Tibial Plateau Fracture Imaging (Show All)

Overview

Although tibial plateau fracture was originally termed a bumper or fender fracture, only 25% of tibial plateau fractures result from impact with automobile bumpers. The most common mechanism of injury involves axial loading, such as results from a fall. Other patterns of injury result from laterally directed forces or from a twisting injury. In all cases, force is directed from the femoral condyles onto the medial and lateral portions of the tibial plateau, resulting in fracture. In younger patients, the most common pattern of fracture is splitting, while in older, more osteoporotic patients, depression fractures typically are sustained.
Examples of tibial plateau fractures are provided in the images below:
Tibial plateau fractures. Line drawings of Schatzker types I, II, and III tibial plateau fractures. Type I consists of a wedge fracture of the lateral tibial plateau, produced by low-force injuries. Type II combines the wedge fracture of the lateral plateau with depression of the lateral plateau. Type III fractures are classified as those with depression of the lateral plateau but no associated wedge fracture. Tibial plateau fractures. Line drawings of Schatzker types IV, V, and VI tibial plateau fractures. Type IV is similar to type I fracture, except that it involves the medial tibial plateau as opposed to the lateral plateau. Greater force is required to produce this type of injury. Type V fractures are termed bicondylar and demonstrate wedge fractures of both the medial and lateral tibial plateaus. Finally, type VI fractures consist of a type V fracture along with a fracture of the underlying diaphysis and/or metaphysis. Tibial plateau fractures. CT image through the tibial plateau shows a fracture of the posterior aspect of the lateral tibial plateau, which is the source of the lipohemarthrosis. Tibial plateau fractures. MRI of the knee in a patient with tibial plateau fracture and lipohemarthrosis. Three layers of effusion are demonstrated on this proton density sequence: fat, red blood cells, and serum. Low-signal intensity in the tibial plateau corresponds to the site of fracture. Tibial plateau fractures. Radiograph of the knee shows lateral plateau splitting, a Schatzker I injury. There is no articular depression. Soft tissue injuries (eg, to cruciate and collateral ligaments) occur in approximately 10% of patients. In particular, medial plateau injuries may result in fracture of the fibular head, which may injure the peroneal nerve or may be associated with popliteal artery occlusion. Patients may present with a knee effusion, pain, and joint stiffness. Finally, although severe fractures often are repaired surgically, both operatively and nonoperatively treated fractures are at risk of developing posttraumatic osteoarthritis as a result of ligamentous injuries with resultant instability as well as articular discongruities, biomechanical alteration of normal compressive forces, and cartilage damage.

Preferred examination

The preferred examination consists of radiographs in multiple obliquities of the knee. Typically, these include anteroposterior (AP), cross-table lateral, patellar (sunrise), and, possibly, oblique views. Cross-table lateral and AP may be the only views possible in the trauma suite. In this setting, the cross-table lateral radiograph may be the most important to detect occult fractures. The presence of these subtle fractures may be inferred by the presence of a lipohemarthrosis on the cross-table lateral radiograph, indicating disruption of an articular surface, most often the tibia. The images below demonstrate the radiographic, computed tomography (CT), and magnetic resonance imaging (MRI) appearance of lipohemarthrosis.
Tibial plateau fractures. Cross-table lateral radiograph of the knee shows the lipohemarthrosis within the suprapatellar bursa. The fracture itself is not seen well. Tibial plateau fractures. CT image through the tibial plateau shows a fracture of the posterior aspect of the lateral tibial plateau, which is the source of the lipohemarthrosis. Tibial plateau fractures. Axial CT image through the knee shows a layering lipohemarthrosis. Tibial plateau fractures. MRI of the knee in a patient with tibial plateau fracture and lipohemarthrosis. Three layers of effusion are demonstrated on this proton density sequence: fat, red blood cells, and serum. Low-signal intensity in the tibial plateau corresponds to the site of fracture. CT is used by most orthopedists to further characterize fractures of the tibial plateau and assess the depression of the tibia and the degree of diastasis (splitting) of the fractured parts to plan for surgical intervention. Generally, slice thickness should be minimized (1 mm is ideal) and high milliamperage-second (mAs) technique used.^{[1, 2, 3]}
MRI may be used as well for this determination but often is not readily available. MRI is excellent for depicting ligamentous and meniscal injuries.
Arteriography (and possibly MR angiography) may be used if popliteal artery injury is suspected.^[4]

Limitations of techniques

Nondepressed tibial plateau fractures occasionally are difficult to appreciate with standard radiographs. Cross-table lateral radiographs may demonstrate a lipohemarthrosis within the joint, with layering of bone marrow fat upon blood. If lipohemarthrosis is present, an intra-articular fracture is present and must be located. In this situation, axial CT is an excellent tool for defining fracture anatomy using reconstructed images in the sagittal and coronal planes.

Recent studies

Brunner et al found that CT scanning improved the interobserver and intraobserver reliability of the Schatzker, OTA/AO, and Hohl classification systems for tibial plateau fractures. The 3 systems showed moderate interobserver reliability and good and moderate intraobserver reliability when based only on findings on plain radiographs. Interobserver and intraobserver reliability improved significantly when CT was added.^[5]
According to Mustonen et al, although postoperative multidetector-row CT (MDCT) scanning of tibial plateau fractures is performed infrequently, it can in most cases reveal clinically significant information. In their study, the main indications for MDCT were assessment and follow-up of the joint articular surface and evaluation of fracture healing. Postoperative MDCT revealed additional clinically important information in 81% of patients, and 39% underwent reoperation. Orthopedic hardware caused no diagnostic problems with MDCT.^[6]

Radiography

Many methods have been developed to classify tibial plateau fractures. The best known method is the Schatzker system, as depicted in the images below:
Tibial plateau fractures. Line drawings of Schatzker types I, II, and III tibial plateau fractures. Type I consists of a wedge fracture of the lateral tibial plateau, produced by low-force injuries. Type II combines the wedge fracture of the lateral plateau with depression of the lateral plateau. Type III fractures are classified as those with depression of the lateral plateau but no associated wedge fracture. Tibial plateau fractures. Line drawings of Schatzker types IV, V, and VI tibial plateau fractures. Type IV is similar to type I fracture, except that it involves the medial tibial plateau as opposed to the lateral plateau. Greater force is required to produce this type of injury. Type V fractures are termed bicondylar and demonstrate wedge fractures of both the medial and lateral tibial plateaus. Finally, type VI fractures consist of a type V fracture along with a fracture of the underlying diaphysis and/or metaphysis. Type I fractures (demonstrated in image below) are split fractures of the lateral tibial plateau, usually in younger patients. No depression is seen at the articular surface.
Tibial plateau fractures. Radiograph of the knee shows lateral plateau splitting, a Schatzker I injury. There is no articular depression. Type II fractures (shown in images below) are split fractures with depression of the lateral articular surface and typically are seen in older patients with osteoporosis.
Tibial plateau fractures. Radiograph of the knee shows a fracture through the lateral tibial plateau with extension to the lateral tibial margin and slight depression at the articular surface. This is a Schatzker II injury. Tibial plateau fractures. A different patient illustrates a Schatzker II injury with subtle lateral articular depression. Tibial plateau fractures. Axial CT image through the tibial shows a fracture through the lateral tibial plateau with slight diastasis between the fragments. This is a Schatzker II injury. Tibial plateau fractures. Axial CT image of the same patient as in the previous image shows the extent of the lateral tibial plateau fracture. In this case, it extends to the lateral tibial margin and an associated fibular head fracture is seen. This is a Schatzker II injury. Type III fractures (shown in image below) are characterized by depression of the lateral tibial plateau, without splitting through the articular surface.
Tibial plateau fractures. Oblique radiograph of the knee demonstrates a fracture of the lateral tibial plateau with slight depression. There is no associated wedge component. This is a Schatzker III injury. Type IV fractures involve the medial tibial plateau and may be split fractures with or without depression.
Type V fractures are characterized by split fractures through both the medial and lateral tibial plateaus.
Type VI fractures (demonstrated in the images below) are the result of severe stress and result in dissociation of the tibial plateau region from the underlying diaphysis.
Tibial plateau fractures. Radiograph of the knee reveals fractures through both the medial and the lateral tibial plateau along with a fibular head fracture and a fracture through the tibial metaphysis. This is a Schatzker VI injury. Tibial plateau fractures. Radiograph of the knee shows a different Schatzker VI fracture. Tibial plateau fractures. Coronal reformatted CT. This image demonstrates a bicondylar fracture of the tibial plateau along with a fracture of the tibial diaphysis, a Schatzker VI fracture. Note the articular incongruity.

Degree of confidence

Most fractures of the tibial plateau are diagnosed readily by conventional radiography.

False positives/negatives

A false-negative radiograph may be encountered on the rare occasions in which a fracture is present but only a lipohemarthrosis is visualized. In these patients, CT or MRI is required to visualize the fracture.

Computed Tomography

In most patients, CT scanning mimics the findings of conventional radiography. With reconstruction of the axial images into coronal and sagittal planes, precise localization of surgical landmarks, as well all fracture fragments, is obtained. CT is critical in formulating a surgical plan for Schatzker type IV, V, and VI fractures.^[7]
Although, as previously mentioned, most fractures of the tibial plateau are diagnosed readily by conventional radiography, CT often is used to confirm the anatomic relationship of fracture fragments with more complex fractures. This is especially true at the articular surface of the tibia, where precise 3-dimensional anatomy is critical to the success of surgical repair. Less comminuted and depressed fractures may not require imaging by CT.
The value of CT is in the speed and availability of the technique. In addition, most patients with extensive injuries also undergo CT of other portions of the body in the trauma setting. With current scanners, image thickness of 1 mm or less is possible, which generally yields unequivocal depiction of fracture patterns. However, for a full depiction of soft tissue injury, such as ligaments and menisci, MRI is superior.

False positives/negatives

CT generally is able to depict all fractures. False-negative errors can occur when only axial imaging is used. If a fracture predominates in the axial plane, it may be overlooked by CT. However, in most instances, sagittal and coronal reconstructions of axial data, as shown in the images below, are used to avoid this problem. By reconstructing the initial data set into different planes, additional information such as articular depression and diastasis may be obtained easily. False positives are not common with CT.
Tibial plateau fractures. Coronal reformatted CT. Initial narrow collimation axial CT data can be reconstructed into sagittal and coronal planes. This technique is useful to evaluate for fracture lines parallel to the axial imaging plane, degree of articular depression, and degree of diastasis between major fracture fragments. The best reconstructions are made when the initial data set consists of axial images of less than 2 mm thickness. In this particular case, an axial data set of 1 mm images was reconstructed into this coronal image demonstrating fractures of the tibial spines. Tibial plateau fractures. Coronal reformatted CT. This image demonstrates a bicondylar fracture of the tibial plateau along with a fracture of the tibial diaphysis, a Schatzker VI fracture. Note the articular incongruity.

Magnetic Resonance Imaging

The role of MRI in the acute management of tibial plateau fractures is under investigation. A study by Kode et al investigated the usefulness of CT and MRI in visualizing fracture patterns.^[8] MRI was superior to CT unless the fracture was extremely comminuted. Meniscal injuries, as well as injuries to the collateral and cruciate ligaments, are depicted better with MRI than with CT. (See the image below.)^[9]
Tibial plateau fractures. MRI of the knee in a patient with tibial plateau fracture and lipohemarthrosis. Three layers of effusion are demonstrated on this proton density sequence: fat, red blood cells, and serum. Low-signal intensity in the tibial plateau corresponds to the site of fracture.

Degree of confidence

MRI is very sensitive to the presence of osseous injury. Injuries to osseous structures manifest as areas of edema within bone marrow. However, fractures through the cortex are less well depicted, as cortical bone appears as an area of low signal (generally black) on MRI sequences. Thus, fractures through cortical bone can be difficult to depict with MRI. Complex and comminuted fractures with multiple cortical fragments are exceedingly difficult to analyze with MRI.

False positives/negatives

False negatives with MRI are uncommon. MRI is used routinely for the detection of occult fracture because of its superior depiction of bone marrow edema, a direct indicator of osseous injury. False-negative information may result when MRI data is analyzed for the presence of cortical fractures. False-negative and false-positive errors may occur if the incorrect MRI sequences are chosen. In general, a fluid sensitive sequence, such as short tau inversion recovery, rather than a simple T2-weighted sequence, is best to detect bone marrow edema.

Nuclear Imaging

Nuclear medicine studies are not used in the diagnosis of tibial plateau fractures, unless a stress-type fracture is suspected or there is concern that osteomyelitis exists.

Angiography

Type IV fractures involving the medial tibial plateau raise concern that the popliteal artery has been injured. These arterial injuries can be clinically silent or present with decreased peripheral pulses.
If clinical concern exists that a popliteal artery injury has occurred with any fracture type, obtain an arteriogram (or possibly an MR angiogram). Surgical manipulation of the tissues surrounding an injured popliteal artery can result in thrombosis, with dire consequences unless the thrombosis is addressed immediately.
However, angiography is not used for the primary detection of tibial plateau fractures