Description of the painful arc and the lesions of the muscles supraspinatus and infraspinatus in individuals with the clinical picture of subacromial impingement syndrome

Abstract

The subacromial impingement syndrome (SIS) is the main diagnosis of shoulder pain. Painful arc presence is one of the most common signs of SIS. However, the painful arc does not appear to represent SIS as initially proposed, since several individuals report pain at amplitudes that offer a reduced risk of compression of the supraspinatus and infraspinatus tendons.Objectives: To describe the painful arc in patients with the clinical presentation of subacromial impingement syndrome and verify if there is an association between the degree of painful arc amplitude and injury in the articular or bursal side of the supraspinatus and infraspinatus tendons.Methods: Individuals with unilateral shoulder pain will be recruited to participate in a cross-sectional study. The clinical presentation of the subacromial impingement syndrome will be verified through clinical history and a series of provocative tests: Neer, Jobe, Hawkins-Kennedy, and external rotation resistance test. The painful arc will be measured with a digital inclinometer and all participants will undergo magnetic resonance imaging. The association between the painful arc and the presence of image alteration will be verified with the point-biserial correlation test. Logistic regression will be used to determine the risk of image alterations occurrence considering characteristics of the painful arc such as the initial or final amplitude. A p< 0.05 will be considered as statistically significant.