Meniscal tears: MR demonstration of experimentally produced injuries

Magnetic resonance (MR) imaging was performed using a 1.5-T magnet on eight immature swine knees with surgically produced vertical and horizontal meniscal tears. Three radiologists, interpreting the images independently, detected all tears. Tears in the middle portion of the meniscus were best seen on sagittal views, while lesions of the anterior and posterior horns of the meniscus were best seen on coronal views. MR has several advantages over arthrography, the current diagnostic method for knee injuries: it is noninvasive, uses no ionizing radiation, and provides excellent soft-tissue contrast resolution.     

Meniscal tears: pathologic correlation with MR imaging

Menisci from 12 autopsies and above-knee amputations were imaged with magnetic resonance (MR) at 1.5 T and then sectioned for gross and histologic examination. A histologic staging system was developed and showed a one-to-one correlation with corresponding grades of MR signal intensities. Histologic stages 1 and 2 represented a continuum of degeneration culminating in stage 3 fibrocartilaginous tears, seen most frequently in posterior-horn segments of the medial meniscus. Correlation of histologic stages with MR signal intensity allows for an improved diagnostic reading of MR images.     

Meniscal tear configurations: categorization with MR imaging

OBJECTIVE: The purpose of this study was to evaluate the accuracy of MR imaging for categorizing the configuration of meniscal tears of the knee. MATERIALS AND METHODS: Fast spin-echo MR images obtained at 1.5 T from 110 patients who had meniscal tears identified at arthroscopy were retrospectively and independently classified by two reviewers into five configurations: horizontal, longitudinal, radial, oblique, and complex. MR imaging categorization was compared with arthroscopic results as the standard of reference. Data were also analyzed with longitudinal and oblique tears combined because these usually are reparable, and with horizontal, radial, and complex tears combined because these usually are not reparable. Interobserver and intraobserver agreements were calculated using kappa coefficients. RESULTS: At arthroscopy, meniscal tears were categorized as horizontal (n = 44), longitudinal (n = 34), complex (n = 22), radial (n = 11), and oblique (n = 5). Sensitivity, specificity, and accuracy of each reviewer for the reparable tears were 82%, 92%, and 89%; and 59%, 97%, and 84%, respectively. Interobserver agreements were fair between reviewer 1 and the first and second interpretations of reviewer 2 (kappa = 0.25, p < 0.005; and kappa = 0.21, p < 0.05, respectively). Intraobserver agreement was substantial (kappa = 0.71, p < 0.001). CONCLUSION: MR imaging was accurate for predicting reparable meniscal tears and was sensitive for the determination of nonreparable tears.     

Meniscal ossicle: MR imaging appearance in three patients

Meniscal ossicles are rare. Radiographically, these ossicles often are mistaken for intra-articular bodies. We evaluated the application of magnetic resonance imaging to determine whether this technique is efficacious in differentiating meniscal ossicles from intra-articular bodies.     

Meniscal tears of the knee: accuracy of MR imaging

Before surgery, 277 menisci in 144 knees were examined with magnetic resonance (MR) imaging. They were then examined directly with arthroscopy or arthrotomy. Menisci were graded on a scale of 1-3 according to the character of the intrameniscal MR imaging signal. At surgery, 137 of 154 (89%) menisci exhibiting only grade 1 or grade 2 signal were found to be normal. One hundred sixteen of 123 (94%) menisci exhibiting intrameniscal signal communicating with a meniscal articular surface (grade 3 signal) had tears. If only a grade 3 signal is considered consistent with meniscal tears, then MR findings and surgical findings agreed in 91.3% of menisci. MR imaging can separate surgically significant from nonsignificant meniscal lesions and is useful in the noninvasive preoperative screening of suspected meniscal tears.     

Knee injuries: high-resolution MR imaging

Recent technologic advances have made high-resolution magnetic resonance (MR) imaging of the knee a clinical reality. Ten healthy volunteers and 30 patients with suspected knee injuries were imaged using receive-only surface coils and two-dimensional multisection or three-dimensional selective acquisition techniques. Arthroscopic and/or surgical correlation was available in 15 patients. Tears of the cruciate ligament, medial collateral ligament, and meniscus are illustrated. Nonorthogonal views of the anterior cruciate ligament are useful for demonstrating both femoral and tibial attachments in the same section. The posterior cruciate ligament is usually well seen on sagittal views. T2-weighted images are helpful for demonstrating collateral ligament tears and meniscal tears when joint effusion is present. Thin sections (1-5 mm) are necessary to define many meniscal and cruciate tears. High-resolution, thin-section MR imaging can be used to diagnose soft-tissue injuries of the knee and has the potential to become a major imaging method in the evaluation of knee injuries.     

Extraadrenal pheochromocytoma: detection during pregnancy using MR imaging

This case report demonstrates the usefulness of magnetic resonance (MR) imaging to demonstrate an abdominal mass during pregnancy. A pregnant woman presented in midgestation with symptoms and chemical evidence of a pheochromocytoma. The use of MR imaging permitted early localization of a retrouterine tumor when it would have been undesirable for the woman to undergo computed tomography because of radiation exposure. Evaluation of the MR images formed the basis of the therapeutic strategy used by the patient's physicians.     

Meniscal tears: comparison of half-Fourier technique and conventional MR imaging

PURPOSE: To determine whether half-Fourier MR image acquisition technique can provide similar information to that of conventional MR acquisition technique for evaluation of meniscal tears. MATERIALS AND METHODS: We studied 101 menisci in 52 patients who were referred for evaluation of meniscal tears. Sagittal MR images of the knee were obtained for all patients by using proton density and T2-weighted SE sequences on a 1-T clinical system. The half-Fourier technique and conventional technique were used for all patients. All other imaging parameters were identical for both sequences (TR/TE=2400/20,70; 3 mm slice thickness; 200 x 256 matrix; field of view, 200; one signal acquired). Both sets of images were filmed with standard window and level settings. Images were randomised and interpreted independently by two radiologists for the presence of meniscal tears. Images were also subjectively assessed for image quality using a five-point grading scale. RESULTS: On half-Fourier images, Reader 1 interpreted 23 menisci as torn, compared to 28 for Reader 2. On conventional images, Reader 1 interpreted 24 menisci as torn, compared to 26 for Reader 2. Agreement between interpretation of the conventional and that of the half-Fourier images was 99% for Reader 1, and 98% for Reader 2. Agreement between readers for the half-Fourier images was 95%, and for the conventional images 96%. No statistically significant difference was found in the subjective evaluation of image quality between the conventional and half-Fourier images. CONCLUSION: The half-Fourier acquisition technique compares favourably with the conventional technique for the evaluation of meniscal tears.     

Meniscal abnormalities in the asymptomatic population at MR imaging

Two hundred eighty meniscal horns in 64 asymptomatic volunteers in the 2nd to 8th decades of life were analyzed for meniscal abnormalities. Grade 1, 2, and 3 changes were present in essentially all decades. There was at least a 25% prevalence of meniscal signal abnormalities as early as the 2nd decade. The prevalence of meniscal abnormalities increased sharply with age. The prevalence of all signal abnormalities correlated with age, grade 2 changes having the highest correlation coefficient (+.88). The correlation coefficient for grades 1 and 3 changes were +.60 and +.71, respectively. The posterior horn of the medial meniscus had a significantly higher (P less than .02) prevalence of abnormalities than did the other meniscal locations. There was no significant correlation between subject weight or sex and meniscal signal. The authors conclude that there is a baseline prevalence of meniscal signal in the asymptomatic population.     

Meniscal position on routine MR imaging of the knee

 Objective. To determine the prevalence of meniscal protrusion (i.e. location of the outer edge of a meniscus beyond the tibial articular surface), and to determine its relationship with internal derangement, joint effusion, and degenerative arthropathy. Design and patients. Sagittal and coronal MR images of 111 abnormal and 46 normal knees were evaluated for the presence of meniscal protrusion. We set 25% as the minimum amount of displacement considered abnormal because this was the smallest amount of displacement we could confidently discern. Presence of meniscal tear, anterior cruciate ligament (ACL) injury, joint effusion, or osteophytosis was also recorded. Results and conclusion. Normal examinations demonstrated protrusion of the medial meniscus in 6.5% of sagittal images and 15% of coronal images, and of the lateral meniscus in 2% and 13%, respectively. Fisher’s exact test demonstrated a statistically significant difference between the normal and abnormal groups for the medial meniscus on both sagittal (P<0.0001) and coronal (P=0.01) images, but not for the lateral meniscus in either plane (P>0.2). A protruding medial meniscus was associated with effusion and osteophytosis (P<0.05) but not with meniscal or ACL tear (P>0.1). Posterior protrusion of the lateral meniscus was only associated with ACL injury (P<0.0001); protruding anterior horns and bodies of lateral menisci were not associated with any of the four abnormalities. It is concluded that the medial meniscus may occasionally protrude more than 25% of its width, but protrusion is more often due to effusion and osteophytes. Protrusion of the posterior horn of the lateral meniscus is associated with ACL insufficiency, while protrusion of the body and anterior horn of the lateral meniscus is a normal variant.     

Meniscal abnormalities of the knee: 3DFT fast-scan GRASS MR imaging

The ability to use fast-scan techniques to obtain MR images without sacrificing diagnostic accuracy is a desirable goal in MR imaging. We describe a series of patients in whom fast-scan MR imaging was found to be equal to conventional spin-echo imaging in the detection and characterization of meniscal abnormalities. Thirty-five patients with suspected meniscal tears were studied with fast-scan imaging (3DFT-GRASS), and the results were compared with those of conventional spin-echo imaging. Three-millimeter contiguous sections through the entire knee were obtained in 5 min by using the 3DFT-GRASS technique. 3DFT-GRASS and spin-echo images agreed in all cases regarding the presence or absence of an abnormality and its degree of severity. We conclude that fast-scan 3DFT-GRASS MR imaging is useful when screening the knee for the presence of meniscal abnormalities.     

Sports-related muscle injuries: evaluation with MR imaging

Sports-related muscle pain is frequent in both trained and untrained persons; however, its severity and significance may be difficult to assess clinically. The authors used magnetic resonance (MR) imaging to evaluate acute strains and delayed-onset muscle soreness in sedentary subjects and postmarathon myalgia in trained runners. MR imaging documented the distribution of affected muscles and the absence of focal hematoma, fascial herniation, subsequent fibrosis, and fatty infiltration. Pain associated with strain and that occurring several days after exercise were both associated with prolongation of muscle T1 and T2. In a prospective evaluation of delayed-onset muscle soreness, abnormalities depicted at MR imaging persisted longer than symptoms by up to 3 weeks, indicating that MR imaging is sensitive to tissue alteration that is not apparent clinically. Highly trained marathon runners tended to have relatively mild abnormalities involving the myotendinous junctions.     

Cholecystitis: detection with MR imaging

The role of magnetic resonance (MR) imaging in the detection of gallbladder disease was evaluated in 39 individuals (16 healthy, five with asymptomatic gallstones, and 18 with clinical symptoms of gallbladder disease). MR imaging was performed after they fasted for 12 hours. Imaging sequences included a combination of repetition times (TR) of 0.5 and 1.5 sec and echo times (TE) of 28 and 56 msec. On the images obtained at TR = 0.5 sec and TE = 56 msec, gallbladder bile was hyperintense compared with the liver in all healthy and asymptomatic subjects and was hypointense (n = 9), isointense (n = 4), or hyperintense (n = 5) in symptomatic patients, eight of whom had surgical confirmation of cholecystitis. Comparison of normal versus pathologically proved cases for the presence of gallbladder disease yielded a specificity of 100%, sensitivity of 75%, and a significant difference of P less than .01. Thus, with a pulse sequence of TR = 0.5 sec and TE = 56 msec, MR was sensitive in detecting gallbladder disease. However, the role of MR in the radiologic workup of gallbladder disease will be determined by more experience with this modality.     

MR imaging of traumatic spinal injuries

Plain films form the initial evaluation in all cases of spinal trauma. In cases of indeterminate or incomplete plain radiographs, further evaluation should be performed by multiplanar computed tomography (CT) and/or magnetic resonance imaging (MRI). Rapid triage is important to distinguish surgical and nonsurgical cases, as this has implications in terms of relief of cord compression and long-term prognosis. CT is unparalleled in its capacity to demonstrate bony abnormalities. MRI is the modality of choice in the evaluation of soft tissue injuries, in particular where there is a suspicion of ligamentous or intervertebral disc injury and spinal cord injury. MRI has the ability to distinguish between spinal cord edema and hemorrhage, which has important prognostic significance.     

Achilles tendon injuries: the role of MR imaging

Eight magnetic resonance (MR) examinations were performed in seven patients with Achilles tendon injuries and correlated with physical examination and surgical and clinical follow-up. The MR examinations depicted the Achilles tendon in excellent detail and Achilles tendon abnormalities with greater accuracy than physical examination. Of five tendons shown to be at least partially torn on MR, palpable tendinous defects were found in only one, and plantarflexion weakness was found in four. The MR and surgical findings precisely correlated in one case. Magnetic resonance proved valuable in the evaluation of clinically equivocal Achilles tendon tears and may ultimately play a greater role as a research tool in the determination of optimal forms of therapy for specific Achilles tendon injuries.     

Common injuries related to weightlifting: MR imaging perspective

Weightlifting has evolved to become a ubiquitous form of exercise. Resistance training has been shown to have beneficial effects on both muscle and osseous maintenance and development. Competitive weightlifting sports continue to enjoy tremendous popularity, with participants striving to establish new standards in performance and more demanding personal goals. Thus, it is not surprising that we have also seen an increase in injuries related to weightlifting. Many of these injuries are radiographically occult and are best suited for evaluation by magnetic resonance (MR) imaging because many involve the soft tissues. In this article, we discuss some of the factors that contribute to these injuries and address the mechanisms of injury and the MR imaging manifestations of the more common injuries.