2025 ISAKOS Congress in Munich, Germany

2025 ISAKOS Biennial Congress Paper


Dynamic Scapular Kinematic Adaptation After Reverse Total Shoulder Arthroplasty

Brett Sanders, MD, Chattanooga, TN UNITED STATES
Elizabeth Raulston, PhD(c), Chattanooga, TN UNITED STATES
John Heick , PhD, Provo, Utah UNITED STATES

Rocky Mountain University of Health Professions, Provo, Utah, UNITED STATES

FDA Status Cleared

Summary

This study aimed to determine if using micro inertial measurement unit sensors to evaluate three-dimensional multiplanar scapular motion can offer more definitive and precise criteria to understand the influence of scapular kinematics of reverse total shoulder arthroplasty.

Abstract

Introduction

The reverse total shoulder introduces a new force coupling mechanism that alters the mechanical load, making it challenging to develop a definitive conclusion about the potential subsets related to the multiplanar dynamic scapular positioning solely based on observational kinematic analysis. This study aimed to determine if using micro inertial measurement unit sensors to evaluate three-dimensional multiplanar scapular motion can offer more definitive and precise criteria to understand the influence of scapular kinematics of reverse total shoulder arthroplasty. Methods: Twelve patients (7 females, 5 males; mean age 68 ±3.74 years) met inclusion criteria and were preoperatively identified candidates for reverse shoulder arthroplasty. Kinematics studies were performed preoperatively and postoperatively using the Alyve system (Carpi, Italy) on the involved and uninvolved shoulder as a comparison immediately postoperatively, at three and six months. Preop and postop American Shoulder and Elbow Surgeons (ASES) scores (Minimally Clinically Important Difference=12) and range-of-motion outcome measures were obtained each time. Scapulohumeral rhythm (SHR) was assessed via quantitative measures of the scapula using the arm-trunk angle (H) and the angle of scapular upward rotation (S) using the following formula: SHR=(H-S)/S assessed via the Alyve system. Results: A two-tailed paired sample t-test revealed a statistically significant difference between the mean preoperative ASES scores (36.16) and six-month postoperative ASES score (76.44) (t(11)=-9.11, p<.001). A two-tailed paired sample t-test revealed a statically significant mean difference in the scapular tilt between the surgical shoulder and contralateral shoulder at three months postoperatively (8.86(0.91, 16.82), p<.05) using the maximum output value. A correlation between dynamic scapulohumeral rhythm revealed no significant difference which proves that this technique and formal produce similar outcomes. Conclusion: The current study's findings suggest that postoperative changes in scapular kinematics following a reverse total shoulder arthroplasty positively impact shoulder function and patient-reported outcome measures. Micro inertial measurement units effectively assess SHR in patients undergoing a reverse total shoulder. By addressing SHR, clinicians can improve patient care and enhance the long-term success and patient satisfaction of undergoing reverse total shoulder arthroplasty.