(Radiographics. 2000;20:S121-S134.)
© RSNA, 2000
Mechanism-based Pattern Approach to Classification of Complex Injuries of the Knee Depicted at MR Imaging1
Curtis W. Hayes, MD,
Monica K. Brigido, MD,
David A. Jamadar, MB and
Tim Propeck, MD
1 From the Department of Radiology, University of Michigan Health System, Taubman Center, Rm 2910A, 1500 E Medical Center Dr, Ann Arbor, MI 48109-0326. Recipient of a Certificate of Merit award for a scientific exhibit at the 1999 RSNA scientific assembly. Received February 10, 2000; revision requested March 16 and received April 25; accepted May 8. Address correspondence to C.W.H. (e-mail: hayescw@umich.edu).
 |
Abstract
|
|---|
Complex knee injuries are common, often resulting from multiple forces: varus, valgus, hyperextension, hyperflexion, internal rotation, external rotation, anterior or posterior translation, and axial load. Certain combinations of forces are known to cause specific injury patterns. After a review of the literature, the authors developed a mechanism-based classification system based on patterns of bone marrow edema and ligament injury for complex knee injuries depicted at magnetic resonance imaging. The classification system takes into account knee position and forces and recognition of patterns of bone injury and complementary soft-tissue injury. Ten mechanism-based injury patterns were recognized: (a) pure hyperextension, (b) hyperextension with varus, (c) hyperextension with valgus, (d) pure valgus, (e) pure varus, (f) flexion with valgus and external rotation, (g) flexion with varus and internal rotation, (h) flexion with posterior tibial translation, (i) patellar dislocation (flexion, valgus, and internal rotation of femur on fixed tibia), and (j) direct trauma. Recognition of these patterns may help assess the full extent of knee injury, particularly at the posterolateral and posteromedial corners of the knee.
Index Terms: Knee, fractures, 45.121411, 45.121415, 45.40 • Knee, injuries, 45.40 • Knee, ligaments, menisci, and cartilage, 45.48 • Knee, MR, 45.121411, 45.121415
|
Introduction
|
|---|
Complex injuries of the knee are common, resulting from accidents or sports mishaps at all levels of competition. These injuries often occur as a result of multiple forces applied to the knee: varus, valgus, hyperextension, hyperflexion, internal rotation, external rotation, anterior or posterior displacement, and axial load. It is widely known that certain forces predictably produce specific individual or combined patterns of injury. Acquisition of a precise history of the mechanism may be difficult, however, as is performance of an accurate physical examination in the setting of acute injury.
Magnetic resonance (MR) imaging is widely used to assess knee injuries more completely. Radiologists are accurate at detecting individual injuries and combinations of injuries. However, little attention has been paid to the use of MR imaging to classify knee injuries into mechanism-based categories. A comprehensive classification system based on mechanisms of injury would be useful because (a) an understanding of the causative mechanism in a given case may improve detection of the complete constellation of injuries and (b) appreciation of the mechanism of injury may help predict both immediate and delayed instability and need for surgery.
In this article, we present a mechanism-based classification system for complex knee injuries. With use of MR imaging patterns of ligamentous, meniscal, and capsular injuries in addition to specific patterns of bone marrow edema, or bone bruising, to infer the causative forces, we found that many complex knee injuries can be categorized on the basis of their specific mechanisms of injury.
First in this article, the pertinent functional anatomy of the knee is briefly reviewed. Then, forces acting on the joint that are typically responsible for knee injuries are listed. The differences between impaction and avulsion bone marrow edema patterns are demonstrated to help categorize the direction of forces responsible for the injury. The classification system is then presented, followed by examples of each pattern.
|
Functional Anatomy
|
|---|
The bones of the knee contribute little to the stability of the joint. Both the static and dynamic stability of the knee are dependent on its supporting soft tissues (1). Menisci, ligaments, tendons, muscles, and fascia all make contributions to knee stability. Dynamically, the supporting structures can be divided by location: anterior, medial, lateral, posterior, and central. The major contributors in each area are demonstrated in Figure 1.
Two areas in the knee are critical for stability: the posteromedial and posterolateral corners. The posteromedial corner consists of the attachments of the semimembranosus tendon, the posterior joint capsule, and the posterior oblique ligament. The posterolateral corner is anatomically complex, consisting of the joint capsule, arcuate ligament, fabellofibular ligament, and popliteus muscle and tendon, with support from adjacent structures. Both the posteromedial and posterolateral corners are major resistors of rotational and translational stresses, particularly in extension. The corners may be thought of as anchors of a sling across the back of the knee; traumatic loss of one corner may allow unstable rotation of the knee joint, with a pivoting out around the other corner. Injury at the posterolateral corner, in particular, may lead to severe disability. Therefore, recognition of injuries to these structures is critical in any MR imaging evaluation of the injured knee.
|
Injury-producing Forces and Resisting Structures
|
|---|
The major forces acting on the knee joint include translation (anterior and posterior), angulation (varus and valgus), rotation (internal and external), hyperextension, axial load, and direct blow. Most knee injuries are the result of two or more forces exerted across either a flexed or extended joint. However, it is still useful to look at pure forces in terms of the structures that are responsible for resistance. Table 1 lists major forces and their primary and secondary resistors.
View this table:
[in this window]
[in a new window]
|
TABLE 1. Forces Responsible for Knee Injuries and Supporting Structures Responsible for Primary and Secondary Resistance to Those Forces
|
|
|
Impaction versus Avulsion Injury Patterns
|
|---|
In general, forces acting on the knee produce an impaction injury at the entry site of the force and a distraction injury, or avulsion, at the opposite, or exit, site of the force. Figure 2 demonstrates a valgus force that produces impaction of the lateral compartment and distraction of the opposite medial compartment. Both types of injuries produce bone marrow edema or frank fractures. However, bone injuries caused by impaction tend to be broad, compared with smaller, more focal areas of bone marrow edema associated with ligament avulsions on the distraction side. Impactions may be further divided into contiguous, "kissing," injuries or noncontiguous injuries, which are produced by the abrupt translation of two bones that occurs after ligamentous rupture. The direction and type of force may be inferred from the patterns of bone marrow edema and soft-tissue injury. Direct blows result in bone contusions and soft-tissue injury at the impaction site only.
View larger version (38K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2. Illustration of impaction bone bruise pattern (dark gray shading in lateral compartment) and avulsion bone bruise pattern (black shading at margins of medial compartment). This pattern is characteristic of a valgus force (large arrow).
|
|
|
Mechanism-based Classification System of Knee Injuries
|
|---|
On the basis of information from the injury patterns to primary and secondary stabilizing structures, plus bone injury patterns, we have classified complex knee injuries into 10 categories, according to the knee position (flexion, extension), direction of force, and presence or absence of rotation (Figure 3): (a) pure hyperextension; (b) hyperextension with varus; (c) hyperextension with valgus; (d) pure valgus; (e) pure varus; (f) flexion with valgus, external rotation; (g) flexion with varus, internal rotation; (h) flexion with posterior tibial translation; (i) patellar dislocation (flexion, valgus, internal rotation of femur on tibia); and (j) direct trauma.
Hyperextension injuries, by virtue of the greater forces exerted on the extended or "locked" knee, produce more pronounced bone injury patterns, often with frank fractures. Severe distraction injuries on the posterior, exit side of the joint are common with this pattern. These injuries are particularly serious in that they involve the critical posteromedial and/or posterolateral corners of the knee.
Flexion injuries, unless combined with significant axial load, tend to show few contiguous impaction bone injuries but have a greater tendency to produce injury due to internal or external rotation. Noncontiguous impaction bone bruises are usually found, as well as smaller avulsion bone bruises. We have observed that flexion injuries with rotation show a greater association with meniscal tears than do hyperextension injuries.
Pure valgus and the rare pure varus categories are characterized by a simple "coup-contrecoup" pattern of impaction bone injuries and opposite-sided distraction ligament injuries.
Dislocation of the patella is typically produced by combined flexion, valgus, and internal rotation of the femur on a fixed tibia. In theory, this is very similar to flexion, valgus, and external rotation (tibia on fixed femur), although we have chosen to separate these two patterns on the basis of their different injury patterns.
Direct trauma is characterized by broad bone contusions located beneath the site of impaction. Typically, there are no injuries on the opposite side of the knee. Direct anterior trauma, which causes patellar and trochlear groove contusions, and lateral or medial blows are most common.
|
Clinical Application
|
|---|
We retrospectively reviewed the MR images in 100 cases of acute knee trauma to determine the ability of our system to help accurate classification of complex knee injuries. In this small sample, 85% of cases could be classified into one of our 10 categories. The pattern of flexion, valgus, and external rotation was most common, accounting for nearly half of all injuries (46%). Next in frequency were the patterns of hyperextension with varus (8%) and flexion with posterior tibial translation (8%), followed by the patterns of pure valgus (6%), patellar dislocation (6%), and direct trauma (5%). As expected, the pattern of pure varus (1%) was rare. Surprisingly, the pattern of flexion, varus, and internal rotation (Segond fracture) was also rare (1%) in this small series. The patterns of pure hyperextension (2%) and hyperextension with valgus (2%) were also uncommon. Common reasons for classification system failure included the presence of insufficient injury, massive injury, or bone marrow edema due to preexisting osteoarthritis.
Examples of the injury categories are presented in Figures 4–13, with details for each pattern in Table 2.
View larger version (140K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4a. Pure hyperextension injury. (a) Axial fast spin-echo (SE), proton-density-weighted, fat-suppressed MR image (repetition time msec/echo time msec = 4,000/15, echo train length of eight) shows impaction type anterior tibial bone bruise (*) and popliteus muscle injury with edema (arrows). (b, c) Sagittal SE proton-density-weighted MR images (1,000/12) show a posterior cruciate ligament (PCL) tear (arrow in b) and posterior capsule disruption (arrow in c).
|
|
View larger version (140K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4b. Pure hyperextension injury. (a) Axial fast spin-echo (SE), proton-density-weighted, fat-suppressed MR image (repetition time msec/echo time msec = 4,000/15, echo train length of eight) shows impaction type anterior tibial bone bruise (*) and popliteus muscle injury with edema (arrows). (b, c) Sagittal SE proton-density-weighted MR images (1,000/12) show a posterior cruciate ligament (PCL) tear (arrow in b) and posterior capsule disruption (arrow in c).
|
|
View larger version (133K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4c. Pure hyperextension injury. (a) Axial fast spin-echo (SE), proton-density-weighted, fat-suppressed MR image (repetition time msec/echo time msec = 4,000/15, echo train length of eight) shows impaction type anterior tibial bone bruise (*) and popliteus muscle injury with edema (arrows). (b, c) Sagittal SE proton-density-weighted MR images (1,000/12) show a posterior cruciate ligament (PCL) tear (arrow in b) and posterior capsule disruption (arrow in c).
|
|
View larger version (163K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5a. Hyperextension with varus injury. (a, b) Axial fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anteromedial femoral condyle impaction bone bruise (* in a) and tibial plateau fracture (* in b) with edema over the posterolateral corner (arrows). (c, d) Sagittal fast SE, proton-density-weighted MR images (1,000/12) show impaction fracture at the anterior femoral condyle (arrow in c) with popliteus tendon tear (arrow in d). (e) Sagittal fast SE, proton-density-weighted, fat-suppressed MR image (3,233/15, echo train length of eight) shows anteromedial bone bruise and posterior capsule tear (arrow). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/17, echo train length of eight) shows a lateral collateral ligament (LCL) tear (arrowhead) with soft-tissue edema laterally.
|
|
View larger version (160K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5b. Hyperextension with varus injury. (a, b) Axial fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anteromedial femoral condyle impaction bone bruise (* in a) and tibial plateau fracture (* in b) with edema over the posterolateral corner (arrows). (c, d) Sagittal fast SE, proton-density-weighted MR images (1,000/12) show impaction fracture at the anterior femoral condyle (arrow in c) with popliteus tendon tear (arrow in d). (e) Sagittal fast SE, proton-density-weighted, fat-suppressed MR image (3,233/15, echo train length of eight) shows anteromedial bone bruise and posterior capsule tear (arrow). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/17, echo train length of eight) shows a lateral collateral ligament (LCL) tear (arrowhead) with soft-tissue edema laterally.
|
|
View larger version (145K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5c. Hyperextension with varus injury. (a, b) Axial fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anteromedial femoral condyle impaction bone bruise (* in a) and tibial plateau fracture (* in b) with edema over the posterolateral corner (arrows). (c, d) Sagittal fast SE, proton-density-weighted MR images (1,000/12) show impaction fracture at the anterior femoral condyle (arrow in c) with popliteus tendon tear (arrow in d). (e) Sagittal fast SE, proton-density-weighted, fat-suppressed MR image (3,233/15, echo train length of eight) shows anteromedial bone bruise and posterior capsule tear (arrow). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/17, echo train length of eight) shows a lateral collateral ligament (LCL) tear (arrowhead) with soft-tissue edema laterally.
|
|
View larger version (148K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5d. Hyperextension with varus injury. (a, b) Axial fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anteromedial femoral condyle impaction bone bruise (* in a) and tibial plateau fracture (* in b) with edema over the posterolateral corner (arrows). (c, d) Sagittal fast SE, proton-density-weighted MR images (1,000/12) show impaction fracture at the anterior femoral condyle (arrow in c) with popliteus tendon tear (arrow in d). (e) Sagittal fast SE, proton-density-weighted, fat-suppressed MR image (3,233/15, echo train length of eight) shows anteromedial bone bruise and posterior capsule tear (arrow). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/17, echo train length of eight) shows a lateral collateral ligament (LCL) tear (arrowhead) with soft-tissue edema laterally.
|
|
View larger version (156K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5e. Hyperextension with varus injury. (a, b) Axial fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anteromedial femoral condyle impaction bone bruise (* in a) and tibial plateau fracture (* in b) with edema over the posterolateral corner (arrows). (c, d) Sagittal fast SE, proton-density-weighted MR images (1,000/12) show impaction fracture at the anterior femoral condyle (arrow in c) with popliteus tendon tear (arrow in d). (e) Sagittal fast SE, proton-density-weighted, fat-suppressed MR image (3,233/15, echo train length of eight) shows anteromedial bone bruise and posterior capsule tear (arrow). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/17, echo train length of eight) shows a lateral collateral ligament (LCL) tear (arrowhead) with soft-tissue edema laterally.
|
|
View larger version (163K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5f. Hyperextension with varus injury. (a, b) Axial fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anteromedial femoral condyle impaction bone bruise (* in a) and tibial plateau fracture (* in b) with edema over the posterolateral corner (arrows). (c, d) Sagittal fast SE, proton-density-weighted MR images (1,000/12) show impaction fracture at the anterior femoral condyle (arrow in c) with popliteus tendon tear (arrow in d). (e) Sagittal fast SE, proton-density-weighted, fat-suppressed MR image (3,233/15, echo train length of eight) shows anteromedial bone bruise and posterior capsule tear (arrow). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/17, echo train length of eight) shows a lateral collateral ligament (LCL) tear (arrowhead) with soft-tissue edema laterally.
|
|
View larger version (142K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6a. Hyperextension with valgus injury. (a) Axial fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows impaction type anterolateral tibial plateau bone bruise (*) with edema over the posteromedial corner (arrowhead). (b-e) Serial sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anterolateral bone bruise (* in b), capsule disruption (arrow in c), PCL tear (arrow in d), and small avulsion type posteromedial tibial plateau bone bruise (* in e) with meniscotibial ligament tear (arrow in e). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows lateral bone bruises with grade II medial collateral ligament (MCL) injury (arrowhead).
|
|
View larger version (147K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6b. Hyperextension with valgus injury. (a) Axial fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows impaction type anterolateral tibial plateau bone bruise (*) with edema over the posteromedial corner (arrowhead). (b-e) Serial sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anterolateral bone bruise (* in b), capsule disruption (arrow in c), PCL tear (arrow in d), and small avulsion type posteromedial tibial plateau bone bruise (* in e) with meniscotibial ligament tear (arrow in e). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows lateral bone bruises with grade II medial collateral ligament (MCL) injury (arrowhead).
|
|
View larger version (150K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6c. Hyperextension with valgus injury. (a) Axial fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows impaction type anterolateral tibial plateau bone bruise (*) with edema over the posteromedial corner (arrowhead). (b-e) Serial sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anterolateral bone bruise (* in b), capsule disruption (arrow in c), PCL tear (arrow in d), and small avulsion type posteromedial tibial plateau bone bruise (* in e) with meniscotibial ligament tear (arrow in e). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows lateral bone bruises with grade II medial collateral ligament (MCL) injury (arrowhead).
|
|
View larger version (149K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6d. Hyperextension with valgus injury. (a) Axial fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows impaction type anterolateral tibial plateau bone bruise (*) with edema over the posteromedial corner (arrowhead). (b-e) Serial sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anterolateral bone bruise (* in b), capsule disruption (arrow in c), PCL tear (arrow in d), and small avulsion type posteromedial tibial plateau bone bruise (* in e) with meniscotibial ligament tear (arrow in e). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows lateral bone bruises with grade II medial collateral ligament (MCL) injury (arrowhead).
|
|
View larger version (141K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6e. Hyperextension with valgus injury. (a) Axial fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows impaction type anterolateral tibial plateau bone bruise (*) with edema over the posteromedial corner (arrowhead). (b-e) Serial sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anterolateral bone bruise (* in b), capsule disruption (arrow in c), PCL tear (arrow in d), and small avulsion type posteromedial tibial plateau bone bruise (* in e) with meniscotibial ligament tear (arrow in e). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows lateral bone bruises with grade II medial collateral ligament (MCL) injury (arrowhead).
|
|
View larger version (152K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6f. Hyperextension with valgus injury. (a) Axial fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows impaction type anterolateral tibial plateau bone bruise (*) with edema over the posteromedial corner (arrowhead). (b-e) Serial sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show anterolateral bone bruise (* in b), capsule disruption (arrow in c), PCL tear (arrow in d), and small avulsion type posteromedial tibial plateau bone bruise (* in e) with meniscotibial ligament tear (arrow in e). (f) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows lateral bone bruises with grade II medial collateral ligament (MCL) injury (arrowhead).
|
|
View larger version (180K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 7a. Pure valgus injury. (a) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows impaction type lateral tibial plateau bone bruise (*) and distraction type grade II MCL injury (arrow). (b) Sagittal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) in this case shows the anterior cruciate ligament (ACL) and PCL to be intact, indicating an injury of mild to moderate severity.
|
|
View larger version (176K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 7b. Pure valgus injury. (a) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows impaction type lateral tibial plateau bone bruise (*) and distraction type grade II MCL injury (arrow). (b) Sagittal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) in this case shows the anterior cruciate ligament (ACL) and PCL to be intact, indicating an injury of mild to moderate severity.
|
|
View larger version (179K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8a. Pure varus injury. Coronal fast SE proton-density-weighted (2,750/30) (a) and T2-weighted (2,750/90) (b) MR images show distraction type iliotibial band injury with irregularity and edema within the adjacent soft tissue (arrow).
|
|
View larger version (187K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8b. Pure varus injury. Coronal fast SE proton-density-weighted (2,750/30) (a) and T2-weighted (2,750/90) (b) MR images show distraction type iliotibial band injury with irregularity and edema within the adjacent soft tissue (arrow).
|
|
View larger version (143K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9a. Flexion with valgus and external rotation injury. (a, b) Sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show the typical combination of noncontiguous posterolateral tibia and lateral femoral condyle bone bruises (* in a) that result from ACL tear (arrow in b) and anterior translation of the tibia. (c) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows tibia bone bruise (*) and grade III MCL tear (arrow). (d, e) In an additional case, fast SE, proton-density-weighted, fat-suppressed MR images (4,000/1517, echo train length of eight) show broad impaction pattern bone bruise in the lateral condyle (large *) and smaller, less specific bruises in the posterolateral and posteromedial tibial plateau and far medial aspect of the medial femoral condyle (small *). Some authors attribute the medial bruises to lesser impactions (contrecoup), whereas others believe they represent avulsion injuries at the MCL and meniscofemoral and meniscotibial ligament attachments. Note the incomplete MCL injury (arrow in d).
|
|
View larger version (154K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9b. Flexion with valgus and external rotation injury. (a, b) Sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show the typical combination of noncontiguous posterolateral tibia and lateral femoral condyle bone bruises (* in a) that result from ACL tear (arrow in b) and anterior translation of the tibia. (c) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows tibia bone bruise (*) and grade III MCL tear (arrow). (d, e) In an additional case, fast SE, proton-density-weighted, fat-suppressed MR images (4,000/1517, echo train length of eight) show broad impaction pattern bone bruise in the lateral condyle (large *) and smaller, less specific bruises in the posterolateral and posteromedial tibial plateau and far medial aspect of the medial femoral condyle (small *). Some authors attribute the medial bruises to lesser impactions (contrecoup), whereas others believe they represent avulsion injuries at the MCL and meniscofemoral and meniscotibial ligament attachments. Note the incomplete MCL injury (arrow in d).
|
|
View larger version (157K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9c. Flexion with valgus and external rotation injury. (a, b) Sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show the typical combination of noncontiguous posterolateral tibia and lateral femoral condyle bone bruises (* in a) that result from ACL tear (arrow in b) and anterior translation of the tibia. (c) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows tibia bone bruise (*) and grade III MCL tear (arrow). (d, e) In an additional case, fast SE, proton-density-weighted, fat-suppressed MR images (4,000/1517, echo train length of eight) show broad impaction pattern bone bruise in the lateral condyle (large *) and smaller, less specific bruises in the posterolateral and posteromedial tibial plateau and far medial aspect of the medial femoral condyle (small *). Some authors attribute the medial bruises to lesser impactions (contrecoup), whereas others believe they represent avulsion injuries at the MCL and meniscofemoral and meniscotibial ligament attachments. Note the incomplete MCL injury (arrow in d).
|
|
View larger version (184K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9d. Flexion with valgus and external rotation injury. (a, b) Sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show the typical combination of noncontiguous posterolateral tibia and lateral femoral condyle bone bruises (* in a) that result from ACL tear (arrow in b) and anterior translation of the tibia. (c) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows tibia bone bruise (*) and grade III MCL tear (arrow). (d, e) In an additional case, fast SE, proton-density-weighted, fat-suppressed MR images (4,000/1517, echo train length of eight) show broad impaction pattern bone bruise in the lateral condyle (large *) and smaller, less specific bruises in the posterolateral and posteromedial tibial plateau and far medial aspect of the medial femoral condyle (small *). Some authors attribute the medial bruises to lesser impactions (contrecoup), whereas others believe they represent avulsion injuries at the MCL and meniscofemoral and meniscotibial ligament attachments. Note the incomplete MCL injury (arrow in d).
|
|
View larger version (178K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9e. Flexion with valgus and external rotation injury. (a, b) Sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show the typical combination of noncontiguous posterolateral tibia and lateral femoral condyle bone bruises (* in a) that result from ACL tear (arrow in b) and anterior translation of the tibia. (c) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows tibia bone bruise (*) and grade III MCL tear (arrow). (d, e) In an additional case, fast SE, proton-density-weighted, fat-suppressed MR images (4,000/1517, echo train length of eight) show broad impaction pattern bone bruise in the lateral condyle (large *) and smaller, less specific bruises in the posterolateral and posteromedial tibial plateau and far medial aspect of the medial femoral condyle (small *). Some authors attribute the medial bruises to lesser impactions (contrecoup), whereas others believe they represent avulsion injuries at the MCL and meniscofemoral and meniscotibial ligament attachments. Note the incomplete MCL injury (arrow in d).
|
|
View larger version (148K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 10a. Flexion with varus and internal rotation injury. (a, b) Sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show typical posterolateral tibial plateau and noncontiguous lateral femoral condyle bone bruises (* in a) with ACL tear (solid arrow in b) and posterior capsule disruption (open arrow in b). (c) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows small cortical avulsion fracture at the lateral tibial rim (Segond fracture, arrow) with a small amount of focal subcortical edema (*).
|
|
View larger version (152K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 10b. Flexion with varus and internal rotation injury. (a, b) Sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show typical posterolateral tibial plateau and noncontiguous lateral femoral condyle bone bruises (* in a) with ACL tear (solid arrow in b) and posterior capsule disruption (open arrow in b). (c) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows small cortical avulsion fracture at the lateral tibial rim (Segond fracture, arrow) with a small amount of focal subcortical edema (*).
|
|
View larger version (184K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 10c. Flexion with varus and internal rotation injury. (a, b) Sagittal fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show typical posterolateral tibial plateau and noncontiguous lateral femoral condyle bone bruises (* in a) with ACL tear (solid arrow in b) and posterior capsule disruption (open arrow in b). (c) Coronal fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows small cortical avulsion fracture at the lateral tibial rim (Segond fracture, arrow) with a small amount of focal subcortical edema (*).
|
|
View larger version (137K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11a. Hyperflexion injury with posterior tibial translation. (a, b) Fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show an isolated PCL tear (arrow in a) with no bone bruise or capsule disruption produced by moderate force. In b, the rule indicates centimeters. (c) Sagittal T2-weighted fast SE (3,270/90) image shows transient posterior dislocation with PCL avulsion (arrow) and additional injuries produced by severe force.
|
|
View larger version (138K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11b. Hyperflexion injury with posterior tibial translation. (a, b) Fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show an isolated PCL tear (arrow in a) with no bone bruise or capsule disruption produced by moderate force. In b, the rule indicates centimeters. (c) Sagittal T2-weighted fast SE (3,270/90) image shows transient posterior dislocation with PCL avulsion (arrow) and additional injuries produced by severe force.
|
|
View larger version (145K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11c. Hyperflexion injury with posterior tibial translation. (a, b) Fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show an isolated PCL tear (arrow in a) with no bone bruise or capsule disruption produced by moderate force. In b, the rule indicates centimeters. (c) Sagittal T2-weighted fast SE (3,270/90) image shows transient posterior dislocation with PCL avulsion (arrow) and additional injuries produced by severe force.
|
|
View larger version (150K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 12. Patellar dislocation (flexion and internal rotation of the femur on a fixed tibia). Axial fast SE, proton-density-weighted, fat-suppressed MR image (4,000/15, echo train length of eight) shows typical medial patella and lateral femoral condyle bone bruises (*)
|
|
View larger version (152K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 13a. Direct trauma. Axial (a) and coronal (b) fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show localized bone contusion (*) in the medial femoral condyle, which is away from the articular surface. Note the absence of other injuries.
|
|
View larger version (164K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 13b. Direct trauma. Axial (a) and coronal (b) fast SE, proton-density-weighted, fat-suppressed MR images (4,000/15, echo train length of eight) show localized bone contusion (*) in the medial femoral condyle, which is away from the articular surface. Note the absence of other injuries.
|
|
|
Discussion
|
|---|
Distinctive MR imaging patterns in certain knee injuries have been recognized by many investigators (2–7). The association between acute ACL tears and bone bruises involving the lateral femoral condyle and posterior lateral tibial plateau is well known. A less frequent association between ACL tears and medial-sided bone bruises is also described, attributed by some authors to avulsion at the semimembranosus attachment (8,9) and by others as a contrecoup impaction due to a secondary rebound rotation (10). Distinctly differing bone marrow edema patterns also accompany the flexion, varus, and internal rotation mechanism, which produces the Segond fracture (11,12). While also associated with ACL tear, this latter pattern can be differentiated from the more common injury mechanism of flexion, valgus, and external rotation that causes the O'Donoghue triad. Other previously described distinctive MR imaging patterns include patellar dislocation and complete knee dislocation (13).
We attempted to consolidate known MR imaging patterns of complex knee injury into a unifying mechanism-based classification system. Owing to the complexity of many knee injuries, this classification system is necessarily incomplete. For example, injuries to the extensor mechanism, including patellar dislocations, are significantly influenced by anatomic variation, which is not addressed in our classification system. Complex injuries characterized by predominantly axial loading forces have also been excluded. These injuries produce such pronounced bone injuries that individual patterns of bone marrow edema become obscured.
We believe our classification system is particularly useful in the distinction between injuries that occur in extension versus flexion. Hyperextension injuries are characterized by broad areas of contiguous bone bruising at the anterior aspect of the knee. Forces required to produce these injuries are substantial, and the degree of soft-tissue injury at the opposite, posterior aspect of the knee can be appreciated on the basis of the extensive edema depicted at MR imaging. These hyperextension injuries involve the critical posteromedial and posterolateral corners of the knee, and a thorough description of the extent of soft-tissue injury is essential.
In comparison, injuries that occur in flexion are characterized by relatively less extensive bone bruising. With the knee in flexion, shearing and rotational forces dominate over impaction forces. Many bone bruises in flexion injuries involve noncontiguous bone surfaces because they are due to secondary rotational impactions after ligamentous rupture. We believe that secondary rotation in flexion injuries may cause a trap-and-twist mechanism, which explains our observation of more frequent meniscal tears in this group of injuries.
The ability to distinguish avulsion from impaction bone marrow edema patterns, as described by Palmer et al (14), is fundamental to our classification system. With increased use of highly sensitive fast SE sequences with fat suppression, the frequency of injury-associated bone marrow edema will be fully appreciated. For example, small areas of bone marrow edema at the margins of the tibia and femur at the sites of meniscal and capsular attachments are now commonly seen. We believe these small bone marrow edema foci usually indicate adjacent avulsion injury secondary to distraction or rotation.
In conclusion, this mechanism-based classification system for complex knee injuries is based on MR imaging patterns of bone and soft-tissue injuries. The position of the knee, direction of force, and presence or absence of rotation combine to produce consistent injury patterns in many but not all cases. A thorough understanding of knee injury patterns and their mechanisms may help achieve more accurate assessment of these complicated injuries.
|
Footnotes
|
|---|
Abbreviations: ACL = anterior cruciate ligament,
LCL = lateral collateral ligament,
MCL = medial collateral ligament,
PCL = posterior cruciate ligament,
SE = spin-echo
|
References
|
|---|
-
Hayes CW, Conway WF. Normal anatomy and magnetic resonance appearance of the knee. Top Magn Reson Imaging 1993; 5:207-227.[Medline]
-
Gentili A, Seeger LL, Yao L, Do HM. Anterior cruciate ligament tear: indirect signs at MR imaging. Radiology 1994; 193:835-840.[Abstract/Free Full Text]
-
Kaplan PA, Walker CW, Kilcoyne RF, et al. Occult fracture patterns of the knee associated with anterior cruciate ligament tears: assessment with MR imaging. Radiology 1992; 183:835-838.[Abstract/Free Full Text]
-
Lynch TCP, Crues JV, Morgan FW, et al. Bone abnormalities of the knee: prevalence and significance at MR imaging. Radiology 1989; 171:761-766.[Abstract/Free Full Text]
-
Murphy BJ, Smith RL, Uribe JW, et al. Bone signal abnormalities in the posterolateral tibia and lateral femoral condyle in complete tears of the anterior cruciate ligament: a specific sign?. Radiology 1992; 182:221-224.[Abstract/Free Full Text]
-
Robertson PL, Schweitzer ME, Bartolozzi AR, Ugoni A. Anterior cruciate ligament tears: evaluation of multiple signs with MR imaging. Radiology 1994; 193:829-834.[Abstract/Free Full Text]
-
Yao L, Lee JK. Occult intraosseous fracture: detection with MR imaging. Radiology 1988; 167:749-751.[Abstract/Free Full Text]
-
Chan KK, Resnick D, Goodwin D, Seeger LL. Posteromedial tibial plateau injury including avulsion fracture of the semimembranosus tendon insertion site: ancillary sign of anterior cruciate ligament tear at MR imaging. Radiology 1999; 211:754-758.[Abstract/Free Full Text]
-
Yao L, Lee JK. Avulsion of the posteromedial tibial plateau by the semimembranosus tendon: diagnosis with MR imaging. Radiology 1989; 172:513-514.[Abstract/Free Full Text]
-
Kaplan PA, Gehl RH, Dussault RG, Anderson MW, Diduch DR. Bone contusions of the posterior lip of the medial tibial plateau (contrecoup injury) and associated internal derangements of the knee at MR imaging. Radiology 1999; 211:747-753.[Abstract/Free Full Text]
-
Dietz GW, Wilcox DM, Montgomery JB. Segond tibial condyle fracture: lateral capsular ligament avulsion. Radiology 1986; 159:467-469.[Abstract/Free Full Text]
-
Weber WN, Neumann CH, Barakos JA, et al. Lateral tibial rim (Segond) fractures: MR imaging characteristics. Radiology 1991; 180:731-734.[Abstract/Free Full Text]
-
Yu JS, Goodwin D, Salonen D, et al. Complete dislocation of the knee: spectrum of associated soft-tissue injuries depicted by MR imaging. AJR Am J Roentgenol 1995; 164:135-139.[Abstract/Free Full Text]
-
Palmer WE, Levine SM, Dupuy DE. Knee and shoulder fractures: association of fracture detection and marrow edema on MR images with mechanism of injury. Radiology 1997; 204:395-401.[Abstract/Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
C. J. Gottsegen, B. A. Eyer, E. A. White, T. J. Learch, and D. Forrester
Avulsion Fractures of the Knee: Imaging Findings and Clinical Significance
RadioGraphics,
October 1, 2008;
28(6):
1755 - 1770.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
K. Helgeson and A R. Smith Jr
Process for Applying the International Classification of Functioning, Disability and Health Model to a Patient With Patellar Dislocation
Physical Therapy,
August 1, 2008;
88(8):
956 - 964.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
L. S. Lohmander, P. M. Englund, L. L. Dahl, and E. M. Roos
The Long-term Consequence of Anterior Cruciate Ligament and Meniscus Injuries: Osteoarthritis
Am. J. Sports Med.,
October 1, 2007;
35(10):
1756 - 1769.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
E. H. G. Oei, J. J. Nikken, A. Z. Ginai, G. P. Krestin, J. A. N. Verhaar, A. B. van Vugt, and M. G. M. Hunink
Acute Knee Trauma: Value of a Short Dedicated Extremity MR Imaging Examination for Prediction of Subsequent Treatment
Radiology,
January 1, 2005;
234(1):
125 - 133.
[Abstract]
[Full Text]
[PDF]
|
|
|
Top
Abstract
Introduction
