Superior Glenohumeral Ligament Research Articles

Static capsuloligamentous restraints to superior-inferior translation of the glenohumeral joint.

The purpose of this study was to determine the contributions of specific capsuloligamentous structures to restraining superior-inferior translation of the glenohumeral joint. Eleven cadaveric shoulders were tested using a four degrees-of-freedom test apparatus. The humerus was free to translate in three planes and free to flex and extend when a superior and inferior force of 50 N was applied. Testing was performed in three positions of abduction (0 degree, 45 degrees, and 90 degrees) and three positions of rotation (neutral, maximum internal, and external). Shoulders were tested intact, vented, and after division of specific capsuloligamentous structures. The primary restraint to inferior translation of the adducted shoulder was the superior glenohumeral ligament. The coracohumeral ligament appeared to have no significant suspensory role. With progressive abduction, the anterior and posterior portions of the glenohumeral ligament become the main static stabilizers resisting inferior translation: the anterior portion was the primary capsular restraint at 45 degrees of abduction, while the posterior portion was the primary restraint at 90 degrees of abduction, neutral rotation. Our results indicate that clinical assessment of glenohumeral translation in the superior-inferior plane should be performed in multiple positions of abduction and rotation.

Anterior shoulder stability: Contributions of rotator cuff forces and the capsular ligaments in a cadaver model

The purpose of this study was to quantify in a biomechanical model the contributions to shoulder joint stability that are made by tensions in the four tendons of the rotator cuff and by static resistance of defined portions of the capsular ligaments. A materials testing machine was used to directly determine anterior joint laxity by measurement of the force required to produce a standard anterior subluxation. Shoulders were tested in external or neutral humeral rotation. Data were analyzed by multiway analysis of variance with regression analysis. This model simulated tensions in the rotator cuff musculature by applying static loads at the tendon insertion sites acting along the anatomic lines of action. A load in any of the cuff tendons resulted in a measurable and statistically significant contribution to anterior joint stability. The contributions between different tendons were not significantly different and did not depend on the humeral rotation (neutral or external). In neutral humeral rotation the superior and middle glenohumeral ligaments together function equally with the inferior glenohumeral ligament as primary stabilizers against anterior humeral translation. The posterior capsule is a secondary stabilizer. The external rotation of the abducted humerus increases anterior stability by more than doubling the stability contribution from the inferior glenohumeral ligament. The stability contribution from the posterior capsule is larger in external rotation than in neutral rotation but is still of secondary magnitude. In external rotation the stability contribution of the anterior capsule, including the superior glenohumeral ligament and the middle glenohumeral ligament, becomes insignificant. The model presented here simulates the combined effect of two major sources of shoulder stability. This versatile model permits the direct measurement of the contributions to anterior shoulder stability that are made by tensions in the rotator cuff tendons and by static resistance of defined capsular zones. The use of multiple regression analysis-a standard statistical technique but one relatively new to the orthopaedic literature-permits quantitative determination of the contribution of each independent variable to the dependent variable, shoulder stability.

The contribution of the glenohumeral ligaments to anterior stability of the shoulder joint

The purpose of this study was to investigate the ligamentous stabilizing mechanisms preventing anterior instability in the glenohumeral joint. Six freshly thawed, unembalmed cadaveric shoulders were dissected, preserving the joint capsule and glenohumeral ligaments, the coracohumeral ligament, and the subscapularis tendon. Hall-effect strain transducers were placed on the superior, middle, and inferior glenohumeral ligaments. The humerus and scapula were fixed in a specifically designed mounting apparatus that allowed the glenohumeral joint to be placed in 0 degree, 45 degrees, or 90 degrees of abduction. The mounting apparatus was placed in a model TTC Instron Universal Testing Instrument, which applied an external rotation torque to the humerus. Strain produced in the three glenohumeral ligaments was recorded on a three-channel X-Y chart recorder. At 0 degree of abduction, the superior and middle glenohumeral ligaments developed the most strain. At 45 degrees of abduction, the inferior and middle glenohumeral ligaments developed the most strain, with considerable strain also being developed in the superior glenohumeral ligament. At 90 degrees of abduction, the inferior glenohumeral ligament developed the most strain, with strain also seen in the middle glenohumeral ligament.

Isolated Avulsion Fracture of the Lesser Tuberosity of the Humerus

An extremely rare isolated avulsion fracture of the lesser tuberosity, not complicated with other proximal humeral fractures or posterior shoulder dislocations, occurred in a 12-year-old girl. The avulsion fracture of the upper part of the lesser tuberosity appears to have been caused by hyperextension and hyperexternal rotation of the shoulder. In this position, the coracohumeral ligament, superior glenohumeral ligament, and subscapularis tendon could have pulled out the upper part of the lesser tuberosity. She gained full recovery of left shoulder function after three months of conservative treatment, although follow-up roentgenograms show nonunion of the fracture. An isolated avulsion fracture of the lesser tuberosity is extremely rare. Only 12 cases, none in children, have been found in the literature since Hartigan's report in 1895.