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Reconstruction of the patello-femoral compartment and by that avoidance of an overstuffing is one of the important steps for a successful TKA. A revision rate of around 15 % due to problems of the patello-femoral compartment demonstrates that this is not achieved in all cases. There can be many reasons for an overstuffing and also the symptoms can be very variable, showing sometimes a limited flexion, patello-femoral maltracking or anterior knee pain. Due to its relevance the following paper demonstrates the different reasons for a patello-femoral overstuffing. Further possible solutions for avoidance of overstuffing are described. The reasons for patello-femoral overstuffing are multiple. The majority is caused on the femoral side, however additional patellar and tibial reasons exist. During positioning of the femora resection blocks, the distal resection plane (extension/flexion) as well as the AP block for sizing is crucial. For that a pre-op analysis and implant planning in the lateral view of the X-ray should be performed in order to optimise implant size and position. For the patella the correct resection height and plane are important to avoid an overstuffing. A lateral patella component position can be another reason for an overstuffing. In conclusion, it can be stated that an anatomic reconstruction of the patello-femoral compartment is an important part of TKA surgery. The avoidance of a patello-femoral overstuffing can be achieved by exact pre-op planning of the femoral component size and position, and by precise surgery with sufficient bone resection., (Georg Thieme Verlag KG Stuttgart · New York.)

Purpose: The purpose of this study was to investigate the effect of a 6-month period of intensive running followed by the participation at a marathon run on cartilage volume and thickness in knees of marathon beginners., Methods: Ten asymptomatic marathon beginners underwent a supervised 6-month training program, which was finalized by the participation at a marathon run. Three-dimensional quantitative magnetic resonance imaging was performed before the training program (baseline measurements) and 1 day after the marathon (follow-up measurements). Cartilage volume and thickness of the medial and lateral femur, medial and lateral tibia, and patella were measured using semiautomated cartilage segmentation and three dimensional data postprocessing., Results: Significant differences between baseline and follow-up measurements were observed at the lateral femur, where cartilage volume and thickness decreased by a mean of 3.2 ± 3.0% (p = 0.012) and 1.7 ± 1.6% (p = 0.010), respectively. No significant changes in cartilage volume and thickness were observed at the medial and lateral tibia, the medial femur, and the patella., Conclusion: Significant cartilage loss was observed at the lateral femur; however, the measured values are comparable to previously reported precision errors for quantitative cartilage measurement and thus most likely not of clinical relevance. High-impact forces during long-distance running are well tolerated even in marathon beginners and do not lead to clinical relevant cartilage loss., Level of Evidence: IV.

Purpose: In a prospective, consecutive study, a navigation-based technique for calculating the sliding distance of the lateral epicondyle prior to osteotomy in TKA surgery of fixed valgus deformity has been developed, and early results have been evaluated., Materials and Methods: Twenty-seven knees with a fixed valgus deformity undergoing TKA received this new treatment. Clinical scores and radiograph evaluation were performed preoperatively and 1-year postoperatively. Static and dynamic kinematic data were obtained from navigation at the beginning and at the end of surgery., Results: The calculated amount of sliding distance varied between 5 and 16 mm. No complications regarding this technique occurred. All clinical scores showed a significant improvement, and radiological evaluation showed a correction of all parameters in 100 % of patients., Conclusion: With this navigation-based technique, it is possible to calculate the amount of sliding distance prior to osteotomy and obtain excellent early results. All axes have been corrected completely, and flexion and extension gaps were balanced. No specific complications of this technique have occurred so far., Level of Evidence: II.

Aim: Changes in glenoid orientation as a primary cause of shoulder instability have been discussed controversially in the literature. The data of a physiological glenoid version vary widely among different authors and techniques. One reason may be that the previously used 2-D techniques suffer from a limited reproducibility and validity. The objective of this study was therefore to compare the 2-D and 3-D analyses of the glenoid version in patients with shoulder instability., Method: The shoulders of 28 healthy volunteers and of 14 patients each with atraumatic/traumatic instability were examined in an open MR scanner (0.2 T). The 2-D glenoid version was determined using post-processing techniques according to the technique of Friedman et al. (1992). Afterwards, the 3-D glenoid version was analysed independently of the slice orientation and patient position. The coefficient of correlation (r) between the 2-D and 3-D glenoid versions was calculated using the correlation z test., Results: The 3-D post-processing technique showed a reproducibility with a coefficient of variation of 8.3 %. Patients with traumatic instability demonstrated no significant difference compared to the healthy control group (4.4 +/- 2.1 degrees vs. healthy: 3.9 +/- 1.3 degrees). In atraumatic shoulder instability the glenoid retroversion was in the mean significantly increased (10.2 +/- 4.9 degrees). The individual values ranged between 2.6 degrees and 16.6 degrees . Also for the contralateral, unaffected side a significantly increased retroversion (6.3 +/- 2.2 degrees) was observed compared to healthy shoulders. There was a significant correlation (r: 0.84) between 2-D and 3-D retroversion., Conclusions: The presented techniques allow for a reproducible assessment of glenoid version independent of the slice orientation and patient position. Our results demonstrate in the mean only a small difference of +/- 3 degrees between 2-D and 3-D glenoid versions. Therefore under standardised conditions the 2-D CT/MRI should be adequate for measuring the glenoid version except for borderline cases. No significant changes in glenoid version were found in patients with traumatic instability. In atraumatic, posterior instability, in the mean an increased retroversion was observed on both sides. However, the magnitude of these changes varied widely among individuals and should be identified to initiate a causal treatment.

We tested the hypothesis that functional malcentering of the humeral head during arm elevation exists in patients with glenohumeral osteoarthritis and influences long-term glenoid loading. Twenty-eight healthy volunteers and 10 patients with primary osteoarthritis, 10 with cuff-arthropathy, and 1 with dysplastic glenoid were examined. Open magnetic resonance imaging and 3-dimensional (3D) digital postprocessing techniques were applied in various arm positions. Osteoabsorptiometry was used to determine 3D subchondral mineralization patterns of the glenoid as an indicator of integral long-term stress distribution. At 30 degrees of abduction, 5 patients demonstrated malcentering of the humeral head posteriorly; all patients with cuff arthropathy had malcentering superiorly. At 90 degrees, most patients displayed significant (P < .001) malcentering in the superior and posterior direction. The shoulders showed maximal subchondral mineralization patterns in the direction of malcentering. Most patients with glenohumeral osteoarthritis displayed functional malcentering, which might be responsible for postoperative glenoid loosening in shoulder arthroplasty if not corrected intraoperatively.

In 3D image-based studies of joint kinematics, 3D registration methods should be automatic, insensitive to segmentation inconsistencies and use coordinate systems that have clinically relevant orientations and locations because this is important for analyzing rotation angles and translation directions. We developed and evaluated a registration method, which is based on the cylindrical geometry of the humerus shaft and an analysis of the inertia moments of the humerus head, in order to consistently and automatically orient the humerus coordinate system according to its anatomy. Registration techniques must be thoroughly evaluated. In this study we used a well-detectable marker as reference, from which coordinate system determination errors of a 3D object could be measured. This allowed us to quantify by means of unique error analysis the translational and rotational errors in terms of how much and about/along which humeral axis errors occurred. The evaluation experiments were performed using virtual rotations of 3D humeral binary image, a humerus model and a 3D image of a volunteer's shoulder. They indicated that the humeral coordinate system determination errors primarily originated from segmentation inconsistencies, which influenced mostly the humeral transverse axes orientation. The error analysis revealed that the developed registration method reduced the effect of manual segmentation inconsistencies on the orientation of the humeral transverse axes up to 37%, in comparison to the commonly used inertia registration.

This study was aimed to investigate the accuracy and time saving of MRI Argus application in the assessment of cartilage volume in osteoarthritic knees. Twelve knees of patients suffering from osteoarthritis were scanned with a 1.5 T MRI using a 3D gradient echo sequence with selective water excitation. Cartilage volume of the tibial and patellar compartment was determined with a validated multiprocessing computer system (Octane Duo, Silicon Graphics, Mountain View, Calif., USA). The calculated cartilage volumes were compared to the results acquired by the Argus (Siemens Inc., Erlangen, Germany) application software using the MRI data sets. Compared to the multiprocessing computer system a time saving of at least 30 min for cartilage volume determination was achieved. The mean differences of Argus versus the multiprocessing computer system were 4.26+/-0.84 and 7.80+/-0.87% for the medial and lateral tibial plateau and 5.94+/-0.59% for the patella (no statistical significant difference; P>0.05). The applied Argus software can be used for fast and accurate determination of cartilage volume in the knee joint.

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.

Introduction: Patients (n=62) with recurrent traumatic anterior or anteroinferior glenohumeral instability were prospectively evaluated with reference to the surgical reconstruction technique performed., Materials and Methods: Neer's T-plasty procedure was performed in group I (n=31) while a modified, anatomically orientated, anteroinferior capsular shift was performed in group II (n=31). All patients underwent an additional Bankart repair. After 18.1 (group II) and 22.2 (group I) months, patients were assessed in terms of subjective satisfaction, objective stability, range of motion, and functional outcome., Results: No significant differences (91.5% group II, 87.8% group I) were noted between the study groups regarding the patient's subjective evaluation (p=0.17106). Results of Rowe's (93.1% group II, 87.9% group I; p=0.14419) and Constant's Score (96.5% group II, 93.8% group I; p=0.16582) showed no significant differences for both collectives. Postoperative lack of external rotation remained significantly smaller in group II (5.6 degrees +/-2.5 degrees ) compared with group I (9.8 degrees +/-2.5; p=0.00028). Although no significant differences (p=0.612) were found, the rate of recurrence was obviously smaller in group II (group II vs group I: 6 patients)., Conclusions: Our results demonstrate no significant differences between the two capsular reconstruction techniques regarding patient's satisfaction, Rowe and Constant Scores. However, the anatomically orientated anteroinferior capsular shift leads to a significantly smaller external rotation deficit and seems to offer a more reliable postoperative stability.

Objective: Quantitative diagnostic tools for osteoarthritis (OA) are important for evaluating the treatment response to structure-modifying drugs. This study was undertaken to test the technical validity (accuracy) of quantitative magnetic resonance imaging (qMRI) for reliable determination of the total bone interface area, percentage of cartilaginous (denuded) joint surface area, and cartilage thickness in OA., Methods: High-resolution MRIs of femorotibial and patellar cartilage were acquired in 21 patients prior to total knee arthroplasty, using a T1-weighted gradient-echo sequence with water excitation. After segmentation of original bone interface areas (before disease onset) and the actual cartilage layer, the percentages of cartilaginous joint surface area, cartilage thickness, and cartilage volume were determined using proprietary software. During surgery, the patella and the medial and lateral tibia were resected. Results obtained with qMRI were compared with those obtained by direct image analysis of surface area, cartilage thickness, and cartilage volume of the surgically removed tissue., Results: Pairwise differences between results obtained with qMRI and morphologic analysis were +/-4.6% for percentage of cartilaginous surface area, +/-8.9% for cartilage thickness, and +/-9.1% for cartilage volume. Correlation coefficients ranged from 0.92 (thickness) to 0.98 (volume)., Conclusion: Quantitative MRI permits technically accurate and differential assessment of increases in eroded joint surface area and reductions in cartilage thickness in OA. The surrogate validity of these parameters requires testing in longitudinal studies. These parameters may be advantageous over determination of cartilage volume alone when diagnosing OA, exploring its progression, or testing responsiveness to new therapies.

Background: No quantitative data on glenohumeral translation exist allowing one to distinguish insufficiency of the active or passive stabilizers in different forms of shoulder instability., Hypothesis: To determine whether 1) in traumatic or atraumatic shoulder instability an increase of glenohumeral translation can be observed in specific relevant arm positions, 2) muscle activity leads to recentering of the humeral head, and 3) there exist differences between traumatic and atraumatic instability., Study Design: Prospective clinical trial., Methods: In 12 patients with traumatic and 10 patients with atraumatic instability, both shoulders were examined in different arm positions-with and without muscle activity-by using open magnetic resonance imaging and a three-dimensional postprocessing technique., Results: At 90 degrees of abduction and external rotation, translation (anterior-inferior) was significantly higher in patients with traumatic unstable shoulders compared with their contralateral side (3.6 +/- 1.5 versus 0.7 +/- 1.6 mm). In patients with atraumatic instability, significantly increased translation (4.7 +/- 2.0 mm) was observed, with the direction being nonuniform. Muscle activity led to significant recentering in traumatic but not in atraumatic instability., Conclusions: In traumatic instability, increased translation was observed only in functionally important arm positions, whereas intact active stabilizers demonstrate sufficient recentering. In atraumatic instability, a decentralized head position was recorded also during muscle activity, suggesting alterations of the active stabilizers., Clinical Relevance: These data are relevant for optimizing diagnostics and therapeutic strategies.

Alterations of ankle cartilage are observed in degenerative and inflammatory joint disease, but cartilage cannot be directly visualized by radiography. The purpose of this study was therefore to analyze the feasibility and precision of quantitative cartilage imaging in the human hind foot (talocrural, talotarsal, and intertarsal joints), and to report the inter-subject variability for cartilage volume, thickness and surface areas. The feet of 16 healthy volunteers were imaged using a 3D gradient-echo magnetic resonance imaging sequence with water-excitation. After interpolation to a resolution of 1 x 0.125 x 0.125 mm3 the cartilage plates were segmented, and the cartilage volume, thickness, and surface areas determined. The precision (four repeated measurements) was examined in eight volunteers, the RMS average CV% being 2.1% to 10.9% in single joint surfaces, and < or = 3% for the cumulative values of all joints. The mean cartilage thickness ranged from 0.57+/-0.08 (navicular surface) to 0.89+/-0.19 mm (trochlear surface for tibia). In conclusion this study shows that it is feasible to quantify thin cartilage layers in the hind foot under in vivo imaging conditions, and that the precision errors are substantially smaller than the inter-subject variability in healthy subjects.

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.

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.

The objective if this study was to obtain quantitative data about cartilage thickness and volume in joints of the upper extremity by applying a high resolution MR imaging technique, and to validate these data by A-module ultrasound and CT arthrography., 10 elbow and 7 shoulder joints (age 20 to 69 yrs) were investigated with a 3D gradient echo sequence with selective water excitation (TR 18 ms; TE 9 ms; FA 250, resolution 1 x 0,25 x 0,25 mm2, imaging time 19 min.). After trilinear interpolation to a 0,125 x 0,125 mm2 in-plane resolution, snake-based segmentation, and 3D reconstruction, cartilage volume and thickness were determined with a 3D Euclidean distance transformation algorithm. For validation the cartilage volume and thickness values were compared with CT arthrography and A-mode ultrasound., The mean cartilage thickness of the elbow joint ranged between 0,99 and 1,35 mm and that of the shoulder between 1,18 and 1,79 mm. 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). Only in the distal humerus, the mean cartilage thickness (average = 1,35 mm) was overestimated relative to CT arthrography (+20,7%, 0,23 mm). In comparison to A-mode ultrasound a slight underestimation was found in the distal humerus (-6,0%, -0,05 mm) and in the shoulder joint surfaces (humeral head: -22%; -0,26 mm; glenoid cavity: -13%; -0,25 mm). With few exception, there were no significant differences between MRI, CT arthrography and ultrasound in the other joint surfaces of the upper extremity joints (random deviations between 0,08 and 0,39 mm)., This specific MR imaging and postprocessing technique can be used for non-invasive determination of cartilage volume and thickness in joints with thin cartilage layers such as the shoulder with a high degree of accuracy.

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.

The objectives of this study were to determine sex-specific differences of the subacromial space width during active and passive arm abduction and to analyze the correlation of this space with general and regional anthropometric variables. Fourteen healthy subjects (7 men, 7 women) were examined with an open magnetic resonance system at 30 degrees and 90 degrees of abduction (with and without muscle activity). After 3-dimensional reconstruction, the minimal acromiohumeral distance, the glenoid size, and the humeral head radius were determined. At 30 degrees of abduction, a significant difference of the acromiohumeral distance was observed between men (8.18 +/- 1.0 mm) and women (6.98 +/- 0.75 mm) (P < .05), but not at 90 degrees (6.7 +/- 2.0 mm versus 5.9 +/- 1.0 mm) or under muscle activity (4.9 +/- 2.4 mm versus 3.5 +/- 2.1 mm). Significant correlations between the acromiohumeral distance and anthropometric variables were found at 30 degrees of abduction (r = 0.48 to 0.72), but not at 90 degrees, with or without muscle activity (r = 0.21 to 0.55). The results demonstrate that at physical rest, the subacromial space width is dependent on sex, but the interindividual variability increases substantially during abduction and under muscle activity.

Aim: Until now, pathological translation of the glenohumeral joint could not be assessed three-dimensionally and in functionally important arm positions in the living. The objektive of this study was therefore to develop an MR-based technique for determining the three-dimensional glenohumeral translation in functionally relevant positions in vivo., Method: In an open MR scanner both shoulder joints of 5 volunteers with an unilateral traumatic instability were examined in different positions of abduction and rotation. After semiautomatic segmentation, 3D reconstruction of the bony structures of the shoulder girdle was performed and the center of mass of the glenoid cavity was determined and used as reference point. In a virtual reality, the midpoint of the humeral head was assessed and its position relative to the center of mass of the glenoid cavity was calculated., Results: At 30 degrees of abduction, in both shoulders, the humeral head was positioned inferior and posterior relative to the glenoid cavity (healthy: 0.42 +/- 1.1 inf., 0.75 +/- 1.0 mm post.; unstable: 1.31 +/- 0.87 mm inf., 0.51 +/- 1.28 mm post.) The maximal translation (to anterior and inferior) was observed both on the healthy side (mean 1.0 mm, max. 1.8 mm) and in the unstable shoulders (mean 2.5 mm, max. 4.6 mm) with the arm in 90 degrees of abduction and external rotation, thus being 1.7 to 2.5 times higher in the pathological shoulders., Conclusions: With this technique the glenohumeral translation can be quantified three-dimensionally in functionally important positions and without projectional artefacts. In the future, this method can be applied to patients with different entities of shoulder instability.

The aim of our study was to develop a 3-D MR-based technique for the analysis of meniscal and femoral translations during flexion of the knee, and under the influence of antagonistic muscle forces in healthy subjects. In an open MR system, 5 knees were examined at 30 degrees and 90 degrees flexion using a T1-weighted 3-D gradient echo sequence. A force of 30 Newtons, first in the extending and then in the flexing direction, was applied to the distal lower leg. After three-dimensional reconstruction, the minimal distances between the centre of the tibial plateau and the posterior edge of the menisci and femoral condyles were determined. At 30 degrees flexion, the minimum distance for the meniscus was larger medially than laterally (23.2 +/- 1.8 mm vs. 16.2 +/- 3.3 mm), and this also applied to the condyles (25.1 +/- 1.5 vs. 19.0 +/- 3.0 mm). During flexion to 90 degrees, a posterior translation of 0.5 +/- 0.2 mm was observed for the lateral, and of 3.4 +/- 1.2 mm for the medial, meniscus. The condyles demonstrated a different posterior translation (lateral 2.2 +/- 0.56 mm; medial 1.8 +/- 1.9 mm). No obvious differences were found between extension and flexion muscle activity for the different positions of the knee. In the present study, a new 3-D technique is presented for the analysis of the femoral and meniscal translation at various positions of the knee, and under muscle activity. The results suggest different translation for the menisci and condyles.

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.

Changes in shoulder motion patterns are relevant in various shoulder diseases, but no in vivo information exists about the relative positions in vivo of the shoulder girdle bones and the supraspinatus muscle in three-dimensional space. Thus, the objective of this study was to perform a motion analysis of these structures during passive arm elevation using open magnetic resonance imaging and three-dimensional image processing. Fourteen volunteers were examined in five positions of abduction (30 degrees-150 degrees) with an open magnetic resonance system. After segmentation and three-dimensional reconstruction, the axis of the supraspinatus, humerus, clavicle, and the plane of the glenoid were determined, and the relative movements were calculated. The ratio for glenohumeral to scapulothoracic motion was 1.5:1 at 60 degrees and 2.4:1 at 120 degrees abduction. At 30 degrees, the axis of the supraspinatus was nearly horizontal, and during abduction a continuous elevation (+123 degrees at 150 degrees abduction) was measured. In the transverse plane, the angle between the supraspinatus and the clavicle axes became larger during abduction because of an increasing retroversion of the clavicle. The study shows specific three-dimensional motion patterns for each bone of the shoulder girdle and the supraspinatus muscle during passive elevation. The technique and results can be used for future studies in patients with pathologic changes of shoulder girdle motion.

The vertebral bodies and vertebral arches show a characteristic distribution of cortical and cancellous bone. The pedicles are loaded by uniplanar bending that is reflected by the arrangement of the Corticalis. The ligaments of the vertebral column consist of longitudinal and (with exception of the lig. longitudinal anterius) horizontal/oblique segmental ligament bundles. In combination with the anulus fibrosus, the ligaments work as a kind of gear system. They regulate the process of movements of adjacent vertebral bodies in a very precise manner and control the final phase of motion. Besides maintaining the necessary amount of pretension the intervertebral disc distributes the loads uniformly onto the adjacent vertebral bodies. The intervertebral joints are important for guided motion, by restricting the extent in specific planes and directions. Because of their position, they are able to take up the shear forces and to simultaneously restrict them in different planes. The integrity of the fascia thoracolumbalis warrants the protective function of the autochthonuos muscles.

Objective: The aim of this study was to per form a three-dimensional analysis of the width of the subacromial space during passive and active arm abduction in healthy volunteers and patients with impingement syndrome., Subjects and Methods: The shoulders of 10 healthy subjects and 10 patients with impingement syndrome were imaged with an open MR system during abduction, with and without activation of the shoulder muscles. An apparatus was designed for applying an adduction force of 10 N to the distal humerus during image acquisition, and the minimal acromiohumeral distance was measured after three-dimensional reconstruction., Results: In the 10 healthy volunteers, muscle activity led to a significant decrease (-32%; p < .05) of the acromiohumeral distance at 60 degrees of abduction, whereas at 120 degrees of abduction the distance was significantly increased (+44%; p < .05). In these volunteers, muscle activation caused no significant effect at 90 degrees of abduction. However, in the 10 patients with impingement syndrome, muscle activity led to a significant decrease in the width of the subacromial space compared with that of the healthy contralateral side (-68%; p < .05)., Conclusion: Muscle activity and arm position were found to cause systematic changes in the width of the subacromial space. However, functional deficits of the supraspinous muscle in patients with early-stage impingement syndrome were not apparent during muscle relaxation.

A non-destructive, three-dimensional technique for microstructural phenotypic characterisation of skeletal elements in genetically altered mice is presented. Preliminary data in bovine growth-hormone transgenic animals and control littermates are shown. The technique is based on microcomputed tomography (microCT) and digital postprocessing and allows for a differential quantitative analysis of the cortical and trabecular bone compartments in the axial and peripheral skeleton. The distal femora and the first lumbar vertebral bodies of six animals were CT scanned in the axial plane with an isotropic resolution of 20 microm. The periostal surface and the marrow spaces were segmented fully automatically, and the trabecular and cortical compartments were separated interactively. After 3-D reconstruction, various regions of interest (diaphyseal, metaphyseal and epiphyseal) were selected for the analysis. The femora and vertebrae of the transgenic animals showed obvious differences in size, shape, and trabecular arrangement compared with the control animals. The total bone mass was increased by a factor of two to three, but the trabecular bone was increased much more (up to 12 times) than the cortical bone. The transgenic animals showed an increased ratio of trabecular vs cortical bone (0.90 to 1.27 vs 0.14 to 0.36 in the femoral diaphysis) and an elevated trabecular bone volume fraction (49% to 73% vs 18% to 43% in the femoral metaphysis). The mean 3-D cortical thickness was similar in the normal and transgenic animals (values between 93 microm and 232 microm in the dia- and metaphyses), but the minimal cortical thickness was lower in the transgenic animals (22 to 31 microm vs 54 microm to 110 microm in the diaphysis). The technique presented is suitable for phenotypic characterisation of bone structure in genetically altered mice.

Introduction: The occurrence of the impingement syndrome of the shoulder is dependent on muscle activity and arm position. However, the current radiological workup is based on conventional radiographs, CT or MRI obtained at 0 degree of abduction and at muscular relaxation. The objective of this study was the development of a technique for simultaneous visualization of the humerus, scapula, clavicle and their relationship to the M. supraspinatus--in different arm abduction positions with and without muscle activity--as well as the determination of the minimal acromio-humeral distance., Method: The shoulder joints of 8 volunteers were examined in an open MRI system at 60 degrees, 90 degrees and 120 degrees of abduction, using a T1 weighted 3D gradient echosequence. Forces of 10 N were applied at the distal humerus. After 3D reconstruction, the acromio-humeral distance was computed with Euclidian distance transformation., Results: With increasing abduction, the acromio-humeral distance decreased significantly (p < 0.05), but the distance vector was localised laterally to the M. supraspinatus at 120 degrees. With muscle activity a reduction of the subacromial space of 29% (p < 0.05) occurred at 60 degrees whereas at 120 degrees a 51% (p < 0.05) increase was noted. At 90 degrees, no significant difference was observed., Conclusion: With the technique presented it is possible to determine the subacromial space width in different arm positions independent of the specific section orientation, with and without muscle activity. The method can be used as a basis for biomechanical investigations and for the clinical diagnosis of impingement syndrome.

In this investigation, patients with atraumatic posterior instability of the shoulder were appraised in order to evaluate the effectiveness of glenoid osteotomy in the correction of excessive retroversion and flatness of the glenoid. In a series of 32 patients, 17 with posterior instability had no history of trauma. Posterior glenoid osteotomy was performed to correct excessive retroversion and to deepen the glenoid; 95% were re-examined after 5 years. In 81% the results were rated as good or excellent (Constant-Murley and Rowe scores), only 12.5% having had a recurrence. The glenoid could be deepened and on average the angle could be altered from -9.35 degrees to -4.62 degrees. In comparison, 50 volunteers had average angles of -4.4 degrees, thus differing significantly from the preoperative group. Twenty-five per cent of the patients showed postoperative degenerative changes in the glenohumeral joint. The study shows that excessive retroversion and flatness of the glenoid in persons with atraumatic posterior instability can be successfully treated by a posterior glenoid osteotomy. Nevertheless, the high rate of postoperative degenerative changes must be taken into account.

The objectives of this study were to determine systematic changes of the normal subacromial space width during abduction and rotation, and to analyze the spatial relationship of the supraspinatus muscle with the acromion and clavicle. 12 healthy volunteers were imaged by an open MR scanner in 5 different positions of abduction and in 3 positions of rotation. After three dimensional (3D) reconstruction and 3D Euclidian distance transformation, the minimal spatial distances between the humerus and the acromion and the humerus and clavicle were computed. The minimal acromio-humeral distance decreased significantly from 30 degrees of abduction (mean 7.0 mm +/- 1.6 mm) to 120 degrees (mean 3.9 mm; +/- 1.8 mm; p < 0.0001). At 30 degrees, the minimal distance penetrated the supraspinatus, whereas at 120 degrees it was always located lateral to the supraspinatus tendon. At 90 degrees with internal rotation (7.6 mm, +/- 2.3 mm) the minimal acromio-humeral distance was larger than in neutral rotation (5.4 mm, +/- 2.3 mm) or external rotation (4.4 mm, +/- 2.2 mm; p < 0.05), but it penetrated the supraspinatus tendon at its most vulnerable part, reaching the acromion at its anterior inferior border. We conclude that the subacromial space width changes during abduction and rotation and that the supraspinatus is in closest contact to the anterior inferior border of the acromion in 90 degrees of abduction with 45 degrees internal rotation. These values obtained in volunteers can be used as a basis for further investigations in patients with the impingement syndrome.

An MR imaging-based technique for three-dimensional determination of subacromial space width in relation to the rotator cuff in arm abduction is presented. Five volunteers were examined in an open MRI in seven arm positions, and coronal images were obtained with a gradient-echo sequence. 3D reconstruction of the bones and the supraspinatus was performed, and the minimal spatial distances between acromion, clavicle, and humerus were calculated. The closest contact between the supraspinatus and the anterior inferior part of the acromion occurred at 90 degrees abduction in internal rotation. The technique presented allows investigation of the morphological basis of the impingement syndrome.

The aim of the study was to non-invasively analyse the cartilage volume and thickness in the human elbow joint with magnetic resonance imaging. 12 fresh frozen specimens (ages 20 to 69 yrs.) were investigated using a 1.5 T magnet, and a water-excitation FLASH-3D sequence at a resolution of 1 x 0.25 x 0.25 mm3. After linear interpolation to 0.125 x 0.125 mm2 in the image plane, the cartilages were segmented interactively with a Snake algorithm. Following three-dimensional reconstruction, the cartilage volumes were determined, and the mean and maximal cartilage thickness computed by Euclidean distance transformation. The total cartilage volume of the human elbow joint amounted to between 3.90 and 7.17 ml (mean 5.5 ml +/- 20%). The humerus occupied 49 to 60%, the radius 15 to 27% and the ulna 20 to 29% of the total volume. The mean cartilage thickness ranged from an average of 0.9 (proximal part of the ulna) to 1.4 mm (capitulum humeri), and the maximal thickness from 2.3 mm (proximal part of the ulna) to 2.9 mm (distal part of the ulna). The ulnar cartilage showed a more inhomogeneous distribution than that of the humerus and radius. The interindividual variability of the cartilage thickness was less than that of the volume. There was no significant relationship of the volume with age (r = 0.11) or body weight (r = 0.51). However, based on the joint size (r = 0.71-medio-lateral extension of the articular surfaces) about 50% of the variability of the total cartilage volume could be predicted. The technique presented is suitable for designing computer models to investigate the load transmission and functional adaptation of diarthrodial joints, and for diagnosing and monitoring joint disease.

Unlabelled: Purpose of this retrospective study was to evaluate the midterm results of glenoid osteotomy in the treatment of posterior instability and furthermore to evaluate the relevance of etiopathogenesis on the outcome., Method: Between Jan. 83 and May 94 32 patients underwent surgery due to posterior instability. Retrospectively these patients were classified based on their etiopathogenesis. 28 patients could be reexamined clinically and radiologically after and average of 4.85 years, of which 21 were treated with a glenoid osteotomy. For evaluation the Constant-Murley and the Rowe-Score were used., Results: The Constant-Score showed 82,2% and the Rowe-Score 71,5% good or excellent results. Evaluation of glenoid osteotomy demonstrated for the patients with atraumatic genesis an excellent result in 76.9% with a recurrence rate of only 15.4%. On the other hand patients with traumatic instability showed a recurrence rate of 50%. The radiologic assessment demonstrated degenerative changes in nearly 30% of cases treated with glenoid osteotomy., Conclusion: This study shows that glenoid osteotomy can provide good result in the surgical treatment of posterior atraumatic instability. For treatment of traumatic instability, however, glenoid osteotomy is not the procedure due to high recurrence and arthrosis rates., Relevance: Posterior glenoid osteotomy should be reserved for patients with atraumatic posterior instability combined with an increased retroversion angle of the glenoid especially because of the high rate of arthrosis.