Analysis of medial tibial plateau fracture injury patterns using quantitative 3D measurements

The Wahlquist system classifies tibial medial plateau fractures into three types based on the sagittal fracture line location, with type C at highest risk of complications. However, the injury mechanism of tibial medial plateau fractures, especially tibial rotation movement, remains unclear. The purpose of the present study was to determine the injury patterns of medial tibial plateau fractures using 3D model simulation and quantitative 3D measurements. Seventy-eight consecutive AO/OTA type 41-B tibial plateau fractures were retrospectively analyzed using CT-based 3D models and quantitative 3D measurements. The knee posture at the moment of fracture occurrence was simulated, and various knee angles in the sagittal, coronal, and axial planes were measured to evaluate the mechanism of medial tibial plateau fracture. The mean valgus-varus, hyperextension-flexion, and internal-external rotation angles were determined, and the chi-square test was used for comparisons of categorical varus and valgus force data to determine the main force direction in Wahlquist type C fractures. Angle measurements in the coronal planes showed that 28 (35.9%) medial tibial plateau fractures resulted from a varus injury pattern, while 50 fractures (64.1%) resulted from a valgus pattern. Valgus force produced significantly more Wahlquist type C fractures (37 of 50 fractures) than varus force (2 of 28 fractures) (p < 0.05). There was no significant difference in the cases of patients with type C fractures between the tibial internal and external rotation injury patterns(P > 0.05). Valgus force was the cause of 64.1% of the medial tibia plateau fractures in the present cohort. Furthermore, valgus force produced more Wahlquist type C fractures than varus force. The present findings will help orthopedists understand the injury mechanism of the Wahlquist classification system, and will facilitate the identification of the common features of medial tibial plateau fractures induced by specific injury patterns.