Anterior Cruciate Ligament Tear: Reliability of MR Imaging to Predict Stability after Conservative Treatment

OBJECTIVE: The aim of this study is to evaluate the reliability of MR imaging to predict the stability of the torn anterior cruciate ligament (ACL) after complete recovery of the ligament's continuity. MATERIALS AND METHODS: Twenty patients with 20 knee injuries (13 males and 7 females; age range, 20-54) were enrolled in the study. The inclusion criteria were a positive history of acute trauma, diagnosis of the ACL tear by both the physical examination and the MR imaging at the initial presentation, conservative treatment, complete recovery of the continuity of the ligament on the follow up (FU) MR images and availability of the KT-2000 measurements. Two radiologists, who worked in consensus, graded the MR findings with using a 3-point system for the signal intensity, sharpness, straightness and the thickness of the healed ligament. The insufficiency of ACL was categorized into three groups according to the KT-2000 measurements. The statistic correlations between the grades of the MR findings and the degrees of ACL insufficiency were analyzed using the Cochran-Mantel-Haenszel test (p < 0.05). RESULTS: The p-values for each category of the MR findings according to the different groups of the KT-2000 measurements were 0.9180 for the MR signal intensity, 1.0000 for sharpness, 0.5038 for straightness and 0.2950 for thickness of the ACL. The MR findings were not significantly different between the different KT-2000 groups. CONCLUSION: MR imaging itself is not a reliable examination to predict stability of the ACL rupture outcome, even when the MR images show an intact appearance of the ACL.

CT Arthrography and Virtual Arthroscopy in the Diagnosis of the Anterior Cruciate Ligament and Meniscal Abnormalities of the Knee Joint

OBJECTIVE: To determine the diagnostic accuracy of CT arthrography and virtual arthroscopy in the diagnosis of anterior cruciate ligament and meniscus pathology. MATERIALS AND METHODS: Thirty-eight consecutive patients who underwent CT arthrography and arthroscopy of the knee were included in this study. The ages of the patients ranged from 19 to 52 years and all of the patients were male. Sagittal, coronal, transverse and oblique coronal multiplanar reconstruction images were reformatted from CT arthrography. Virtual arthroscopy was performed from 6 standard views using a volume rendering technique. Three radiologists analyzed the MPR images and two orthopedic surgeons analyzed the virtual arthroscopic images. RESULTS: The sensitivity and specificity of CT arthrography for the diagnosis of anterior cruciate ligament abnormalities were 87.5%-100% and 93.3-96.7%, respectively, and those for meniscus abnormalities were 91.7%-100% and 98.1%, respectively. The sensitivity and specificity of virtual arthroscopy for the diagnosis of anterior cruciate ligament abnormalities were 87.5% and 83.3-90%, respectively, and those for meniscus abnormalities were 83.3%-87.5% and 96.1-98.1%, respectively. CONCLUSION: CT arthrography and virtual arthroscopy showed good diagnostic accuracy for anterior cruciate ligament and meniscal abnormalities.

MR Imaging Findings of Avulsion Fracture of the Tibial Spine of the Knee, Focusing on Cruciate Ligament Tear

PURPOSE: To determine the presence of cruciate ligament tears following avulsion injuries involving the ACL and PCL, and to correlate the findings with those of surgery. MATERIALS AND METHODS: Between March 1997 and May 2002, avulsion injury involving the ACL or PCL was diagnosed in 19 patients. Ten of these [8 males and 2 females aged 10-51 (avergae, 27.7) years] were included in this study. We assessed the presence of cruciate ligament tears at MR imaging, correlating the findings with those of surgery. Associated intra-articular injuries, treatment methods and follow-up results were also evaluated. RESULTS: Among Seven patients with ACL avulsion injury, this was assessed at MR imaging as complete tear (n=1), partial tear (n=5), or intact (n=1), while all MR images of PCL avulsion injury (n=3) showed that this was partial tear. All imaging findings corresponded with the surgical findings. In four patients there was associated knee injury involving, respectively, tears of the medial meniscus, lateral meniscus, PCL and MCL, and popliteal ligament. CONCLUSION: Our findings showed that with one exception, patients with avulsion injury of the ACL or PCL had suffered either a partial or complete tear. MR imaging may be useful in the diagnosis of tears of the cruciate ligament which have not been noticed at surgery or arthroscopy in avulsion injuries involving the ACL and PCL.

Evaluation of Meniscal Tears of the Knee: The Usefulness of Fat-Suppressed Conventional Spin-Echo T1-Weighted MR Imaging

PURPOSE: To determine the usefulness of the fat-suppressed (FS) conventional spin-echo (CSE) sequence for the diagnosis of meniscal tears. MATERIALS AND METHODS: We retrospectively reviewed 323 MR images of the knee, the standard of reference being the findings of arthroscopy. In all knees, fast SE proton density-weighted and T2-weighted sagittal and coronal images and double-echo in steady state (DESS) sagittal images were obtained, and during 202 MR Procedures, FS-CSE T1-weighted sagittal images were also obtained. The results of MR imaging were then correlated with those of arthroscopy, the accuracy with which meniscal tears were diagnosed being compared between two groups: group I (202 knees for which FS-CSE T1-weighted sagittal images were obtained), and group II (121 knees for which these images were not obtained). For statistical analysis the chi-square test was used. RESULTS: In group 1, sensitivity, specificity and accuracy were 94.7%, 92.4% and 93.5%, respectively, for the medial meniscus, and 83.3%, 95.7% and 90.5% for the lateral meniscus. In group II, the corresponding findings were 92.5%, 94% and 93.3%; and 87.3%, 98.2% and 92.5%. The differences between the groups were not statistically significant (p>0.05) CONCLUSION: For meniscal tears of the knee, the addition of FS-CSE T1-weighted MR imaging to the fast SE proton density-weighted, T2-weighted and DESS sequences does not enhance diagnostic accuracy.

Evaluation of Chondromalacia in the Knee Joint using Three Dimensional Fourier Transformation Constructive Interference in Steady State(CISS)

PURPOSE: To assess the usefulness of three-dimensional Fourier transformation constructive interference in steady state (CISS) for the evaluation of chondromalacia. MATERIALS AND METHODS: In 110 knee joints which underwent both MR imaging and arthroscopy, the findings were retrospectively reviewed. MR imaging sequences included two-dimensional dual-echo turbo spin-echo imaging along the sagittal and coronal planes, two-dimensional fast low-angle shot (FLASH) with magnetization transfer along the axial plane, and three-dimensional CISS along the sagittal plane. After the cartilage surfaces of each joint were divided into eight areas (each medial and lateral area of patellar facets, trochlear surfaces, femoral condyles, and tibial plateaux), a total of 880 areas were assessed. Using both combined two-dimensional (2-D turbo spin-echo and FLASH) and CISS imaging during different sessions, each chondromalacia case was assigned one of five grades. RESULTS: Arthroscopy revealed the presence of chondromalacia in 162 areas. This was first grade in 77 areas, second grade in 38, third grade in 21, and fourth grade in 26. The sensitivity, specificity, and accuracy of 2-D and CISS imaging were 48.1%, 93.7% and 85.3%, and 45.7%, 95.3% and 86.1%, respectively. Agreement between MR and arthroscopic staging occurred in 81.48% of 2-D imaging procedures and 82.16% of CISS procedures. If a difference of one grade was accepted, these proportions rose to 84.32% and 85.22%, respectively, though this increase was statistically insignificant. CONCLUSION: Though CISS imaging was less sensitive than 2-D imaging in the grading of chondromalacia, additional CISS imaging can help improve the accuracy of this grading.

The Anterior Cruciate Ligament: The Value of Thin-section Proton Density Oblique Sagittal MR Imaging

PURPOSE: To evaluate the usefulness of thin-section proton density oblique sagittal MR imaging in the diagnosis of tear involving the anterior cruciate ligament (ACL). MATERIALS AND METHODS: In 61 arthroscopically confirmed cases (29 patients with ACL injury and 32 normal subjects), thin section proton-density images (TSPDI) were obtained and compared with conventional oblique sagittal PDI and T2-weighted images (T2WI). In TSPD imaging, the scan plane was parallel to the course of the ACL, based on a coronal scanogram; the parameters used were TR/TE 2000 msec/20 -33 msec, 2-mm slice thickness, 16 x16 cm FOV, 256 x192 matrix, two excitations, and no intersection gap. We evaluated the sensitivity and specificity of MR images for diagnosing ACL tear, and their quality, on the basis of whether or not they successfully visualised the anterior/posterior margin of the ACL and linear signal intensities within the ACL fascicles. We also investigated the effects of partial volume averaging between the proximal portion of the ACL and the lateral femoral condyle. RESULT: The sensitivity/specificity of TSPD imaging for diagnosing ACL tear were not significantly different from those of conventional oblique sagittal PDI and T2WI. In the ACL injury group, TSPDI was better in detecting increased signal intensity, ACL thickening, and visualization of torn ACL than conventional oblique sagittal PDI and T2WI. In normal subjects, image quality was constantly better on TSPDI than on conventional oblique sagittal PDI and T2WI. TSPDI clearly revealed the anterior margin in 31/32 cases (97%) and linear signal intensities within the ACL fascicles in all 32 (100%), and also markedly reduced the partial volume effect of the proximal ACL and lateral femoral condyle. CONCLUSION: In evaluating the ACL, the use of TSPD imaging is likely to lead to improved image quality. In addition, where routine MR imaging reveals indeterminate ACL injury, TSPDI can provide additional clues to diagnosis.

Absent Bow-Tie Sign in Knee MRI

PURPOSE: 'Absent bow-tie sign'is interpreted as positive when a bow-tie-shaped body segment is seen on only one or no slice of 4- or 5-mm thick sagittal images, and is a well known as a useful sign in diagnosing bucket-handle meniscal tears. In practice, however, we have found that this sign was also positive in certain cases other than bucket-handle tears. We have assumed that if the normal range of meniscal body width, as determined among Westerners, is transferred to the Korean population without verification and modification this might lead to misdiagnosis. The purpose of this study, therefore, is to examine the reliability of the 'absent bow-tie sign'. MATERIALS AND METHODS: Among 454 cases in which knee MRI had been performed, we retrospectively evaluated 862 menisci, the total remaining after cases of discoid meniscus or those involving previous meniscectomy had been excluded. Among the 862 menisci, 614 were normal, 97 showed degeneration, 43 showed buck-et-handle tearing, and 108 showed tears other than bucket-handle tear. In all cases, proton-denwity and T2-weighted images were obtained in both sagittal and coronal planes, with 3mm section thickness and 1mm gap. We recorded the number of sagittal images in which the body segment of each meniscus had a bow-tie appear-ance, and measured the width of each meniscal body, as seen on midcoronal images. RESULTS: In all cases but one of bucket-handle tears (97.7%), the bow-tie sign was absent, as it was in 73.2% ofnon-bucket-handle tears, 35.0% of degenerated menisci and 27.5% of normal menisci. Among the non-tear group, 56.4% of menisci in the female group and 27.1% in the male group had bodies less than 9mm wide. CONCLUSION: In the diagnosis of bucket-handle tears, the 'absent bow-tie sign'is a very sensitive indicator. It is nonspecific, however, and merely suggests some significant deficiency in the meniscus body or small menis-ci,so can be positive in other cases. Thus the interpreter should be aware of the characteristics of this sign especially when used to interpret MRI of the knee of a female Korean patient.

Complete and Partial-Thickness Tears of the Anterior Cruciate Ligament: Differential Features Seen on MRImaging

PURPOSE: To evaluate the differential features of complete and partial-thickness tears of the anteriorcruciate ligament, as seen on magnetic resonance imaging(MRI). MATERIALS AND METHODS: We retrospectvely reviewedMR images of 36 patients with ACL injuries (complete tear 16, incomplete tear 20). In all cases, the presence ofan ACL tear was determined by arthroscopy or surgery. Primary and secondary signs of ACL injury and associatedinjuries were assessed. RESULTS: Ligamentous discontinuity of the ACL was observed in ten complete tears (63 %),but in only four (10%) of those that were partial (p=0.009). In addition, complete tears were more likely to showa low degree of ACL axis, less than 45 degree(11/16 : 2/20, p=0.001). There was, however, no statistically significantdifference between complete and partial tears with regard to signal intensity of ACL, PCL buckling or angle,anterior dis-placement of the tibia, uncovered meniscus sign, deep notch sign, empty notch sign, and associatedinjuries. CONCLUSION: Ligamentous discontinuity and the ACL axis are features which usefully differentiatebetween complete and partial tears of the ACL.

Diagnostic Value of MR Imaging in Differentiation of Meniscal Tear Patterns

PURPOSE: To evaluate the diagnostic accuracy of magnetic resonance (MR) imaging in the differentiation ofmeniscal tear patterns of the knee. MATERIALS AND METHODS: MR images of 93 patients with meniscal tear wereincluded in this study. On the basis of arthroscopic findings, the configuration of meniscal tears was classifiedas horizontal (n=44), longitudinal (n=34), transverse (n=11), or oblique (n=5). Oblique sagittal and coronal MRimages were obtained and com-pared with the arthroscopic findings. RESULTS: Among 94 cases ofarthroscopically-proven meniscal tears, 35 of 44 horizontal and 27 of 34 longitudi-nal configurations werecorrectly interpreted on MR images. Sensitivity and specificity for horizontal configu-ration were 80 % and 80 %,respectively, while the corresponding values for longitudinal configuration were 79 % and 95 %. On MR images, tworadial configurations were correctly interpreted from 11 confirmed tears and only one oblique configuration fromfive confirmed tears. CONCLUSION: MR imaging was useful for the differentiation of horizontal and longitudinaltears, but inaccurate in cases involving radial or oblique tears.

Usefulness of Fat-Suppressed Turbo SE MR Imaging for the Evaluation of Meniscal Tears

PURPOSE: Suppression of the relatively high signal intensity of fat leads to more efficient use of thedynamic range for display of tissue contrast. In order to evaluate meniscal tears, we compared a fat-suppressedturbo spin-echo(FSTSE) sequence with turbo SE(TSE). MATERIALS AND METHODS: One hundred and seven knees in 103consecutive patients referred for MR study of the knee were imaged using both FSTSE and TSE sequence. The turbo SEsequence provided proton density-weighted and T2-weighted images (dual echo technique) with an effectiveecho-train length of five. For fat-suppression, a frequency-selective chemical presaturation pulse was applied.Forty-two knees (84 menisci) were studied arthroscopically and the findings were taken as the reference standard.FSTSE and TSE images were reviewed retrospectively by two radiologists. Next, for each patient, the quality ofFSTSE and TSE images was compared;the former were scored by each reviewer as either superior to, equal to, orinferior to TSE images. RESULTS: Among the 214 menisci evaluated, the results of FSTSE and TSE imaging were verysimilar (kappa index 0.87). Twenty four tears were found during arthroscopy in 84 menisci. FSTSE imaging was moresensitive than TSE (96% versus 83%), though specificity was equal(98%). Among the 107 cases, FSTSE images wererated by both observers as superior to TSE images for overall quality and visualization of the meniscus itself.CONCLUSION: For the evaluation of meniscal tears, FSTSE sequences were more sensitive than those obtained withTSE, and their image quality was superior. For the study of meniscus tears among a large population, FSTSE istherefore more useful than TSE.

MR Imaging of Articular Cartilage: Comparison of Magnetization Transfer Contrast and Fat - Suppression inMultiplanar and 3D Gradient-Echo, Spin-Echo, Turbo Spin-Echo Techniques

PURPOSE: The purpose of this study was to evaluate the effects of magnetization transfer contrast(MTC) andfat-suppression(FS) in variable spin-echo and gradient-echo sequences for articular cartilage imaging and todetermine the optimal pulse sequences. MATERIALS AND METHODS: Using variable 7-pulse sequences, the knees of 15pigs were imaged Axial images were obtained using proton density and T2-weighted spin-echo (PDWSE and T2WSE),turbo spin-echo (TSE), multiplanar gradient-echo (MPGR), and 3D steady-state gradient-echo (3DGRE) sequences, andthe same pulse sequences were then repeated using MTC. Also T1-weighted spin-echo(T1WSE) and 3D spoiledgradient-echo(3DSPGR) images of knees were also acquired, and the procedure was repeated using FS. For each knee,a total of 14 axial images were acquired, and using a 6-band scoring system, the visibility of and thevisibilities of the the articular cartilage was analyzed. The visual effect of MTC and FS was scored using a4-band scale. For each image, the signal intensities of articular cartilage, subchondral bone, muscles, and salinewere measured, and signal-to-noise ratios(SNR) and contrast-to-noise ratios(CNR) were also calculated. RESULTS: Visibility of the cartilage was best when 3DSPGR and T1WSE sequences were used. MTC imaging increased the negativecontrast between cartilage and saline, but FS imaging provided more positive contrast. CNR between cartilage andsaline was highest when using TSE with FS(-3 5 1 . 1 +/-15.3), though CNR between cartilage and bone then fell to-1 4 . 7 +/-10.8. In MTC imaging using MPGR showed the greatest increase of negative contrast between cartilage andsaline(CNR change=-74.7); the next highest was when 3DGRE was used(CNR change=-34.3). CNR between cartilage andbone was highest with MPGR(161.9 +/-17.7), but with MTC, the greatest CNR decrease(-81.8) was observed. Thegreatest CNR increase between cartilage and bone was noted in T1WSE with FS. In all scans, FS provided acartilage-only positive contrast image, though the absolute value of CNR was lower than that of MTC imaging. CONCLUSION: The most prominent effects of MTC and FS were seen in MPGR and T1WSE, respectively, though forcartilage, optimal high signal intensity and contrast can be achieved using 3DGRE with MTC, and 3DSPGR with FS.

Analysis of MR Imaging with FSE and DESS for the Diagnosis of Meniscal Tears in 316 Patients

PURPOSE: To evaluate the accuracy of a magnetic resonance(MR) imaging strategy that primarily uses fast spinecho(SE) sequences for the diagnosis of meniscal tears. MATERIALS AND METHODS: The original clinical interpretations of MR images in 316 patients who underwent imaging for suspected internal derangement of a knee joint were correlated with results from subsequent arthroscopy (mean interval : 48.9 days). In all patients, MR examinations included double-echo fast SE T2- weighted sagittal and coronal imaging and double-echo steady state (DESS) sequence sagittal imaging. In 199 patients fat-suppressed conventional SE T1-weighted sagittal imaging was used. In cases in which interpretation was erroneous, imaging findings and arthroscopy reports were reviewed. RESULTS: For ISO confirmed tears of the medial meniscus, sensitivity, specificity, and accuracy were 94 %, 93 %, and 94 %, respectively, while respective values for 147 confirmed tears of the lateral meniscus were 85%, 97 %, and 91%. These values are within the ranges recently reported for imaging strategies relying predominantly on conventional SE sequences. Of the 12 false-positive tears of the medial meniscus, five menisci showed a high signal contacting the surface on only one image and seven, that in all cases were located in the periphery of the posterior horn, showed such signal on more than one image. Of the six false-positive tears of the lateral meniscus, three menisci showed a high signal contacting the surface on only one image. Of the nine false-negative tears of the medial meniscus, eight menisci showed an abnormal signal that did not demonstrate definitive contact with the surface. Of the 22 false-negative tears of the lateral meniscus, 18 menisci showed this same type of signal. CONCLUSION: Fast SE imaging of the knee can be an alternative to conventional SE imaging for the detection of meniscal tears. Most errors in our series were due to either an abnormal signal that failed to show definitive contact with the surface, a high signal which contacted the surface on only one image, or a signal of this type that was located in peripheral posterior horn of the medial meniscus, on more than one image.

MRI of Bucket-Handle Tears of the Meniscus of the Knee

PURPOSE: To determine the frequency of the MRI signs of meniscal bucket - handle tears already known as the double PCL sign, the flipped meniscus sign, the absent bow-tie sign, and the fragment-in-notch sign, and to compare the sagittal with the coronal images. MATERIALS AND METHODS: We retrospectively rev i ewed the MR findings of 37 patients in whom an initial interpretation of MR images had suggested meniscal bucke t - handle tears. All underwent subsequent arthroscopic evaluation and in 28, bucke t - handle tears were confirmed. Sagittal double-echo and coronal fat-suppressed double-echo T 2 - weighted images were obtained. Sagittal images were evaluated to determine whether or not signs of bucket-handle tear were evident, and coronal images we r e checked for a torn meniscus with displaced fragment. We also evaluated the MR findings of the nine false positive cases. RESULTS: The prevalence rate of absent bow-tie, double PCL, fragment-in-notch, and flipped meniscus signs was 96.4%, 53.6%, 17.9%, and 10.7%, respective l y. The detection rate for displaced fragment was higher with coronal images (92.9%) than with sagittal images (78.6%). Among the nine false positive cases, a longitudinal tear in the discoid meniscus was most common. A false-positive diagnosis was much more frequent on sagittal than on coronal images. CONCLUSION: The prevalence rate of absent bow-tie sign was very high, but was accompanied by a relatively high rate of misinterpretation. Coronal fat-suppressed T2- weighted images provided more reliable clues for the diagnosis of bucket-handle tears, with a high detection rate of displaced fragment.

MRI of Bucket-Handle Tears of the Meniscus of the Knee

PURPOSE: To determine the frequency of the MRI signs of meniscal bucket - handle tears already known as the double PCL sign, the flipped meniscus sign, the absent bow-tie sign, and the fragment-in-notch sign, and to compare the sagittal with the coronal images. MATERIALS AND METHODS: We retrospectively rev i ewed the MR findings of 37 patients in whom an initial interpretation of MR images had suggested meniscal bucke t - handle tears. All underwent subsequent arthroscopic evaluation and in 28, bucke t - handle tears were confirmed. Sagittal double-echo and coronal fat-suppressed double-echo T 2 - weighted images were obtained. Sagittal images were evaluated to determine whether or not signs of bucket-handle tear were evident, and coronal images we r e checked for a torn meniscus with displaced fragment. We also evaluated the MR findings of the nine false positive cases. RESULTS: The prevalence rate of absent bow-tie, double PCL, fragment-in-notch, and flipped meniscus signs was 96.4%, 53.6%, 17.9%, and 10.7%, respective l y. The detection rate for displaced fragment was higher with coronal images (92.9%) than with sagittal images (78.6%). Among the nine false positive cases, a longitudinal tear in the discoid meniscus was most common. A false-positive diagnosis was much more frequent on sagittal than on coronal images. CONCLUSION: The prevalence rate of absent bow-tie sign was very high, but was accompanied by a relatively high rate of misinterpretation. Coronal fat-suppressed T2- weighted images provided more reliable clues for the diagnosis of bucket-handle tears, with a high detection rate of displaced fragment.

MR Findings of Chondromalacia Patella: Correlation of the Grade and Associated Lesions with ArthroscopicFindings

PURPOSE: To assess the MR findings of chondromalacia patella and correlate the grade and associated lesionswith the arthroscopic findings. MATERIALS AND METHODS: Twenty-five patients with pain in the anterior part of theknee underwent fat-suppressed axial and coronal T2-weighted, dual echo sagittal proton density-weighted andT2-weighted, and in some cases, T1-weighted and T2*-weighted imaging, using a 10-cm field of view, and a 5-inchgeneral purpose coil. We retrospectively assessed these find dings, and the locations, grades and associatedlesions, and correlated these with the arthroscopic findings. RESULTS: Fourteen cases(56%) of chondromalaciapatellae were arthroscopic grade I / II, nine(36%) were grade III, and two(8%) were grade IV; associated lesionswere medial synovial plicae (16 cases, 64%), meniscus tear (10 ; 40%), cruciate ligament injury (two ; 8%),complete or incomplete discoid meniscus (four ; 16%), bipartite patella (one ; 4%) and Osgood-Schlatter disease(one ; 4%). In 24 cases, MR imaging indicated chondromalacia patella ; 17 cases were grade I / II, five were gradeIII, and two were grade IV. the location of chondromalacia patella was the medial facet (five cases ; 20%), lateralfacet (three ; 12%), junction of the medial and odd facet (13 ; 52%), and diffuse involvement (four ; 16%). Thesensivity and specificity of MR imaging were 72% and 96% respectively. CONCLUSION: We evaluated the exact locationand grade of chondromalacia patella and associated lesions, as seen on MR images. These and the arthroscopicfindings showed close correlation, and in cases involving this condition, MRI is thus a useful indicator of anappropriate surgical method and plan.

Usefulness of T2-weighted Oblique Coronal MR Imaging In Anterior Cruciate Ligament Injury

PURPOSE: To evaluate the usefulness of T2-weighted oblique coronal imaging in the diagnosis of anteriorcruciate ligament (ACL) injury. MATERIALS AND METHODS: The MRI findings of 12 patients with ACL injury and a groupof 12 with normal ACL were respectively reviewed in terms of nonvisualization or focal defect, morphologic changeand increased signal intensity of ACL. Diagnostic accuracy in the conventional sagittal or coronal plane and inthe T2-weighted oblique coronal plane was also compared. T2-weighted oblique coronal scanning was performed, withthe imaging plane parallel to the direction of the intercondylar roof. RESULTS: In the ACL injury group,conventional MR imaging showed nonvisualization or focal defect (10/12), morphologic change (7/12), displacement(4/12), and increased signal intensity (9/12). T2-weighted oblique coronal imaging showed nonvisualization orfocal defect (11/12), morphologic change (5/12), and increased signal intensity(9/12). In the normal ACL group,conventional MR imaging demonstrated false-positive findings, i.e. these mimicked ACL injuries. Nonvisualizationor focal defect (2/12), and morphologic change (1/12), and increased signal intensity (5/12) were seen.T2-weighted oblique coronal imaging demonstrated normal ACL as an anteromedial and posterolateral band ; therewere no false-positive cases. On T2-weighted oblique coronal scan, no normal ACL showed increased signal intersity; compared with conventional MR imaging, this difference was statistically significant(P < 0.005). Overall, thesensitivity, specificity, and accuracy of conventional sagittal or coronal plane and T2-weighted oblique coronalplane imaging were, respectively 92% and 92%, 58% and 100%, and 75% and 96%. CONCLUSION: On T2-weighted obliquecoronal scans, the visualization of all normal anterior cruciate ligaments was better than on conventional MRimages. When ACL injury is vague on conventional MR imaging, T2-weighted oblique coronal imaging is considered tobe useful for the differentiation of ACL injury and normal ACL.

Natural Evolution of Grafted Anterior Cruciate Ligament of the Knee: Prospective Follow-up MR Studies

PURPOSE: To described the MR findings in the periodic changes of the size and signal intensity ofreconstructed anterior cruciate ligament (ACL) of the knee and the efficacy of oblique axial imaging in patientswho underwent arthroscopic ACL reconstruction using autogenous patellar tendon. MATERIALS AND METHODS: Twenty-onepatients who had undergone ACL reconstruction were evaluated by follow-up MRI at postoperative 1 week, 1, 2, 3 and6 months, and 1 year, Conventional Fast-Spin-Echo (FSE) sagittal and coronal images and oblique axial images(proton density and T2-WI; VEMP TR/TE, 2000/20/70) were obtained perpendicular to the ligament, and using an ROIcurve in the intra-articular area, periodic changes in the cross-sectional area were evaluated by proton densityimaging and signal intensity by T2WI imaging. Cross-sectional morphology was categorized as either smooth, andround or notch-shaped and periodic changes in configuration were observed. In three cases, we evaluated the retearof reconstructed ACL by comparing the oblique axizl image obtained by conventional sagittal and coronal imaging. RESULTS: The cross-sectional area and signal intensity of grafted ACL increased significantly (p<0.05) after 3months and at 1 year, respectively. Cross-sectional morphology was smooth and round in 86% of cases, and notchedin 14%, and during follow-up MR studies, no periodic changes were seen. Notch-shaped ACL and decreased perigraftsignal intensity, as seen on sagittal images, could lead to a misdiagnosis of partial tear ; on oblique axialimages, ACL and perigraft signal intensity were found to be normal. CONCLUSION: During the natural evolution ofgrafted ACL, cross-sectional area and signal intensity increased significantly after 3 months and at 1 year,respectively ; on follow-up MR studies, cross-sectional morphology did not change, however. Oblique axial imagingprovides important information for evaluating whether the reconstructed ACL is torn or not.

Meniscal Tears of the Knee: Diagnosis with Fast Spin-Echo MR Imaging and Role of Gadolinium-Enhancement

PURPOSE: The usefulness of fast spin-echo MR imaging for the diagnosis of meniscal tear of the knee is amatter of debate. The purpose of this study was to evaluate the accuracy of diagnosis of meniscal tears by fastspin-echo MR imaging and the role of gadolinium enhancement. MATERIALS AND METHODS: Between October 1994 andDecember 1996, 68 consecutive patients with arthroscopically proven meniscal tears participated in this study. AllMR examinations performed on a 1.5-T MR imager with an extremity knee coil. All patients underwent sagittal andcoronal MR imaging, using a fast spin-echo sequence with echo train length(ETL) 8. Sagittal and coronal fatsuppressed T1-weighted MR images were obtained after gadolinium infusion. RESULTS: In 68 cases ofarthroscopically-proven meniscal tears, MR sensitivity to tear was 93% (63/68) for fast spin-echo alone and 96%(65/68) for combined fast spin-echo and fat-suppressed gadolinium enhanced T1-weighted MR images. MR sensitivityto medial meniscus tear was 98% (40/41) for fast spin-echo alone and 98% (40/41) for combined fast spin-echo andfat-suppressed gadolinum-enhanced T1-weighted MR images. MR sensitivity to lateral meniscus tear was 85% (23/27)for fast spin-echo alone and 93% (25/27) for combined fast spin-echo and fat-suppressed gadolinium-enhancedT1-weighted MR images. CONCLUSION: Fast spin-echo MR imaging with adequate imaging parameters is suitable for thediagnosis of meniscal tears, and additional fat-suppressed gadolinium-enhanced T1-weighted MR imaging may increasediagnostic sensitivity to such tears.

The Significance of Alteration of Anterior Cruciate Ligament Axis as a Secondary Sign of Tear

PURPOSE: To assess the significance of alteration of the anterior cruciate ligament (ACL) axis as seen on magnetic resonance imaging of anterior cruciate ligament tear. MATERIALS AND METHODS: ACL angle (angle between lateral tibial plateau and ACL) and ACL-Blumensaat line angle (angle between ACL and Blumensaat line) were measured in 76 patients with ACL tear and 55 patients with normal ACL. The significance of the change in orientation of the ACL was evaluated. RESULTS: ACL angle was significantly smaller in the tear group (35.07 degrees +/- 10.34 degrees, mean+/-standard deviation) than in the normal group(54.11degrees+/-4.61degrees)(p<0.001); when cutoff value was less than 45 , sensitivity, specificity and accuracy were 85.5%, 98.2% and 90.8%, respectively. The ACL-Blumensaat line angle was significantly greater in the tear group (20.33degree+/-9.56degree) than in the normal group (2.55degree+/-4.86degree)(p<0.001). when cutoff value was more than 10degree, sensitivity, specificity and accuracy were 90.8%, 94.5%, and 92.4%, repectively. CONCLUSION: The change in orientation of the ACL was an important associated finding in cases of ACL tear. We suggest that cutoff values should be an ACL angle of less than 45 , and an ACL-Blumensaat line angle of more than10degree .

Anterior Cruciate Ligament Tear: Comparison of MR Features between Complete and Partial Tear

PURPOSE: To determine the MRI features which distinguish complete and partial tear of the anterior cruciate ligament (ACL) and to thus improve MRI interpretation. MATERIALS AND METHODS: In 80 patients, we analyzed MR findings of direct and indirect signs of ACL tear (complete tear, 61 cases, partial tear, 19 cases) confirmed by arthroscopy or surgery, and compared the relative incidence of each sign in cases of complete and partial tear. RESULTS: Direct and indirect signs were found in 61 (100%) and 60 cases (98.4%), respectively, in complete tears, but in 16 (84.2%) and 15 cases (78.9%), respectively, in partial tears. Poor visualization, discontinuity and hyperintensity were seen in all complete tears but in only nine case (47.4%) of partial tear. A wavy or abnormal contour was seen in 53 cases (86.9%) of complete tear and 14 (73.7%) of partial tear. A wavy contour without other direct signs was seen in only five cases (26.3%) of partial tear. Three cases (15.8%) of partial tear showed normal MR finding. Indirect signs, i. e. abnormal ACL angle, abnormal ACL-Blumensaat line angle, abnormal posterior cruciate ligament (PCL) line, abnormal PCL angle, PCL buckling, anterior displacement of tibia, posterior displacement of lateral meniscus, bone bruise, Segond fracture, tear of collateral ligaments, PCL, and tear of meniscus were commoner in complete than in partial tears. Two cases of O'Donoghue's triad and two of popliteus injury were seen only in complete tears. CONCLUSION: Direct and indirect signs of ACL tear were more commonly noted in complete than in partial tears. The latter showed MR features varying from normal to almost complete tear. We suggest that a wavy contour other direct signs is indicative of a partial tear, and that O'Donoghue's triad and popliteus muscle injury are indirect signs of a complete tear.