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Factors Influencing Stem Subsidence in 135-Degree Inlay Reverse Shoulder Arthroplasty
Suguru Mori1, Katsumasa Nakazawa2, Tomoya Manaka2
1Department of Orthopedic Surgery, Kishima Hon-in Hospital, 3-3-33 Eiwa, Yao-shi 581-0853, Osaka, Japan.
Journal of Clinical Medicine
|October 29, 2025
Summary
In reverse shoulder arthroplasty (RSA) with a 135-degree stem, inadequate proximal fit (<80%) is a significant risk factor for stem subsidence. Proper sizing and alignment are crucial for initial stability.
Area of Science:
- Orthopedic Surgery
- Biomedical Engineering
- Radiology
Background:
- Reverse shoulder arthroplasty (RSA) with 135-degree inlay-type humeral stems offers a bone-preserving design.
- Stem subsidence is a potential complication, but its incidence and contributing factors remain unclear.
Purpose of the Study:
- To determine the incidence of stem subsidence in RSA using a 135-degree inlay-type stem.
- To identify factors associated with stem subsidence in this patient population.
Main Methods:
- Retrospective analysis of 44 shoulders treated with uncemented Tornier Perform® Reversed Stems.
- Radiographic evaluation of stem alignment and canal filling ratio.
- Subsidence defined as >5 mm inferior migration.
Main Results:
- Subsidence occurred in 13.6% of cases (6 shoulders).
- Subsidence was associated with greater stem alignment and lower proximal filling ratio.
- Proximal filling ratio <80% was an independent risk factor (OR: 70.0).
Conclusions:
- Inadequate proximal fit may contribute to subsidence in 135-degree inlay RSA.
- Proper stem sizing and alignment are essential for initial stability and clinical outcomes.
- Larger, long-term studies are needed to confirm these findings.
