574, R² ​= ​0.004) or lateral slopes (coefficient of −0.08, p ​= ​0.459, R² ​= ​0.007). Conclusion: Corrective osteotomy of increased PTS to lower the risk of ACL injury may be performed in high injury risk adult patients. However, such invasive procedures are not recommended for the skeletally immature because osteotomy in the growth plates in the proximal tibia could induce growth disturbance. In a unique skeletally immature patient with high risk of recurrent ACL injury, guided growth might be an option in high risk for lowering PTS in a controlled manner. As younger patients have some of the higher risks of primary and recurrent ACL injury, future research in this area may offer another approach to lower the risk of these injuries. Level of Evidence: Level III.