Perforation tolerance of glenoid implants to abnormal glenoid retroversion, anteversion, and medialization

Loosening of the glenoid implant is a common complication of total shoulder arthroplasty. To prevent this, we need to ensure the glenoid vault is not perforated during insertion of the glenoid implant to allow for cement containment and maximum pressurization. Factors affecting perforation potential include glenoid implant design and alignment. This study looks at the perforation tolerance of 15 commercially available glenoid implants to increased retroversion, increased anteversion, and medialization.

Accurate 3-dimensional models of the 15 glenoid implants were created from exact dimensions obtained from the manufacturers and virtually implanted into 3-dimensional reconstructed models of 40 nonarthritic scapulae. Perforation tolerances of each implant to increased retroversion, increased anteversion, and medialization were determined through computer simulation to represent asymmetrical arthritic posterior wear, anterior wear, and eccentric corrective reaming, respectively.

In all 15 glenoid implants, the overall mean increased retroversion tolerated before perforation was 19°, increased anteversion was 16°, and abnormal version fully corrected by eccentric reaming was 17°. Each glenoid implant was evaluated individually to allow for direct comparison and, finally, size-matched and downsized glenoid implants in relation to the size of the humeral head.

The results from this study help surgeons, when faced with a severely arthritic glenoid, to choose the appropriate glenoid implant to minimize perforation potential, and provide guidance on how much abnormal version and how much corrective reaming can be tolerated before perforation occurs and fixation is compromised. These results can also help with future implant designs.