Potential problem and solution of lateral plate postposition for the posterolateral tibial plateau fracture

Background There has been controversial for the treatment of the posterolateral tibial plateau fractures (PTPF). This study aimed to evaluate clinic outcomes of the lateral locking compression plate (LCP) postposition, analyze the feasibility of LCP postposition through anatomical measurement, and address the potential problems of LCP postposition through the biomechanical assessment. Methods 39 patients with PTPF undergoing LCP fixation between June 2019 and June 2022 were retrospectively evaluated. All cases were divided into two group: Group A (15 cases) employed plate transverse arm postpositioning with posterolateral (PL) fracture fixation using two raft screws, while Group B (24 cases) utilized non-postpositioning with fixation by a single raft screw. Surgical duration, intraoperative blood loss, the change of lateral tibial plateau angle (LTPA), lateral tibial plateau posterior slope angle (LPSA) and fracture collapse between immediate postoperative and last follow up, range of motion (ROM), HSS knee score, and Lysholm knee score were recorded. CT measurements of the fibular head superior space and LCP transverse arm were taken in 50 healthy adult knees to assess postposition feasibility. Finally, three fracture models were established using finite element analysis: Model A with plate postposition and PL split fracture fixed by two raft screws of transverse arm, Model B with plate non-postposition and PL split fracture fixed by one raft screw, and Model C with plate non-postposition and PL split fracture fixed by one raft screw and anterior–posterior tension screws. Loadings of 250N, 500N, and 750N were applied for the analysis of the displacement degree, von Mises stress distribution. Results Results indicate comparable operative duration and intraoperative hemorrhage between groups. Complications were minimal in both groups. Group A demonstrated superior outcomes in terms of radiographic parameters, functional scores, and fracture collapse prevention. CT measurements revealed compatibility in 72% of healthy knees with the postpositioning technique. Finite element analysis indicated favorable biomechanical stability. Conclusion Not all patients with PTPF were applicable to the management of the plate postposition and two raft screws fixation, even though this technique exerted good biomechanical stability and achieved satisfactory clinic outcomes. When the PL fracture was fixed by only raft screw through LCP owing to various reasons, two anterior–posterior tension screws might be necessitated to maintain the fracture stability.