MR imaging of the knee. Part I. Traumatic disorders

One hundred thirty patients with a diversity of knee joint injuries were evaluated with a high-resolution magnetic resonance (MR) imaging technique. The authors report the accuracy of this technique in the evaluation of 105 patients with suspected meniscal tears, 26 patients with suspected cruciate ligament tears, and eight patients with suspected patellar tendon injuries. Of those menisci rated as definitely or probably torn on MR imaging, 80% were found to be torn at subsequent arthroscopy. The predictive value of negative MR imaging results was 100%. MR imaging was 92% accurate in predicting the clinical outcome in patients with suspected meniscal tears who did not undergo surgery. MR permitted complete disruption of the patellar tendon to be differentiated from partial tears, ligamentous inflammation, and localized effusion of the infrapatellar bursa. Injuries to the anterior and posterior cruciate ligaments were identified on MR images, and the status of synthetic grafts of the anterior cruciate ligament was ascertained.     

Magnetic resonance diagnosis of meniscal tears in patients with acute anterior cruciate ligament tears

OBJECTIVE: To evaluate the accuracy of magnetic resonance imaging in the diagnosis of meniscal tear in patients with acute anterior cruciate ligament tears. METHODS: Magnetic resonance images obtained from 41 patients imaged within 6 weeks of injury who had acute anterior cruciate ligament tears identified at arthroscopy were retrospectively reviewed for meniscal tear. RESULTS: With MR imaging the sensitivity, specificity and accuracy for diagnosing meniscal tears in the presence of acute anterior cruciate ligament tears were 71%, 93%, and 88%; for the lateral meniscal tears were 57%, 100% and 85%; and for the medial meniscal tears were 100%, 88%, 90%. All false negative cases (n = 6) involved the posterior horn of the lateral meniscus. CONCLUSION: In the presence of acute anterior cruciate ligament tears, MRI imaging has relatively low sensitivity for detecting meniscal tears due to missed tears in the lateral meniscus.     

Healing potential of meniscal tears without repair in knees with anterior cruciate ligament reconstruction

BACKGROUND: Few previous studies have documented the healing potential of meniscal tears that are left to heal without repair. PURPOSE: To determine the healing rates of meniscal tears left without repair in knees with anterior cruciate ligament reconstruction. STUDY DESIGN: Prospective cohort study. METHODS: One hundred and ninety-two knees were evaluated at the time of anterior cruciate ligament reconstruction and repeat arthroscopy. The healing rates of 41 medial and 42 lateral torn menisci without repair were evaluated by the same 2 surgeons in an identical fashion. RESULTS: Of 41 medial torn menisci left without repair, 22 (56%) were considered completely healed, 3 (7%) were incompletely healed, 11 (24%) were unhealed, and 5 (10%) had expanded unhealed lesions. Of 42 lateral torn menisci, 31 (74%) were considered completely healed, 2 (5%) were incompletely healed, 6 (14%) were unhealed, and 3 (7%) had expanded unhealed lesions. The healing rate of a medial meniscal tear was length dependent and not related to reconstructed ligament stability. CONCLUSIONS: Stable meniscal tears at the time of anterior cruciate ligament reconstruction possibly could be left in situ. However, longer medial meniscal tears are thought to require additional stabilizing procedures.     

MR imaging of the menisci and cruciate ligaments: a systematic review

PURPOSE: To systematically review and synthesize published data on the diagnostic performance of magnetic resonance (MR) imaging of the menisci and cruciate ligaments and to assess the effect of study design characteristics and magnetic field strength on diagnostic performance. MATERIALS AND METHODS: Articles published between 1991 and 2000 were included if at least 30 patients were studied, arthroscopy was the reference standard, the magnetic field strength was reported, positivity criteria were defined, and the absolute numbers of true-positive, false-negative, true-negative, and false-positive results were available or derivable. Pooled weighted and summary receiver operating characteristic (ROC) analyses were performed for tears of both menisci and both cruciate ligaments separately and for the four lesions combined, by using random effects models. Differences were assessed according to lesion type. RESULTS: Twenty-nine of 120 retrieved articles were included. Pooled weighted sensitivity was higher for medial meniscal tears than that for lateral meniscal tears. However, pooled weighted specificity for the medial meniscus was lower than that for the lateral meniscus. In summary ROC analyses performed per lesion, various study design characteristics were found to influence diagnostic performance. Higher magnetic field strength significantly improved discriminatory power only for anterior cruciate ligament tears. When all lesions were combined in one overall summary ROC analysis, magnetic field strength was a significant but modest predictor of diagnostic performance. CONCLUSION: Diagnostic performance of MR imaging of the knee is different according to lesion type and is influenced by various study design characteristics. Higher magnetic field strength modestly improves diagnostic performance, but a significant effect was demonstrated only for anterior cruciate ligament tears.     

Lateral tibial rim (Segond) fractures: MR imaging characteristics

The magnetic resonance (MR) imaging characteristics of lateral tibial rim (Segond) fractures and their associated injuries were reviewed in 12 patients with radiographic evidence of this fracture. Bone marrow adjacent to the fracture emitted a focally abnormal MR signal, which indicated an injury of the lateral capsular junction. The Segond fragment, however, was seen on MR images in only four of 12 patients. Associated ligamentous and meniscal injuries identified with MR imaging and arthroscopy involved the anterior (n = 11) and medial (n = 7) cruciate ligaments and the lateral (n = 4) and medial (n = 1) menisci. Focal bone marrow edema was due to injury of the lateral capsular junction. MR imaging evidence of such edema should indicate the presence of a lateral capsular injury and fracture, if one has not already been demonstrated with conventional radiography. A high association of Segond fractures with tears of the anterior cruciate ligament was confirmed, and MR imaging signs of a Segond fracture may therefore be used as indirect evidence for tears of that ligament.     

The quadruple cruciate sign of simultaneous bicompartmental medial and lateral bucket-handle meniscal tears

We report the second known case of bicompartmental bucket-handle tears of the medial and lateral menisci and the first documented case of the bucket-handle tears occurring simultaneously following trauma, which occurred after a motorcycle accident. Both bucket-handle fragments were displaced into the intercondylar notch. An anterior cruciate ligament tear was also present. Coronal images demonstrated four structures in the intercondylar notch: the anterior and posterior cruciate ligaments and the medial and lateral bucket-handle meniscal fragments.     

Tears of the anterior cruciate ligament and menisci of the knee: MR imaging evaluation

In 242 of 3,000 patients who underwent magnetic resonance (MR) imaging of the knee between September 1986 and August 1987, original MR imaging reports were compared with subsequent arthroscopic reports to determine the value of MR imaging in the evaluation of suspected meniscal and complete tears of the anterior cruciate ligament. The overall accuracy for the menisci was 93% (sensitivity, 95%; specificity, 91%) with a false-negative rate of 4.8%. For the anterior cruciate ligament the overall accuracy was 95%. T2-weighted sequences were associated with greater sensitivity, specificity, and accuracy than were T1 sequences; the false-negative rate was 0% in the T2-weighted group. MR imaging of the knee is an extremely accurate means for noninvasive assessment of the integrity of the menisci and anterior cruciate ligament, and the accuracy exceeds that usually reported for arthrography.     

1.5-T surface-coil MRI of the knee

Five normal knees and 20 knees with suspected abnormalities involving the menisci or articular surfaces were examined with high-resolution surface-coil MRI. Surgical correlation was available in 15 cases. Signal-to-noise ratios were optimized using a field strength of 1.5 T and a round 7.6-cm surface coil. Spatial resolution was maximized by using fields of view reduced to as small as 8 cm. Separate examinations of the medial and lateral joint compartments were performed with the surface coil positioned vertically adjacent to the meniscus of interest. Ten meniscal tears were identified using sagittal and coronal images. T1-weighted images were adequate to detect most meniscal tears, and T2-weighted images were useful for providing an "arthrogram effect" in the presence of a joint effusion. Extrameniscal lesions that were examined included osteonecrosis of the femoral condyle, subchondral cysts, rheumatoid arthritis, degenerative arthritis, and anterior cruciate ligament tears. MRI was useful in determining the integrity of articular cartilage overlying defects in the subchondral bone and in detecting gross cartilage lesions in arthritis, but was less sensitive than arthroscopy in evaluating moderate changes in the hyaline cartilage.     

The knee: surface-coil MR imaging at 1.5 T1

Seven normal knees (in five volunteers) and seven injured knees (in seven patients) were examined by high-resolution magnetic resonance (MR) imaging at 1.5 T with a surface coil. Seven medial meniscal tears, three anterior cruciate ligament tears, one posterior cruciate ligament avulsion, an old osteochondral fracture, femoral condylar chondromalacia, and one case of semimembranous tendon reinsertion were identified. MR images correlated well with recent double-contrast arthrograms or results of surgery. All tears were identified in both the sagittal and coronal planes. Because of its ability to demonstrate small meniscal lesions and ligamentous injuries readily, MR imaging with a surface coil may eventually replace the more invasive arthrography.     

Magnetic resonance imaging of the knee. Preliminary study of non-neoplastic osteoarticular pathology

Magnetic Resonance Imaging (MRI) has been applied to musculoskeletal pathoanatomy and has proved to be useful in the detection and characterization of knee pathology. Thirty-two acutely injured knees and 8 normal knees were examined. The images were obtained in the Diagnostic Centre RMRC of Naples on a 0.5 T superconductive magnet system, using a surface coil and a spin-echo pulse sequence (SE 600/28 ms). The examined limb was immobilized and bent at 8-10 degrees, extrarotated for the examination of the anterior cruciate ligament (ACL) only. Images were obtained on a 256 x 256 matrix and had a 2 or 4-mm thickness. MRI clearly showed all the anatomical structures. The anterior and posterior cruciate ligaments (ACL and PCL) and the patellar ligament were shown by sagittal SE images through the intercondylar notch; the tibial and fibular collateral ligaments (TCL and FCL) were evaluated on coronal SE images; the articular capsula and menisci on axial transverse SE images. Objective criteria for ACL and PCL tears were: lack of continuity of the signal and change in signal intensity; in meniscal pathology, menisci with small linear regions of increased signal or with grossly truncated shape were interpreted as tears. Preliminary results of this study indicate that MRI together with clinical evaluation may be an useful non-invasive procedure in the assessment of acute injuries of the knee.     

Diagnostic efficacy in knee MRI comparing conventional technique and multiplanar reconstruction with one-millimeter FSE PDW images

Background: Magnetic resonance (MR) imaging has proved to be an excellent tool in diagnosing injuries of the cruciate ligaments and menisci. However, multiple planes and sometimes optimal oblique or double-oblique scan planes are needed due to the variability in the positioning of important structures, which means there is a lower throughput and longer scanning time.

Purpose: To compare the performance of a 1-mm-thickness fast spin-echo (FSE) proton-density-weighted (PDW) MR imaging technique with multiplanar reconstruction (MPR) in diagnosing tears of the menisci and cruciate ligaments with that of conventional MR imaging.

Material and Methods: Twenty-five consecutive patients underwent preoperative conventional and 1-mm-thickness FSE PDW MR imaging with subsequent knee arthroscopic surgery. Two musculoskeletal radiologists evaluated the status of the cruciate ligaments and menisci using two sets of MR images (method A: conventional images including seven sequences, taking 26 min; method B: 1-mm-thickness FSE PDW images with MPR, taking 7 min 20 s). The diagnostic efficacies of both methods for tears of the cruciate ligament and menisci were calculated and compared.

Results: Arthroscopic surgery revealed 10 anterior cruciate ligament (ACL) tears, one posterior cruciate ligament (PCL) tear, and 26 meniscal tears. The diagnostic values of both methods were 100% for a cruciate ligament tear. The diagnostic values (sensitivity, specificity, accuracy, positive predictive value, and negative predictive value) for meniscal tears were 90%, 100%, 96%, 100%, and 94% for method A, and 95%, 100%, 98%, 100%, and 97% for method B, respectively. There were no significant differences in the diagnostic values between methods A and B.

Conclusion: 1-mm-slice-thickness FSE PDW imaging with MPR showed comparable performance in diagnosing tears of the cruciate ligaments and menisci to conventional sequences but the scan time was much shorter. Therefore, this technique (method B) might improve the throughput of a 3T MR imaging system.     

Three-dimensional axial volume acquisition on meniscal lesions of the knee]

Axial three-dimensional volume scans obtained by magnetic resonance (MR) imaging were used to evaluate meniscal lesions of the knee in 28 knees of 26 cases. Axial 0.7 mm thin-sliced images with volume scan outlined the overall meniscal appearance for the first time. Axial volume scan was essential to the diagnosis of discoid lateral meniscus because only it could depict the characteristic elongated appearance of discoid lateral meniscus. Radial meniscal tears were depicted only by this technique: conventional sagittal and coronal views could not detect this type of meniscal tear. Volume scan could detect the precise extent of lesions with horizontal meniscal tears and meniscal degeneration. These MR findings obtained by axial volume scans were confirmed by arthroscopy in all cases. We concluded that volume scans were extremely useful in the evaluation of meniscal lesions because they offered axial views that provided much information on menisci located horizontally in the knee.     

Anterior cruciate ligament tears: MR imaging-based diagnosis in a pediatric population

PURPOSE: To evaluate the diagnostic accuracy of primary and secondary magnetic resonance (MR) imaging findings of anterior cruciate ligament (ACL) tears in young patients with immature skeletal systems. MATERIALS AND METHODS: MR images obtained in 43 patients aged 5-16 years who underwent arthroscopy were retrospectively reviewed. Two reviewers evaluated primary findings (abnormal signal intensity, abnormal course as defined by Blumensaat angle, and discontinuity), secondary findings (bone bruise in lateral compartment, anterior tibial displacement, uncovering of posterior horn of lateral meniscus, posterior cruciate ligament line, and posterior cruciate angle), and meniscal and other ligamentous injuries. RESULTS: There were 19 ACL tears and 24 intact ACLs. Overall sensitivity and specificity of MR imaging in detecting ACL tears were 95% and 88%, respectively. Sensitivities of the primary findings were 94% for abnormal Blumensaat angle; 79%, abnormal signal intensity; and 21% discontinuity. The specificity of all primary findings was 88% or greater. The sensitivity and specificity of the secondary findings, respectively, were 68% and 88% for bone bruise; 63% and 92%, anterior tibial displacement; 42% and 96%, uncovered posterior horn of lateral meniscus; 68% and 92%, positive posterior cruciate line; and 74% and 71%, abnormal posterior cruciate angle. Fifteen (79%) patients had meniscal tears, and five (26%) had collateral ligament injuries. CONCLUSION: Primary and secondary findings of ACL tears in young patients have high specificity and are useful for diagnosis.     

The Segond fracture of the proximal tibia: a small avulsion that reflects major ligamentous damage

The Segond fracture is a small vertical avulsion injury of the lateral aspect of the proximal tibia just distal to the plateau. It results from excessive internal rotation and varus stress. The plain film and arthrographic findings were studied in nine patients with the fracture. Although previous publications have relied primarily on the anteroposterior projection for diagnosis, the injury was apparent only on the tunnel view in two of our cases. The arthrogram was particularly important in identifying abnormalities of the anterior cruciate ligament (nine of nine cases) and/or meniscal tears (six of nine cases). The arthrographic findings related to the lateral ligamentous damage depended on the severity of the injury and on the interval between the injury and the arthrogram. In our series, the Segond fracture was uniformly associated with detachment of the capsular portion of the lateral collateral ligament and tears of the anterior cruciate ligament. In the majority of cases, there were associated injuries of the menisci and other supporting ligaments.     

All-inside meniscal repair using a new flexible, tensionable device

BACKGROUND: A new generation of flexible all-inside meniscal repair devices is available, but clinical studies with these devices are lacking. HYPOTHESIS: The RapidLoc has an intermediate-term meniscal healing rate that is equivalent to literature reports of inside-out suture technique in patients undergoing concurrent anterior cruciate ligament reconstruction. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Retrospective analysis was performed for 75 meniscal tears in 66 consecutive patients undergoing anterior cruciate ligament reconstruction who underwent meniscal repair with the RapidLoc. Patients with at least 2 years' follow-up were evaluated for symptoms suggestive of a meniscal tear and were assessed with the International Knee Documentation Committee form and the Knee Disorders Subjective History visual analog scale. Subjects were asked to return for a clinical examination to include evaluation for an effusion and joint line tenderness as well as McMurray test and KT-1000 arthrometry readings. Patients with symptoms consistent with meniscal repair failure underwent magnetic resonance arthrography and repeat arthroscopy. RESULTS: Twenty patients with 21 meniscal tears were excluded, resulting in 54 meniscal tears in 46 patients. At a mean follow-up of 34.8 months, the clinical success rate for meniscal repair was 90.7% (49/54), with 5 failures requiring meniscectomy. Univariate analysis revealed predictive variables for failure: bucket-handle configuration, multiplanar tears, tear length greater than 2 cm, and chronicity longer than 3 months. Non-predictive variables included compartment, zone, ligament graft choice, gender, age, follow-up, and visual analog scale score. Analysis of healed patients revealed a negative correlation between chronicity of tear and International Knee Documentation Committee score. CONCLUSIONS: The RapidLoc has an acceptable intermediate-term clinical healing rate in patients undergoing concurrent anterior cruciate ligament reconstruction. Predictive variables for failure should be considered during operative decision making.     

Characteristics of displaceable and nondisplaceable meniscal tears at kinematic MR imaging of the knee

PURPOSE: To prospectively determine if kinematic magnetic resonance (MR) imaging of the knee may demonstrate displacement of menisci with tears and, if so, to characterize displaceable and nondisplaceable meniscal tears. MATERIALS AND METHODS: The study was approved by the hospital's review board, and informed consent was obtained. Forty-two patients (30 men, 12 women; mean age, 36.9 years) with 43 arthroscopically documented meniscal tears visible at 1.5-T MR imaging underwent kinematic MR imaging with an open-configuration 0.5-T MR imager with their knees in supine neutral, supine with 90 degrees flexion and external or internal rotation, and upright weight-bearing positions. Analysis of meniscal movement was performed in different knee positions in the coronal MR imaging plane. Meniscal displacement--that is, meniscal movement of 3 mm or more (in the medial direction for the medial meniscus, in the lateral direction for the lateral meniscus)--was compared with the patient's pain level as assessed with a visual analog scale by using analysis of variance. RESULTS: Between the different knee positions, meniscal displacement of 3 mm or more (displaceable meniscal tears) was noted in 18 (42%) of 43 menisci with tears. Simultaneous occurrence of grade II or III ipsilateral collateral ligament lesions was present in all 18 displaceable meniscal tears, whereas a normal-appearing collateral ligament or collateral ligament lesion (grade I) was present in 22 of 25 nondisplaceable tears (P < .05). Displaced menisci most commonly had complex, radial, or longitudinal tear configurations (16 of 18, 89%). Patients with displaceable meniscal tears had significantly more pain than did patients with nondisplaceable meniscal tears (P < .001), independent of the concomitant knee abnormalities. CONCLUSION: Displaceable meniscal tears usually have longitudinal, radial, or complex configurations; such tears are associated with substantial ipsilateral collateral ligament lesions and pain.     

Medial and lateral meniscal tear patterns in anterior cruciate ligament-deficient knees. A prospective analysis of 575 tears

We used our database to evaluate the locations of meniscal tears associated with anterior cruciate ligament injuries. Five hundred seventy-five meniscal tears were seen in 476 patients. Each tear was categorized prospectively according to the side (medial/lateral), the radial zone of the tear, and the circumferential zone of the tear. The different tear locations were then compared for the medial and lateral menisci and evaluated for statistical significance. We found a nearly equal number of tears on the medial (305) and lateral (270) sides. A significantly greater number of tears on the medial side as compared with the lateral side were posterior (99.4% versus 87.8%) and peripheral (75.4% versus 44.1%). Peripheral posterior horn tears of the medial meniscus were the most common type of tear (230 of 575, 40%) by a statistically significant amount.     

Magnetic resonance imaging of the knee

Magnetic resonance imaging (MRI) is an accepted non-invasive modality for evaluation of soft tissue pathology without exposure to ionizing radiation. Current applications demonstrate excellent visualization of the anatomy and pathology of various organs. Preliminary studies in the knee reveal fine resolution of anatomy and pathology involving the meniscus. The purpose of this study is to determine a prospective correlation between MRI scans and actual meniscal pathology as documented at the time of arthroscopy. MRI scans were obtained in 155 patients, on 156 knees (one patient with bilateral scans), with 86 patients (87 knees) eventually undergoing diagnostic and operative videoarthroscopy performed by the same surgeon (DWJ). All images were obtained on the same high-resolution 1.5 Tesla GE Signa Magnetic Resonance Scanner with the same radiologist performing all readings (PEB). The knees were studied in the coronal and sagittal plane using a spin echo sequence and 5 mm slice thicknesses. The menisci were described as having Grade 1, 2, or 3 changes, with Grade 3 reserved for complete tears. Using arthroscopy as the diagnostic standard, the accuracy of MRI in diagnosing medial and lateral meniscal tears was 93.1% and 96.6%, respectively with a Grade 3 MRI reading. For tears of the ACL, the accuracy was 96.6% as confirmed at arthroscopy. Five tears of the PCL were also documented by MRI and correlated with clinical evaluation. Other abnormalities seen were articular cartilage and osteochondral defects, bone tumors, tibial plateau fractures, Baker's cysts, and meniscal cysts. The MRI scan is a highly accurate, noninvasive modality for documentation of meniscal pathology as well as cruciate ligament tears in the knee.     

Long-term results of meniscal allograft transplantation

Between May 1984 and December 1986, 23 patients with a history of medial meniscectomy and anterior knee instability were entered into a long-term prospective study of the results of medial meniscal transplantation combined with reconstruction of the anterior cruciate ligament. In 17 cases a lyophilized meniscal allograft was used and in 6 cases a deep-frozen meniscal allograft was used. The patients' clinical outcomes were evaluated 3 and 14 years postoperatively by clinical assessment, Lysholm score, radiographs, magnetic resonance imaging, arthrography, and, in some cases, arthroscopy. Two anterior cruciate ligament reconstruction control groups were used for comparison, one group having previously undergone meniscectomy and one with intact menisci. The follow-up rate was 100% after 14 years. The Lysholm score was 84 +/- 12 points at 3 years postoperatively and 75 +/- 23 points at 14 years. Patients with deep-frozen meniscal transplants generally had better results than patients with lyophilized meniscal transplants. Magnetic resonance imaging evaluation showed good preservation of the deep-frozen meniscal transplants, even after 14 years. The lyophilized meniscal transplants were reduced in size at the second-look arthroscopy and as seen on magnetic resonance imaging examination. When the control groups were compared with the study group, the deep-frozen meniscal allografts were found to be more comparable with an intact meniscus and the lyophilized meniscal allografts were more comparable with the control group knees that had undergone meniscectomy.