This matched-pair cadaveric biomechanical study compares two commercially available glenoid designs in total shoulder arthroplasty. It tests a traditional onlay pegged glenoid against an inset inlay glenoid under simulated rocking-horse loading. The question: which design better resists gross loosening and edge force concentration?
Glenoid loosening is the classic weak link in anatomic TSA. Radiolucent lines appear in 30% to over 75% of cases by 2 to 10 years, and 2% to over 10% progress to revision. The mechanism to understand is the rocking-horse: as the humeral head translates and edge-loads the glenoid, it levers the opposite edge off bone. This paper shows why an inset design blunts that lever.
The inlay wins on two mechanical principles worth memorizing. Its smaller 20 mm diameter shortens the moment arm and torque at the edge. Its inset position adds circumferential bone and cement support and lets the native rim share load, cutting edge force to near native levels.
Remember the limits: this is a single onlay design tested against the one commercially available inlay, funded by the inlay manufacturer, with no soft tissues and no bone ingrowth or remodeling captured in a cadaver. Treat it as a mechanistic signal, not clinical survivorship data.
This matched-pair cadaveric biomechanical study compares two commercially available glenoid designs in total shoulder arthroplasty. It tests a traditional onlay pegged glenoid against an inset inlay glenoid under simulated rocking-horse loading. The question: which design better resists gross loosening and edge force concentration?
Glenoid loosening is the classic weak link in anatomic TSA. Radiolucent lines appear in 30% to over 75% of cases by 2 to 10 years, and 2% to over 10% progress to revision. The mechanism to understand is the rocking-horse: as the humeral head translates and edge-loads the glenoid, it levers the opposite edge off bone. This paper shows why an inset design blunts that lever.
The inlay wins on two mechanical principles worth memorizing. Its smaller 20 mm diameter shortens the moment arm and torque at the edge. Its inset position adds circumferential bone and cement support and lets the native rim share load, cutting edge force to near native levels.
Remember the limits: this is a single onlay design tested against the one commercially available inlay, funded by the inlay manufacturer, with no soft tissues and no bone ingrowth or remodeling captured in a cadaver. Treat it as a mechanistic signal, not clinical survivorship data.