OTA 1999 Posters

Posterolateral Corner Injuries in High-Energy Tibial Plateau Fractures Diagnosed by MRI

Russell T. Nevins, MD; Stephan V. Yacoubian, MD; Hollis G. Potter, MD; J. G. Sallis, MD; Dean G. Lorich, MD, Albert Einstein College of Medicine, Bronx, NY

Purpose: To determine the incidence and significance of posterolateral corner injuries in high-energy tibial plateau fractures evaluated by magnetic resonance imaging.

Methods: Forty-nine (49) consecutive high-energy tibial plateau fractures were evaluated between April 1998- January 1999 by MRI prior to definitive treatment. The MRI was then read by an experienced MRI radiologist. All of these injuries were high-energy in nature by mechanism (pedestrians struck, motor vehicle accidents, or jumpers). Posterolateral corner injury was considered significant when the lateral collateral ligament was damaged in combination with the popliteus tendon, the popliteal muscle tendon junction, or the popliteal-fibular ligament. This injury was considered severe when there was high-grade lateral collateral ligament damage in this complex. In additional, all plain films (anterior-posterior/lateral/oblique) were evaluated for depression and lateral displacement of the fracture fragment. These values were statistically evaluated for any correlation with posterolateral corner injuries found on MRI.

Results: This study revealed that six patients (13%) had severe injury to the posterolateral corner. Additionally, seven patients (15%) had posterolateral corner injury consisting of a partial tear of the lateral collateral ligament in conjunction with an injury to one of the above-described ligaments. Therefore, 28% of all high-energy tibial plateau fractures have positive MRI findings for posterolateral corner damage (P=.025). Statistical analysis also correlated lateral joint depression on plain film with injury to the popliteus muscle tendon junction in all AO and Schatzker classifications (p=.05), as well as popliteus tendon injury in Schatzker II (p=.05). Lateral displacement of the fracture fragment correlated with popliteus muscle tendon junction injury (p=.05).

Discussion: Posterolateral corner injury in this study is defined by lateral collateral ligament damage in combination with the popliteus tendon, the popliteal muscle tendon junction, or the popliteal fibular ligament. Biomechanically, loss of the lateral and posterolateral soft tissue restraints results in increased tensile forces on the lateral side of the knee and subsequently increased compressive forces on the medial aspect of the knee. In this study by MRI criteria, significant posterolateral injury was seen in 28% of all high-energy tibial plateau fractures. This complex of injuries may lead to clinically evident posterolateral corner instability. Although posterolateral corner injury is not routinely evaluated by the traumatologist, we recommend evaluation for posterolateral corner instability immediately following definitive fixation under general anesthesia. Although clinical significance of these MRI findings will not be determined until one-year follow-up, timely knowledge of the injury may enhance patient care. In addition, in high-energy tibial plateau fractures, depression and lateral displacement of the fracture fragment on plain films has a statistical correlation to MRI-observed injuries with the posterolateral corner.

Conclusion: There is a significant incidence of acute posterolateral corner injuries in high-energy tibial plateau fractures diagnosed by MRI. Although there are no prospective studies available on the natural history of posterolateral complex injuries, awareness that this injury pattern exists in tibial plateau fractures is necessary and further clinical follow-up is indicated.