Use of the thoracic aorta for renal revascularization

OBJECTIVE: The primary role of the anterior cruciate ligament is to resist anterior subluxation of the tibia. When the ligament is torn, the tibia is free to sublux anteriorly when the leg is pulled forward. In addition to visualizing the anterior cruciate ligament directly, MR imaging can show joint alignment. The purpose of this study was to test the efficacy of MR images of anterior subluxation of the tibia for diagnosing complete tears of the anterior cruciate ligament. MATERIALS AND METHODS: We evaluated the records of 120 consecutive patients who underwent MR imaging of the knee and subsequently had arthroscopy. Arthroscopy showed a complete tear of the anterior cruciate ligament in 21 patients, a partial tear in eight patients, and an intact anterior cruciate ligament in 91 patients. Two radiologists together reviewed the MR images, and interpretation of anterior cruciate ligament integrity was reached by consensus. The anterior cruciate ligament was categorized as intact, completely torn, or partially torn on the basis of conventional MR imaging criteria. The degree of anterior subluxation of the tibia was measured on a separate occasion in random order by a radiologist who used a sagittal section through the middle of the lateral femoral condyle. On the selected image, two vertical lines parallel to the left and right margins of the image frame were drawn tangent to the posterior cortical margins of the lateral femoral and tibial condyles. Anterior subluxation of the tibia was determined by the distance in millimeters between these two lines and measured with calipers by using the 5-cm scale on the images. Measurements were considered reliable only to one half of the smallest increment of this scale (i.e., 5 mm). Accordingly, tibial subluxation (x) was measured in 5-mm increments, with x < or = 0 mm designated grade 0, 0 mm < x < or = 5 mm designated grade 1, 5 mm < x < or = 10 mm designated grade 2, and so forth. RESULTS: Conventional MR imaging criteria had 90% sensitivity and 94% specificity for diagnosing complete tears of the anterior cruciate ligament. According to the receiver-operating-characteristic (ROC) curve, anterior subluxation of the tibia greater than 5 mm (grade 2 or greater) was considered to be the optimal threshold (sensitivity, 86%; specificity, 99%) for diagnosing complete tears of the anterior cruciate ligament. Notably, none of the six false-positive diagnoses of complete tears by conventional criteria (three partial tears and three intact ligaments at arthroscopy) were misdiagnosed when tibial subluxation was used as the diagnostic criterion. Subluxation greater than 5 mm can be falsely negative with chronic tears of the anterior cruciate ligament (n = 2) or when a displaced bucket-handle tear of the lateral meniscus blocks anterior subluxation of the tibia (n = 1). CONCLUSION: An anterior tibial subluxation greater than 5 mm (grade 2 or greater) is a simple objective measurement that serves as a helpful adjunctive sign in the diagnosis of complete tears of the anterior cruciate ligament. This sign also offers improved discrimination of complete from partial tears of the anterior cruciate ligament.     

Accuracy of direct signs of tears of the anterior cruciate ligament

OBJECTIVE: To evaluate the accuracy of direct magnetic resonance imaging (MRI) signs of tears of the anterior cruciate ligament. PATIENTS AND METHODS: Over the period April 1991 to February 1994, 92 consecutive MRI studies of the knee were obtained for which arthroscopic data were also available. The MRI studies were retrospectively evaluated for course, continuity, signal intensity, morphologic features, contour and visualization of the anterior cruciate ligament. Arthroscopic findings were correlated with individual primary signs and the overall MRI diagnosis. RESULTS: Among the cases studied were 4 partial and 32 complete tears of the anterior cruciate ligament (as determined by arthroscopy). Because of the low number of partial tears, it was not possible to draw any meaningful conclusions about the MRI diagnosis of this type of tear. For complete tears, the criteria with the highest accuracy were abnormal course of the ligament (96.0%) and high signal intensity (89.3%). The overall diagnostic accuracy of MRI was 98.8%. CONCLUSIONS: The most accurate direct MRI finding in patients with a complete tear of the anterior cruciate ligament was abnormal course of the ligament, followed by abnormally high signal intensity.     

MR imaging of the anterior cruciate ligament: frequency of discordant findings on sagittal-oblique images and correlation with arthroscopic findings

OBJECTIVE: The purposes of this study were to determine the frequency of discordant MR findings of the anterior cruciate ligament (ACL) using sagittal-oblique images and the arthroscopic integrity of the ACL in knees with a discordant MR appearance. MATERIALS AND METHODS: The frequency of discordant MR features was determined by independently reviewing the sagittal-oblique images of 53 consecutive patients undergoing subsequent arthroscopic surgery. The first 25 consecutive knees were examined using a conventional, dual-echo, T2-weighted spin-echo (SE) sequence; the subsequent 28 consecutive knees were examined using both a T1-weighted SE(T1) and a fat-suppressed, fast spin-echo (FSE) T2-weighted sequence. Two examiners who were unaware of patient identification and arthroscopic results evaluated only the sagittal images that included the ACL. Each reviewer graded the ACL as torn or intact. The MR appearance was considered discordant when one MR sequence showed disrupted or poorly seen ACL fibers and the other sequence showed intact ACL fibers. The arthroscopic integrity of the ACL was determined for the 20 knees with a discordant MR appearance. RESULTS: A discordant MR appearance of the ACL was seen in 20 of the 53 knees (38%), including 10 knees evaluated using conventional T2-weighted sequences (40%) and 10 knees using T1/FSE T2 (36%) sequences. Arthroscopic examination of these knees showed intact ACL fibers in all 20 knees; the ACL was normal in 18 knees and a partial tear was questioned in two knees. CONCLUSION: A discordant appearance of the ACL was frequently encountered (38%) using either conventional T2-weighted sequences or T1 and FSE MR sequences in the sagittal-oblique plane. Intact ACL fibers were found during arthroscopy in all 20 knees with a discordant MR appearance.     

Comparison of "catheter" and conventional arthroscopy in the diagnosis of knee derangements

The diagnostic efficiency of the Optical Catheter System (OCS), which uses a 1.7-mm arthroscope, was compared with that of conventional arthroscopy in 50 patients with various knee derangements in standard arthroscopic conditions. Correct diagnoses were obtained with the OCS in 98% of anterior cruciate ligament derangements--92%-98% of those involving the medial and lateral meniscus, respectively--and 96% of cartilage disorders. No false-positives were noted for anterior cruciate ligament and meniscus injuries. False-negatives were caused by abundant intraarticular bleeding (no tourniquet was applied) and peripheral meniscus tears and false-positives by synovial superposition resulting in a mistaken diagnosis of patellar chondromalacia. The OCS proved a good diagnostic tool. Its employment, especially in an outpatient setting, should be restricted to a small number of patients and entrusted to expert arthroscopists.     

Correlations between clinical examination/MRI/arthroscopy in the acute traumatic knee

Authors study retrospectively 81 cases of isolated recent (less than three months) knee traumas. These include clinical aspects, NMR, arthroscopy. Clinical examinations have been graded: 1. possible lesion; 2. likely lesions; 3. confirmed lesions. Clinical examinations and NMR results are compared to arthroscopy considered as reference. Clinical examination of acute traumatic knee is essential. Nevertheless, its value for detecting precise lesions is poor, except for knee locking well correlated with meniscal tears. Results show that NMR provide better results than clinical examination. NMR is reliable for detecting tears of posterior cruciate ligament, tears of posterior horn of menisci (sensibility: 93%; specificity: 80%). Its results are less effective for appreciation of lesion of anterior cruciate ligament (sensibility: 88%; specificity: 78%) because of partial tears and functional but not morphologic damage. It is the only method able to evidence osteochondral injuries and soft-tissues associated lesions in traumatic knees. Emergency NMR scans show results no differences in results compared with routine examinations. However, one should keep in mind that negative NMR cannot exclude small cartilaginous lesions and partial tears of anterior cruciate ligament. According to these results and the known qualities of NMR (non invasive), we propose that this type of investigation should be more largely included in diagnostic attitude for acute injured knee. Emergency diagnostic arthroscopy could be efficiently replaced by NMR knee examination.     

Pulmonary embolism; lung scanning interpretation: about words

OBJECTIVE: The purpose of this study was to determine the prevalence and nature of a horizontal cleft in the posterior aspect of Hoffa's infrapatellar fat pad and to show pathologic processes involving this cleft. MATERIALS AND METHODS: Fifty consecutive MR imaging examinations of the knee were evaluated for the presence and appearance of a cleft in the infrapatellar fat pad. Examples of abnormalities involving the cleft were collected from additional MR studies. MR imaging, gross dissection, and histologic examination of a cadaveric knee were also performed to evaluate the anatomy and histology of the cleft. RESULTS: The cleft in the infrapatellar fat pad was revealed on MR imaging in 45 of 50 knees and had a variable shape, either linear (82%), pipe-shaped (7%), or globular-shaped (11%). Joint effusion or anterior cruciate ligament tear did not affect the appearance of the cleft. The cleft was located anterior to the distal insertion of the anterior cruciate ligament on the tibia. At gross dissection of the cadaveric knee, the roof of the cleft was formed by the ligamentum mucosum (infrapatellar plica), and the cleft was lined with synovium. The prospective evaluation of additional MR imaging examinations of the knee revealed pathologic entities of the cleft such as ganglion cysts, loose bodies, nodular synovitis, and amyloid. CONCLUSION: A horizontal cleft located in the posterior aspect of the infrapatellar fat pad is a common and normal MR imaging finding with a prevalence of 90%. The horizontal cleft is lined with synovium and its roof is formed by the ligamentum mucosum (infrapatellar plica). This cleft communicates with the knee joint. A distended cleft can form a prominent recess mimicking pathologic processes; conversely, disorders can arise in the cleft.     

Internal derangement of the knee after ipsilateral femoral shaft fracture: MR imaging findings

OBJECTIVE: This study uses magnetic resonance (MR) imaging to delineate the types and frequencies of injuries seen in the knee after ipsilateral femoral shaft fracture. We also compare the results of the orthopedic knee examination with the MR findings. DESIGN AND PATIENTS: MR imaging of the ipsilateral knee was performed on 34 patients with closed femoral shaft fractures. Indications for knee MR imaging included knee pain at the time of fracture, soft tissue swelling or an effusion of the knee, or a positive knee examination under anesthesia. The patients had a mean age of 27 years and all were stabilized with intramedullary nails. Imaging was performed a mean time of 2.5 days after surgery. All patients had knee examinations done under anesthesia, and the MR results were compiled and compared with the clinical examinations. RESULTS: Ninety-seven percent of patients demonstrated knee effusions. Twenty-seven percent of patients demonstrated meniscal tears, with the posterior horn of the medial meniscus most frequently torn. The medial collateral ligament was the most frequent site of ligamentous injury (38%) followed by the posterior cruciate ligament (21%). Fifty percent of patients had injuries of the extensor mechanism. Bone bruises were noted in 32% of patients. Articular cartilage injuries were confined to the patella in four cases. One occult tibial plateau fracture and one meniscocapsular separation were seen. CONCLUSIONS: There is a common incidence of both ligamentous and meniscal injury to the knee after ipsilateral femoral shaft fracture. MR imaging can be useful in assessing the extent of injury, and may reveal findings unsuspected after clinical examination of the knee.     

A 2-year-old child with acute respiratory difficulty. Pneumomediastinum and subcutaneous emphysema due to foreign body aspiration

Using familiar anatomic references viewed during a standard arthroscopic evaluation, an arthroscopic Lachman test can help the surgeon identify anterior cruciate ligament deficiency. This test is especially useful in those patients where a false-negative report as a result of guarding, meniscal tears or other factors is suspected. Additionally, this test can be used after anterior cruciate ligament reconstruction to verify that the abnormal anterior laxity has been eliminated.     

Multishot echoplanar MR imaging of the female pelvis: comparison with fast spin-echo MR imaging in an initial clinical trial

OBJECTIVE: The purpose of this study was to apply multishot echoplanar MR imaging (EPI) to the female pelvis and compare image quality with that of fast spin-echo MR imaging. SUBJECTS AND METHODS: Twenty-one patients with suspected pelvic disease and five healthy female volunteers were prospectively examined. MR imaging was obtained using an EPI-capable 1.0-T imager and a pelvic phased-array coil. Axial EPI and fast Spin-echo sequences were obtained at identical image locations in each patient and volunteer. Spin-echo EPI images were obtained using a multishot number of 16. Acquisition time for each EPI sequence was 2 min 10 sec. Fat-suppressed T2-weighted fast spin-echo images were obtained in 2 min 12 sec. Paired EPI and fast spin-echo MR images were independently evaluated by three reviewers. RESULTS: Delineation of the perivaginal and parametrial venous plexus on EPI was rated superior to the fast spin-echo images in 62 (77%) of 81 cases. On EPI, uterine zone anatomy and ovary visualization were judged to be inferior in 44 (56%) of 78 cases and in 18 (33%) of 54 cases, respectively. For delineation of uterine abnormalities, including leiomyoma and adenomyosis, both sequences performed almost equally well. However, ovarian cystic lesions were revealed more precisely by the fast spin-echo sequence. An overall fat-suppression effect was seen on EPI images in 62 (77%) of 81 cases. CONCLUSION: Multishot EPI cannot replace fast spin-echo sequences for imaging the female pelvis; however, because EPI has a potent fat-suppression effect and heavily T2-weighted contrast, EPI sequences can be a valuable adjunct to routine examination.     

Paroxetine in the treatment of generalized social phobia: open-label treatment and double-blind placebo-controlled discontinuation

Sixty-nine patients with traumatic knee hemarthrosis were evaluated an average of 3 days after trauma by high field (1.5T) magnetic resonance imaging (MRI) using sagittal T1, T2-weighted and coronal 3D-gradient echo images. All knees were arthroscopically examined shortly afterwards. The diagnostic validity of MRI for intraarticular pathology was determined using arthroscopy as golden standard. All patients had pathological findings on arthroscopy. The injuries were sports-related in 77% of the cases. MRI was highly sensitive (86%) and specific (92%) for diagnosis of anterior cruciate ligament tears. Diagnosis of medial meniscal tears showed a 74% sensitivity and 66% specificity. MRI detected lateral meniscal tears in 50% with an 84% specificity. As such, MRI missed 10 significant meniscus ruptures requiring surgical treatment. The sensitivity for partial or total medial collateral ligament tears was 56%, the specificity 93%. Rupture of the medial retinaculum in cases with patellar dislocation or significant damage of articular cartilage were only detected by MRI in a few cases (27% and 20% sensitivity, respectively). MRIs low diagnostic validity for intraarticular pathology with hemarthrosis may be attributed to the shifting paramagnetic properties of the blood remains and catabolic processes in meniscal and chondral tissues during the hemoglobin degradation process. Accordingly, MRI, with the technique used, could neither replace arthroscopy in the diagnosis and screening of acute knee injuries, nor select patients with need for immediate arthroscopic meniscal surgery.     

Use of self-expanding metallic stents in the management of obstruction of the sigmoid colon

PURPOSE: To compare the occurrence at magnetic resonance (MR) imaging of clinically important knee abnormalities in patients referred by orthopedic surgeons with that in patients referred by other physicians. MATERIALS AND METHODS: Knee MR images in all patients referred for evaluation of internal derangement for 12 months were retrospectively reviewed. Meniscus, ligament, and articular cartilage abnormalities were tabulated. The numbers of abnormalities detected in the patients referred by orthopedic surgeons were compared with those in the patients referred by all other physicians by using chi(2) analysis. Significance was defined at P less than .05. RESULTS: Knee MR images in 439 patients were reviewed; 328 patients were referred by orthopedic surgeons, and 111 were referred by other physicians. There was no significant difference in the rates of occurrence of meniscus tear (149 [45%; orthopedic surgeon referrals] vs 50 [45%; other physician referrals], P = .96); ligament tear (82 [25%] vs 21 [19%], P = .25); isolated hyaline cartilage defect (77 [23%] vs 20 [18%], P = .29); meniscus or ligament tear (167 [51%] vs 55 [50%], P = .86); or meniscus, ligament, or articular cartilage tear (242 [74%] vs 72 [65%], P = .34). The proportion of patients who subsequently underwent surgery of the knee was also similar (39% [118 of 300] vs 28% [23 of 82], P = .14). CONCLUSION: There was no significant difference in the occurrences of clinically important knee internal derangement at MR imaging between patients referred by orthopedic surgeons and those referred by other physicians.     

Office arthroscopy: a diagnostic alternative

Twenty patients with enigmatic knee symptoms were selected for evaluation by both magnetic resonance imaging (MRI) and office arthroscopy. Office arthroscopy was performed in a standard examination room using a miniature (1.7 mm) fiberoptic arthroscope under local anesthesia. All MRI scans were performed on a state-of-the-art 1.5-T magnet unit, and included specialized cartilage sequences in 7 patients. In 14 patients, 26 areas showed articular cartilage changes by arthroscopy (grade 2-3). Only nine of these areas were detected by MRI (sensitivity 34.6%). There were five false-positive and four false-negative readings of meniscal tears by MRI as compared with office arthroscopy. These results improved when postoperative menisci were excluded. Only one of three anterior cruciate ligament (ACL) disruptions identified by MRI could be verified by arthroscopy. The one posterior cruciate ligament (PCL) disruption was confirmed by both techniques. MRI was superior to arthroscopy in identifying bone contusions, subchondral sclerosis, and medial cruciate ligament (MCL) sprains. Office arthroscopy is an accurate and cost-efficient alternative to MRI in diagnostic evaluation of knee pathology in patients with enigmatic symptomatology.     

Comparison of fat-saturation fast spin echo versus conventional spin-echo MRI in the detection of rotator cuff pathology

The purpose of this study was to compare the diagnostic performance of fat-saturation fast-spin-echo (FSE) T2-weighted (T2W) sequences with conventional spin-echo (CSE) T2W sequences in the detection of rotator cuff pathology using surgery as the reference standard. Oblique coronal dual-echo CSE and FSE T2W images with fat saturation from 50 surgically confirmed MR shoulder examinations were acquired on a 1.5-T MR scanner. Blinded MR readers retrospectively analyzed each imaging sequence separately and ultimately correlated both sequences together with findings at surgery. FSE was 100% sensitive and 94% specific in detection of full-thickness tears (n = 19) and 73% sensitive and 97% specific in the detection of partial-thickness rotator cuff tears (n = 13). There was no statistically significant difference in the performance of FSE with fat saturation compared with CSE. The two discrepancies between imaging sequences related to the extent of partial-thickness tears. Our findings suggest that fat-saturation FSE imaging can effectively replace CSE imaging in the evaluation of rotator cuff pathology.     

MRI of meniscal bucket-handle tears

OBJECTIVE: A meniscal bucket-handle tear is a tear with an attached fragment displaced from the meniscus of the knee joint. Low sensitivity of MRI for detection of bucket-handle tears (64% as compared with arthroscopy) has been reported previously. We report increased sensitivity for detecting bucket-handle tears with the use of coronal short tau inversion recovery (STIR) images. DESIGN AND PATIENTS: Three hundred and twenty-seven patients who had MRI of the knee between October 1994 and December 1996 and subsequently underwent arthroscopy were included in the study. We prospectively and retrospectively reviewed the MR examinations of the 30 patients with arthroscopically proven bucket-handle tears. Each of two observers examined each scan for the three traditional findings of bucket-handle tears: a double posterior cruciate ligament sign, a flipped meniscus sign and/or a fragment in the intercondylar notch. We also assessed STIR images in the coronal plane through the menisci looking for an area of increased signal within either meniscus with a displaced meniscal fragment. RESULTS: By using four criteria for diagnosis of meniscal bucket-handle tears, our overall sensitivity compared with arthroscopy was 93% (28 of 30 meniscal bucket-handle tears seen at arthroscopy were detected by MRI). The meniscal fragment was well visualized in all 28 cases on coronal STIR images. The double posterior cruciate ligament sign was seen in 8 of 30 cases, the flipped meniscus was seen in 10 of 30 cases and a fragment in the intercondylar notch was seen in 18 of 30 cases. CONCLUSION: By using four criteria for diagnosis of bucket-handle tears, overall diagnostic sensitivity of MRI compared with arthroscopy increased from the previously reported 64% to 93%. Coronal STIR images are useful for detecting small meniscal bucket-handle tears.     

Lateral-compartment bone contusions in adolescents with intact anterior cruciate ligaments

PURPOSE: To determine how often lateral-compartment bone contusions are seen on magnetic resonance (MR) images of knees in adolescents with intact anterior cruciate ligaments (ACLs). MATERIALS AND METHODS: MR images obtained in 53 adolescent patients (30 male, 23 female; aged 10-20 years) were reviewed to detect bone contusions in the posterolateral tibial plateau or the lateral femoral condyle. ACLs were also evaluated with accepted criteria for the diagnosis of ligamental disruption. Only patients referred for evaluation of a knee injury or mechanical symptoms were included. RESULTS: Five patients with bone contusions had an intact ACL at MR imaging. One of the five had arthroscopic confirmation. Fifteen other patients had complete ACL disruptions: 13 of these patients had typical bone contusions; the other two had no bone abnormalities but had chronic ACL tears. Thus, 28% of the 18 patients with typical bone contusions had intact ACLs. CONCLUSION: Adolescents may have the same pattern of contusions as adults but may maintain an intact ACL owing to increased ligamentous laxity.     

Chronic pulmonary histoplasmosis in Brazil: report of two cases with cavitation diagnosed by transthoracic needle biopsy

OBJECTIVE: To compare fat-suppressed fast spin-echo (FSE) T2-weighted images with gradient-recalled echo (GRE) T2*-weighted images in the evaluation of anteroinferior labral tears. DESIGN: MR images were retrospectively reviewed by two radiologists masked to the history and arthroscopic findings. They separately interpreted the anteroinferior labrum as torn or intact, first on one pulse sequence and then, 4 weeks later, on the other sequence. The MR interpretations were correlated with the arthroscopic findings. PATIENTS: Nine patients with anteroinferior labral tears, and nine similarly-aged patients with normal, labra were studied. RESULTS AND CONCLUSIONS: Observer 1 had a sensitivity of 0.56 on the GRE images and 0.67 on the FSE images (P > 0.5), with a specificity of 1.0 for both sequences. Observer 2 had a sensitivity of 0.78 and a specificity of 0.89 for both sequences. In this small study there is no significant difference between GRE and fat-suppressed FSE images in their ability to diagnose anteroinferior labral tears. When evaluating the labrum with conventional MRI, axial fat-suppressed FSE T2-weighted images can be used in place of GRE images without a loss of accuracy.     

Magnetic resonance imaging of knee injuries in children

The appearances of knee injuries on MR imaging are less well documented in children than adults. Some patterns of injury are shared by both groups of patients, e. g. meniscal damage. The frequency of specific injuries may differ, e. g. anterior cruciate ligament (ACL) tear. Congenital abnormality, coexistent pathology and previous treatment of the knee appear to be associated with meniscal problems. Discoid menisci are seen most frequently in children and have unique features on MR scans. Cruciate ligament tears are difficult to diagnose in the smallest children. The ACL may not be identified due to its small size. Normal bone marrow signal may be confused with marrow infiltration or bone microfracture. Radiographically occult fractures around the knee appear to be strongly associated with ligamentous injury as in adult patients. Osteochondral fractures, osteochondral lesions and articular cartilage damage are revealed on MR scans, but their long-term effects are uncertain. It is possible to diagnose a range of knee injuries on MR scans in children. The biggest diagnostic challenge is in pre-school children.     

Injury of the posterior ligament complex in patients with acute spinal trauma: evaluation by MR imaging

OBJECTIVE: We undertook this study to use MR imaging to determine the frequency of injury to the posterior ligament complex of the thoracolumbar spine in patients who have undergone acute thoracolumbar trauma. SUBJECTS AND METHODS: Sixty-eight patients with varying severity of thoracolumbar trauma were examined prospectively. The majority of injuries were related to motor vehicle accidents. The second most common cause was falls. Patients were examined with plain radiography and MR imaging. In addition to conventional MR imaging sequences consisting of T1-weighted and fast spin-echo T2-weighted sagittal and axial images, a fat-suppressed T2-weighted sagittal sequence was performed. The findings were correlated with surgery in six cases and with follow-up clinical examination that included physical examination and conventional anteroposterior and lateral radiographs. RESULTS: Posterior ligament complex injury was detected in 53% (n = 36) of all patients. Such injury was most common in patients with flexion-distraction (n = 15) and patients with dislocation fracture (n = 4). Of the patients with dislocation fracture, all had posterior ligament complex injury. Of the 24 patients with burst fractures, posterior ligament complex tear occurred in 42% (n = 10). Of the 23 patients with compression fractures, 26% (n = 6) had posterior ligament complex tear. Injury to the interspinous ligaments occurred with decreasing frequency in patients with injury to the supraspinous ligament, flaval ligaments, posterior longitudinal ligament, and anterior longitudinal ligament. Surgical findings correlated with MR imaging in all six patients who underwent surgery. CONCLUSION: Injury to the posterior ligament complex, which is often encountered in patients with burst and compression fractures, can be reliably revealed by MR imaging.     

Synovial cyst of the cruciate ligament. Findings with magnetic resonance in 8 symptomatic cases

Intraarticular ganglion cysts are uncommon findings: only 30 cases have been reported since the first paper by Caan in 1924 and they were all associated with cruciate ligaments. Many different cystic or pseudocystic lesions are found in articular knee conditions: the most common cystic lesions are popliteal cysts (Baker's cysts), followed by synovial pseudocysts of the posterior cruciate ligament, meniscal cysts and, finally, ganglion cysts of the cruciate ligaments. In our series of 1600 knee MR exams carried out in our MR department since June, 1994, we have found 8 ganglion cysts of the cruciate ligaments. MR studies are always performed on a dedicated 0.2-T permanent magnet (Artoscan, Esaote Biomedica, Genoa, Italy). Five patients were operated on with arthroscopy. The ganglion cysts affected the anterior cruciate ligaments in 4 cases and the posterior cruciate ligaments in 4 cases. The symptoms were mainly pain radiating to the medial side and worsening in forced flexion or extension. The diagnostic suspicion was meniscal tears in 4 patients, chondral lesions in 3 and a loose intraarticular body in one patient. The shape and structure of ganglion cysts in the cruciate ligaments are clearly depicted with MRI. The ganglion cysts in the anterior cruciate ligaments are usually spindle-shaped and within the ligament, while those in the posterior cruciate ligaments have a well-defined outline, with multilocular appearance, and they are usually localized along the ligament, most often on the dorsal aspect. MR signal studies show intermediate signal intensity on SE T1-weighted images and markedly increased signal intensity on SE T2-weighted images. These typical patterns may change depending on lesion content, for instance in the presence of hemoglobin due to an associated angioma. The origin of ganglion cysts in the cruciate ligaments is still unknown, even though many theories have been suggested, including a synovial herniation in ligament fibers, the ectopic inclusion of synovial tissue, a posttraumatic connectival degeneration and, finally, the proliferation of totipotent mesenchymal cells. From a histologic point of view, "synovial ganglion" is a much better definition than "synovial ganglion cyst", because the typical wall of real synovial cysts is missing. The MR patterns are typical of the morphological features described and of the presence of high protein fluid content.     

MR imaging of tears of discoid lateral menisci

OBJECTIVE: The purpose of this study was to determine the positive predictive value (PPV) for diagnosis of discoid lateral meniscal tear using MR imaging and to describe various patterns of such tears in the knee. SUBJECTS AND METHODS: MR reports of 77 patients (10-67 years old) who underwent prospective MR imaging that led to a diagnosis of discoid lateral meniscal tear were correlated with arthroscopic results. MR images obtained in 71 patients confirmed to have discoid lateral meniscial tear were retrospectively reviewed for the presence, site, and pattern of discoid lateral meniscal tear, including type of displacement of the torn segment. MR abnormalities were correlated with arthroscopic findings. RESULTS: For the prospective MR interpretations, the PPV for discoid meniscus was 92%. PPV for discoid meniscal tear was 57%. PPVs for individual types of discoid meniscal tears were 46% (peripheral tear, 19/41), 76% (peripheral tear with horizontal tears, 16/21), 56% (horizontal tear, 5/9), 50% (transverse tear, 1/2), 67% (horizontal tear combined with transverse tear, 2/3), and 100% (longitudinal tear, 1/1). Peripheral tear alone and peripheral tear with horizontal tear were the most common types of tears (n = 20, 28%). Multiple tears (n = 34, 48%) were common. Displacement of the torn segments was seen in 51 patients (72%). CONCLUSION: MR imaging has a low PPV for diagnosing discoid lateral meniscal tear. Peripheral tear alone and peripheral tear with horizontal tear were the most common types of tears, and displacement of the torn segment was frequent.