This in vitro wear simulation compared 32-mm and 40-mm glenospheres in reverse total shoulder arthroplasty. Six implants per group underwent 5 million cycles of alternating flexion-extension and abduction-adduction loading. The study asked how glenosphere diameter affects polyethylene wear, a relationship not previously characterized in RTSA.
When you upsize a glenosphere in RTSA to improve stability and impingement-free motion, you are trading one problem for another: more volumetric polyethylene debris. That matters because wear-induced osteolysis and aseptic glenoid loosening are the leading cause of RTSA revision, per the Norwegian registry.
The mental model is borrowed directly from hip arthroplasty. Bigger ball, more total volumetric wear. Smaller ball, deeper focal (linear) wear. The smaller 32-mm sphere is not a free win either. It concentrates wear into the inferior liner, which the authors note could contribute to instability through lost range of motion.
This is basic science, non-cross-linked polyethylene, only two sizes tested, and the clinical impact of the wear difference is unknown. Treat it as a biomechanical principle, not a directive to avoid larger glenospheres.
This in vitro wear simulation compared 32-mm and 40-mm glenospheres in reverse total shoulder arthroplasty. Six implants per group underwent 5 million cycles of alternating flexion-extension and abduction-adduction loading. The study asked how glenosphere diameter affects polyethylene wear, a relationship not previously characterized in RTSA.
When you upsize a glenosphere in RTSA to improve stability and impingement-free motion, you are trading one problem for another: more volumetric polyethylene debris. That matters because wear-induced osteolysis and aseptic glenoid loosening are the leading cause of RTSA revision, per the Norwegian registry.
The mental model is borrowed directly from hip arthroplasty. Bigger ball, more total volumetric wear. Smaller ball, deeper focal (linear) wear. The smaller 32-mm sphere is not a free win either. It concentrates wear into the inferior liner, which the authors note could contribute to instability through lost range of motion.
This is basic science, non-cross-linked polyethylene, only two sizes tested, and the clinical impact of the wear difference is unknown. Treat it as a biomechanical principle, not a directive to avoid larger glenospheres.