Split-depression fractures of the lateral tibial plateau (Schatzker II) are associated with a significant risk of capsuloligamentous and meniscal injury. We hypothesized that the amount of fracture depression and widening on anteroposterior (AP) plain radiographs would correlate with the incidence of injury to these structures on magnetic resonance imaging (MRI).

Sixty-two consecutive patients with Schatzker II tibial plateau fractures had a knee x-ray series and MRI preoperatively. AP plain radiographs were measured for lateral joint line depression and condylar widening, and MRIs were evaluated for injury to soft-tissue structures around the knee. For each structure, the threshold of depression and widening that led to the greatest disparity in soft-tissue injury was determined. Multiple logistic regressions were applied to calculate whether depression and/or widening above the thresholds were predictive for injury to individual soft-tissue structures.

When depression was greater than 6 mm and widening was greater than 5 mm, lateral meniscal injury occurred in 83% of fractures, compared with 50% of fractures with less displacement (p < 0.05). When either depression or widening was at least 8 mm, medial meniscal injury occurred more frequently (depression 53%, p < 0.05; widening 78%, p < 0.05; versus neither 15%). Lateral collateral ligament and posterior cruciate ligament tears were not seen with minimally displaced fractures (< 4 mm), but the incidence of injury approached 30% with increasing displacement.

Due to the limited availability of MRI in some centers, correlation of lateral condylar depression and widening, as measured on plain radiographs, to injury of various soft-tissue structures may be extremely helpful in planning open or arthroscopic treatment methods. Using these guidelines, Schatzker II fractures with depression or widening approaching 5 mm deserve heightened vigilance in diagnosing and treating these concomitant soft-tissue injuries.