A 2018 systematic review found at least 38 different classification systems to describe TPFs. Schatzker's classification is the most frequently used classification system (Figure 2). This system groups TPFs into six groups based on common fracture patterns.
Schatzker I fractures occur when the lateral femoral condyle is driven into the lateral tibial plateau. The lateral tibial condyle is fractured into a wedge-shaped fragment that is displaced distally and inferiorly. This is a high-energy fracture pattern that tends to occur in a relatively younger population.
The lateral femoral condyle is again split with a wedge displaced distally and inferiorly in a Schatzker II, but in this pattern, there is depression or comminution of the remaining lateral tibial plateau articular surface. Schatzker II fractures are most common in high-energy injury events, but lower energy events in the setting of osteoporosis are also associated with the articular depression seen in this pattern.[1,17]
Schatzker III fractures are characterized by pure central depression of the lateral tibial plateau into the lateral tibial condyle with an intact tibial cortex and no split fracture. This fracture pattern is exceedingly rare, is strongly associated with osteoporosis, and most commonly occurs in low-energy events such as slips or falls.[17,18]
Schatzker IV patterns describe fractures of the medial tibial condyle and can be divided into two subtypes. The first subtype involves a fracture of the medial condyle with a split-off wedge, comparable to Schatzker I on the lateral condyle. Given the relatively high BMD of the medial plateau, this injury subtype more commonly occurs in younger populations in the setting of high-energy events. The second subtype of Schatzker IV fractures are characterized by depression or comminution of the medial tibial plateau, most often seen in the setting of poor bone quality. The high-energy subtype fracture-dislocation mechanism of injury associated with Schatzker IV injuries in younger patient populations is associated with significant risk of damage to the popliteal artery or peroneal nerve, and the presence of this pattern should alert the clinician to this increased risk. Compared with Schatzker I to III fractures, type IV fracture patterns are associated with high rates of posttraumatic osteoarthritis and delayed improvement in patient-reported functional outcomes.[20,21]
Schatzker types V and VI are bicondylar TPFs that typically are seen in high-energy events. In both types, both medial and lateral plateaus are involved. The distinguishing feature is that in a type V, the metaphysis-diaphysis connection remains, whereas in a type VI there is complete dissociation of the metaphysis from the diaphysis. Type VI fractures occur more commonly than type V.
The Hohl and Moore classification system defines fracture-dislocations of the knee that are not easily classified by the Schatzker classification. This system emphasizes injury patterns that are associated with soft-tissue injuries of the ligaments and capsule. Recognition of these fracture patterns on radiograph alerts the clinician to evaluate the knee thoroughly for the presence of ligamentous and neurovascular injury. This classification system is divided into five types, with type I being associated with the lowest rates of knee instability and neurovascular injury and type V associated with the highest rates of instability and neurovascular injury.
Type I patterns (the coronal split pattern) occur in the medial plateau with distal displacement of a fragment that is typically uncomminuted. When not displaced, this pattern is difficult to appreciate on anteroposterior radiographs because of the fracture line being in the coronal plane. This pattern is associated with relatively lower rates of soft-tissue injury, although avulsion fractures of the fibular styloid and anterior spine are common.
Type II patterns occur in either the medial or the lateral condyle, with a fracture line in the sagittal plane involving the entire condyle with avulsion of part or all the median eminence. This avulsion is functionally equivalent to a rupture of the cruciate ligaments.
Type III patterns describe avulsion of the lateral rim. Avulsion of the fibular styloid and tibial spines is also seen in this pattern. Occult ligament ruptures should be suspected in this injury.
Type IV patterns involve compression of either the medial or lateral rim in contrast to the avulsion seen in type III patterns. These injuries are associated with high rates of ligamentous injury of the opposite condyle; for example, a compression fracture of the lateral condylar rim should raise a high index of suspicion for injury to the medial collateral ligament.
Type V patterns are characterized by separation of the median eminence from the condyles as well as the tibial shaft. Up to half of injuries in this pattern are associated with neurovascular injury.
The AO/OTA classification system is another commonly used classification system. This system uses a schematic organized by bone, location along bone (proximal, middle, or distal third), articular involvement, and fracture pattern. As an example, a split lateral TPF occurs at the proximal end of the tibia and in this classification is labeled a 41B1.1 fracture. The 4 corresponds to the tibia, the initial 1 corresponds to proximal end of the tibia, B corresponds to partial articular involvement, the second 1 corresponds to split fracture, and the third 1 describes the location along the lateral plateau. In this system, unicondylar TPFs are often described only using 41B, without the trailing descriptors. This description offers enough detail of a fracture pattern without the reduced intraobserver and interobserver reliability associated with more complex descriptors.
The Schatzker and AO/OTA are the most widely used classification methods and demonstrate moderate interobserver reliability.[16,25,26] However, there is limited evidence to support any use of these classifications beyond a general description of fractures because there is a high level of interobserver variation in fracture classification and the treatment plan that follows.[16,24,27] A major limitation of these classification systems is that they rely only on anteroposterior radiographs for classification. This has most significant implications for the classification and treatment of fractures of the posterior tibial plateau.[16,28–31] Failure to detect these posterior fragments leads to knee instability and unacceptable functional outcomes. Ligamentous injuries are also frequently seen in the setting of tibial plateau injuries, yet these classification systems do not account for those associations.[16,33–36] The inclusion of CT into the evaluation of TPFs is associated with significantly higher agreement in classification and treatment plans.[37–40] Recent modifications to previous systems and the introduction of new classifications have attempted to incorporate CT into the classification of TPFs.
Kfuri and Schatzker provided an update to the Schatzker classification in 2018 by utilizing CT to provide a third dimension to the classification. They introduced the concept of the virtual equator, a line drawn from the anterior aspect of the fibular collateral ligament across the plateau and exiting medially posteriorly to the superficial medial collateral ligament, to divide the plateau into anterior (A) and posterior (P) quadrants (Figure 3). A lateral split-depression fracture of the tibial plateau that bisects the anterior aspect of the tibial rim is a type II A in this classification, and a comminuted fracture that bisects both the anterior and posterior aspects of the tibial plateau would be a type II A + P.
The "three-column" method of fracture classification is one of the first that was developed with the use of CT as the imaging method of choice.[42,43] It divides the tibial plateau into lateral, medial, and posterior columns (Figure 4). A unicondylar fracture is classified according to the column it occurs in. A fracture that breaks both the anterolateral and posterolateral wall is classified as a two-column fracture. A pure articular depression fracture is defined as a zero-column fracture. The three-column system of classification improves upon the initial radiograph-based systems of classification by more effectively accounting for posterior fractures with a high-level of intraobserver and interobserver agreement.[44,45] A ten-segment classification system developed by Krause et al. takes the CT model of the three-column method further, classifying the tibial plateau into ten segments. The ten-segment model provides more information about specific fracture locations, but there is no evidence that it maintains the same level of interobserver reliability as the three-column classification or improves treatment plans and outcomes.
Curr Orthop Pract. 2022;33(1):85-93. © 2022 Lippincott Williams & Wilkins