Application of MR imaging for internal derangement of the knee (orthopedic surgeon' view)

Magnetic resonance imaging is a noninvasive imaging modality with clear contrast and superior spatial resolution. These characteristics are especially useful for detecting pathology of the soft tissue of the knee joint, such as the menisci, ligaments and articular cartilage, which are difficult to diagnose using plain X-ray examination. MRI has become one of the first choice diagnostic modalities for the internal derangement of the knee joint, and is generally replacing some invasive arthrographic or arthroscopic examination. Pathology of the articular cartilage cannot yet be depicted clearly by MRI. We expect further development of the spatial resolution of MRI to make possible the detection of chondral lesions more clearly and precisely in the near future.     

Imaging of the knee joint with emphasis on magnetic resonance imaging

The knee joint is frequently affected by trauma as well as degenerative and inflammatory disorders, involving the internal structures (i.e. ligaments, menisci, cartilage, synovial membrane) and the adjacent bones. Plain radiographs represent an indispensable basis for diagnosis. For further analysis magnetic resonance imaging (MRI) has become the method of choice, and has widely replaced computed tomography, arthrography and stress examinations. Extensive experience has been accumulated in MRI of the knee joint in recent years. In addition, advances in MRI technology have had a major impact on diagnostic accuracy. In this paper, diagnosis of various lesions of the knee joint, such as meniscal and ligamental injuries, aseptic necrosis, lesions of the hyaline cartilage, occult fractures and inflammatory lesions will be discussed. Offprint requests to: M. F. Reiser     

Magnetic resonance imaging ofarticular cartilage injuries of the knee

Magnetic resonance imaging (MRI) is a widely available, powerful imaging modality in the United States that has rapidly become a mainstay for evaluation of the musculoskeletal system, largely because of its unparalleled depiction of most osseous and soft-tissue pathology. The application of MRI to detect cartilage injuries has evolved to the point where it is possible to noninvasively diagnose cartilage lesions that previously required an invasive examination, eg, arthrography or arthroscopy. However, successful cartilage imaging requires knowledge of the unique technical considerations and limitations of MRI. In this chapter we review current state-of-the-art knee MRI for three groups of chondral disorders: acute osteochondral fractures, osteochondritis dissecans, and degenerative lesions. The role of MRI in osteochondral fractures includes the demonstration of purely chondral intra-articular fragments and the identification of associated injuries, especially previously unrecognized subchondral bruises. MRI may also play a role in surveillance for osteochondral sequelae after injury. For osteochondritis dissecans, MRI can provide evidence supporting the diagnosis of a loose fragment and may aid in the evaluation of cartilage overlying osteochondral defects. Current MRI techniques can show moderate and severe lesions of chondromalacia and chondrosis. Newer techniques show potential for diagnosing these degenerative conditions at earlier stages when the changes are mild. We review these issues and provide examples showing the MRI appearance of common articular injuries.     

Magnetic resonance imaging of the knee: an overview

Magnetic resonance imaging (MRI) provides a new and important tool for investigating knee disorders. This article reviews the basic techniques available for investigation of the knee using MRI and describes the anatomy as delineated by this method. A large number of disorders are best evaluated by MRI, including internal abnormalities such as those of the cruciate ligaments and the menisci. Other disorders include abnormalities of the patella and quadriceps mechanism, cartilage, and synovium. Bony abnormalities such as osteonecrosis and tumors, as well as bone contusions and fractures, also may be detected. MRI is rapid and safe. Where available it is probably the best method by which to examine diseases of the knee.     

Magnetic Resonance Imaging of Cruciate Ligament Injuries of the Knee

The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) are important stabilizers of the knee. These ligaments are commonly injured in sports and motor vehicle accidents. An accurate diagnosis of cruciate ligament injuries is vital in patient care. Magnetic resonance imaging (MRI) can diagnose cruciate ligament injuries with high accuracy. The imaging diagnosis should be based on primary signs, although the secondary signs are sometimes useful, particularly in chronic cases. The detection of associated injuries of other structures of the knee, including menisci, collateral ligaments, cartilage, and bone, are also important. Accurate interpretation of the MRI examination requires a meticulous MRI technique, knowledge of the imaging anatomy, and understanding of the lesion appearance. This pictorial essay reviews the MRI appearance of normal and injured cruciate ligaments. Mechanisms of injury, primary and secondary MRI signs, and associated abnormalities are discussed.     

MR imaging in the evaluation of trauma

Although computed tomography (CT) and radiographs are primary modalities in the evaluation of patients undergoing trauma, the indications for magnetic resonance (MR) imaging in trauma have grown. MR has been most useful in patients with central nervous system or musculoskeletal trauma. In head trauma, MRI is most useful in the evaluation of patients with neurologic deficit greater than that expected from CT findings. MRI is useful in such situations because of its improved sensitivity to nonhemorrhagic and microhemorrhagic lesions as well as posterior fossa pathology. In the spine, MRI provides detailed assessment of the disc space, spinal cord, and ligamentous structures; guiding therapeutic decisions; and offering prognostic information. In the musculoskeletal system, MRI offers a noninvasive means of imaging injuries to the muscles, tendons, ligaments, and cartilage of the knee, shoulder, ankle, and elbow. Additionally, MRI may define a subset of radiographically occult bony injuries.     

Imaging of the knee

MR imaging has become the primary imaging modality of the knee. Its advantages include its noninvasive nature, multiplanar imaging capability, excellent soft-tissue contrast, and high resolution. The need for multiple imaging modalities is obviated, as the menisci, cruciate ligaments, synovium, articular cartilage, marrow, and periarticular soft tissues can be simultaneously evaluated. Other imaging modalities may occasionally be helpful in the evaluation of specific problems including CT in tibial plateau fractures, real-time ultrasound for the confirmation of a popliteal cyst or popliteal artery aneurysm, and arthrography for the detection of prosthetic joint loosening.     

膝关节退行性骨关节病的MRI表现

目的 :探讨MRI对膝关节退行性骨关节病的诊断价值。方法 :对手术、关节镜或临床证实的 2 1例 2 6个膝关节退行性骨关节病的MRI表现进行回顾性分析。结果 :MRI能较好地显示膝关节病变的关节软骨、半月板、韧带、骨质等改变 ,还能对关节软骨、半月板损伤和退变进行分级 ,明显优于传统X线检查。结论 :MRI检查能清楚显示退行性骨关节病的病变特点和严重程度 ,为临床选择合适的治疗方案提供了依据。     

Assessment of knee cartilage in cadavers with dual-detector spiral CT arthrography and MR imaging

PURPOSE: To assess dual-detector spiral CT arthrography in the evaluation of the entire knee cartilage obtained from cadavers. MATERIALS AND METHODS: Two independent observers characterized articular cartilage in 12 cadaver knees in which MR imaging and dual-detector spiral CT arthrography were performed and compared their findings to those found during macroscopic assessment. The sensitivity and specificity of MR imaging and spiral CT arthrography for detecting grade 2A or higher and grade 2B or higher cartilage lesions, the Spearman correlation coefficient between arthrographic and macroscopic grading, and kappa statistics for assessing interobserver reproducibility were determined. RESULTS: At spiral CT arthrography, sensitivities and specificities ranged between 80% and 88% for the detection of grade 2A or higher cartilage lesions and ranged between 85% and 94% for the detection of grade 2B or higher cartilage lesions. At MR imaging, sensitivities and specificities ranged between 78% and 86% and between 76% and 91% for the detection of grade 2A or higher and grade 2B or higher cartilage lesions, respectively. Spearman correlation coefficients between spiral CT arthrography or MR imaging and macroscopic grading of articular surfaces were 0.797 and 0.702, respectively. CONCLUSION: Dual-detector spiral CT arthrography of the knee is a valuable method for the assessment of open cartilage lesions of the entire knee.     

Subchondral bone infractions in acute ligamentous knee injuries demonstrated on bone scintigraphy and magnetic resonance imaging.

Bone scintigraphy is used to detect radiographically silent fractures. Magnetic resonance imaging (MRI) is currently used to screen knee injuries for cartilage and ligament damage. MRI also delineates bone marrow and fractures. We investigated the bone scintigraphic findings in patients who had subchondral bone injuries demonstrated on MRI. Thirteen patients underwent MRI, three-phase bone scintigraphy with SPECT, and arthroscopic surgery after sustaining acute traumatic hemarthrosis of a knee. They all had clinically unsuspected subchondral bone injuries demonstrated on MRI with normal radiographs and normal overlying articular cartilage at arthroscopy, consistent with occult fractures. All showed focal bone repair on scintigraphy. Two of the 13 patients showed additional bone injuries only on bone scan. Two other patients scintigraphically showed focal bone repair at the medial femoral condyle due to avulsion of the medial collateral ligament. SPECT was easier to interpret than multi-view planar imaging. Bone scintigraphy confirms subchondral fractures demonstrated on MRI but also demonstrates ligament avulsion injuries and additional more subtle bone injuries.     

Wertigkeit der radiologischen Bildgebung beim Kniegelenk für den Orthopäden

Extended radiographic examinations offer excellent options for diagnosis and strategy for treatment of the knee joint. The whole-leg radiograph is indispensable in measuring alignment for osteotomy or total knee arthroplasty (TKA). Fluoroscopically assisted varus-valgus stress radiographs provide the possibility for verifying mechanical function of the implanted knee prosthesis. Ultrasound examinations have been widely replaced by magnetic resonance imaging (MRI). MRI is the golden standard to examine intra-articular structures of the knee (meniscus, ligaments, cartilage) and surrounding soft tissue. For evaluating femoral and tibial torsion and determining axial rotation of TKA, computed tomography (CT) is best qualified. Imaging of the patellofemoral joint (patella instability) is difficult; CT scans in combination with true lateral radiographs seem to be helpful.     

Magnetic resonance imaging of the wrist: Bone and cartilage injury

Magnetic resonance imaging (MRI) is particularly useful for imaging the wrist due to its superior soft tissue contrast and ability to detect subtle bone marrow changes and occult fractures. A high field (1.5T or greater) strength, dedicated wrist coil, and high in‐plane and through‐plane resolution must be utilized to successfully visualize the relatively thin cartilage of the wrist. MRI can be used to detect occult carpal bone fractures, identify complications following scaphoid fractures, and assess for avascular necrosis in the setting in Kienböck's and Preiser's disease. MRI is useful to identify secondary soft tissue and chondral pathology in impaction/impingement syndromes. The use of an intermediate‐echo time fast spin echo sequence allows for accurate assessment of articular cartilage, allowing evaluation of chondral wear in the setting of primary osteoarthritis and posttraumatic degenerative arthrosis. MRI is the most sensitive imaging modality for the detection of early inflammatory arthropathies and can detect synovitis, bone marrow edema, and early erosions in the setting of negative radiographs. J. Magn. Reson. Imaging 2013;37:1005–1019. © 2012 Wiley Periodicals, Inc.     

Does marathon running cause acute lesions of the knee? Evaluation with magnetic resonance imaging

An investigation was conducted into whether running a marathon causes acute alterations in menisci, cartilage, bone marrow, ligaments, or joint effusions, which could be evaluated by magnetic resonance imaging (MRI). Twenty-two non-professional marathon runners underwent MRI of the knee before and immediately after running a marathon. Lesions of menisci and cartilage (five-point scale), bone marrow, ligaments (three-point scale), joint effusion, and additional findings were evaluated and a total score was assessed. Before the marathon, grade 1 lesions of the menisci were found in eight runners, and grade 2 lesions in five runners. After the marathon, an upgrading from a meniscal lesion grade 1 to grade 2 was observed in one runner. Before the marathon, grade 1 cartilage lesions were found in three runners, and grade 2 lesions in one runner, all of which remained unchanged after the marathon. Before and after the marathon, unchanged bone marrow edema was present in three runners and unchanged anterior cruciate ligament lesions (grade 1) were seen in two runners. Joint effusions were present in 13 runners in the pre-run scans, slightly increased in four runners after the marathon, and newly occurred in one runner after the marathon. A total score comprising all knee lesions in each runner showed an increase after the marathon in two runners, whereas no runner showed an improvement of the radiological findings (Wilcoxon signed-rank test, P>0.05). The evaluation of lesions of the knee with MRI shows that marathon running does not cause severe, acute lesions of cartilage, ligaments, or bone marrow of the knee in well-trained runners. Only subtle changes, such as joint effusions or increased intrameniscal signal alterations, were imaged after running a marathon.     

胫骨平台骨折及膝关节附属结构损伤的MRI诊断

目的评价胫骨平台骨折合并膝关节附属结构损伤的MRI表现.资料与方法 27例胫骨平台骨折病例经X线平片检查后作MRI扫描,分析不同类型胫骨平台骨折所合并的膝关节附属结构损伤的MRI形态学表现.结果 MRI能准确显示骨折所合并的膝关节附属结构的损伤性病变,包括关节软骨断裂、半月板撕裂和移位、侧副韧带和肌腱的撕裂、关节腔脂肪血性积液等,其中双髁骨折引起的损伤最为严重,撕脱骨折引起的损伤较轻.结论 MRI能准确诊断胫骨平台骨折合并的膝关节附属结构损伤,应作为膝关节外伤的常规检查手段.     

Sport injuries of the extensor mechanism of the knee

Injuries of the extensor mechanism of the knee occur frequently during sport activity. For a successful treatment they must be diagnosed early. Besides osseous structures the patellar tendon, the patella, the quadriceps muscle and tendon, retinacula and bursae can be affected. After initial clinical examination there are different noninvasive imaging modalities available for assessment of bone, cartilage, ligaments, tendons and soft tissue. Conventional radiographs are still the basic imaging tool for the clinician. Additional information about the osseous status is provided by computed tomography, whereas sonography plays an important role concerning diagnosis of soft tissue injuries. For the detection of cartilagenous, ligamentous or tendon lesions MRI is the superior non-invasive imaging modality.     

Magnetic resonance imaging in menisco-ligamentous lesions. Comparison with arthroscopy. Apropos of 37 cases

Results of magnetic resonance imaging of 37 cases of lesions of meniscus and ligaments of knee are reported and compared with arthroscopy findings. Use of MRI appears to be an excellent non-invasive diagnostic method, with current major indications in acute knee injuries and for evaluation of chronic laxity. It also allows guidance of surgical procedures. In the future, MRI should replace the more aggressive arthrography, this with a relatively short examination time, since sagittal section imaging in TI permits detection of the majority of lesions.     

Cross-sectional imaging of the patellofemoral joint and surrounding structures

Computed tomography (CT) and magnetic resonance (MR) imaging are extremely useful in the accurate diagnosis of anterior knee pain, a common complaint arising from numerous causes (including fracture, chondromalacia patellae, and alignment and tracking abnormalities). Plain CT is effective for evaluating intraosseous lesions of the knee. Although CT arthrography provides excellent visualization of the patellar articular cartilage, the technique is expensive and invasive. Cine CT is an excellent method for assessing patellofemoral tracking and alignment. Kinematic MR imaging can also perform this function. In addition, MR imaging can provide valuable information concerning the status of patellar cartilage. Although MR imaging can accurately show high-grade chondromalacia patellae, it is less accurate in the detection of low-grade disease. The authors believe that MR imaging and plain radiography offer radiologists the greatest latitude in making a specific diagnosis of the cause of anterior knee pain; however, CT is a useful alternative.     

Assessment of the diagnostic value of dual-energy CT and MRI in the detection of iatrogenically induced injuries of anterior cruciate ligament in a porcine model

Introduction

Magnetic resonance imaging (MRI) is the standard of reference for the non-invasive evaluation of ligament injuries of the knee. The development of dual-energy CT (DE-CT) made it possible to differentiate between tissues of different density by two simultaneous CT measurements with different tube voltages. This approach enables DE-CT to discriminate ligament structures without intra-articular contrast media injection. The aims of this study were on the one hand to determine the delineation of the anterior cruciate ligament (ACL) and on the other hand to assess the diagnostic value of DE-CT and MRI in the detection of iatrogenically induced injury of the ACL in a porcine knee joint model.

Materials and methods

Twenty porcine hind legs, which were placed in a preformed cast in order to achieve a standardized position, were scanned using DE-CT. Thereafter, a 1.5-T MRI using a standard protocol was performed. The imaging procedures were repeated with the same parameters after inducing defined lesions (total or partial incision) on the ACL arthroscopically. After post-processing, two radiologists and two orthopedic surgeons first analyzed the delineation of the ACL and then, using a consensus approach, the iatrogenically induced lesions. The result of the arthrotomy was defined as the standard of reference.

Results

The ACL could be visualized both on DE-CT and MRI in 100% of the cases. As for the MRI, the sensitivity and specificity of detecting the cruciate ligament lesion respectively compared with the defined arthrotomy was 66.7% and 78.6% for intact cruciate ligaments, 100% and 75% in the case of a complete lesion, 33.3% and 78.6% for lesions of the anteromedial bundle, and 0% and 100% for lesions of the posterolateral bundle. In comparison, DE-CT demonstrated a sensitivity and specificity of 66.7% and 71.4% in the case of intact cruciate ligaments, 75% and 68.8% in the case of completely discontinued ACLs, 0% and 92.9% in the case of lesions of the anteromedial bundle, and 25% and 87.5% in the case of lesions of the posterolateral bundle.

Conclusions

The present ex vivo experiment shows that both study modalities (DE-CT and MRI) are equal with regard to the delineation of the ACL, while MRI achieved higher sensitivity and specificity regarding iatrogenically induced complete ACL lesions. DE-CT could be a possible alternative to MRI for certain indications in the diagnosis of a knee ligament injury.     

Impact of cartilage invasion on treatment and prognosis of laryngeal cancer

Invasion of laryngeal cartilage has long been considered as a contraindication to radiation treatment and to all types of conservation surgery. With the advent of axial imaging techniques clarification of the submucosal extent of disease became possible. However, controversies regarding diagnosis (preferred modality, accuracy of detection of cartilage invasion) and treatment of cartilage invasion (Is cartilage invasion really a contraindication for irradiation treatment?) arose. Based on currently accepted criteria, CT appears to be more specific in detecting neoplastic cartilage invasion than MRI, but tends to underestimate invasion and may therefore result in undertreatment. Magnetic resonance has a higher sensitivity than CT for detection of cartilage invasion. The superiority of MRI lies in its ability to detect intracartilaginous tumor spread. Unfortunately, MR findings suggesting neoplastic cartilage invasion may be false positive in a considerable number of instances. Two MRI-dependent parameters appear to be significant as a prognostic factor for success of radiation therapy: tumor volume and abnormal MR signal pattern in cartilage. Minimal abnormal MR signal patterns in cartilage in patients with small tumors (under 5 cc) does not appear to be a very ominous finding for tumor recurrence after radiation therapy. On the other hand, abnormal MR signal pattern in cartilage combined with large tumor volume (above 5 cc) appears to worsen the prognosis significantly. If voice conservation surgery is being considered, MR imaging is useful for assesing those structures (such as cartilages) whose involvement would contraindicate partial laryngectomy. Magnetic resonance imaging appears to be the optimal method of examination in cooperative patients. If MRI fails or if it is contraindicated, CT may still be recommended. The radiologist's experience with CT or MRI also determines the choice between the two modalities.     

眶内占位性病变的MRI诊断价值

笔者分析了４０例眶内占位性病变的ＭＲＩ表现并与ＣＴ比较。结果表明ＭＲＩ对眶内占位性病变发现率极高，特别是对视神经的管内段和颅内蔓延或眶外软组织浸润范围的确定较ＣＴ更准确，其多方位扫描功能使定位诊断符合率高达１００％，特别是冠状面对定位诊断的作用极大。据不同组织有不同的ＭＲＩ信号强度变化的特点，结合形态学变化，ＭＲＩ对一些病变可作出定性诊断。