Anterior deltoid muscle tension quantified with shear wave ultrasound elastography correlates with pain level after reverse shoulder arthroplasty

Abstract

Introduction Reverse shoulder arthroplasty (RSA) leads to medialization and distalization of the centre of rotation of the shoulder joint resulting in lengthening of the deltoid muscle. Shear wave ultrasound elastography (SWE) is a reliable method for quantifying tissue stiffness. The purpose of this study was to analyse if deltoid muscle tension after RSA correlates with the patients’ pain level. We hypothesized that higher deltoid muscle tension would be associated with increased pain. Material and methods Eighteen patients treated with RSA were included. Constant score (CS) and pain level on the visual analogue scale (VAS) were analysed and SWE was performed on both shoulders. All three regions of the deltoid muscle were examined in resting position and under standardized isometric loading. Results Average patient age was 76 (range 64–84) years and average follow-up was 15 months (range 4–48). The average CS was 66 points (range 35–89) and the average pain level on the VAS was 1.8 (range 0.5–4.7). SWE revealed statistically significant higher muscle tension in the anterior and middle deltoid muscle region in patients after RSA compared to the contralateral non-operated side. There was a statistically significant correlation between pain level and anterior deltoid muscle tension. Conclusion SWE revealed increased tension in the anterior and middle portion of the deltoid muscle after RSA in a clinical setting. Increased tension of the anterior deltoid muscle portion significantly correlated with an increased pain level. SWE is a powerful, cost-effective, quick, dynamic, non-invasive, and radiation-free imaging technique to evaluate tissue elasticity in the shoulder with a wide range of applications. Level of evidence Diagnostic study, Level III.

The Fate of the Shoulder Post Rotator Cuff Repair: Biomechanical Properties of the Supraspinatus Tendon and Surrounding Structures

“…14,15 Recently, several studies have used SWE to examine the biomechanical properties of the deltoid muscle post reverse shoulder arthroplasty and noted that the stiffness of the deltoid muscle increased post reverse shoulder arthroplasty. [16][17][18] Therefore, when rehabilitating the shoulder post rotator cuff repair, it is important to consider both the rotator cuff and the deltoid muscle.…”

“…Two biomechanical cadaveric studies demonstrated that in the presence of a rotator cuff tear, significantly increased force in the deltoid muscle was required to achieve stable glenohumeral abduction without excessive superior humeral head translation 14,15 . Recently, several studies have used SWE to examine the biomechanical properties of the deltoid muscle post reverse shoulder arthroplasty and noted that the stiffness of the deltoid muscle increased post reverse shoulder arthroplasty 16–18 . Therefore, when rehabilitating the shoulder post rotator cuff repair, it is important to consider both the rotator cuff and the deltoid muscle.…”