A Distinct Posterior Cruciate Ligament Avulsion Fracture Involving the Weight-bearing Lateral Tibial Plateau as a Single Fragment: A Case Report.

Posterior cruciate ligament (PCL) avulsion fractures usually involve the tibial insertion as a discrete fragment. Although combined PCL avulsion and tibial plateau fractures have been described, a continuous fracture fragment involving both the PCL insertion and the weight-bearing lateral tibial plateau is rarely reported and may require different treatment considerations. We report a woman, aged 38 years, with a neglected PCL avulsion fracture involving the weight-bearing region of the lateral tibial plateau as a single, continuous fragment. This morphology created a specific surgical dilemma because reduction of the PCL avulsion component directly influenced articular congruity. Arthroscopic reduction and fixation were performed to allow direct evaluation of the joint surface while securing the PCL insertion in a balanced position. The fracture achieved radiographic union by 3 months. Computed tomography at 6 months demonstrated a smooth, well-aligned articular surface with maintained congruity of the lateral tibial plateau. At 2-year follow-up, plain radiographs showed maintained reduction and articular alignment without loss of congruity after elective Kirschner-wire removal. The patient had good functional recovery (Knee injury and Osteoarthritis Outcome Score, 93), with no symptomatic posterior instability and only grade 1+ posterior drawer laxity on examination. This case describes a distinct PCL avulsion fracture pattern that differs from both conventional PCL avulsion fractures and typical tibial plateau fractures. Recognition of this morphology is important because it may alter reduction priorities and fixation strategy.