Heiko Graichen

Magnetic resonance based motion analysis of the shoulder during elevation

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°-150°) 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° and 2.4:1 at 120° abduction. At 30°, the axis of the supraspinatus was nearly horizontal, and during abduction a continuous elevation (+123° at 150° 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.

Relevance of arm position and muscle activity on three-dimensional glenohumeral translation in patients with traumatic and atraumatic shoulder instability.

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° 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 Clinical Relevance: These data are relevant for optimizing diagnostics and therapeutic strategies.

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.

Quantitative cartilage imaging of the human hind foot: Precision and inter‐subject variability

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 ± 0.125 ± 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 ⩽ 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.

Influence of adducting and abducting muscle forces on the subacromial space width.

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.

Functional malcentering of the humeral head and asymmetric long-term stress on the glenoid : potential reasons for glenoid loosening in total shoulder arthroplasty

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.

Simultaneous 3D Assessment of Glenohumeral Shape, Humeral Head Centering, and Scapular Positioning in Atraumatic Shoulder Instability: A Magnetic Resonance–Based In Vivo Analysis

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° ± 4.8° vs healthy 3.9° ± 1.3°; P < .05) with a range of 2.6° to 16.6°. 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.

Direct, Cementless, Metaphyseal Fixation in Knee Revision Arthroplasty With Sleeves—Short-Term Results

Different options for implant fixation in revision TKA exist. Small series have been published on direct cementless fixation with sleeves. The objective of this study was to analyze the short- and mid-term results of sleeve-fixation in a large revision TKA series. In this prospective study 121 patients with 193 sleeves (119 tibial and 74 femoral) were included. Mean follow-up was 3.6 years (2-6.1 years). Analysis included clinical and radiographic assessment. ROM, KSS and Functional Score improved significantly. Fourteen patients (11.4%) underwent operative re-revision during the follow-up period. Direct cementless fixation in the metaphysis by sleeves is a promising option for implant fixation in revision TKA, both on the tibial and femoral side.

Tibiofemoral and patellofemoral joint 3D-kinematics in patients with posterior cruciate ligament deficiency compared to healthy volunteers

BackgroundThe posterior cruciate ligament (PCL) plays an important role in maintaining physiological kinematics and function of the knee joint. To date mainly in-vitro models or combined magnetic resonance and fluoroscopic systems have been used for quantifying the importance of the PCL. We hypothesized, that both tibiofemoral and patellofemoral kinematic patterns are changed in PCL-deficient knees, which is increased by isometric muscle flexion. Therefore the aim of this study was to simultaneously investigate tibiofemoral and patellofemoral 3D kinematics in patients suffering from PCL deficiency during different knee flexion angles and under neuromuscular activation.MethodsWe enrolled 12 patients with isolated PCL-insufficiency as well as 20 healthy volunteers. Sagittal MR-images of the knee joint were acquired in different positions of the knee joint (0°, 30°, 90° flexion, with and without flexing isometric muscle activity) on a 0.2 Tesla open MR-scanner. After segmentation of the patella, femur and tibia local coordinate systems were established to define the spatial position of these structures in relation to each other.ResultsAt full extension and 30° flexion no significant difference was observed in PCL-deficient knee joints neither for tibiofemoral nor for patellofemoral kinematics. At 90° flexion the femur of PCL-deficient patients was positioned significantly more anteriorly in relation to the tibia and both, the patellar tilt and the patellar shift to the lateral side, significantly increased compared to healthy knee joints. While no significant effect of isometric flexing muscle activity was observed in healthy individuals, in PCL-deficient knee joints an increased paradoxical anterior translation of the femur was observed at 90° flexion compared to the status of muscle relaxation.ConclusionsSignificant changes in tibiofemoral and patellofemoral joint kinematics occur in patients with isolated PCL-insufficiency above 30 degrees of flexion compared to healthy volunteers. Since this could be one reasonable mechanism in the development of osteoarthritis (OA) our results might help to understand the long-term development of tibiofemoral and/or patellofemoral OA in PCL-insufficient knee joints.

Fixierte und funktionelle Dezentrierung des Humeruskopfes bei Patienten mit Omarthrose

ZusammenfassungFragestellung: Existiert bei bestimmten Formen der Omarthrose neben einer fixierten Dezentrierung auch eine stellungsabhängige, funktionelle Dezentrierung des Glenohumeralgelenks? Methodik: In einem offenen MRT wurden die Schultern von 10 gesunden Probanden und 16 Patienten mit Omarthrose in verschiedenen Abduktions- und Rotationsstellungen untersucht. Nach Segmentation und 3D-Rekonstruktion von Humerus und Skapula wurde der Humeruskopfmittelpunkt errechnet und seine Stellung relativ zum Glenoid bestimmt. Ergebnisse: In 4 von 16 Fällen zeigte sich bei 30° Abduktion eine fixierte dorsale (12,9±2,8 mm) Position sowie in 8 Fällen (alle Patienten mit Cuffarthropathie) eine fixierte superiore (6,6±2,6 mm) Position des Humeruskopfes. Bei 90° Abduktion wiesen die Patienten eine signifikante (p<0,001) kombinierte Fehlstellung nach superior und posterior im Vergleich zur gesunden Kontrollgruppe auf (funktionelle Dezentrierung). Schlussfolgerungen: Bei einem Großteil der Patienten mit Omarthrose kommt es zu einer signifikanten funktionellen Dezentrierung unter Abduktion bzw. Außenrotation, auch wenn diese in der Ausgangstellung keine fixierte Dezentrierung des Humeruskopfes aufweisen.AbstractAim: 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° 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° 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° of abduction.