Fracture morphological characteristics and associated soft-tissue injuries in flexion varus tibial plateau fractures

Aims: Flexion varus tibial plateau fracture (FVTPF) is associated with a substantial reoperation rate and poor outcomes. This study aims to clarify its fracture characteristics, investigate concomitant ligament and meniscus injuries, and explore correlations between fracture morphology and soft-tissue involvement. Methods: FVTPF patients with available CT and MRI data were included. Fracture mapping was used to present the fracture line and depression area in a spatial manner. Fracture morphological parameters were measured on CT, and ligament and meniscus injuries were assessed on MRI. Association between fracture morphological parameters and ligament/meniscus injuries was analyzed. Receiver operating characteristic (ROC) analysis was adopted to determine the reliable fracture parameter for diagnosing lateral meniscus (LM) entrapment. Results: There were 108 patients who met the inclusion criteria. The medial fragment of FVTPF exhibited various morphological patterns, with the posterolateral depression area representing a mean 16.7% (SD 7.0) of the entire plateau. FVTPF cases with comminuted medial fragments were associated with greater lateral plateau widening, maximal depression depth, and medial plateau displacement (p < 0.001, respectively). The rate of anterior cruciate ligament (ACL) avulsion fractures was 85.2% (92 patients). The rate of overall LM injuries was 54.6% (59 patients), which was significantly higher in FVTPF cases with comminuted medial fragments (80.0% (24 patients), p = 0.001). ROC analysis revealed that maximal depression depth was a favourable predictor for LM entrapment, with a cut-off point of 18.4 mm (sensitivity 88.9%; specificity 94.4%). Conclusion: FVTPF showed various morphologies of the main medial fragment, with the depression area located in the posterolateral plateau. The ACL avulsion fractures were predominant in FVTPF, followed by LM injuries. FVTPF cases with comminuted medial fragments were associated with a significantly higher rate of LM injuries. Among the bony fracture parameters, maximal depression depth showed a considerable value in predicting LM entrapment.