Glenohumeral Muscle Activation During Provocative Tests Designed to Diagnose Superior Labrum Anterior-Posterior Lesions

Abstract

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...

Identifying shoulder testing positions and movements that isolate infraspinatus from supraspinatus

“…The highest activity for infraspinatus was seen in Wood et al 22 during the active compression test, palms down, for SLAP tears (182%MVIC). This test involves the participant standing with the shoulder flexed to 90u u and adducted 10-15u u medial to the sagittal plane, the elbow fully extended.…”

The O’Brien test demonstrates a higher diagnostic value in identifying posteroinferior labral tears than superior labral anterior to posterior (SLAP) tears

“… 12 However, biomechanically one would expect an opposite result to the test as the tensile load onto the tendon of the long head biceps is increased in external rotation of the shoulder, when one expects a pain relieve during the second part of the test. 7 , 21 Green et al suggested that this failure to support its proposed anatomic basis may partly explain the variable likelihood ratios obtained in clinical accuracy studies of the O'Brien test. 5 , 7 , 19 , 20 …”

“… 6 Moreover, based upon our clinical experience and recent biomechanical data, we hypothesized that the O’Brien test would be the most predictive of posteroinferior labral tears. 7 , 15 , 21 Therefore, the primary aim was to determine the diagnostic value of the O’Brien test in localizing labral tears of the shoulder.…”

Do surface electrode recordings validly represent latissimus dorsi activation patterns during shoulder tasks?

“…A simple, electronic search of the literature between 2011 and 2013 found over 20 papers reporting LD activity recorded with the use of surface electrodes. The scope of these studies ranged from investigating LD activity during: normal shoulder function (Hawkes et al, 2012b;Rota et al, 2013); various sporting activities including rowing (Bazzucchi et al, 2013), tennis (Rota et al, 2012), pole vaulting (Frere et al, 2012), skiing (Nilsson et al, 2013), baseball (Reyes et al, 2011), golf (Lim et al, 2012) and swimming (Ikuta et al, 2012); exercises (Marchetti and Uchida, 2011); shoulder and trunk dysfunction (Hawkes et al, 2012a;Ntousis et al, 2013;Wood et al, 2011); classical singing (Watson et al, 2012); and muscle fatigue (Balasubramanian et al, 2014).…”