The Incidence of Posterolateral Tibial Plateau Fractures in the Setting of Knee Dislocations

Abstract

Background: Acute knee dislocations are devastating injuries that can be challenging for surgeons to treat. The bony integrity of the tibial plateau and the lateral femoral condyle has a fundamental meaning for translational and rotational knee joint stability. Posterolateral tibial plateau depression fractures (PLTPFs) and lateral femoral condyle impaction fractures (LFCIFs) can influence clinical outcomes, but their frequency and characteristics in the setting of acute knee dislocations are unknown.

Purpose: To report the incidence of PLTPFs and LFCIFs in acute knee dislocations as well as to describe concomitant soft tissue lesions associated with these bony injuries.

Study design: Cross-sectional study; Level of evidence, 3.

Methods: In this retrospective multicenter study, acute knee dislocations (at least bicruciate ligament injuries) were identified from hospital information systems based on diagnosis-related group coding as well as operation and procedure classification coding at 5 participating level 1 trauma centers from 2018 to 2022. The knee dislocations were categorized according to the Schenck classification. Soft tissue injuries were assessed on magnetic resonance imaging within 2 weeks of the trauma. PLTPFs and LFCIFs were categorized on magnetic resonance imaging and computed tomography according to the Menzdorf and Bernholt classifications.

Results: A total of 157 knee dislocations were identified, comprising 106 men and 51 women with a mean age of 39.3 ± 15.1 years. A PLTPF was detected in 42 (26.8%) knee dislocations, with the highest frequency in Schenck type III medial dislocations. Of these 42 cases, 26 (61.9%) PLTPFs were rated as high-grade fractures, theoretically requiring reduction and fixation. An LFCIF was found in 31 (19.7%) of the cases.

Conclusion: A PLTPF was observed in one-quarter, and an LFCIF in one-fifth, of acute knee dislocations. They occurred particularly in knee dislocations with medial collateral ligament ruptures. Almost two-thirds of all PLTPFs presented as high-grade fractures according to the Menzdorf or Bernholt classification, potentially requiring a surgical intervention.

Keywords: apple-bite fracture; knee dislocation; lateral femoral notch sign; multiligament injury; posterolateral tibial plateau depression fracture.

Figure 1.

A 26-year-old soccer player with a Schenck type III medial knee dislocation and a Menzdorf type 2b posterolateral tibial plateau depression fracture (PLTPF). (A) On axial T2-weighted magnetic resonance imaging (MRI), the red circle marks the torn medial collateral ligament, and the red “&” marks the torn anterior cruciate ligament and posterior cruciate ligament. (B) On sagittal T2-weighted MRI, the arrowhead marks the lateral femoral condyle impaction fracture (LFCIF), the small arrow marks the lateral meniscus (which is no longer supported by bone), and the large arrow marks the PLTPF. (C) Coronal T2-weighted MRI. (D) Axial, (E) sagittal, and (F) coronal computed tomography. Here, the large arrow marks the PLTPF.

Figure 2.

The same soccer player with a Schenck type III medial knee dislocation and a Menzdorf type 2b posterolateral tibial plateau depression fracture (PLTPF) from Figure 1. Immediately postoperative (A) coronal radiography and (B) sagittal and (C) axial magnetic resonance imaging demonstrating posterior cruciate ligament (PCL) suture augmentation, anterior cruciate ligament (ACL) reconstruction, medial collateral ligament repair, and anatomic arthroscopic reduction and internal fixation of the PLTPF (red circle) using cannulated screws with the jail technique.^,, Stress radiography at 12-month follow-up of (D) the ACL at 30° of flexion and (E) the PCL at 90° of flexion, demonstrating stable ligaments.

Figure 3.

Subgroup analysis of injured and noninjured soft tissue structures in the presence of a posterolateral tibial plateau depression fracture (PLTPF). The asterisk indicates that there was a significant difference between injured and intact soft tissue structures in the presence of a PLTPF. The y-axis shows the number of cases with a PLTPF and an intact or injured soft tissue structure. dMCL, deep medial collateral ligament; LCL, lateral collateral ligament; LM, lateral meniscus; LMAH, lateral meniscus anterior horn; LMB, lateral meniscal body; LMPH, lateral meniscus posterior horn; MCL, medial collateral ligament; MM, medial meniscus; MMAH, medial meniscus anterior horn; MMB, medial meniscal body; MMPH, medial meniscus posterior horn; MPFL, medial patellofemoral ligament; PFL, popliteofibular ligament; PL capsule, posterolateral capsule; PLT, popliteus tendon; POL, posterior oblique ligament; sMCL, superficial medial collateral ligament.

Figure 4.

Subgroup analysis of injured and noninjured soft tissue structures in the presence of a lateral femoral condyle impaction fracture (LFCIF). The asterisk indicates that there was a significant difference between injured and intact soft tissue structures in the presence of an LFCIF. The y-axis shows the number of cases with an LFCIF and an intact or injured soft tissue structure. dMCL, deep medial collateral ligament; LCL, lateral collateral ligament; LM, lateral meniscus; LMAH, lateral meniscus anterior horn; LMB, lateral meniscal body; LMPH, lateral meniscus posterior horn; MCL, medial collateral ligament; MM, medial meniscus; MMAH, medial meniscus anterior horn; MMB, medial meniscal body; MMPH, medial meniscus posterior horn; MPFL, medial patellofemoral ligament; PL capsule, posterolateral capsule; PLT, popliteus tendon; POL, posterior oblique ligament; sMCL, superficial medial collateral ligament.