Patient-specific instrumentation for total shoulder arthroplasty: not as accurate as it would seem

There is an increasing body of literature suggesting that the use of patient-specific instrumentation (PSI) in total shoulder arthroplasty (TSA) results in improved positioning of the glenoid component. The aim of this in vivo study was to assess the accuracy of PSI of the glenoid component in TSA in a consecutive series at a single center.

Eleven consecutive TSAs (7 TSAs and 4 reverse TSAs) were performed using custom-made patient-specific positioning guides for the glenoid component. Each patient had preoperative computed tomography scans and guides produced to allow 0° of glenoid inclination and version in anatomic TSAs and 10° of inferior inclination for reverse TSAs. Postoperative computed tomography imaging was performed to determine accuracy of component implantation. Patients were observed to the 1-year mark.

For the conventional TSA group, the mean version was measured at 8° ± 10° retroversion and 1° ± 4° inclination. For reverse TSAs, mean version was 10° ± 10° retroversion and -1° ± 5° inclination. There were 5 cases classified as outliers in terms of version (>10° anteversion or retroversion). We had a mean correction of version of 22° ± 9° and 17° ± 9° in inclination compared with preoperative measurements.

Our results suggest that the in vivo accuracy of PSI-guided glenoid positioning is not as successful as suggested in the literature.