JSES - 2026-08-07 - Journal Article; Review
Risk Factors for instability and dislocation after reverse total shoulder arthroplasty: a systematic review.
Ulenberg N, Herbstreit S, Dudda M, Vogel C, Mester B
Topics
Key Takeaway
This systematic review of 10 retrospective studies identifies 11 significant risk factors for instability after rTSA, with loss of compression as the predominant mechanism and absence of subscapularis repair, cemented humeral stem, and glenosphere lateralization >9mm as implant-modifiable factors.
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Summary
This systematic review queried PubMed and Google Scholar through February 2025 to identify risk factors for instability and dislocation after rTSA, classifying mechanisms using the Frankle classification by Abdelfattah et al. Eleven statistically significant risk factors were identified including male sex, younger age, opioid use disorder, depressive disorder, revision surgery, nonunion, rotator cuff disease, prior subluxation, absent subscapularis repair, cemented humeral stem, and glenosphere lateralization >9mm. Loss of compression was the most common instability mechanism, followed by impingement.
Key Limitation
The aggregate patient sample size is unreported and all source studies are retrospective, making it impossible to determine effect sizes with precision or establish causality for any identified risk factor.
Original Abstract
BACKGROUND
The number of reverse total shoulder arthroplasties has increased due to demographic changes, leading to more revision surgeries. Postoperative instability or dislocation is a frequent and challenging complication that impairs clinical outcomes. This study aimed to identify risk factors for instability following reverse total shoulder arthroplasty and to evaluate the underlying mechanisms described by Abdelfattah et al.
METHODS
A systematic literature review was conducted using PubMed and Google Scholar with MeSH terms and keywords including "shoulder replacement," "shoulder arthroplasty," "joint instability," "risk factors," and "odds ratio." The search was completed on February 21, 2025. Instability mechanisms were classified according to the Frankle classification by Abdelfattah et al.. A meta-analysis of odds ratios was performed for risk factors reported in multiple studies.
RESULTS
Ten retrospective studies (six cohort studies, four case series) were included. Eleven significant risk factors were identified: male sex, younger age, opioid use disorder, depressive disorder, revision surgery, nonunion, rotator cuff disease, prior postoperative subluxation, absence of subscapularis repair, cemented humeral stem, and a expanded/ lateralized glenosphere >9mm. Additional less conclusive factors included high body-mass index, malunion, hypertension, electrolyte disorders, prior ipsilateral shoulder surgery, acute fractures, and glenosphere-related factors (size, positioning, neck-shaft angle). The most common mechanism of instability was loss of compression, followed by impingement.
CONCLUSION
Both established and novel risk factors for instability were identified, including younger age, opioid use disorder, depressive disorder, nonunion, and lack of bony lateralization. Loss of compression was the predominant mechanism. These findings may improve preoperative risk assessment and support individualized surgical planning. However, due to the retrospective nature of the available evidence and potential confounding by indication, particularly for implant-related factors, these findings should be considered hypothesis-generating rather than causal. Future studies should link risk factors to instability mechanisms to enable targeted treatments and develop a validated risk score.
LEVEL OF EVIDENCE
Level IV, Systematic Review.