A DYNAMIC ANALYSIS OF GLENOHUMERAL MOTION AFTER SIMULATED CAPSULOLABRAL INJURY - A CADAVER MODEL

We used a dynamic shoulder-testing apparatus and nine fresh-frozen, en tire upper extremities from cadavera to evaluate the effects of varyin g degrees of capsulolabral injury on the kinematics of the glenohumera l joint during abduction in the scapular plane and external rotation. Joint kinematics were recorded with use of a six-degrees-of-freedom ma gnetic tracking device before and after the creation of each capsulola bral lesion in a progressive manner. Dislocation did not occur after s imulation of a large Bankart lesion or even after sectioning of the an terior aspect of the joint capsule, However, division of the entire jo int capsule (that is, both the anterior aspect and the posterior aspec t) resulted in a significant increase (p < 0.05) in posterior translat ion during abduction in the scapular plane, and two of the nine should ers dislocated posteriorly, External rotation of the abducted extremit y produced no increase in anterior or posterior translation. CLINICAL RELEVANCE: We concluded that dynamic stability can be maintained by th e rotator-cuff muscles even when the anterior aspect of the capsule is divided and the anterior portion of the labrum is separated. Thus, an terior glenohumeral instability is a complex phenomenon that may inclu de a combination of muscle imbalance and capsulolabral injury. Our fin dings suggest that the importance of the active stabilizers of the gle nohumeral joint should be considered when capsulolabral injuries and d efects are reconstructed and when rehabilitation regimens are formulat ed.