Clinical and MRI considerations in sports-related knee joint cartilage injury and cartilage repair

Cartilage injuries of the knee occur frequently in professional and amateur athletes and can be associated with severe debilitation and morbidity. They are commonly associated with ligament injuries but also may be frequently isolated. Increasing awareness and advances in magnetic resonance imaging (MRI) have led to increasing diagnosis and recognition of these injuries. Articular cartilage is just 2 to 4 mm thick and is avascular, alymphatic, and aneural. It has a limited capacity for healing, and there has been increasing use of cartilage repair techniques to treat these lesions in the active population. Strategies for cartilage repair include marrow stimulation techniques such as microfracture/drilling, osteochondral grafting, and autologous chondrocyte transplants. MRI is an important tool in the diagnosis and grading of cartilage injury and is useful in the follow-up and monitoring of these repair procedures. It is important for radiologists and clinicians to be aware of the capabilities and limitations of MRI in assessing cartilage injury and to be familiar with common postsurgical appearances to facilitate assessment and follow-up in this population. This article reviews the clinical findings and MRI imaging appearances of cartilage injury. The management options are discussed as well as common postsurgical appearances following the various interventions.     

Postoperative evaluation of the knee

New developments and improvements in ligamentous and meniscal surgery and cartilage repair procedures have led to an increased incidence ot these procedures being performed. Subsequently, there has been a corresponding increase in postoperative imaging studies. and it is imperative for radiologists to be comfortable with the normal imaging appearance of these procedures and associated complications.     

Magnetization transfer contrast and T2 mapping in the evaluation of cartilage repair tissue with 3T MRI

PURPOSE: To use magnetization transfer (MT) imaging in the visualization of healthy articular cartilage and cartilage repair tissue after different cartilage repair procedures, and to assess global as well as zonal values and compare the results to T2-relaxation. MATERIALS AND METHODS: Thirty-four patients (17 after microfracture [MFX] and 17 after matrix-associated autologous cartilage transplantation [MACT]) were examined with 3T MRI. The MT ratio (MTR) was calculated from measurements with and without MT contrast. T2-values were evaluated using a multiecho, spin-echo approach. Global (full thickness of cartilage) and zonal (deep and superficial aspect) region-of-interest assessment of cartilage repair tissue and normal-appearing cartilage was performed. RESULTS: In patients after MFX and MACT, the global MTR of cartilage repair tissue was significantly lower compared to healthy cartilage. In contrast, using T2, cartilage repair tissue showed significantly lower T2 values only after MFX, whereas after MACT, global T2 values were comparable to healthy cartilage. For zonal evaluation, MTR and T2 showed a significant stratification within healthy cartilage, and T2 additionally within cartilage repair tissue after MACT. CONCLUSION: MT imaging is capable and sensitive in the detection of differences between healthy cartilage and areas of cartilage repair and might be an additional tool in biochemical cartilage imaging. For both MTR and T2 mapping, zonal assessment is desirable.     

MRI of articular cartilage: revisiting current status and future directions

OBJECTIVE: The purpose of this article is to review the current understanding of the MRI appearance of articular cartilage and its relationship to the microscopic and macroscopic structure of articular cartilage, the optimal pulse sequences to be used in imaging, the appearance of both degenerative and traumatic chondral lesions, the appearance of the most common cartilage repair procedures, and future directions and developments in cartilage imaging. CONCLUSION: Articular cartilage plays an essential role in the function of the diarthrodial joints of the body but is frequently the target of degeneration or traumatic injury. The recent development of several surgical procedures that hold the promise of forming repair tissue that is hyaline or hyalinelike cartilage has increased the need for accurate, noninvasive assessment of both native articular cartilage and postoperative repair tissue. MRI is the optimal noninvasive method for assessment of articular cartilage.     

Knee MR images: what the orthopaedic surgeon needs to know

Ideally, the orthopaedic surgeon works together with the radiologist in order to understand and contextualize the data obtained from a knee magnetic resonance imaging study. In this article we review the information most useful to the practice of orthopaedic surgery obtained from these MRI scans, including sections on ligaments, menisci, articular cartilage, limb alignment, bone, and surrounding soft tissues. We place special emphasis on evaluating the postoperative knee, ligament grafts, cartilage integrity, and other conditions that present challenges to both orthopaedic surgeons and radiologists.     

MR imaging of the postoperative knee

Advances in orthopedic and arthroscopic surgical procedures of the knee such as, knee replacement, ligamentous reconstruction as well as articular cartilage and meniscus repair techniques have resulted in a significant increase in the number of patients undergoing knee arthroscopy or open surgery. As a consequence postoperative MR imaging examinations increase. Comprehensive knowledge of the normal postoperative MR imaging appearances and abnormal findings in the knee associated with failure or complications of common orthopedic and arthroscopic surgical procedures currently undertaken is crucial. This article reviews the various normal and pathological postoperative MR imaging findings following anterior and posterior cruciate ligament, medial collateral ligament and posterolateral corner reconstruction, meniscus and articular cartilage surgery as well as total knee arthroplasty with emphasis on those surgical procedures which general radiologists will likely be faced in their daily clinical routine.     

Advanced morphological and biochemical magnetic resonance imaging of cartilage repair procedures in the knee joint at 3 Tesla

Morphological and biochemical magnetic resonance imaging (MRI) is due to high field MR systems, advanced coil technology, and sophisticated sequence protocols capable of visualizing articular cartilage in vivo with high resolution in clinical applicable scan time. Several conventional two-dimensional (2D) and three-dimensional (3D) approaches show changes in cartilage structure. Furthermore newer isotropic 3D sequences show great promise in improving cartilage imaging and additionally in diagnosing surrounding pathologies within the knee joint. Functional MR approaches are additionally able to provide a specific measure of the composition of cartilage. Cartilage physiology and ultra-structure can be determined, changes in cartilage macromolecules can be detected, and cartilage repair tissue can thus be assessed and potentially differentiated. In cartilage defects and following nonsurgical and surgical cartilage repair, morphological MRI provides the basis for diagnosis and follow-up evaluation, whereas biochemical MRI provides a deeper insight into the composition of cartilage and cartilage repair tissue. A combination of both, together with clinical evaluation, may represent a desirable multimodal approach in the future, also available in routine clinical use.     

Evaluation of chondral repair using quantitative MRI

Various quantitative magnetic resonance imaging (qMRI) biomarkers, including but not limited to parametric MRI mapping, semiquantitative evaluation, and morphological assessment, have been successfully applied to assess cartilage repair in both animal and human studies. Through the interaction between interstitial water and constituent macromolecules the compositional and structural properties of cartilage can be evaluated. In this review a comprehensive view of a variety of quantitative techniques, particularly those involving parametric mapping, and their relationship to the properties of cartilage repair is presented. Some techniques, such as T2 relaxation time mapping and delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC), are well established, while the full potential of more recently introduced techniques remain to be demonstrated. A combination of several MRI techniques is necessary for a comprehensive characterization of chondral repair. J. Magn. Reson. Imaging 2012; 36:1287–1299. © 2012 Wiley Periodicals, Inc.     

Roles of magnetic resonance imaging in management of bone tumors

The roles of magnetic resonance imaging (MRI) in the diagnosis and treatment of bone tumors are reviewed. Most bone tumors can be detected on plain radiography or bone scintigraphy. MRI is helpful in detecting tumors that do not destroy bone matrix or suppress reactive bone formation. Detailed analysis by plain radiography is still the most reliable method for differentiating between benign and malignant bone tumors. The T1 and T2 values, internal texture, and peritumoral edema depicted on MRI are not helpful for this differentiation. In characterizing the histologic types of bone tumors, MRI is of some advantage. For example, MRI can demonstrate cartilage matrix, hemoglobin metabolites, vascular components, and fat contents more clearly than conventional radiological techniques. MRI is now indispensable for the preoperative delineation of malignant bone tumors, because of its excellent soft tissue contrast and multiplanar imaging capability. In this article, the guidelines for evaluation of the surgical margin advocated by the JOA Musculo-skeletal Tumor Committee are introduced for radiologists. MRI monitoring of malignant bone tumors after chemotherapy or surgery can reveal change in the size of enhanced areas that may reflect viable tumors. Dynamic MRI is helpful to differentiate recurrent tumors from granulation tissue.     

MR imaging of osteochondral grafts and autologous chondrocyte implantation

Surgical articular cartilage repair therapies for cartilage defects such as osteochondral autograft transfer, autologous chondrocyte implantation (ACI) or matrix associated autologous chondrocyte transplantation (MACT) are becoming more common. MRI has become the method of choice for non-invasive follow-up of patients after cartilage repair surgery. It should be performed with cartilage sensitive sequences, including fat-suppressed proton density-weighted T2 fast spin-echo (PD/T2-FSE) and three-dimensional gradient-echo (3D GRE) sequences, which provide good signal-to-noise and contrast-to-noise ratios. A thorough magnetic resonance (MR)-based assessment of cartilage repair tissue includes evaluations of defect filling, the surface and structure of repair tissue, the signal intensity of repair tissue and the subchondral bone status. Furthermore, in osteochondral autografts surface congruity, osseous incorporation and the donor site should be assessed. High spatial resolution is mandatory and can be achieved either by using a surface coil with a 1.5-T scanner or with a knee coil at 3 T; it is particularly important for assessing graft morphology and integration. Moreover, MR imaging facilitates assessment of complications including periosteal hypertrophy, delamination, adhesions, surface incongruence and reactive changes such as effusions and synovitis. Ongoing developments include isotropic 3D sequences, for improved morphological analysis, and in vivo biochemical imaging such as dGEMRIC, T2 mapping and diffusion-weighted imaging, which make functional analysis of cartilage possible.     

Magnetization transfer analysis of cartilage repair tissue: a preliminary study

Purpose To evaluate the magnetization transfer ratio (MTR) after two different cartilage repair procedures, and to compare these data with the MTR of normal cartilage.Design and patients Twenty-seven patients with a proven cartilage defect were recruited: 13 were treated with autologous chondrocyte implantation (ACI) and 14 were treated with the microfracture technique (MFR). All patients underwent MRI examinations with MT-sequences before the surgical treatment, after 12 months (26 patients) and after 24 months (11 patients). Eleven patients received a complete follow-up study at all three time points (five of the ACI group and six of the MFR group). All images were transferred to a workstation to calculate MTR images. For every MT image set, different ROIs were delineated by two radiologists. Means were calculated per ROI type in the different time frames and in both groups of cartilage repair. The data were analyzed with unpaired t- and ANOVA tests, and by calculating Pearson’s correlation coefficient.Results No significant differences were found in the MTR of fatty bone marrow, muscle and normal cartilage in the different time frames. There was a significant but small difference between the MTR of normal cartilage and the cartilage repair area after 12 months for both procedures. After 24 months, the MTR of ACI repaired cartilage (0.31±0.07) was not significantly different from normal cartilage MTR (0.34±0.05). The MTR of MFR repaired cartilage (0.28±0.02), still showed a significant difference from normal cartilage.Conclusion The differences between damaged and repaired cartilage MTR are too small to enable MT-imaging to be a useful tool for postoperative follow-up of cartilage repair procedures. There is, however, an evolution towards normal MTR-values in the cartilage repair tissue (especially after ACI repair).     

Modeling the growth plates in the pediatric knee: implications for anterior cruciate ligament reconstruction.

The authors develop 3-D models of the pediatric knee from magnetic resonance imaging (MRI) image files, with the goal of minimizing injury to the pediatric growth plate during surgery. Computerized tomography (CT) scans have better resolution and contrast between bone and soft tissue than MRI scans; however, surgeons rely upon MRI scans to plan knee-joint surgeries such as anterior cruciate ligament (ACL) reconstruction. Surgeons can use the virtual models to plan and verify surgical procedures such as hole drilling and ligament attachments, and to determine volume removed from a growth plate due to different drill-hole placements with various drill sizes.     

T1 mapping联合常规MRI扫描方案评估膝关节软骨损伤

目的评估在常规MRI扫描方案中加入T1 mapping成像能否提高对膝关节软骨损伤的诊断效能。方法选取86例患者的88个膝关节接受了膝关节MRI检查和关节镜检查。MRI检查采用常规方案并加入T1 mapping成像。术前2位影像科医师对所有MRI检查图像进行一致的诊断,评估是否存在软骨损伤并进行软骨损伤MRI分级,首先评估常规MRI扫描方案的图像,然后评估T1 mapping联合常规MRI扫描方案的图像。由1位骨科医师在关节镜下进行软骨损伤关节镜分级并作为金标准。计算两种MRI扫描方案评估软骨损伤的敏感度和特异度,统计分析两种扫描方案的诊断结果是否存在差异。结果关节镜检出的256个软骨损伤,常规MRI扫描方案的敏感度、特异度分别为59.0%和98.6%,T1 mapping联合常规MRI扫描方案的敏感度、特异度分别为85.9%和93.2%。T1 mapping联合常规MRI扫描方案显著提高了MRI扫描诊断早期关节软骨损伤的敏感度,关节镜1级软骨损伤的敏感度从18.6%提高至71.2%,关节镜2A级软骨损伤的敏感度从74.3%提高至94.3%。上述两种扫描方案的结果差异均有统计学意义(P<0.05)。结论常规MRI扫描方案中加入T1 mapping成像,可提高对膝关节软骨损伤的敏感度,为临床诊断早期膝关节软骨损伤提供影像学依据。     

Advanced gastrointestinal endoscopic procedures: indications,imaging findings,and implications for the radiologist

There are a variety of advanced gastrointestinal endoscopic procedures, many of which are guided by endosonography, which are performed by interventional gastroenterologists or minimally-invasive surgeons. The purpose of this pictorial review is to briefly describe several advanced gastrointestinal endoscopically guided procedures, to review the implications for radiologists interpreting the associated imaging examinations, and to demonstrate the expected preprocedural imaging findings, as well as the expected and the unexpected postprocedural findings, in patients undergoing these procedures.     

MR imaging of the postoperative knee: a pictorial essay.

Magnetic resonance (MR) imaging of the postoperative knee has become more common because more arthroscopic repair procedures are being performed. The most common procedures include partial meniscectomy and meniscal repair, anterior cruciate ligament (ACL) reconstruction, and cartilage repair procedures. Specific findings of a retorn meniscus following meniscal repair or partial meniscectomy are increased signal intensity extending through the site of repair on T2-weighted images, displaced meniscal fragments, and abnormal signal intensity at a site distant from the repair. Findings of ACL graft disruption on T2-weighted MR images include absence of intact graft fibers and increased signal intensity similar to that of fluid within the expected region of the graft. Partial tears of the graft appear as areas of increased signal intensity affecting a portion of the graft with some intact fibers still present. An impinged ACL graft may appear to be draped over the anterior inferior edge of the intercondylar roof or be posteriorly bowed. Localized anterior arthrofibrosis appears on T1-weighted MR images as a focal nodular lesion of low signal intensity that is anterior to the ACL graft in the intercondylar notch and is indistinguishable from adjacent joint fluid. On T2-weighted images, the nodule is well differentiated from high-signal-intensity joint fluid. Finally, MR imaging has been shown to be accurate in the evaluation of cartilage repair tissue. Knowledge of the normal MR imaging appearance of the knee after the more common repair procedures will allow radiologists to recognize complications associated with such procedures.     

Hirnnerven – Spektrum entzündlicher und tumoröser Veränderungen

Inflammatory processes as well as primary and secondary tumorous changes may involve cranial nerves causing neurological deficits. In addition to neurologists, ENT physicians, ophthalmologists and maxillofacial surgeons, radiologists play an important role in the investigation of patients with cranial nerve symptoms. Multidetector computed tomography (MDCT) and particularly magnetic resonance imaging (MRI) allow the depiction of the cranial nerve anatomy and pathological neural changes. This article briefly describes the imaging techniques in MDCT and MRI and is dedicated to the radiological presentation of inflammatory and tumorous cranial nerve pathologies.     

MR imaging of cartilage repair surgery of the knee

Articular cartilage is a complex tissue with unique properties that are essential for normal joint function. Many processes can result in cartilage injury, ranging from acute trauma to degenerative processes. Articular cartilage lacks vascularity, and therefore most chondral defects do not heal spontaneously and may require surgical repair. A variety of cartilage repair techniques have been developed and include bone marrow stimulation (microfracture), osteochondral autograft transfer system (OATS) or osteochondral allograft transplantation, autologous chondrocyte implantation (ACI), matrix-assisted chondrocyte implantation (MACI), and other newer processed allograft cartilage techniques. Although arthroscopy has long been considered as the gold standard for evaluation of cartilage after cartilage repair, magnetic resonance (MR) imaging is a non-invasive method to assess the repair site and can be scored using Magnetic resonance Observation of Cartilage Repair Tissue (MOCART). MR also provides additional evaluation of the subchondral bone and for other potential causes of knee pain or internal derangement. Conventional MR can be used to evaluate the status of cartilage repair and potential complications. Compositional MR sequences can provide supplementary information about the biochemical contents of the reparative tissue. This article reviews the various types of cartilage repair surgeries and their postoperative MR imaging appearances.     

MR imaging of cartilage repair surgery of the knee

Articular cartilage is a complex tissue with unique properties that are essential for normal joint function. Many processes can result in cartilage injury, ranging from acute trauma to degenerative processes. Articular cartilage lacks vascularity, and therefore most chondral defects do not heal spontaneously and may require surgical repair. A variety of cartilage repair techniques have been developed and include bone marrow stimulation (microfracture), osteochondral autograft transfer system (OATS) or osteochondral allograft transplantation, autologous chondrocyte implantation (ACI), matrix-assisted chondrocyte implantation (MACI), and other newer processed allograft cartilage techniques. Although arthroscopy has long been considered as the gold standard for evaluation of cartilage after cartilage repair, magnetic resonance (MR) imaging is a non-invasive method to assess the repair site and can be scored using Magnetic resonance Observation of Cartilage Repair Tissue (MOCART). MR also provides additional evaluation of the subchondral bone and for other potential causes of knee pain or internal derangement. Conventional MR can be used to evaluate the status of cartilage repair and potential complications. Compositional MR sequences can provide supplementary information about the biochemical contents of the reparative tissue. This article reviews the various types of cartilage repair surgeries and their postoperative MR imaging appearances.