Biomechanical Evaluation of Provocative Tests for Superior Glenoid Labrum Lesions

During the recent era of arthroscopic surgery, many distinct shoulder pathologies such as the superior labrum anterior to posterior (SLAP) lesion have been identified. The unfortunate fact of arthroscopy is that it is invasive and extremely costly. There are clinical examinations that aid in the diagnosis of SLAP lesions, but they are not considered stand-alone diagnoses like arthroscopy. Therefore, it is beneficial to improve the overall accuracy of the current clinical tests used to diagnose SLAP lesions. Of the existing tests, 10 are meant to actively engage the long head of the biceps brachii (LHBB) to create tension in the biceps tendon. The tension in the LHBB elicits pain and/or apprehension in the superior glenoid region, a positive sign of superior labral pathology. Eleven male subjects with no history of shoulder pathology were recruited to participate in the study. Their average age was 25 years. Each subject was subjected to 10 provocative tests for SLAP lesions. The ten tests were: Active Compression, Anterior Slide, Biceps Load, Biceps Load II, Compression Rotation, Crank, Pronated Load, Resisted Supination External Rotation, Speed\u27s and Supination Sign test. Each test was performed three times in a random order. During the tests electromyography (EMG) of seven muscles surrounding the shoulder was monitored (Noraxon Telemyo 900, 1250Hz). The muscles monitored included: long and short head of biceps brachii, anterior deltoid, pectoralis major, latissimus dorsi, infraspinatus, and supraspinatus. Six of the muscles were monitored with surface electrodes while the supraspinatus was monitored using an indwelling electrode. Maximum voluntary isometric contractions (MVIC) were used to normalize the EMG data among subjects. The variables analyzed from the EMG data were LHBB activation (% MVIC) and selectivity, which measured the contribution of the LHBB to the total muscle activation recorded during the test. Of the 11 subjects, six were instrumented with electromagnetic motion capture hardware (Polhemus Fastrak, 30Hz) to monitor the translation of the humeral head relative to the scapula. The subjects were instrumented with sensors on the thorax (C7), humerus (proximal to epicondyles), and scapula (scapular tracker). There was a statistical difference between tests based on LHBB activation (p=0.000), selectivity (p=0.005), and superior/inferior translation of the humeral head (p=0.023). The Biceps Load, Biceps Load II, Speed\u27s and Active Compression (palm up) tests yielded the highest activation. The Biceps Load, Biceps Load II, Speed\u27s, and Resisted Supination External Rotation tests elicited the best selectivity. The Supination Sign test had the most superior translation of all the tests. The top tests based on EMG were the Biceps Load, Biceps Load II, and Speed\u27s tests. The Supination Sign test was the best based on the amount of superior humeral head translation generated