This review examines lateralization strategies in reverse shoulder arthroplasty and how they address the flaws of the original medialized Grammont design. It compares glenoid-sided, humeral-sided, and bony (BIO-RSA) lateralization by their biomechanical trade-offs. The question: which approach best reduces scapular notching and external rotation loss without new complications?
When you see scapular notching and poor external rotation after a Grammont-style RTSA, the fix is lateralizing the center of rotation, but the route you choose carries different penalties.
Glenoid-sided lateralization is the most effective at reducing notching, yet it increases torque at the glenoid interface and raises loosening rates (8.8% vs 1.8%). Reserve this awareness for the board question that pairs "lateralized glenoid" with "early loosening."
Humeral-sided lateralization, achieved with a lower neck-shaft angle and an onlay stem, tensions the residual cuff and lengthens the deltoid moment arm without stressing glenoid fixation. This is why it improves deltoid efficiency without raising joint load. Remember the Routman thresholds cold: glenoid lateralized at >5 mm, humeral at >15 mm.
The honest bottom line the authors stress: no clinical study yet proves one design superior. The current rationale rests on biomechanical data, so treat design choice as an area of active debate.
This review examines lateralization strategies in reverse shoulder arthroplasty and how they address the flaws of the original medialized Grammont design. It compares glenoid-sided, humeral-sided, and bony (BIO-RSA) lateralization by their biomechanical trade-offs. The question: which approach best reduces scapular notching and external rotation loss without new complications?
When you see scapular notching and poor external rotation after a Grammont-style RTSA, the fix is lateralizing the center of rotation, but the route you choose carries different penalties.
Glenoid-sided lateralization is the most effective at reducing notching, yet it increases torque at the glenoid interface and raises loosening rates (8.8% vs 1.8%). Reserve this awareness for the board question that pairs "lateralized glenoid" with "early loosening."
Humeral-sided lateralization, achieved with a lower neck-shaft angle and an onlay stem, tensions the residual cuff and lengthens the deltoid moment arm without stressing glenoid fixation. This is why it improves deltoid efficiency without raising joint load. Remember the Routman thresholds cold: glenoid lateralized at >5 mm, humeral at >15 mm.
The honest bottom line the authors stress: no clinical study yet proves one design superior. The current rationale rests on biomechanical data, so treat design choice as an area of active debate.