This computational geometric modeling study virtually tested 486 RTSA implant configurations across small, medium, and large shoulder models to determine which combination of surgical placement and implant-design parameters best restores native deltoid and rotator cuff muscle-tendon lengths — a determinant of post-implant force generation largely ignored by prior moment-arm-focused literature.
When selecting RTSA implants, default to a 135° neck-shaft angle and place the humeral socket at the anatomic neck plane (inlay/0 mm offset) before adding other adjustments — these two parameters have the strongest independent influence on restoring native muscle-tendon lengths.
If you need to increase rotator cuff tension intraoperatively, reach for glenoid lateralization (subscapularis lengthens ~8.4% per 10 mm); if you need more deltoid length for stability in cuff tear arthropathy, increase neck-shaft angle or humeral offset rather than upsizing the glenosphere.
This computational geometric modeling study virtually tested 486 RTSA implant configurations across small, medium, and large shoulder models to determine which combination of surgical placement and implant-design parameters best restores native deltoid and rotator cuff muscle-tendon lengths — a determinant of post-implant force generation largely ignored by prior moment-arm-focused literature.
When selecting RTSA implants, default to a 135° neck-shaft angle and place the humeral socket at the anatomic neck plane (inlay/0 mm offset) before adding other adjustments — these two parameters have the strongest independent influence on restoring native muscle-tendon lengths.
If you need to increase rotator cuff tension intraoperatively, reach for glenoid lateralization (subscapularis lengthens ~8.4% per 10 mm); if you need more deltoid length for stability in cuff tear arthropathy, increase neck-shaft angle or humeral offset rather than upsizing the glenosphere.