Kinematics of the glenohumeral joint: Influences of muscle forces, ligamentous constraints, and articular geometry

Abstract

Despite recent interest in the study of shoulder kinematics, there is considerable controversy in the literature regarding translations at the glenohumeral joint. The purpose of this study was to investigate the key factors that control shoulder motions, thus leading to a better understanding of joint function. Translation and rotation patterns were studied in fresh-frozen glenohumeral joints of human cadavers with a six-degrees-of-freedom magnetic tracking device. Shoulders were positioned from maximal internal to external rotation at several arm positions (various elevations and planes of motion). In order to determine the effect of muscle forces, joints were positioned both actively and passively. Additionally, articular surface geometry and ligament origin-insertion wrap lengths were measured to assess their influences on joint kinematics. When joints were positioned passively, large translations were observed at the extremes of motion. With active positioning, muscle forces tended to limit humeral head translations, principally by restricting rotational ranges of motion. However, when data from the passive model were reanalyzed by considering only the rotational ranges of motion seen actively, no significant differences in translation were found between the two models. Joint conformity was found to have a significant influence on translations during active positioning but not during passive positioning. Glenohumeral ligament wrap lengths, however, correlated with translations when joints were positioned passively but not when positioned actively. Findings from this study emphasize the importance of muscle forces in keeping the humeral head centered in the glenoid. Although large translations are possible, they can be achieved only with increases in rotational ranges of motion associated with the removal of muscle force. Additionally, joint conformity appears to play a role in controlling translations during active motions, whereas capsular constraints become more important during passive motions.

The Effect of Anterior Versus Posterior Glide Joint Mobilization on External Rotation Range of Motion in Patients With Shoulder Adhesive Capsulitis

“…Our results do, however, support the concept that the capsule plays an important role 9,33 in dictating the humeral head translation, possibly in the opposite direction to the expected effect of joint geometry if restricted. 19,43 Thus, the normal shoulder joint requires adequate coordination of all passive and active stabilizers 1,58 to maintain shoulder stability 9,59,31,66 and pathological changes in any of these can lead to unphysiological translations of the humeral head relative to the glenoid fossa. 23 Karduna et al 31 found that joint conformity had an influence on translations during active positioning but not during passive positioning.…”

“…19,43 Thus, the normal shoulder joint requires adequate coordination of all passive and active stabilizers 1,58 to maintain shoulder stability 9,59,31,66 and pathological changes in any of these can lead to unphysiological translations of the humeral head relative to the glenoid fossa. 23 Karduna et al 31 found that joint conformity had an influence on translations during active positioning but not during passive positioning. Joint mobilization is a passive movement applied to the joint surfaces, 42 so shoulder mechanics under passive conditions need to be considered.…”

A finite element model of the shoulder: application to the comparison of normal and osteoarthritic joints

“…The insertions of the three muscles on the humerus and the scapula were accurately located. Using a Polhemus 3Space Fastrak Stylus (Polhemus 3Space Fastrak, Colchester, Vermont, USA) [15], the exact insertion and origin of the three muscles were digitized. Four points at the corner of each muscle were recorded to represent the insertions (eight points per muscle).…”

In vivo three-dimensional motion analysis of the shoulder joint during internal and external rotation

“…However, each of these methods has limitations and disadvantages that have not yet been resolved. Cadaveric experiments possess several limitations in terms of methodology [13,14]. In addition to skin and soft tissues, outer muscles are excised, as are the clavicle and ribs, but these muscles may exert major influences on the kinematics of the shoulder joint.…”