# Glenohumeral Instability and Clinical Outcomes Following Proximal Humerus Resection and Megaprosthesis Implantation: A Systematic Review

## TL;DR

This paper reviews how shoulder instability after a specific type of surgery affects recovery and outcomes, finding it to be a common and serious issue.

## Contribution

The study systematically analyzes the incidence and impact of glenohumeral instability after proximal humerus megaprosthesis implantation.

## Key findings

- Glenohumeral instability occurred in 32% of patients following proximal humerus resection and megaprosthesis implantation.
- Unstable shoulders had significantly worse DASH scores compared to stable ones.
- Soft tissue reconstruction, especially of the rotator cuff and deltoid, was crucial for postoperative stability.

## Abstract

Background: Glenohumeral instability is one of the most frequent and clinically impactful complications following proximal humerus resection and reconstruction with a megaprosthesis, especially in patients treated for bone tumors or complex fractures. Its incidence, risk factors, and influence on functional recovery remain variably reported in the literature. Methods: A systematic review was conducted according to PRISMA guidelines, searching PubMed, Scopus, and Google Scholar up to April 2025. Studies reporting on postoperative instability, dislocation, functional outcomes (MSTS, DASH), and related complications were included. Two independent reviewers performed data extraction and quality assessment. A pooled analysis was performed using random-effects models. Results: A total of 17 studies including 387 patients were analyzed. The pooled incidence of glenohumeral instability was 32%, with a revision surgery rate of 10% due to instability. The most common reconstruction technique was modular megaprosthesis (47%), followed by allograft–prosthesis composites (APCs) and reverse total shoulder arthroplasty (RSA). Functional outcomes were reported in 12 studies using the Musculoskeletal Tumor Society (MSTS) score, with a weighted mean of 22.3 ± 3.8 (74.3% ± 12.7%). Disabilities of the Arm, Shoulder, and Hand (DASH) scores, reported in 3 studies, showed worse outcomes in unstable shoulders (mean 61.4 ± 5.2 vs. 26.6 ± 4.1). Soft tissue reconstruction, particularly involving the rotator cuff and deltoid, significantly influenced postoperative stability and function. Conclusions: Glenohumeral instability after proximal humerus megaprosthesis is a common and disabling complication that adversely affects functional outcomes and revision rates. Optimizing soft tissue management and prosthetic design is essential to improve joint stability and long-term results.