Electromyographic and kinematic study of reverse total shoulder arthroplasty: an observational prospective cohort study

Abstract

Background: Reverse total shoulder arthroplasty (RTSA) procedures have significantly increased in the last decade as an alternative to the current treatments for cuff-tear arthropathy. Since Grammont's theory in 1987, few data about the in vivo kinetics of the shouldergirdle musculature in patients with RTSA have been available. The goals of this study are to (1) describe the contribution of principal muscles around the shoulder by electromyography and (2) access the range of motion of 5 movements of patients with RTSA compared with normal shoulders. Methods: This is an observational prospective cohort study of 21 patients divided into 11 patients with RTSA and 10 controls. The muscular activity was recorded with bipolar cutaneous electrodes, whereas the range of motion was synchronized and recorded by 8 motion cameras. Five movements (flexion, abduction, neutral external rotation, external rotation in 90 of abduction, and internal rotation in 90 of abduction) were studied. Results: The upper trapezius is the main activator in all directions with early and constant activity (P < .01). The latissimus dorsi demonstrates increased muscular activity in internal rotation (P < .01) as well as the posterior deltoid in external rotation in the RTSA group compared with control (P < .01). Conclusion: RTSA shoulder muscle activation is significantly different than in normal shoulders. The significant contribution of the trapezius in all directions, latissimus dorsi in internal rotation, and posterior deltoid in external rotation has never been described within the same study until today. New rehabilitation protocols targeting those muscles could demonstrate better and more homogeneous results and increase patient satisfaction.

Comparison of Clinical Performance of Inlay versus Onlay Humerus Implants in Reverse Total Shoulder Arthroplasty

“…According to the electromyographic result reported by Pelletier-Roy et al, 23) RTSA intervenes in cuff-defect shoulders by modifying the scapulothoracic sequence. Further lengthening of the distance between the medial border of the scapula and the glenohumeral joint by lateralization not only affects the tension of rotators, but also the scapulothoracic muscles, especially the upper trapezius and latissimus dorsi, which are known to be the main activator muscles in RTSA shoulders.…”

“…Further lengthening of the distance between the medial border of the scapula and the glenohumeral joint by lateralization not only affects the tension of rotators, but also the scapulothoracic muscles, especially the upper trapezius and latissimus dorsi, which are known to be the main activator muscles in RTSA shoulders. 23) However, this theory only can be applied in the setting of implants with increased offset on the glenoid side. So far, numerous clinical studies have compared two or three different products that represent either medialized or lateralized RTSA systems.…”

Comparison of Lateralized Versus Medialized Reverse Total Shoulder Arthroplasty: A Systematic Review and Meta-analysis

“…In our view, scapulothoracic motion, which is differentiated by lateralization, might affect the ER gain. Using electromyography, Pelletier-Roy et al 23 demonstrated that shoulder motion intervention using rTSA was affected by modified scapulothoracic sequencing. They reported that the upper trapezius and latissimus dorsi are the main activator muscles in the rTSA shoulder.…”

Surface Electromyography Reveals Middle Deltoid as The Functionally Dominant Shoulder Muscle After Reverse Total Shoulder Arthroplasty

“…Muscle activity or adaptation can be assessed through muscle tests, invasively using small needle electrodes, or with surface electrodes adhered to the skin. Surface electromyography (sEMG) has recently shown to be a valid and noninvasive tool for quantifying individual muscle activation in the shoulder and has been used extensively in clinical diagnostic and rehabilitation settings [3,[6][7][8][9][10][11][12][13][14].…”