Background
Despite considerable medical advances, arthroscopy remains the only definitive means of Superior Labrum Anterior-Posterior (SLAP) lesion diagnosis. Natural shoulder anatomic variants limit the reliability of radiographic findings and clinical evaluations are not consistent. Accurate clinical diagnostic techniques would be advantageous due to the invasiveness, patient risk, and financial cost associated with arthroscopy.
Purpose
The purpose was to examine the behavior of the joint stabilizing muscles in provocative tests for SLAP lesions. Electromyography was used to characterize the muscle behavior, with particular interest in the long head biceps brachii (LHBB), as activation of the long head and subsequent tension in the biceps tendon should, based on related research, elicit labral symptoms in SLAP lesion patients.
Study Design
Controlled Laboratory Study
Methods
Volunteers (N=21) without a history of shoulder pathology were recruited. The tests analyzed were Active Compression, Speed's, Pronated Load, Biceps I, Biceps II, Resisted Supination External Rotation, and Yergason's. Tests were performed with a dynamometer to improve reproducibility. Muscle activity was recorded for the long and short heads of the biceps brachii, anterior deltoid, pectoralis major, latissimus dorsi, infraspinatus, and supraspinatus. Muscle behavior for each test was characterized by peak activation and proportion of muscle activity.
Results
Speed's, Active Compression Palm-Up, Bicep I and Bicep II, produced higher long head activations. Resisted Supination External Rotation, Bicep I, Bicep II, and Yergason's, produced a higher LHBB proportion.
Conclusion
Bicep I, and Bicep II elicited promising long head behavior (high activation and selectivity). Speed's and Active Compression Palm-Up elicited higher activation of the LHBB , and Resisted Supination and Yergason's elicited selective LHBB activity. These top performing tests utilize a unique range of test variables that may prove valuable for optimal SLAP test design and performance.
Clinical Relevance
This study examines several provocative tests that are frequently used in the clinical setting as a means of evaluating a potential SLAP lesion.
[Review Only] What is known about the subject
Detecting SLAP lesions in the clinical setting has been frequently examined in the relevant literature. In general, most studies report the accuracy of a SLAP lesion test after a group of patients with suspected SLAP lesions are diagnosed following arthroscopy, and very few of these studies have examined the biomechanical implications of these tests.
[Review Only] What this study adds to existing knowledge
To the best of the authors' knowledge this is the first study to examine these seven provocative test in parallel and in subjects with no history of shoulder pathology. Again, to the best of the authors' knowledge this study is also the first to examine both activation and selectivity of the long head of the biceps and six other joint stabilizing muscles. In this study...