Work

Do subscapularis integrity and posterosuperior cuff tear severity affect scapular impingement and joint stability during external rotation in lateralized reverse total shoulder arthroplasty?

Year: 2026

Type: article

Abstract: Aims: The biomechanical effects of varying rotator cuff tear severities on medialized versus lateralized reverse total shoulder arthroplasty (RTSA) remain unclear. This study aimed to compare medialized and lateralized RTSA designs based on subscapularis integrity and the severity of posterosuperior cuff tears. Methods: A total of 12 human in vivo experimental datasets were collected during external rotation (ER) from a neutral position to 45°, with the elbow fixed at 90° and the palm facing inward. These datasets were used as inputs for musculoskeletal shoulder models of both medialized and lateralized RTSA. Inverse dynamic simulations were conducted under two subscapularis conditions-repaired (all bundles intact) and torn (all bundles torn)-across three stages of posterosuperior cuff tear severity. The scapular notching-related impingement stress, joint subluxation, and muscle-tendon forces were compared between the two RTSA configurations. Results: Subscapularis repair in lateralized RTSA led to greater reductions in impingement stress (16.7% to 26.2%; p < 0.05) and joint subluxation (27.5% to 58.9%; p < 0.001) compared to medialized RTSA (14.1% to 18.6%; p < 0.05 and 14.7% to 22.4%; p < 0.001, respectively) across all posterosuperior cuff tear conditions. Additionally, with subscapularis repair, posterior deltoid force increased more markedly with tear severity in lateralized RTSA (from 2.6% (p = 0.007) to 918.5% (p < 0.001)) than in medialized RTSA (from 4.7% to 784.5%, both p < 0.001). Conclusion: Lateralizing RTSA and repairing the subscapularis can significantly reduce scapular notching-related impingement, improve joint stability, and support ER torque generation by increasing posterior deltoid force in patients with posterosuperior cuff tears. These findings provide critical insights for surgical planning, supporting the use of a lateralized implant and subscapularis repair to reduce the risk of scapular notching and joint subluxation while enhancing ER torque generation.

Source: Bone and Joint Research

DOI: 10.1302/2046-3758.152.bjr-2025-0174.r1

Authors: Donghwan Lee, Sungwook Jung, Choongsoo S. Shin, Joo Han Oh

Institutions: Sogang University, Korea University, Seoul National University, Seoul National University Bundang Hospital

Language: English

Topic: Shoulder Injury and Treatment

Subfield: Surgery

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $1,594