Hybrid rendering of aortic aneurysms after endoluminal stent-graft repair.
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Aortic Aneurysm, Thoracic↗
Biomedical subjects
K-H Englmeier
Publications and source records attributed to K-H Englmeier.
Effect of abducting and adducting muscle activity on glenohumeral translation, scapular kinematics and subacromial space width in vivo.
It is currently unknown in which ways activity of the ab- and adductor shoulder muscles affects shoulder biomechanics (scapular kinematics and glenohumeral translation), and whether these changes are relevant for alterations of the subacromial space width. The objective of this experimental in vivo study was thus to test the hypotheses that potential changes of the subacromial space width (during antagonistic muscle activity) are caused by alterations of scapular kinematics and/or glenohumeral translation. The shoulders of 12 healthy subjects were investigated with an open MRI-system at 30 degrees, 60 degrees, 90 degrees, 120 degrees and 150 degrees of arm elevation. A force of 15N was applied to the distal humerus, once causing isometric contraction of the abductors and once contraction of the adductors. The scapulo-humeral rhythm, scapular tilting and glenohumeral translation were calculated from the MR image data for both abducting and adducting muscle activity. Adducting muscle activity led to significant increase of the subacromial space width in all arm positions. The scapulo-humeral rhythm (2.2-2.5) and scapular tilting (2-4 degrees) remained relatively constant during elevation, no significant difference was found between abducting and adducting muscle activity. The position of the humerus relative to the glenoid was, however, significantly (p < 0.05) different (inferior and anterior) for adducting versus abducting muscle activity in midrange elevation (60-120 degrees). These data show that the subacromial space can be effectively widened by adducting muscle activity, by affecting the position of the humerus relative to the glenoid. This effect may be employed for conservative treatment of the impingement syndrome.
Acromioclavicular Joint↗
In vivo cartilage deformation after different types of activity and its dependence on physical training status.
BACKGROUND: Knowledge of the deformational behaviour of articular cartilage in vivo is required to understand the pathogenesis of osteoarthritis and the mechanical target environment of prospective cartilage transplant recipients. OBJECTIVES: To study the in vivo deformational behaviour of patellar and femorotibial cartilage for different types of physiological activities; and to test the hypothesis that in vivo deformation of cartilage is modified by intense physical exercise. METHODS: Magnetic resonance imaging and 3D digital image analysis were used to determine cartilage volume before and after physical activity in the patella of 12 volunteers (knee bends, squatting, normal gait, running, cycling). Deformation of femorotibial cartilage was investigated in 10 subjects (knee bends, static compression, high impact loading). Patellar cartilage deformation after knee bends was compared in seven professional weight lifters, seven sprinters, and 14 untrained volunteers. RESULTS: Patellar cartilage deformation was -5.9% after knee bends, -4.7% after squatting, -2.8% after normal walking, -5.0% after running, and -4.5% after cycling. The pattern of patellar cartilage deformation corresponded to the range of motion involved in the particular activity. Tibial cartilage deformation was greatest under high impact loading (-7%), but small for other activities. No significant difference was found between athletes and non-athletic controls. CONCLUSIONS: Patellar cartilage deformation shows a "dose dependent" response, where more intense loading leads to greater deformation. Relatively little deformation was observed in the femorotibial joint, except during high impact activities. The findings provide no evidence that adult human cartilage properties are amendable to training effects in vivo.
Adult↗
A new in vivo technique for determination of 3D kinematics and contact areas of the patello-femoral and tibio-femoral joint.
Patello-femoral disorders are often caused by changes of patello-femoral and/or tibio-femoral kinematics. However, until now there has been no quantitative in vivo technique, that is able to obtain 3D kinematics and contact areas of all knee compartments simultaneously on a non-invasive basis. The aim of this study was therefore to develop and apply a technique which allows for determination of 3D kinematics and contact areas of the patello-femoral and tibio-femoral joint during different knee flexion angles and under neuromuscular activation patterns. One knee of each of the 10 healthy volunteers was examined in an open MR system under flexing isometric muscle activity at 30 degrees and 90 degrees. Three-dimensional kinematics and contact areas of the patello-femoral and tibio-femoral joints were analyzed by 3D image postprocessing. The reproducibility of the imaging technique yielded a coefficient of variation of 4.6% for patello-femoral, 4.7% for femoro-tibial displacement and 8.6% for contact areas. During knee flexion (30-90 degrees ), patella tilt (opened to medial) decreased (8.8+/-3.4 degrees vs. 4.6+/-3.1 degrees, p<0.05), while lateral patellar shift increased significantly (1.6+/-2.3mm vs. 3.4+/-3.0mm, p<0.05). Furthermore, a significant posterior translation and external rotation of the femur relative to the tibia was observed. Patello-femoral contact areas increased significantly in size (134+/-60mm(2) vs. 205+/-96 mm(2)) during knee flexion. This technique shows a high reproducibility and provides physiologic in vivo data of 3D kinematics and contact areas of the patello-femoral and the tibio-femoral joint during knee flexion. This allows for advanced in vivo diagnostics, and may help to improve therapy of patello-femoral disorders in the future.
Adolescent↗
Femoro-tibial and menisco-tibial translation patterns in patients with unilateral anterior cruciate ligament deficiency--a potential cause of secondary meniscal tears.
OBJECTIVE: To analyze menisco-tibial and femoro-tibial translation patterns in healthy and ACL-deficient knees in different knee flexion angles under muscle activity. METHODS: The ACL-deficient and contralateral healthy knees of 10 patients were examined with an open MRI system at 30 degrees and 90 degrees of knee flexion, under isometric contraction of the extensors or flexor muscle groups. Translations between the tibia, the femoral condyles and the menisci were analyzed by three-dimensional image postprocessing. RESULTS: Posterior translation of the femur and menisci relative to the tibia occurred during knee flexion (30-90 degrees) in all knees. In ACL-deficient knees, posterior translation of the medial femoral condyle (+1.3 +/- 3.8 mm) was significantly larger than in healthy knee (-0.9 +/- 2.9 mm; p<0.05), while the translation pattern of the menisci was similar (med. meniscus 0.6 +/- 2.3 mm vs. 0.6 +/- 2.7 mm). Under isometric contraction of the extensors (relative to the flexor muscle group), an increased posterior position of the femur and menisci was observed at 30 degrees knee flexion, but not at 90 degrees. This applied to ACL-deficient and healthy knees. CONCLUSIONS: This study shows a significant increase of translation of the medial femoral condyle in ACL-deficient knees, whereas menisco-tibial translation remains almost unchanged. This difference in translation patterns indicates that the posterior horn of the medial meniscus might encounter shear, potentially explaining the high rate of secondary medial meniscal tears in patients with ACL-deficiency.
Adolescent↗
Correlation and sex differences between ankle and knee cartilage morphology determined by quantitative magnetic resonance imaging.
OBJECTIVE: To study the correlation between ankle and knee cartilage morphology to test the hypothesis that knee joint cartilage loss in gonarthritis can be estimated retrospectively using quantitative MRI analysis of the knee and ankle and established regression equations; and to test the hypothesis that sex differences in joint surface area are larger in the knee than the ankle, which may explain the greater incidence of knee osteoarthritis in elderly women than in elderly men. METHODS: Sagittal MR images (3D FLASH WE) of the knee and hind foot were acquired in 29 healthy subjects (14 women, 15 men; mean (SD) age, 25 (3) years), with no signs joint disease. Cartilage volume, thickness, and joint surface area were determined in the knee, ankle, and subtalar joint. RESULTS: Knee cartilage volumes and joint surface areas showed only moderate correlations with those of the ankle and subtalar joint (r = 0.33 to 0.81). The correlations of cartilage thickness between the two joints were weaker still (r = -0.05 to 0.53). Sex differences in cartilage morphology at the knee and the ankle were similar, with surface areas being -17.5% to -23.5% lower in women than in men. CONCLUSIONS: Only moderate correlations in cartilage morphology of healthy subjects were found between knee and ankle. It is therefore impractical to estimate knee joint cartilage loss a posteriori in cross sectional studies by measuring the hind foot and then applying a scaling factor. Sex differences in cartilage morphology do not explain differences in osteoarthritis incidence between men and women in the knee and ankle.
Adult↗
Morpho-functional visualization of dynamic MR-mammography.
In view of an increasing use of breast MRI supplementing X-ray mammography, the purpose of this study was the development of a method for fast and efficient analysis of dynamic MR image series of the female breast. The image data sets were acquired with a saturation-recovery-turbo-FLASH sequence facilitating the detection of the kinetics of the contrast agent concentration in the whole breast with a high temporal and spatial resolution. In addition, a morphological 3D-FLASH data set was acquired. The dynamic image data sets were analyzed by tracer kinetic modeling in order to describe the physiological processes underlying the contrast enhancement in mathematical terms and thus enable the estimation of functional tissue specific parameters, reflecting the status of microcirculation. To display morphological and functional tissue information simultaneously, a multidimensional real-time visualization system (using 3D-texture mapping) was developed, which enables a practical and intuitive human-computer interface in virtual reality. The spatially differentiated representation of the computed functional tissue parameters superimposed on the anatomical information offers several possibilities: improved discernibility of contrast enhancement, inspection of the data volume in 3D-space and localization of lesions in space and thus fast and more natural recognition of topological coherencies. In a feasibility study, it could be demonstrated that multidimensional visualization of contrast enhancement in virtual reality is practical. Especially, detection and localization of multiple breast lesions may be an important application
Breast Neoplasms↗
Feasibility of T and Z scores from magnetic resonance imaging data for quantification of cartilage loss in osteoarthritis.
OBJECTIVE: T scores (an indicator of the difference between patients and young healthy subjects) and Z scores (an indicator of the difference between patients and age-matched healthy subjects) are used in the diagnosis of osteoporosis and form the current basis for the definition of osteoporosis by the World Health Organization. We tested the feasibility of using T and Z scores derived from quantitative cartilage imaging with magnetic resonance imaging (MRI) for the diagnosis of osteoarthritis (OA). METHODS: High-resolution MR images of tibial cartilage were acquired from 126 young healthy adults (ages 20-35 years), 24 age-matched elderly healthy adults (ages 50-75 years), 7 OA patients prior to tibial osteotomy, and 7 OA patients prior to knee arthroplasty. Cartilage volume, thickness, surface area, and original joint surface area (before onset of disease) were determined in the medial and lateral tibia. RESULTS: The cartilage volume of the medial tibia of osteotomy patients with varus malalignment displayed moderate T scores (-1.0), and more negative T scores (-3.8) were observed in knee arthroplasty patients with varus malalignment. Normalization of the cartilage volume to the original joint surface area substantially enhanced the scores in patients undergoing osteotomy (-2.3) and in patients undergoing knee arthroplasty (-5.5), and this was superior to the normalization ratios of cartilage volume to body height and cartilage volume to body weight, in terms of distinguishing the loss of articular cartilage. CONCLUSION: Quantitative analysis of OA by MRI is feasible using T and Z scores. However, cartilage volume should be normalized to the individual joint surface area in order to maximize the discriminatory power of this technique for the diagnosis of OA.
Adult↗
Validation of cartilage volume and thickness measurements in the human shoulder with quantitative magnetic resonance imaging.
OBJECTIVE: To validate quantitative magnetic resonance imaging (qMRI) for the assessment of cartilage volume and thickness in thin and curved cartilage layers, such as the shoulder. METHODS: Eight shoulder specimens from healthy individuals (aged 31-69 years) were investigated using a 3D gradient echo sequence with selective water excitation. After segmentation with a B-spline Snake algorithm, the cartilage volume and thickness were determined three dimensionally. The cartilage volume data were compared with water displacement of surgically removed tissue, and the thickness with A-mode ultrasound. RESULTS: The glenoid and humeral head cartilage volume from qMRI agreed highly with that from water displacement (systematic difference, +/-1 to +/-3%; absolute difference, 4 to 7%). For the cartilage thickness, the mean systematic difference ranged from -17% (mean cartilage thickness of the glenoid) to +7% (maximal cartilage thickness of the glenoid); the standard error of the estimate was 3.7% for the humeral head, and 6.4% for the glenoid. CONCLUSIONS: The applied technique can be used for accurate determination of cartilage volume and thickness in human joints with highly curved and thin cartilage layers, such as the shoulder. In vivo application of this method will depend on the development of efficient surface coils that allow high resolution imaging under in situ conditions.
Adult↗
Dynamic MR-mammography in virtual reality.
In view of an increasing use of breast MRI supplementing X-ray mammography, the purpose of this study was the development of a method for fast and efficient analysis of dynamic MR image series of the female breast. The image data sets were acquired with a saturation-recovery-turbo-FLASH sequence facilitating the detection of the kinetics of the contrast agent concentration in the whole breast with. In addition, a morphological 3D-FLASH data set was acquired. The dynamic image data sets were analyzed by tracer kinetic modeling in order to describe the physiological processes underlying the contrast enhancement in mathematical terms and thus to enable the estimation of functional tissue specific parameters, reflecting the status of microcirculation. To display morphological and functional tissue information simultaneously, a multidimensional real-time visualization system (using 3D-texture mapping) was developed, which enables a practical and intuitive human-computer interface in virtual reality. The spatially differentiated representation of the computed functional tissue parameters superimposed on the anatomical information offers several possibilities: improved discernibility of contrast enhancement; inspection of the data volume in 3D-space using the features of rotation and transparency variation; localization of lesions in space and thus fast and more natural recognition of topological coherencies. In a feasibility study, it could be demonstrated that multidimensional visualization of contrast enhancement in virtual reality is a practicable idea. Especially, detection and localization of multiple breast lesions may be an important application.
Computer Simulation↗
Functional adaptation of human joints to mechanical stimuli.
OBJECTIVE: This study tests the hypothesis that functional adaptation occurs in human joints, and that substantial differences in joint 'loading history' explain the phenotypic variability observed in human cartilage morphology. METHOD: We examined 18 triathletes (nine men and nine women) who had been physically active throughout life (training for >10 h per week for the last 3 years), and 18 volunteers that had never been physically active on a regular basis. The right knee joints were imaged with a previously validated fat-suppressed gradient-echo MR sequence. Cartilage volume, thickness, joint surface areas, and normalized cartilage signal intensity were determined with post-processing software, specifically designed for these applications. RESULTS: The knee joint cartilage thickness, and signal intensity were not significantly different between athletes and inactive volunteers, but male athletes displayed significantly larger knee joint surfaces (P< 0.01; +8.8%). Female athletes displayed a significantly larger medial tibia (P< 0.05; +18.9%), the difference in the total knee surface area reaching borderline significance (P=0.08; +7.0%). CONCLUSIONS: The results suggest that joint size can be modulated during growth, but that (opposite to muscle and bone) the thickness of the cartilage does not adapt to mechanical stimulation. This finding may reveal a general principle in the development and functional adaptation of diarthrodial joints, elucidating an important mechanism for reducing mechanical stress in biphasic cartilage layers.
Adaptation, Physiological↗
Side differences of knee joint cartilage volume, thickness, and surface area, and correlation with lower limb dominance--an MRI-based study.
OBJECTIVE: To test the hypotheses that absolute side differences in knee joint cartilage morphology are substantially smaller than intersubject variability, and that systematic side differences are determined by (force) dominance of the lower limbs. METHODS: Fifteen healthy volunteers with definite dominance of one lower limb were studied. Knees were imaged sagittally with a validated, high-resolution MR sequence. Transverse MR images of the thigh and calf were acquired with a spin echo sequence. Knee joint cartilage volume, thickness and joint surface areas, as well as muscle cross sectional areas were determined with in house post-processing software. RESULTS: Absolute side differences amounted to 5.0+/-3.7% for the knee cartilage volume, 3.8+/-3.1% for cartilage thickness, and 3.4+/-1.7% for joint surface areas. The intersubject variability was 24.8%, 14.4%, and 14.1%, respectively. Volunteers with dominance of one of both lower limbs did not display significant side differences in cartilage morphology, but the side differences of the thigh musculature correlated positively with side differences of knee joint cartilage volume (r=+0.68; P< 0.01). CONCLUSIONS: The results advocate the use of cartilage parameters from the contra-lateral limb for retrospectively estimating cartilage loss in patients with unilateral osteoarthritis (OA), and for determining local risk factors of OA in cross-sectional epidemiological studies, which are specific to pre-morbid cartilage morphology. Functional (force) dominance of one of both lower limbs does not explain side differences of articular cartilage morphology, but side differences are positively associated with side differences in muscle cross sectional areas.
Adult↗
Long-term and resegmentation precision of quantitative cartilage MR imaging (qMRI).
OBJECTIVE: Follow up of osteoarthritis (OA) and evaluation of structure modifying OA drugs require longitudinal data on cartilage structure. The aim of this study was to analyse the long term and resegmentation precision of quantitative cartilage analysis with magnetic resonance imaging (qMRI) in vivo, and to relate precision errors to the estimated cartilage loss in OA. METHOD: Sagittal MR images of the knee were obtained in 14 individuals, four datasets being acquired in a first imaging session. In 12 subjects, two further datasets were acquired over the next months. Image analysis was performed in the same session for image data obtained under short-term and long-term imaging conditions, and in three different sessions (months apart) for the first data set (resegmentation precision). RESULTS: Long-term precision errors ranged from 1.4% (total knee) to 3.9% (total femur) for cartilage volume and thickness and were only marginally higher than those under short term conditions. In the medial tibia, the error was 84 mm(3) compared with an estimated loss of >1,200 mm(3) in varus OA. Precision errors for resegmentation were somewhat higher, but considerably smaller than the intersubject variability. CONCLUSIONS: Scanner drift and changes in imaging or patient conditions appear not to represent a critical problem in quantitative cartilage analysis with magnetic resonance imaging (qMRI). In longitudinal studies, image analysis of sequential data should be performed within the same post-processing session. Under these conditions, qMRI promises to be a very powerful method to assess structural change of cartilage in OA.
Adult↗
[MR-based 3D-analysis of the pathomechanics of traumatic and atraumatic shoulder instability].
AIM: Until now it is unknown to what extent malpositioning of the scapula is a relevant factor in shoulder instability that should be considered in therapy. The objective was to analyse 3D-scapular kinematics and humeral head (de-)centering in patients with atraumatic and/or traumatic shoulder instability and to investigate the correlation between the two factors. METHOD: The shoulders of 28 healthy volunteers and of 14 patients each with atraumatic or traumatic instability were examined in various arm positions - with and without muscle activity - using open MR imaging. After 3D reconstruction, analyses of scapular kinematics and glenohumeral translation were performed. RESULTS: In atraumatic unstable shoulders, the scapular position [30 degrees of abduction: scapulo-humeral rhythm: 3.5 +/- 2.6 : 1 vs. healthy 2.4 +/- 1.3 : 1; internal rotation: 59 +/- 9 degrees vs. healthy 49 +/- 3 degrees (p < 0.05)] and humeral head position was significantly decentered in both planes (p < 0.05). While the correlation between the two factors was high during passive elevation (r = 0.60-0.87), it was low during muscular activity (r = 0.25-0.62). In patients with traumatic instability no alterations of the scapula kinematics were observed. Significant humeral head decentering (p < 0.05) occurred only during abduction and external rotation. CONCLUSIONS: Patients with atraumatic instability demonstrated significant alterations of scapular kinematics and decentering of the humeral head. In traumatic instability a decentering occurred only in specific arm positions with no changes in scapula position. Because of the high correlation between the two factors, physiotherapeutic strategies for the scapula-stabilising muscles should be adapted to the direction of instability.
Adolescent↗