CONTRIBUTION OF CAPSULOLIGAMENTOUS STRUCTURES TO PASSIVE STATIC INFERIOR GLENOHUMERAL STABILITY

Objective. This study attempted to determine the relative stabilizing effect of the capsuloligamentous structures to inferior humeral displa cement. Design. This was an in vitro study, utilizing cadaveric should er specimens. Background. Inferior glenohumeral instability has come u nder increasingly close scrutiny in the literature in recent years, ye t a description of the precise pathoanatomy is still lacking. Methods. Thirteen shoulder specimens were cleaned of soft tissue superficial t o the vented joint capsule. The position of the humeral head relative to the glenoid was determined. The humeri were subjected to an inferio r load. Static position recordings were obtained for each specimen: (1 ) with the humerus adducted and abducted, (2) before and after section ing the superior and inferior capsuloligamentous structures. These rec ordings were analyzed. Results. In adduction, the humeral head migrate d inferiorly as the capsuloligamentous structures were sectioned, but no capsuloligamentous structure was seen to be most important. In abdu ction, when the inferior capsuloligamentous structures were sectioned first, the humeral head migrated inferiorly (P<0.001). When the superi or structures were sectioned first, the humeral head position did not significantly change. Conclusions. In this experimental model, the inf erior capsuloligamentous structures are the primary inferior stabilize rs of the abducted shoulder. The primary stabilizers of the adducted s houlder remain unclear. Relevance Since venting the capsule renders th e glenohumeral joint unstable, the clinical relevance of this study (o r any shoulder study which vents the capsule) is legitimately question ed. However, this study therefore casts doubt on the legitimacy of sev eral previous studies of glenohumeral stability. (C) 1998 Elsevier Sci ence Ltd. All rights reserved.