MR Imaging of the Anatomy of and Injuries to the Lateral and Posterolateral Aspects of the Knee

Transcription

1 Downloaded from by on 07/15/16 from IP address opyright RRS. For personal use only; all rights reserved Pictorial Essay MR Imaging of the natomy of and Injuries to the Lateral and Posterolateral spects of the Knee ndrew H. Haims 1, Michael J. Medvecky 2, Raymond Pavlovich, Jr. 2, Lee D. Katz1 he lateral and posterolateral aspects of the knee have gained attention in recent years both for their complex anatomy and their clinical relevance. Injuries to the posterolateral corner and lateral structures of the knee are infrequent and are usually associated with anterior or posterior cruciate ligament tears or a combination of both [1]. The significance of a missed injury can be profound; reconstructed anterior or posterior cruciate ligaments can fail, and unrecognized injuries may also lead to pain, instability, and possibly degenerative changes [2]. Physical examination in the acutely injured, nonanesthetized or polytrauma setting may be difficult because of pain, guarding, swelling, or associated injuries. Symptoms related to the posterolateral corner may also be masked in these situations. MR imaging is invaluable in evaluating normal anatomy and diagnosing injuries to the lateral structures of the knee and in providing essential preoperative information [3 5]. lthough indirect evidence of injury to some of the lateral structures may be obtained arthroscopically, most often open exploration is needed to analyze and repair these structures. In this pictorial essay, we use MR imaging to illustrate both the normal structures of the lateral and posterolateral aspects of the knee and the various injury patterns, and we briefly comment on treatment. T Fig. 1. natomic drawings illustrate structures of lateral and posterolateral knee. (ourtesy of eltran S, lbons, Gerona, Spain), Lateral drawing shows insertion of iliotibial band, 1; mid third capsular ligament, 2; lateral collateral ligament, 3; fabellofibular ligament, 4; and popliteus muscle and tendon, 5., Posterior drawing shows biceps femoris tendon attachment, 1; lateral collateral ligament, 2; popliteofibular ligament, 3; and popliteus muscle and tendon, 4. Received pril 2, 2002; accepted after revision ugust 13, Department of Radiology, Yale University School of Medicine, 333 edar St., P. O. ox , New Haven, T ddress correspondence to. H. Haims. 2 Department of Orthopedic Surgery, Yale University School of Medicine, New Haven, T JR 2003;180: X/03/ merican Roentgen Ray Society JR:180, March

2 Haims et al. Downloaded from by on 07/15/16 from IP address opyright RRS. For personal use only; all rights reserved Fig. 2. Normal appearance of iliotibial band. oronal fast spin-echo proton density weighted MR image of 24year-old woman shows insertion of superficial fibers of iliotibial band (arrows) on Gerdy s tubercle of anterior tibia. This tendinous insertion is main one for iliotibial band. Fig. 3. Injuries to iliotibial band., oronal fast spin-echo proton density weighted MR image illustrates disruption of fibers of iliotibial band (arrows) in 34-year-old man with multiple ligamentous knee injuries., oronal fast spin-echo proton density weighted MR image shows avulsion and retraction of iliotibial band (arrows) and its tibial donor site (arrowheads) in 18-year-old woman injured in motor vehicle crash., oronal reformatted T scan of same patient as in illustrates bony avulsion fragment (arrows) better than MR image (). Fig. 4. Normal appearance of popliteus tendon., oronal fast spin-echo proton density weighted MR image shows femoral attachment of popliteus tendon in anterior aspect of popliteus groove (arrows) in 14-year-old boy., oronal fast spin-echo proton density weighted MR image shows inferior medial course of popliteus tendon (arrows) in 21-year-old woman. 648 JR:180, March 2003

3 Downloaded from by on 07/15/16 from IP address opyright RRS. For personal use only; all rights reserved MR Imaging of the Knee The anatomy of the lateral and posterolateral aspects of the knee can be difficult to understand because of the number of structures and their variability both in form and nomenclature. The structures of the lateral and posterolateral aspects of the knee reviewed in this article con- sist of the iliotibial band, popliteus muscle and tendon, popliteofibular ligament, biceps femoris tendon, lateral collateral ligament (fibular collateral ligament), lateral gastrocnemius tendon, fabellofibular ligament, and mid third lateral capsular ligament (Fig. 1). We do not comment on the additional structures of the lateral and posterolateral aspects of the knee because of the lack of consistent visualization both at imaging and dissection. The iliotibial band is a combination of the tendon of the tensor fascia lata and the deep Fig. 5. Normal appearance of popliteofibular ligament. oronal fast spin-echo proton density weighted MR image of 28-year-old woman illustrates origin of popliteofibular ligament on medial fibular styloid (black arrow) and insertion on popliteus tendon just proximal to myotendinous junction (white arrow). D Fig. 6. Injuries to popliteus tendon., oronal fast spin-echo proton density weighted MR image shows abnormal signal at femoral origin of popliteus tendon (arrows) in 34-year-old man with surgically confirmed tear., oronal fast spin-echo proton density weighted MR image shows bony avulsion of femoral origin of popliteus tendon (arrows) in 13-year-old boy., nteroposterior radiograph confirms bony avulsion (arrows) in same patient as in. D, Sagittal fast spin-echo fat-suppressed T2-weighted MR image of 22-year-old woman shows edema at myotendinous junction of popliteus (arrows), consistent with partial tear in this region. JR:180, March

4 Downloaded from by on 07/15/16 from IP address opyright RRS. For personal use only; all rights reserved Haims et al. Fig. 7. Normal appearance of biceps femoris tendon. oronal fast spin-echo proton density weighted MR image of 29-year-old woman shows long and short heads of biceps femoris tendons (arrows) inserting into lateral aspect of fibular styloid. Fig. 8. Injuries of biceps femoris tendon., oronal fast spin-echo T2-weighted MR image shows avulsion of biceps femoris tendon (arrows) off fibula in 18-year-old man., oronal fast spin-echo T2-weighted MR image illustrates edema at myotendinous junction of biceps femoris (arrows) consistent with tear in 21-year-old female gymnast. Fig. 9. Normal appearance of lateral (fibular) collateral ligament. oronal fast spin-echo proton density weighted MR image of 29-year-old woman shows course of lateral collateral ligament (arrows), extending from lateral femoral condyle to lateral aspect of fibular head. This ligament frequently has oblique course and often must be visualized on sequential coronal MR images. Fig. 10. Various injury patterns of lateral (fibular) collateral ligament depicted on coronal fast spin-echo proton density weighted MR imaging., Image shows tear of proximal fibers of lateral collateral ligament (arrows) in 21-year-old woman., Image illustrates complete disruption of midsubstance of lateral collateral ligament (arrows) in 34-year-old man., Image shows avulsion and retraction of lateral collateral ligament (arrows) in 18-year-old man. 650 JR:180, March 2003

5 Downloaded from by on 07/15/16 from IP address opyright RRS. For personal use only; all rights reserved MR Imaging of the Knee Fig. 11. Normal appearance of femoral origin of lateral head of gastrocnemius tendon. Sagittal T1weighted MR image of 27-year-old woman shows origin of lateral head of gastrocnemius tendon in supracondylar process of lateral femur (arrows). Fig. 12. Normal variations of fabellofibular ligament., oronal fast spin-echo proton density weighted MR image of 19-year-old woman illustrates attenuated appearance of normal fabellofibular ligament (arrows), extending from posterolateral aspect of fabella to fibular styloid., oronal fast spin-echo proton density weighted MR image of 23-year-old man shows similar but more robust appearance of normal fabellofibular ligament (arrows). Fig. 13. Normal appearance of mid third lateral capsular ligament. oronal fast spinecho proton density weighted MR image of 36-year-old woman shows tibial attachment of mid third lateral capsular ligament (arrows), which is just below articular surface and just posterior to attachment of superficial fibers of iliotibial band. Fig year-old boy with avulsion of mid third lateral capsular ligament (Segond fracture) and associated anterior cruciate ligament tear., oronal fast spin-echo proton density weighted MR image shows bony avulsion of mid third capsular ligament (arrowheads) and medial collateral ligament tear (black arrows). nterior cruciate ligament tear (white arrows) can also be seen., Sagittal fast spin-echo fat-suppressed T2-weighted MR image shows disruption of fibers of anterior cruciate ligament (arrows). and superficial fibers of the fascia lata. The iliotibial band consists of deep and superficial layers. The superficial layer is the main tendinous component and inserts onto Gerdy s tubercle on the anterior lateral tibia [6] (Fig. 2). The deep layer inserts on the intermuscular septum of the distal femur [4]. Isolated tears of the iliotibial band are rare, but these tears may occur in patients with injuries to multiple ligaments of the knee, including complete transection or avulsion of JR:180, March 2003 its tibial insertion (Fig. 3). If part of a broader injury pattern, repair of a ruptured iliotibial band is generally indicated. The popliteus tendon originates on the anterior aspect of the popliteus groove just anterior and inferior to the origin of the lateral collateral ligament and extends inferiorly and medially to insert on the posterior medial aspect of the tibia (Fig. 4). The popliteus tendon has strong attachments to the lateral meniscus posteriorly. The popliteofibular ligament, one of the most important stabilizers in the posterolateral corner [7], inserts on the posterior medial fibular styloid and attaches to the popliteus tendon just proximal to the myotendinous junction (Fig. 5). Injuries to the popliteus musculotendinous junction or femoral insertion are common in high-grade injuries to the posterolateral corner of the knee (Fig. 6). cute repair or reconstruction is performed when operative treatment of combined injuries is undertaken. Isolated injuries are less common. 651

6 Haims et al. Fig. 15. one bruising pattern frequently associated with acute injuries to posterolateral corner. Sagittal fat-suppressed fast spin-echo T2-weighted MR image illustrates bone bruises (arrows) in anterior medial femur in 21-year-old woman with acute posterolateral corner injury (as shown in Figs. 8 and 10). Downloaded from by on 07/15/16 from IP address opyright RRS. For personal use only; all rights reserved Fig. 16. MR imaging equivalent of arcuate sign in 16-year-old boy with recent knee dislocation., Sagittal fast spin-echo fat-suppressed T2-weighted MR image shows edema in proximal fibula (arrows), consistent with avulsion injury at insertion of biceps femoris tendon and lateral collateral ligament., oronal oblique fast spin-echo proton density weighted MR image shows avulsion and retraction of biceps femoris tendon (arrows)., oronal oblique fast spin-echo proton density weighted MR image illustrates avulsion, retraction, and lateral displacement of lateral collateral ligament (large arrows). Partial avulsion of femoral attachment of popliteus tendon (small arrows) is also present. The biceps femoris tendon consists of long and short heads. In this article, we discuss only the insertions of the direct arms of both the long and short heads. The long head inserts onto the middle of the posterolateral aspect of the fibula, and the short head inserts just medial to the long head. These insertions cannot be seen as separate (Fig. 7). Injuries to the biceps femoris tendon are seen in conjunction with posterolateral ligamentous injuries in the knee. iceps femoris imjuries are most commonly described as avulsion or partial avulsion injuries or as tears of the distal myotendinous junction (Fig. 8). n association of partial tendinous avulsion in conjunction with Segond fractures has been described as well. In patients with acute injuries, primary repair is usually undertaken with repair of all injured structures. The lateral collateral ligament (fibular collateral ligament) arises from the lateral femoral condyle and inserts on the lateral aspect of the middle third of the fibular head, sometimes joining the biceps femoris tendon (Fig. 9). This ligament has a posterior and oblique course and is seldom seen entirely on one coronal image. The lateral collateral ligament can be injured in isolation or in conjunction with other knee ligamentous structures, especially those of the posterolateral corner and the cruciate ligaments. The location of the injury relative to the lateral collateral ligament can be proximal, mid substance, or at the tibial insertion (Fig. 10). First- or second-degree lateral collateral ligament sprains are usually treated nonoperatively with protected mobilization and rehabilitation. Third-degree lateral collateral ligament sprains or combined ligament injuries are usually treated with early operative repair, augmentation, or reconstruction. The lateral gastrocnemius tendon inserts on the supracondylar process of the femur just posterior to the lateral collateral ligament (Fig. 11). Injuries to this tendon are uncommon [4]. The fabellofibular ligament attaches to the posterolateral aspect of the fa- 652 JR:180, March 2003

7 MR Imaging of the Knee Downloaded from by on 07/15/16 from IP address opyright RRS. For personal use only; all rights reserved bella and inserts on the fibular styloid (Fig. 12). This ligament can be present even in the absence of a fabella [6]. The mid third lateral capsular ligament is a thickening of the lateral joint capsule with attachments to the femoral condyle and lateral tibia. The tibial attachment is just below the articular surface and just posterior to Gerdy s tubercle (Fig. 13). apsular attachments to the lateral meniscus are also present. ony avulsion at the tibial attachment of the mid third lateral capsular ligament is also known as a Segond fracture [8] (Fig. 14). This fracture has a high association (92%) with anterior cruciate ligament injury. Ross et al. [3] showed that an anterior medial femoral condylar bone bruise, sometimes associated with an anterior tibial bone bruise, was a consistent finding in all five of their patients with acute posterolateral corner injuries (Fig. 15). These authors note that the medial femoral contusion is evidence of a hyperextension varus movement associated with many posterolateral corner injuries. The arcuate sign or fracture is an avulsion fracture of the fibular head and styloid at the attachment of the lateral collateral ligament and biceps femoris tendon, and the MR imaging findings associated with this avulsion fracture have recently been described [9]. lthough the avulsion fracture may occasionally not be visualized on conventional radiographs, the presence of edema in the proximal fibula can be a helpful sign of this injury (Fig. 16). In conclusion, MR imaging can provide an excellent and noninvasive means of evaluating the complex anatomy and injury patterns of the lateral and posterolateral structures of the knee and assisting in the preoperative planning of these injuries. cknowledgment We thank Salvador eltran for his work on the anatomic drawings. References 1. Veltri DM, Warren RF. Posterolateral instability of the knee. J one Joint Surg m 1994;76: ovey D. Injuries to the posterolateral corner of the knee. J one Joint Surg m 2001;83: Ross G, hapman W, Newberg R, Scheller D. Magnetic resonance imaging for the evaluation of acute posterolateral complex injuries of the knee. m J Sports Med 1997;25: LaPrade RF, Gilbert TJ, ollom TS, Wentorf F, haljub G. The magnetic resonance imaging appearance of individual structures of the posterolateral knee: a prospective study of normal knees and knees with surgically verified grade III injuries. m J Sports Med 2000;28: Yu JS, Salonen D, Hodler J, Haghighi P, Trudell D, Resnick D. Posterolateral aspect of the knee: improved MR imaging with a coronal oblique technique. Radiology 1996;198: Terry G, LaPrade RF. The posterior lateral aspect of the knee: anatomy and surgical approach. m J Sports Med 1996;24: Watanabe Y, Moriya H, Takahashi K, et al. Functional anatomy of the posterior lateral structures of the knee. rthroscopy 1993;9: Weber WN, Neumann H, arakos J, Petersen S, Steinbach LS, Genant HK. Lateral tibial rim (Segond) fractures: MR imaging characteristics. Radiology 1991;180: Juhng SK, Lee JK, hoi SS, Yoon KH, Roh S, Won JJ. MR evaluation of the arcuate sign of posterolateral knee instability. JR 2002;178: JR:180, March