An evaluation of the anatomical basis of the Biceps Load tests I and II for superior labral anterior and posterior (SLAP) lesions

Glenohumeral muscle activation during provocative tests designed to diagnose superior labrum anterior-posterior lesions

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 because of the invasiveness, patient risk, and financial cost associated with arthroscopy.

PURPOSE

The purpose of this study 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 of the 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 injury were recruited. The tests analyzed were active compression, Speed's, pronated load, biceps load I, biceps load 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

Biceps load I and biceps load 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.

Testing procedures for SLAP lesions of the shoulder involving contraction and torsion of biceps long head and glenohumeral glides

Testing procedures for SLAP lesions of the shoulder can combine resisted elbow flexion, forearm pronation and supination, and glenohumeral glides. These procedures reproduce symptoms by increasing biceps long head active tension or passive torsion, and by placing the shoulder in an unstable position. We compared activation of biceps long head and pain intensity, between supinated and pronated forearm positions, between different glides, and between individuals with and without shoulder impairment. A case control study. Twelve participants with suspected SLAP lesions and twelve with no history of shoulder injury volunteered. Electromyography measured muscle activity in biceps long head, normalised against maximum voluntary isometric contraction (MVIC). Subjective pain intensity scores were recorded. Biceps long head activity was greater in forearm supination (mean 39% MVIC) than pronation (mean 24% MVIC), but pain was higher in pronation (mean 4.5/10) than supination (3.2/10). Biceps long head activity was greater when testing without a glide, but there was no difference in pain comparing the glide conditions. The impaired group experienced more pain (mean 3.9/10) than controls (mean 0.3/10) but there was no difference in shoulder muscle activity. No one combination of testing procedures appeared to be diagnostic of SLAP lesions in our sample. This study supports the theory that biceps long head acts as a stabiliser of the shoulder, and suggests that clinical testing procedures for SLAP lesions may need to inhibit biceps long head activity. The addition of glides to SLAP testing procedures did not affect the reproduction of pain.