The anatomical basis of the resisted supination external rotation test for superior labral anterior to posterior lesions

Abstract

The majority of clinical tests used to diagnose superior labral anterior to posterior (SLAP) lesions of the shoulder have poor diagnostic accuracy, possibly related to a lack of anatomical validity for test procedures. The resisted supination external rotation (RSER) test is suggested to reproduce symptoms associated with a SLAP lesion by placing stress on the labrum through increasing tension in biceps brachii long head. The test requires supination of the forearm against resistance, while the shoulder is externally rotated passively. It was hypothesized that the RSER would increase activity in biceps brachii long head, thereby providing evidence of the anatomical validity of the test. Electromyography (EMG) was used to measure activity in biceps brachii long head and five other muscles potentially recruited during the RSER test in 12 healthy subjects. EMG amplitude was normalized against maximum voluntary isometric contraction for each muscle. Muscle activity values were averaged across five RSER trials and graded descriptively. Moderately strong activity was recorded in biceps brachii long head and supinator muscle throughout all phases of the RSER test. Brachialis was minimally active throughout the test. The results provide support for the anatomical basis of the RSER test, with the resisted forearm supination component of the test recruiting moderately strong levels of activity in biceps brachii long head throughout the test. Although the evidence of anatomical validity provides support for the RSER test as a clinical test for SLAP lesions of the shoulder, further tests of diagnostic accuracy are required.