Influence of Lateralization and Distalization on Joint Function after Primary Reverse Total Shoulder Arthroplasty

Area of Science:

• Orthopedic surgery
• Biomechanics
• Rehabilitation

Background:

• Reverse total shoulder arthroplasty (RTSA) is a common procedure for complex shoulder pathologies.
• Understanding the impact of implant positioning on patient outcomes is crucial for optimizing surgical results.

Purpose of the Study:

• To investigate the relationship between lateralization shoulder angle (LSA) and distalization shoulder angle (DSA) with clinical and kinematic results after RTSA.
• To assess the reliability of LSA and DSA measurements.

Main Methods:

• Thirty-three patients undergoing RTSA were evaluated postoperatively.
• Clinical outcomes were assessed using SANE, CMS, SST, and VAS scores.
• Shoulder kinematics were measured using a stereophotogrammetric system.
• Inter-rater reliability for LSA and DSA was determined using the interclass correlation coefficient (ICC).
• Regression and correlation analyses were performed to identify relationships between angles, clinical scores, and kinematics.

Main Results:

• Good to excellent inter-rater reliability was found for both LSA (ICC = 0.93) and DSA (ICC = 0.97).
• Higher LSA values were significantly associated with increased peak internal rotation (R² = 0.188) and range of motion (ROM) (R² = 0.133).
• Positive correlations were observed between external rotation and SANE, CMS, and SST scores, while VAS showed a negative correlation.
• Abduction peaks and ROM were positively related to CMS and SANE scores.

Conclusions:

• LSA is a reliable and important parameter in RTSA, correlating positively with internal rotation and overall ROM.
• Specific shoulder angles and kinematic parameters are associated with improved clinical outcomes, guiding surgical technique for better functional recovery.