Research Mentor Name

Dr. Stephanie Muh

Research Mentor Email Address

Institution / Department

Henry Ford Health Systems

Document Type

Research Abstract

Research Type


Level of Research



Background: Deltoid muscle function is central in reverse total shoulder arthroplasty (RTSA) function; however, there is limited information available regarding changes in deltoid activity before and after surgery. Few tests exist to evaluate specific muscle metrics pre and post operatively. Surface Electromyographic (EMG) is non-invasive and allows for observation of motions with multifaceted analysis of movement with minimal patient demand. Understanding the changes in shoulder muscle activation, namely in the deltoid, in patients pre and post-RTSA can further advance understanding of the procedure and rehabilitation efforts.

Methods: Nine individuals were recruited for this study: all patients underwent RTSA by a single fellowship trained shoulder and elbow surgeon. Participants executed shoulder abduction, forward flexion, internal and external rotation at slow, medium and fast speeds as well as static maximum contraction of these motions against force at each EMG testing session. EMG activation of the anterior, middle and posterior aspects of the deltoid, upper and middle trapezius, supraspinatus, infraspinatus, teres major and teres minor was recorded on the surgical shoulder preoperatively, and 6 weeks, 3 months and 6 months postoperatively. Delsys EMG acquisition software linked to Bluetooth sensors captured shoulder motion. Statistical comparisons between pre-RTSA and post-RTSA shoulders, as well as consecutive post-RTSA shoulders were performed using one-way ANOVA (p<0.05).

Results: Analysis pending- will be fully available at the symposium.

Preliminary data show an overall significant increase in concentric muscle activity (RMS) of the anterior and lateral deltoid during abduction when comparing: 6 week post-RTSA patients (6w-RTSA) to pre-RTSA and 6w-RTSA to 3 month post-RTSA (3m-RTSA). Furthermore, there was a significant increase in frequency (PSD) in anterior and lateral deltoid during abduction when comparing the same groups. There were no significant changes in RMS or PSD when comparing 3m to 6m-RTSA during abduction. During forward flexion in the sagittal plane, an overall significant increase in RMS and PSD of the anterior and lateral deltoid was observed in 3m-RTSA compared to pre-RTSA. Deltoid muscle activation time significantly decreased for abduction and forward flexion at medium and fast speeds when comparing 6w-RTSA to 3m-RTSA and 3m-RTSA to 6m-RTSA. There was an insignificant increase in posterior deltoid activation during external rotation when comparing 6w- to 3m-RTSA.

Conclusion: Post-RTSA patients showed increased concentric muscle activity and muscle fiber frequency in the anterior and lateral deltoid muscle fibers when compared with pre-RTSA patients during abduction, forward flexion and external rotation. Some degree of increase in deltoid activation was seen when comparting specific post-RTSA groups. Overall, these findings suggest the deltoid muscle has an increased role in abduction, forward flexion and external rotation in RTSA patients.


Kinesiotherapy | Medicine and Health Sciences | Musculoskeletal Diseases | Musculoskeletal System | Occupational Therapy | Orthopedics | Other Rehabilitation and Therapy | Physical Therapy