Passive glenohumeral joint stabilization: A biomechanical study

Passive glenohumeral joint stability was tested in 10 cadaveric shoulder specimens, before and after venting of the intraarticulor space. Force-displacement diagrams were measured with anterior, posterior, and inferior excursion, in neutral position, in 90° of abduction, and in a combination of 90° of abduction and 90° of external rotation. Displacement at 50 Ns before venting averaged 11.17 mm posteriorly (SD = 6.48 mm), 7.15 mm anteriorly (SD = 5.51 mm), and 3.41 mm inferiorly (SD = 3.37 mm). Venting of the joint increased displacement by 47% anteriorly, 49% posteriorly, and 61 % inferiorly. In addition, mathematic model calculation was used to estimate the destabilizing forces at the glenohumeral joint during physiologic arm motion. This force approximated 970 N, cldarly more than passive stabilizers alone seem to be able to provide. It is therefore assumed that, in addition to passive joint stability, active stabilization plays a major role at the glenohumeral joint.