Scapular inclination and glenohumeral joint stability: a cadaveric study.
ABSTRACT In shoulders with multidirectional instability, translation of the humeral head on the glenoid is increased in the midrange because of the following three reasons: the increased retroversion, a hypoplastic posteroinferior rim, and decreased scapular abduction during arm elevation. This study aimed to clarify the relationship between glenoid inclination and glenohumeral joint stability.
Nine fresh-frozen cadaveric shoulders were tested. With a 50-N compressive load, the translation force was measured in the 3-o'clock, 6-o'clock, 9-o'clock, and 12-o'clock directions by using a tilt of 0 degrees , 5 degrees , 10 degrees , 15 degrees , and 20 degrees . When the glenoid was tilted in one direction, the translation force was measured in the direction of inclination and in the opposite direction. The stability ratio was then calculated.
The stability ratio in the 3-o'clock direction significantly decreased with a tilt of more than 5 degrees in the 3-o'clock direction. The stability ratio in the 9-o'clock direction significantly decreased with a tilt of more than 15 degrees in the 9-o'clock direction and significantly increased with a tilt of more than 5 degrees in the 3-o'clock direction. The stability ratio in the 6-o'clock direction significantly increased with a tilt of more than 10 degrees in the 6-o'clock direction.
The posterior and inferior stability increased with an anterior tilt of more than 5 degrees and with a superior tilt of 10 degrees , respectively. The anterior and posterior stability decreased with an anterior tilt of 5 degrees and with a posterior tilt of 15 degrees , respectively.
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ABSTRACT: To evaluate diagnostic signs and measurements in the assessment of capsular redundancy in atraumatic multidirectional instability (MDI) of the shoulder on MR arthrography (MR-A) including abduction/external rotation (ABER) images. Twenty-one MR-A including ABER position of 20 patients with clinically diagnosed MDI and 17 patients without instability were assessed by three radiologists. On ABER images, presence of a layer of contrast between the humeral head (HH) and the anteroinferior glenohumeral ligament (AIGHL) (crescent sign) and a triangular-shaped space between the HH, AIGHL and glenoid (triangle sign) were evaluated; centring of the HH was measured. Anterosuperior herniation of the rotator interval (RI) capsule and glenoid version were determined on standard imaging planes. The crescent sign had a sensitivity of 57 %/62 %/48 % (observers 1/2/3) and specificity of 100 %/100 %/94 % in the diagnosis of MDI. The triangle sign had a sensitivity of 48 %/57 %/48 % and specificity of 94 %/94 %/100 %. The combination of both signs had a sensitivity of 86 %/90 %/81 % and specificity of 94 %/94 %/94 %. A positive triangle sign was significantly associated with decentring of the HH. Measurements of RI herniation, RI width and glenoid were not significantly different between both groups. Combined assessment of redundancy signs on ABER position MR-A allows for accurate differentiation between patients with atraumatic MDI and patients with clinically stable shoulders; measurements on standard imaging planes appear inappropriate. • MR arthrography has the possibility to accurately identify patients with atraumatic MDI. • Imaging of the shoulder in abduction and external rotation provides additive information. • Capsular enlargement of the shoulder can be diagnosed on MR arthrography.European Radiology 03/2014; · 4.34 Impact Factor
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ABSTRACT: The most commonly recommended treatment for multidirectional instability (MDI) of the glenohumeral joint is exercise-based management. The primary objective of this review was to evaluate the effectiveness of exercise-based management in patients with MDI. The secondary aim was to observe the types of exercise protocols and outcomes used, as well as any adverse results associated with exercise. The Cochrane Database of Systematic Reviews, Medline, Embase, CINAHL (Cumulative Index to Nursing and Allied Health Literature), PEDro, Current Contents, Allied and Complementary Medicine (AMED), Australasian Medical Index (AMI), Ausport, and Clinical Trials Registers were searched for published and unpublished studies from the inception date to June 2012 using the keywords multidirectional instability, glenohumeral, and exercise. Selection criteria included all study designs (except case reports and case series) and participants with clinically diagnosed MDI using exercise-based management. Inclusion criteria were not limited by outcomes. The authors' own risk-of-bias tool was used for quality assessment of studies. The GRADE approach (Grading of Recommendations, Assessment, Development and Evaluation) was used to synthesize the evidence. The risk of bias was high in all 7 included studies. For before-and-after comparisons of exercise-based management, GRADE assessment showed very low-quality evidence for improvements in shoulder kinematics, the Rowe score, overall status rating, and peak muscle strength. The effect of exercise-based management on MDI was variable across the included studies because of study heterogeneity and a high level of bias. There is a need for high-quality intervention studies to be undertaken to validate the effect of exercise for MDI.Journal of shoulder and elbow surgery / American Shoulder and Elbow Surgeons ... [et al.] 01/2014; 23(1):128-142. · 1.93 Impact Factor
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ABSTRACT: The humeral head and glenoid cavity are not perfectly spherical, nor do they have matching radii of curvature. We hypothesized that glenohumeral stability is dependent on axial humeral rotation. Seven cadaveric shoulders were investigated. For each test, the humeral head was translated relative to the glenoid in 2 directions (starting from neutral), anterior and anteroinferior. Contact forces and lateral humeral displacement were recorded. Joint stability was quantified using the stability ratio and energy to dislocation. The humerus was set in 60° of abduction for all tests. Testing was performed in neutral rotation and 60° of external rotation. The force displacement curves differed between rotations. In both displacement directions, the peak translational force occurred with less displacement in neutral rotation than in external rotation. The stability ratio and energy to dislocation in the anteroinferior direction were greater than in the anterior direction for both rotation positions. While there were no significant differences in the stability ratio or energy to dislocation between rotation conditions at complete dislocation, the energy required to move the humeral head 10% of the glenoid width was significantly greater with the arm in neutral rotation. The energy to dislocation, a new parameter of dislocation risk, and the stability ratio, indicate that the glenohumeral joint is more stable in the anteroinferior direction than the anterior direction. During initial displacement, axial rotation of the humeral head contributes to glenohumeral geometrical stability. However, humeral head rotation does not have a significant effect when looking at complete dislocation.Clinical biomechanics (Bristol, Avon) 09/2013; · 1.76 Impact Factor