Multidirectional Instability of the Shoulder in the Female Athlete

Multidirectional instability (MDI) of the shoulder is a complex entity characterized by symptomatic global laxity of the glenohumeral joint. Because symptoms vary widely, making the diagnosis of MDI is not always straightforward. Additionally, relatively few series of patients with this disorder have been reported. Thus, precise definition, causes, and treatment remain elusive. This article reviews the current literature regarding anatomy, biomechanics, clinical diagnosis, and treatment of MDI that are relevant to the care of the female athlete. MDI was recognized as an entity different from unidirectional instability in 1980 by Neer. Since then only a few series report on the operative outcome of shoulder stabilization (most commonly inferior capsular shift) in the population with MDI. In these studies, female patients treated with an inferior capsular shift for MDI accounted for less than half of the total patients.1, 3, 6, 8, 20, 24, 25, 34 Most of these patients were athletes. Generalized ligamentous laxity was present in 25% to 100% of the patients in each study. Although laxity was not broken down by gender, it is generally believed that women tend to have greater ligamentous laxity than men. As athletes, women may be more prone to overuse syndromes and microtrauma, with an increased risk of converting global laxity to symptomatic instability. It is important to remember that global laxity of the shoulder does not imply MDI. Laxity implies the ability to sublux or dislocate; instability refers to symptomatic laxity. MDI is distinguished from other types of instability by two features. First, symptoms are experienced in the midrange positions of glenohumeral motion, such as during normal activities of daily living. Second, clinical examination reveals the ability to dislocate or sublux the glenohumeral joint anteriorly, posteriorly, and inferiorly with concurrent reproduction of symptoms in at least two of these directions, one of which must be inferior.29