Risk factors for instability after reverse shoulder arthroplasty

Area of Science:

• Orthopedic surgery
• Arthroplasty research
• Biomechanical engineering

Background:

• Postoperative instability is a complication of reverse shoulder arthroplasty.
• Identifying risk factors and treatment outcomes is crucial for improving patient results.

Purpose of the Study:

• To identify risk factors for postoperative instability after reverse shoulder arthroplasty.
• To evaluate treatment modalities and outcomes for instability in a large patient cohort.

Main Methods:

• Retrospective analysis of 1035 Grammont type reverse shoulder arthroplasties (1992-2010).
• Inclusion of patients with bony lateralization on the glenoid side (19.9%).
• Minimum five-year follow-up with clinical review and radiography.

Main Results:

• Overall instability rate was 3.0% at a mean eight-year follow-up.
• Higher instability in revision cases, younger patients, scapular notching, and tuberosity resorption.
• Lateralized implants showed lower instability; 70% of cases required reoperation with reduced functional improvement.

Conclusions:

• Younger patients are at increased risk for instability following Grammont reverse shoulder arthroplasty.
• Lateralized reverse shoulder arthroplasties demonstrate a protective effect against instability.
• Reoperation or revision surgery can restore stability but may compromise functional outcomes.