Variability in total shoulder arthroplasty planning software compared to a control CT-derived 3D printed scapula.
Background
Two techniques exist from which all 3D preoperative planning software for total shoulder arthroplasty are based. One technique is based on measurements constructed on the mid-glenoid and scapular landmarks (Landmark). The second is an automated system using a best-fit sphere technique (Automated). The purpose was to compare glenoid measurements from the two techniques against a control computed tomography-derived 3D printed scapula.


Methods
Computed tomography scans of osteoarthritic shoulders of 20 patients undergoing primary total shoulder arthroplasty were analyzed with both 3D planning software techniques. Measurements from a 3D printed scapula (Scapula) from the true 3D computed tomography scan served as controls. Glenoid version and inclination measurements from each group were blinded and reviewed.


Results
In 65% (Automated) and 45% (Landmark) of cases, either inclination or version varied by 5° or more versus 3D printed scapula. Significant variability in version differences compared to the scapula group existed (p = 0.007). Glenoid version from the Scapula = 13.0° ± 10.6°, Automated = 15.0° ± 13.9°, and Landmark = 12.2° ± 7.8°. Inclination from Scapula = 5.4° ± 7.9°, Automated = 6.1° ± 12.6°, and Landmark = 6.2° ± 9.1°.


Discussion
A high percentage of cases showed discrepancies in glenoid inclination and version values from both techniques. Surgeons should be aware that regardless of software technique, there is variability compared to measurements from a control 3D computed tomography printed scapula.
['Shah|Sarav S|SS|https://orcid.org/0000-0002-7656-8482', 'Sahota|Shawn|S|', 'Denard|Patrick J|PJ|', 'Provencher|Matthew T|MT|', 'Parsons|Bradford O|BO|', 'Hartzler|Robert U|RU|', 'Dines|Joshua S|JS|']
Total shoulder arthroplasty preoperative planning glenoid version glenoid inclination patient-specific instrumentation three-dimensional analysis