Infraspinatus strength assessment before and after scapular muscles rehabilitation in professional volleyball players with scapular dyskinesis
We previously had a post about the effectiveness of the scapular assistance test in clinical patients with sub-acromial impingement. Another similar clinical test that is commonly used to determine if the scapula is contributing to rotator cuff weakness is the scapular retraction test. This test is performed by first testing external rotation rotator cuff strength with a manual muscle test (MMT) then the scapula is manually retracted and stabilized with the tester’s forearm and the MMT is repeated. If the strength increases with the manual retraction then the test is positive for weak and deficit scapular stabilizers. This study recruited 31 professional volleyball players with pain and weakness of the infraspinatus. MRIs were performed to rule out any internal soft tissue damage of the shoulder. Scapular dyskinesis was categorized for all participants using methods described by Kibler (https://www.ncbi.nlm.nih.gov/pubmed/12469078). Following the initial evaluation, a 6 month scapular specific rehabilitation protocol was administered on all participants. This protocol focused on reestablishing a normal balance between the upper trapezius, middle and lower trapezius, as well as the serratus anterior. Infraspinatus strength testing with and without scapular retraction was preformed at baseline, 3 and 6 month post rehabilitation, using a hand held dynamometer. Pain was measured using a visual analog scale at each evaluation. They found that at both 3 and 6 months infraspinatus strength increased for the MMT without scapular retraction. They also found that when comparing the difference in strength between the MMT with and without retraction the difference significantly decreased at both 3 and 6 months. Pain scores also decreased at 3 and 6 months compared to baseline.
This study found that volleyball players with scapular dyskinesis can improve infraspinatus strength and shoulder pain after 3 and 6 months of a scapular-specific rehabilitation program. This demonstrates the importance of the scapula in providing a stable base of support for the infraspinatus and that the scapular retraction test can successfully identify rotator cuff weakness related to scapular instability. This is an easy screening tool that can be used by clinicians to identify patients with strength deficits that are associated with scapular instability and not necessarily the rotator cuff. Focusing on reestablishing the normal force couple between the upper, middle, and lower trapezius as well as the serratus anterior can improve the overall stability of the glenohumeral joint by allowing the cuff to conduct its primary function of maintaining the humeral head within the glenoid fossa. The primary goal in any scapular program should be to improve neuromuscular control and not increases in strength or endurance (potential secondary goals). Increases in strength and endurance will follow if proper neuromuscular control is enforced during rehabilitation. What is everyone’s experience with the retraction test and the use of scapular neuromuscular control programs for improving shoulder function and pain in overhead athletes?
Written by: Stephen Thomas
Reviewed by: Jeff Driban