Tibial Plateau Fracture Imaging
- Author: Amilcare Gentili, MD; Chief Editor: Felix S Chew, MD, MBA, MEd more...
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:
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.
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.
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.[2, 3, 4] 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.[5, 6, 7, 8]
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.
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.
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.
Many methods have been developed to classify tibial plateau fractures. The best known method is the Schatzker system, as depicted in the images below :
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.
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.
Type III fractures (shown in image below) are characterized by depression of the lateral tibial plateau, without splitting through the articular surface.
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.
Degree of confidence
Most fractures of the tibial plateau are diagnosed readily by conventional radiography.
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.
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.
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.[6, 8]
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.
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. 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.)[13, 7, 8]
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 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 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.
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.
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