Implantation of the glenoid component of a total shoulder prosthesis can be facilitated by using a patient-specific guide (PSG) designed to ensure replication of the preoperatively planned position. The objective of this study was to assess the reliability and accuracy of a PSG in replicating the planned glenoid component position during total shoulder arthroplasty (TSA).

Additional criteria should be used for 3D preoperative planning and PSG design to further improve the accuracy of glenoid component positioning.

We studied 10 patients who underwent TSA with use of a PSG to position the glenoid component after preoperative 3D planning. Postoperative glenoid version and tilt were measured and compared to the planned values. We also used new criteria to assess implant rotation and global 3D position, as well as accuracy of the 3D pilot hole for the glenoid guide-pin.

Mean errors in glenoid position were −1.7°±4.4° for version, −0.4°±4.9° for tilt, and 6.0°±13.5° for rotation. Mean difference in global orientation of the glenoid implant versus the planned value was 4.9°±2.5°. Mean 3D discrepancy in glenoid pilot hole position was 2.9±0.5mm; the discrepancy was greater in the mediolateral direction (1.9±0.9mm) than in the supero-inferior (1.1±1.2mm) and antero-posterior (0.8±1.2mm) directions.

The poor performance of the PSG in controlling rotation and reaming may explain the difference in global glenoid position compared to the planned value. Improvements in PSG design to incorporate these two parameters deserve consideration.

II, prospective cohort study.