This instructional course lecture reviews the evolution of humeral component design in anatomic total shoulder arthroplasty. It traces four generations from Neer's monoblock prosthesis to modern short stem and stemless implants. The focus is on the rationale, indications, and outcomes for shorter and stemless fixation.
The central design question is where you want humeral fixation to live: diaphysis or metaphysis. A long stem gains fixation in the canal, but if the stem is slightly wider than the diaphysis you get premature diaphyseal contact, head protrusion, and a forced non-anatomic head. Shorter and stemless implants free the head position from the shaft axis.
The trade-offs are worth knowing for boards. Stemless implants preserve bone, cut blood loss and operative time, lower diaphyseal stress shielding, and simplify revision by avoiding stem extraction.
The cost is a dependence on good metaphyseal bone. That is why osteoporosis, large subchondral cysts, and rheumatoid arthritis are relative contraindications, and why acute fracture, nonunion, and revision of a stemmed implant are unsuitable.
Remember that short-term Constant scores are comparable to standard stems, but no long-term data exist yet, so the durability question is genuinely unsettled.
This instructional course lecture reviews the evolution of humeral component design in anatomic total shoulder arthroplasty. It traces four generations from Neer's monoblock prosthesis to modern short stem and stemless implants. The focus is on the rationale, indications, and outcomes for shorter and stemless fixation.
The central design question is where you want humeral fixation to live: diaphysis or metaphysis. A long stem gains fixation in the canal, but if the stem is slightly wider than the diaphysis you get premature diaphyseal contact, head protrusion, and a forced non-anatomic head. Shorter and stemless implants free the head position from the shaft axis.
The trade-offs are worth knowing for boards. Stemless implants preserve bone, cut blood loss and operative time, lower diaphyseal stress shielding, and simplify revision by avoiding stem extraction.
The cost is a dependence on good metaphyseal bone. That is why osteoporosis, large subchondral cysts, and rheumatoid arthritis are relative contraindications, and why acute fracture, nonunion, and revision of a stemmed implant are unsuitable.
Remember that short-term Constant scores are comparable to standard stems, but no long-term data exist yet, so the durability question is genuinely unsettled.