Biomedical subjects

H Graichen

Publications and source records attributed to H Graichen.

At least 19 recordsLinked to original sources

PubMed2005

Femorotibial and patellar cartilage loss in patients prior to total knee arthroplasty, heterogeneity, and correlation with alignment of the knee.

OBJECTIVE: To analyse tibial, femoral, and patellar cartilage loss in patients prior to total knee arthroplasty (TKA), and its correlation with alignment of the knee. METHODS: 26 patients (aged 58 to 86 years) with a clinical indication for TKA were investigated. Quantitative end points of cartilage morphology (T scores for cartilage volume normalised to total subchondral bone area) were determined from coronal and axial magnetic resonance image data, using proprietary software. The static alignment of the knee was determined from standing full limb radiographs. RESULTS: The magnitude of cartilage loss (T score of normalised cartilage volume) was highly variable within the knee, correlation coefficients ranging from r = 0.17 to 0.51 between cartilage plates. The correlation of cartilage loss with static alignment of the knee (as a continuous variable) was r = -0.52 (p<0.05) for the medial tibia, -0.38 (not significant) for the medial femur, +0.76 (p<0.001) for the lateral tibia, +0.31 (not significant) for the lateral femur, and -0.09 for the patella. When analysing alignment independent of direction (valgus or varus), the correlation for the patella increased to r = 0.30, but remained non-significant. CONCLUSIONS: Cartilage loss was highly variable among patients and among cartilage plates before knee arthroplasty. Its correlation with alignment was stronger for the tibia than for the femur. There was some evidence for an association of alignment and patellar cartilage loss. These findings stimulate further research on the mechanism and cause-effect relation of alignment and knee osteoarthritis using quantitative magnetic resonance imaging technology.

Aged↗

PubMed2005

Accuracy of quantitative magnetic resonance imaging in the detection of ex vivo focal cartilage defects.

BACKGROUND: No established, non-invasive diagnostic procedure for quantifying focal cartilage defects is currently available. OBJECTIVE: To test the accuracy of quantitative magnetic resonance imaging (qMRI) for reliable determination of cartilage defect size in various compartments of the human knee. METHODS: 24 tibial and patellar cartilage plates were harvested during knee arthroplasty. 74 cylindrical defects with diameters of 3, 5, and 8 mm were created with a punch. In 15 specimens (51 defects), the cartilage cylinders (inside the punch) were removed (approach 1), while in 9 specimens (23 defects) the surrounding tissue was removed mechanically and the cartilage cylinder was left in place (approach 2). All plates were imaged with a T(1) weighted water excitation gradient echo sequence at a resolution of 1.5 mm x 0.31 mm x 0.31 mm. The defect size was computed from the image data after interactive segmentation and compared with the known dimensions of the cylinders. RESULTS: Although there was a significant overestimation of the defect size by qMRI in 3 mm defects (mean (SD) +1.3 (0.58) mm = +/-42%; p<0.001), the overestimation was only +1.0 (0.57) mm (+/-21%; p<0.05) in 5 mm defects and +0.1 (0.39) mm (+/-4%; p = 0.31) in 8 mm defects (approach 1). Values were similar for approaches 1 and 2 and for patellar and tibial cartilage plates. CONCLUSIONS: These findings show that qMRI allows accurate quantification of focal cartilage defects. It may therefore represent a valuable tool in the diagnosis of traumatic cartilage lesions, osteochondrosis dissecans, and osteochondral fractures, and in monitoring their responsiveness to surgical or other treatments.

Cartilage, Articular↗

PubMed2005

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↗

PubMed2005

In vivo contact areas of the knee in patients with patellar subluxation.

OBJECTIVE: Ex vivo studies have suggested that cartilage contact areas and pressure are of high clinical relevance in the etiology of osteoarthritis in patients with patellar subluxation. The aims of this study were therefore to validate in vivo measurements of contact areas with 3D open magnetic resonance imaging (MRI), and to study knee joint contact areas in patients with patellar subluxation at different angles of knee flexion in comparison with healthy subjects. METHODS: 3D-MRI data sets of 12 healthy volunteers and eight patients with patellar subluxation were acquired using a standard clinical (1.5 T) and an open (0.2 T) MRI scanner. We compared femoro-patellar and femoro-tibial contact areas obtained with two different sequences from open MRI [dual-echo-steady-state (DESS) and fast-low-angle-shot (FLASH) sequences] with those derived from standard clinical 1.5 T MRI. We then analyzed differences in joint contact areas between healthy subjects and patients with patellar subluxation at 0 degree, 30 degrees, and 90 degrees of knee flexion using open MRI. RESULTS: The correlation of the size of contact areas from open MRI with standard clinical MRI data ranged from r = 0.52 to 0.92. Open-MRI DESS displayed a smaller overestimation of joint contact areas (+21% in the femoro-patellar, +12% in the medial femoro-tibial, and +19% in the lateral femoro-tibial compartment) than FLASH (+40%, +37%, +30%, respectively). The femoro-patellar contact areas in patients were significantly reduced in comparison with healthy subjects (-47% at 0 degree, -56% at 30 degrees, and -42% at 90 degrees of flexion; all p < 0.01), whereas no significant difference was observed in femoro-tibial contact areas. CONCLUSIONS: Open MRI allows one to quantify joint contact areas of the knee with reasonable accuracy, if an adequate pulse sequence is applied. The technique permits one to clearly identify differences between patients with patellar subluxation and healthy subjects at different flexion angles, demonstrating a significant reduction and lateralization of contact areas in patients. In the future, application of this in vivo technique is of particular interest for monitoring the efficacy of different types of surgical and conservative treatment options for patellar subluxation.

Adult↗

PubMed2005

Pathomechanics in atraumatic shoulder instability: scapular positioning correlates with humeral head centering.

The objective was to analyze three-dimensional scapular positioning and glenohumeral centering of normal and atraumatic unstable shoulders. We hypothesized that changes of humeral head position correlate with alterations of scapular positioning. The shoulders of 28 healthy volunteers and 14 patients with atraumatic instability were examined in various arm positions using open magnetic resonance imaging. After segmentation and three-dimensional reconstruction, three-dimensional analyses of scapular positioning and humeral head position relative to the glenoid were done. The coefficient of correlation (r) between both parameters was determined using the correlation z test. The glenohumeral to scapulothoracic ratio in the scapular plane was increased in nine of 14 patients and decreased in three patients, whereas the scapular internal rotation in the transverse plane was increased in all unstable shoulders. The unstable shoulders also had malcentering (greater than two times the standard deviation in the healthy volunteers) of the humeral head in the direction of instability during various arm positions. In healthy and unstable shoulders, the correlation between scapular position and glenohumeral positioning was high during passive elevation (r = 0.60-0.87). The high correlation suggests that scapular positioning is relevant for humeral head decentering. Therefore, physiotherapeutic strategy should consider the malpositioning of the scapula and be adapted to the direction of instability.

Adolescent↗

PubMed2004

Influence of a mono-centric knee brace on the tension of the collateral ligaments in knee joints after sectioning of the anterior cruciate ligament--an in vitro study.

OBJECTIVE: To analyze the influence of knee bracing on the tension of the medial and lateral collateral ligaments in anterior cruciate ligament deficiency. DESIGN: The tension of the collateral ligaments in anterior cruciate ligament deficient knees was measured with and without knee bracing using an in vitro model. BACKGROUND: Anterior cruciate ligament deficiency increases the tension in both collateral ligaments at the knee joint. Therefore knee braces should reduce that tension increase. However, that effect has never been proven quantitatively. METHODS: After anterior cruciate ligament-transection, the forces of the medial (anterior/posterior part) and lateral collateral ligament were measured in ten fresh human cadaver knees at 0 degrees, 20 degrees, 40 degrees, 60 degrees, 80 degrees and 100 degrees of flexion, with and without application of a mono-centric knee brace. To quantify the ligament forces, strain gauges were fixed at the bony origins of the ligaments. RESULTS: Bracing led to a significant decrease of ligament forces (20-100 degrees: P < 0.0001) in the anterior part of the medial collateral ligament in all joint positions. In the posterior aspect, this effect was observed only at 40 degrees (P < 0.0001) and 80 degrees (P = 0.001) of flexion. In the lateral collateral ligament, bracing caused a strain reduction from 60 degrees to 100 degrees of flexion (P < 0.0001). Therefore a flexion angle dependent effect of knee bracing on the strain was seen in the posterior aspect of the medial and in the lateral collateral ligament in anterior cruciate ligament deficient knee joints. CONCLUSIONS: Application of a mono-centric knee brace leads to a significant position dependent reduction of collateral ligament tension after anterior cruciate ligament-rupture.

Anterior Cruciate Ligament Injuries↗

PubMed2004

Patella kinematics and patello-femoral contact areas in patients with genu varum and mild osteoarthritis.

BACKGROUND: Patients with genu varum of the knee and moderate to severe osteoarthritis often suffer from additional symptoms of the patello-femoral joint. These patients have a poor prognosis following high tibial osteotomy. It is unclear whether varus knees with only mild femoro-tibial osteoarthritis are also associated with alterations of patella biomechanics, and affect the prognosis of intended high tibial osteotomy. METHODS: Fifteen patients with genu varum and mild osteoarthritis and 15 healthy volunteers were assessed in an open MRI-scanner. 3D-GRE sequences of the knee were obtained in 0 degrees, 30 degrees and 90 degrees with and without activity of the extensor muscles. After segmentation of patella, femur, tibia and the adjacent cartilage, a patella-based local coordinate system was established. Femoral and tibial reference points allowed definition of the spatial position of the patella. Contact areas were defined by intersection of opposing cartilage volumes. FINDINGS: No significant differences in patella kinematics and patello-femoral contact areas could be found (P > 0.05) between varus knees with mild osteoarthritis and healthy knees either at different flexion angles or under extending muscle activity. INTERPRETATION: In knees with genu varum and mild medial osteoarthritis we could detect no alterations in patello-femoral kinematics. Since the alterations of patients with genu varum and mild osteoarthritis are restricted to the medial femoro-tibial joint high tibial osteotomy might be successful.

Adult↗

PubMed2004

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↗

PubMed2004

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↗

PubMed2004

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↗

PubMed2003

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↗

PubMed2002

[Fixed and functional decentering of the head of the humerus in patients with omarthrosis].

AIM: To determine whether in patients with specific types of osteoarthritis of the shoulder not only a fixed but also a functional decentering of the humeral head exist. METHOD: The shoulder joints of 10 healthy volunteers and of 16 patients with osteoarthritis of the shoulder were examined in various arm-positions, using an open MR scanner. After segmentation, 3D reconstruction of the scapula and humerus were performed and the position of the midpoint of the humeral head calculated relative to the center of mass of the glenoid cavity. RESULTS: At 30 degrees of abduction, 4 of 16 patients demonstrated a fixed posterior (12.9 +/- 2.8 mm) position and 8 (all patients with cuff-arthropathy) a fixed superior (6.6 +/- 2.6 mm) position of the humeral head. At 90 degrees of abduction the patients showed a significant (p < 0.001) combined decentering in the superior and posterior direction as compared to the healthy shoulders (functional decentering). CONCLUSIONS: This study demonstrates, that in most of the patients with osteoarthritis of the shoulder, a significant functional decentering occurred during abduction and external rotation, even if they showed no fixed decentering of the humeral head at 30 degrees of abduction.

Aged↗

PubMed2002

Quantitative image analysis of the cartilage in Virtual Reality.

The objective of this work is to develop image processing methods for analysing the morphology of the joint cartilage with magnetic resonance imaging. Quantitative data on the morphological distribution of the joint cartilage are of great interest for both research as well as for diagnosis. The cartilage thickness provides information on the local cartilage occurance and may therefore be helpful in early and objective diagnosing degenerative cartilage changes, monitoring the pathogenesis of osteoarthritis, and controlling the success of chondroprotective treatment. In biomechanics, the thickness distribution serves to analyse the functional adaptation or the compression of the cartilage under loading and may be used for numerical simulation of load transmission in the joint.

Biomechanical Phenomena↗

PubMed2001

[Effect of muscle activity on the 3-dimensional movement pattern of the shoulder. Study with open MRI].

The objective of this study was to analyze the influence of shoulder muscle activity on the three-dimensional motion pattern of the shoulder girdle in the living. 14 healthy volunteers were investigated with an open MRI system at 60-120 degrees abduction--with and without activity of the shoulder abductors. The 3D motion pattern of the humerus, scapula, clavicle and M. supraspinatus were computed. Under muscle activity, the glenoid demonstrated a slightly reduced elevation at 60 degrees of abduction (20.5 degrees +/- 8.2 degrees vs. 23.1 degrees +/- 6.3 degrees; not significant), and at 120 degrees a significantly higher degree of rotation under muscle activity (43.3 degrees +/- 8.6 degrees vs. 36.1 degrees +/- 5.2 degrees; p < 0.01), whereas at 90 degrees no difference was observed. This caused a significant reduction of the scapulo-humeral rhythm at 120 degrees (2.6 vs. 1.5; p < 0.01), a significant increase of the supraspinatus angle (123.3 degrees +/- 6.7 degrees vs. 117.3 degrees +/- 6.5 degrees; p < 0.05) as well as a reduction of the supraspinato-humeral relationship (1.0 vs. 0.97). The study demonstrates that muscle activity leads to an alteration of shoulder girlde motion patterns at higher degrees of abduction, with increased rotation of the scapula, an altered spatial relationship between the supraspinatus and humerus.

Adult↗

PubMed2001

An in vivo technique for determining 3D muscular moment arms in different joint positions and during muscular activation - application to the supraspinatus.

OBJECTIVE: To develop a 3D in vivo technique for determining the moment arm and insertion angle of muscles in different joint positions and under muscular activity. DESIGN: An open magnetic resonance imaging system and 3D processing techniques were used for determining the moment arm and insertion angle of the supraspinatus in healthy volunteers. BACKGROUND: Muscular moment arms are important parameters for the computation of joint forces, however, so far in vivo measurements have not considered the influence of muscle activity and were restricted to two dimensions. METHODS: 10 healthy shoulders were investigated in 30-150 degrees abduction with and without abducting muscular activity, using an open magnetic resonance imaging. The minimal distance between the midpoint of the humeral head and the line of action of the supraspinatus was determined in 3D. The insertion angle was derived by calculating the angle between the humerus and the supraspinatus. RESULTS: During elevation a significant (P < 0.001) increase of the supraspinatus moment arm was observed (19.9 mm (SD, 2.3 mm) at 30 degrees; 23.3 mm (SD, 2.5 mm) at 150 degrees ), being significantly larger at 90 degrees and 120 degrees under muscle activity. The insertion angle also increased significantly during elevation (P < 0.001), the values becoming larger under muscle activity at 60 degrees (P < 0.01) and at 90 degrees (P < 0.05). CONCLUSIONS: This 3D technique permits to determine the moment arm and insertion angle of muscles in vivo not only in various joint positions but also under in vivo muscle activity. For the supraspinatus, we observed a constant increase of both parameters during arm abduction. RELEVANCE: The technique and these data can be used for improved computation of joint forces in biomechanical model, and for precise diagnostics in patients with altered scapulohumeral motion patterns.

Adult↗

PubMed2001

Three-dimensional analysis of shoulder girdle and supraspinatus motion patterns in patients with impingement syndrome.

Alterations of the shoulder girdle motion have been suggested to be associated with shoulder disorders. The objective of this study was to perform a three-dimensional (3D) motion analysis of the supraspinatus muscle and shoulder girdle in patients with different stages of impingement syndrome. 20 patients with unilateral impingement and 14 normal controls were investigated at 30 degrees, 90 degrees, and 120 degrees of abduction with and without abducting muscle activity. The spatial relationship between the shoulder girdle elements and the supraspinatus was quantified from open MRI data. No significant alterations in glenoid rotation were observed between the patients and asymptomatic volunteers. However, while in the healthy volunteers the values showed a normal distribution (28.5+/-3.6 degrees at 90 degrees abduction with muscle activity), the patients (30.5 degrees+/-9.7 degrees) contained a subset of five individuals with an obvious increase in glenoid rotation angle (>40 degrees) compared with controls (>2.5 standard deviations higher than the mean) and with the healthy contralateral side. These five patients also displayed alterations in the scapulo-humeral rhythm and supraspinatus motion, but not in clavicular position. The study shows that only a specific subset of patients with impingement syndrome demonstrates complex changes in shoulder girdle and supraspinatus motion patterns, suggesting that this subset may benefit from an alternative type of treatment.

Adult↗

PubMed2000

Glenohumeral translation during active and passive elevation of the shoulder - a 3D open-MRI study.

Despite its importance for the understanding of joint mechanics in healthy subjects and patients, there has been no three-dimensional (3D) in vivo data on the translation of the humeral head relative to the glenoid during abduction under controlled mechanical loading. The objective was therefore to analyze humeral head translation during passive and active elevation by applying an open MR technique and 3D digital postprocessing methods. Fifteen healthy volunteers were examined with an open MR system at different abduction positions under muscular relaxation (30-150 degrees of abduction) and during activity of shoulder muscles (60-120 degrees ). After segmentation and 3D reconstruction, the center of mass of the glenoid and the midpoint of the humeral head were determined and their relative position calculated. During passive elevation, the humeral head translated inferiorly from +1.58mm at 30 degrees to +0. 36mm at 150 degrees of abduction, and posteriorly from +1.55mm at 30 degrees to -0.07mm at 150 degrees of abduction. Muscular activity brought about significant changes in glenohumeral translation, the humeral head being in a more inferior position and more centered, particularly at 90 and 120 degrees of abduction (p<0.01). In anterior/posterior direction the humeral head was more centered at 60 and 90 degrees of abduction during muscle activity. The data demonstrate the importance of neuromuscular control in providing joint stability. The technique developed can also be used for investigating the effect of muscle dysfunction and their relevance on the mechanics of the shoulder joint.

Biomechanical Phenomena↗

PubMed2000

Validation of high-resolution water-excitation magnetic resonance imaging for quantitative assessment of thin cartilage layers.

OBJECTIVE: To employ a magnetic resonance (MR) imaging technique for quantitative assessment of thin cartilage layers, and to validate the cartilage volume and thickness measurements. METHODS: We investigated 10 normal elbow joints (age 20 to 69 years) with a 3D gradient echo sequence with selective water excitation (TR 18 ms; TE 9 ms; FA 25 degrees, resolution 1x0.25x0.25 mm2, imaging time 19 min). After interpolating the image data to a 0.125x0.125 mm2 in-plane resolution, the cartilage plates were segmented, reconstructed in 3D, and the cartilage volume and thickness determined with a 3D Euclidean distance transformation algorithm, independent of the original section plane. The cartilage volume and thickness values were compared with CT arthrography and A-mode ultrasound. RESULTS: The mean systematic difference between the elbow cartilage volume obtained from MR imaging and CT arthrography was -0.11% (-6.0 mm3) and the mean random difference 5.7% (314 mm3). Except for the fovea capitis radii, the deviations were not statistically significant (range -7.6 to +11.7%). In the humerus, the mean cartilage thickness (average = 1.35 mm) was overestimated relative to CT arthrography (+20.7%/+0.23 mm), and slightly underestimated relative to A-mode ultrasound (-6.0%/-0.05 mm). With few exceptions, there were no significant differences between MRI, CT arthrography and ultrasound in the other joint surfaces of the elbow (random deviations between 0.08 and 0.39 mm). CONCLUSIONS: The technique presented can be applied for determining the cartilage volume and 3D thickness in joints with thin cartilage layers with a reasonable degree of accuracy.

Adult↗