This in vivo study measured glenohumeral translation during five manual laxity tests using a six-degree-of-freedom tracking system pinned to the scapula and humerus. It asked whether the amount of translation could distinguish normal shoulders from traumatic (TUBS) and atraumatic (AMBRII) instability.
The clinical rule from this paper: do not diagnose or plan surgery for shoulder instability based on how far the humeral head translates on exam. Laxity and instability are different things. Laxity is passive translation, which normal shoulders have in abundance. Instability is symptomatic, unwanted translation. A healthy volunteer here out-translated surgical patients by more than 2 cm.
What actually drives the diagnosis is the history and the reproduction of symptoms. Does the load-and-shift or apprehension maneuver reproduce the patient's problem? Does the shoulder feel like it will give way? That qualitative response, plus the injury mechanism, sorts TUBS from AMBRII.
This distinction is not academic. A standard anterior Bankart-type repair fails in the AMBRII patient and can force subluxation in the opposite direction, risking degenerative arthritis. AMBRII needs an inferior capsular shift and rotator interval closure instead.
This in vivo study measured glenohumeral translation during five manual laxity tests using a six-degree-of-freedom tracking system pinned to the scapula and humerus. It asked whether the amount of translation could distinguish normal shoulders from traumatic (TUBS) and atraumatic (AMBRII) instability.
The clinical rule from this paper: do not diagnose or plan surgery for shoulder instability based on how far the humeral head translates on exam. Laxity and instability are different things. Laxity is passive translation, which normal shoulders have in abundance. Instability is symptomatic, unwanted translation. A healthy volunteer here out-translated surgical patients by more than 2 cm.
What actually drives the diagnosis is the history and the reproduction of symptoms. Does the load-and-shift or apprehension maneuver reproduce the patient's problem? Does the shoulder feel like it will give way? That qualitative response, plus the injury mechanism, sorts TUBS from AMBRII.
This distinction is not academic. A standard anterior Bankart-type repair fails in the AMBRII patient and can force subluxation in the opposite direction, risking degenerative arthritis. AMBRII needs an inferior capsular shift and rotator interval closure instead.