Search

Background: Success rates in the treatment of atraumatic shoulder instability differ, and in vivo identification of the individual insufficient stabilizers is difficult., Hypothesis: Atraumatic shoulder instability is an inhomogeneous entity with varying alterations of the active and passive stabilizers. This might be a reason for inferior treatment results., Study Design: Case control study; Level of evidence, 3., Methods: Shoulders of 28 healthy volunteers and both shoulders of 14 patients with atraumatic instability and multidirectional laxity were examined in different arm positions using open magnetic resonance imaging. Three-dimensional postprocessing techniques were applied to determine 3D glenoid size and retroversion, radius of the humeral head, and curvature of the glenoid. The results of static stabilizers were compared with those of glenohumeral and scapular positioning in the same patients for identification of the individual insufficient stabilizers., Results: The atraumatic unstable shoulders showed an increased mean retroversion on both sides, the difference being significant on the affected side (9.4 degrees +/- 4.8 degrees vs healthy 3.9 degrees +/- 1.3 degrees ; P < .05) with a range of 2.6 degrees to 16.6 degrees . The curvature analysis demonstrated a pronounced flatness of the glenoid with a significantly increased mean radius (103.8 mm vs healthy 41.7 mm). The extent of these changes varied widely among patients. Comparison of the static stabilizers with glenohumeral and scapular positioning revealed that isolated changes of the active stabilizers exist in some patients, whereas no isolated changes of passive stabilizers were found., Conclusion: All active and passive stabilizers need to be analyzed in patients with atraumatic instability because the magnitude of alteration varied widely among individuals. Different combinations of alterations of the stabilizers were found. The presented technique allows for in vivo identification of the specific alterations. This is necessary for a better understanding of individual pathomechanics and for initiating a specific causal treatment.

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.

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.

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.

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.

Purpose: Strengthening of the shoulder depressors is an important component in the treatment of impingement syndrome. However, the quantitative effect of various muscle forces on the width of the subacromial space has never been demonstrated in vivo. Therefore, the purpose of this study was to analyze the influence of adducting and abducting muscle forces on the subacromial space width in healthy volunteers in various arm positions., Methods: The shoulders of 12 healthy volunteers were imaged with an open MR system at 30 degrees, 60 degrees, 90 degrees, 120 degrees, and 150 degrees of arm elevation under both isometric adducting and abducting muscle activity (15 N). After segmentation and three-dimensional reconstruction of anatomically relevant structures, the minimal spatial acromiohumeral and claviculohumeral distances were quantified., Results: Adducting muscle forces led to a significant increase of the acromiohumeral distance in all arm positions (P < 0.01), varying from 32% (30 degrees ) to 138% (90 degrees ) relative to abducting muscle forces. The claviculohumeral distance showed an increase of 9% (30 degrees ) to 24% (90 degrees ), this increase being also statistically significant at all positions (P < 0.05). During elevation of the arm (30-120 degrees ), the absolute subacromial space width was reduced significantly (P = 0.001) by 30% under isometric contraction of the adductors compared with 53% (P = 0.001) under activation of the abductors., Conclusion: This in vivo study shows for the first time that adducting muscle forces lead to a significant increase of the subacromial space width compared with abducting muscle activity. In the future, this technique and data can be used to objectively quantify the effect of physical therapy protocols focused on increasing the depressor effect of adducting muscles in the postoperative and conservative treatment of impingement syndrome of the shoulder.

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.

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.

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.

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.

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.

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.

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.

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.