Magnetic resonance imaging of the hip at 3 Tesla: clinical value in femoroacetabular impingement of the hip and current concepts.
ABSTRACT Magnetic resonance imaging (MRI) is the most promising noninvasive modality for hip joint evaluation, but it has limitations in diagnosing cartilage lesion and acetabular labrum changes, especially in early stages. This is significant due to superior outcome results of surgery intervention in hip dysplasia or femoroacetabular impingement in patients not exceeding early degeneration. This emphasizes the need for accurate and reproducible methods in evaluating cartilage structure. In this article, we discuss the impact of the most recent technological advance in MRI, namely the advantage of 3-T imaging, on diagnostic imaging of the hip. Limitations of standard imaging techniques are shown with emphasis on femoroacetabular impingement. Clinical imaging examples and biochemical techniques are presented that need to be further evaluated.
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ABSTRACT: Advances in computational mechanics, constitutive modeling, and techniques for subject-specific modeling have opened the door to patient-specific simulation of the relationships between joint mechanics and osteoarthritis (OA), as well as patient-specific preoperative planning. This article reviews the application of computational biomechanics to the simulation of joint contact mechanics as relevant to the study of OA. This review begins with background regarding OA and the mechanical causes of OA in the context of simulations of joint mechanics. The broad range of technical considerations in creating validated subject-specific whole joint models is discussed. The types of computational models available for the study of joint mechanics are reviewed. The types of constitutive models that are available for articular cartilage are reviewed, with special attention to choosing an appropriate constitutive model for the application at hand. Issues related to model generation are discussed, including acquisition of model geometry from volumetric image data and specific considerations for acquisition of computed tomography and magnetic resonance imaging data. Approaches to model validation are reviewed. The areas of parametric analysis, factorial design, and probabilistic analysis are reviewed in the context of simulations of joint contact mechanics. Following the review of technical considerations, the article details insights that have been obtained from computational models of joint mechanics for normal joints; patient populations; the study of specific aspects of joint mechanics relevant to OA, such as congruency and instability; and preoperative planning. Finally, future directions for research and application are summarized.Journal of Biomechanical Engineering 02/2013; 135(2):021003. · 1.52 Impact Factor
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ABSTRACT: Beim femoroazetabulären Impingement (FAI) bewirkt ein anatomisches Missverhältnis zwischen proximalem Femur und Azetabulum eine frühzeitige Abnützung der Gelenkflächen. Um Symptome wie eingeschränkte Beweglichkeit und Schmerzen zu beheben, aber auch um dem degenerativen Prozess vorzubeugen oder ihn zu verlangsamen, ist häufig eine Operation notwendig. Dabei hängt das Resultat vom präoperativen Gelenkstatus ab – mit schlechten Ergebnissen bei bereits fortgeschrittener Hüftgelenkarthrose. Dies erklärt die Notwendigkeit einer akkuraten Diagnostik, um Frühstadien der Gelenkschädigung erkennen zu können. Die Diagnostik des FAI beinhaltet klinische Untersuchung, Röntgendiagnostik und Magnetresonanztomographie (MRT). Die Standardröntgen-radiologische Untersuchung beim FAI wird anhand von 2 Röntgenaufnahmen durchgeführt, der a.p.-Beckenaufnahme sowie einer seitlichen Aufnahme des proximalen Femurs wie z.B. der“lateralen cross-table”- oder der Lauenstein-Aufnahme. Hierbei müssen Positionskriterien eingehalten werden, um Verzerrungsartefakte auszuschließen. Die MRT-Bildgebung ermöglicht eine Untersuchung der Hüfte in 3 Ebenen und sollte zudem radial geplante Sequenzen für eine verbesserte Darstellung der randnahen Strukturen wie Labrum und peripherem Knorpel beinhalten. Die Verwendung von Kontrastmittel für ein direktes MR-Arthrogramm (MRA) hat sich insbesondere für die Darstellung von Labrumschäden als vorteilhaft erwiesen. Die Datenlage in Hinblick auf die Knorpelbildgebung ist noch unklar. Weiterentwicklungen der Techniken werden in naher Zukunft die Diagnostik der Hüfte verbessern können. Hierzu zählen u.a. biochemisch sensitive MRT-Anwendungen. Femoroacetabular impingements (FAI) are due to an anatomical disproportion between the proximal femur and the acetabulum which causes premature wear of the joint surfaces. An operation is often necessary in order to relieve symptoms such as limited movement and pain as well as to prevent or slow down the degenerative process. The result is dependent on the preoperative status of the joint with poor results for advanced arthritis of the hip joint. This explains the necessity for an accurate diagnosis in order to recognize early stages of damage to the joint. The diagnosis of FAI includes clinical examination, X-ray examination and magnetic resonance imaging (MRI). The standard X-radiological examination for FAI is carried out using two X-ray images, an anterior-posterior view of the pelvis and a lateral view of the proximal femur, such as the cross-table lateral or Lauenstein projections. It is necessary that positioning criteria are adhered to in order to avoid distortion artifacts. MRI permits an examination of the pelvis on three levels and should also include radial planned sequences for improved representation of peripheral structures, such as the labrum and peripheral cartilage. The use of contrast medium for a direct MR arthrogram has proved to be advantageous particularly for representation of labrum damage. The data with respect to cartilage imaging are still unclear. Further developments in technology, such as biochemical-sensitive MRI applications, will be able to improve the diagnosis of the pelvis in the near future.Der Radiologe 49(5):425-433. · 0.47 Impact Factor
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ABSTRACT: To evaluate 7-T MRI of both hips using a multi-channel transmit technology to compensate for inherent B1 inhomogeneities in volunteers and patients with avascular necrosis of the femoral head. A self-built, eight-channel transmit-receive coil was utilized for B1 modification at 7 T. Two shim modes (individual shim vs. CP2+ mode) were initially compared and the best shim result was used for all further imaging. Robustness of sequences against B1 inhomogeneities, appearance of anatomic and pathologic changes of the femoral heads of MEDIC, DESS, PD/T2w TSE, T1w TSE, and STIR sequences at 7 T were evaluated in 12 subjects on a four-point scale (1-4): four male volunteers and eight patients (seven males, one female) suffering from avascular necrosis treated by advanced core decompression. Successful MRI of both femoral heads was achieved in all 12 subjects. CP2+ mode proved superior in ten of 12 cases. DESS proved most robust against B1 inhomogeneity. Anatomical details (labrum, articular cartilage) were best depicted in PDw, MEDIC, and DESS, while for depiction of pathological changes PDw, DESS (0.76 mm(3)) and T1w were superior. Our initial results of ultra-high-field hip joint imaging demonstrate high-resolution, high-contrast images with a good depiction of anatomic and pathologic changes. However, shifting areas of signal dropout from the femoral heads to the center of the pelvis makes these areas not assessable. For clinical workflow CP2+ mode is most practical. Seven-Tesla MRI of the hip joints may become a valuable complement to clinical field strengths.Skeletal Radiology 08/2013; · 1.74 Impact Factor