Translation of the humeral head on the glenoid with passive glenohumeral motion.

TLDR

The study examined how passive glenohumeral motions produce humeral head translation by measuring joint position and applied forces in seven fresh cadaveric glenohumeral joints with a six‑degree‑of‑freedom sensor and six‑axis force‑torque transducer. Passive flexion caused reproducible anterior translation that could not be stopped by 30–40 N opposing force, while extension produced posterior translation; cross‑body movement also translated the head, and tightening the posterior capsule increased anterior translation earlier in the arc and produced significant superior translation during flexion.

Abstract

We have demonstrated that certain passive motions of the glenohumeral joint are reproducibly accompanied by translation of the head of the humerus on the glenoid. We investigated the relationship of these translations to the position of the glenohumeral joint and to applied torques and forces in seven isolated glenohumeral joints from fresh cadavera, using a six-degrees-of-freedom position sensor and a six-axis force and torque transducer. Reproducible and significant translation occurred in an anterior direction with glenohumeral flexion and in a posterior direction with extension. We also observed translation with cross-body movement. The translation occurring with flexion was obligate in that it could not be prevented by the application of an oppositely directed force of thirty to forty newtons. Operative tightening of the posterior portion of the capsule increased the anterior translation on flexion and cross-body movement and caused it to occur earlier in the arc of motion compared with the intact glenohumeral joint. Operative tightening of the posterior part of the capsule also resulted in significant superior translation with flexion of the glenohumeral joint.