Safety and utility of computer-aided shoulder arthroplasty

This study evaluated the safety and utility of a novel, image-free, shoulder navigation system in a cadaver and in on initial cohort of shoulder arthroplasty patients. Shoulder arthroplasty was performed on a cadaver and 27 patients using an image-free navigation system (NaviPro (TM); Kinamed Navigation Systems LLC, Camarillo, CA). Optical trackers were attached to the proximal humerus and the coracoid process. Prior to and following humeral head resection, the anatomic neck axis (retroversion, inclination) and humeral head diameter were measured with the navigation system. Native glenoid surface orientation was registered, and a navigation tracker was attached to the glenoid reamer. The navigation system recorded change in inclination and version relative to the native glenoid during reaming. The cadaver results demonstrated that the trackers did not impede surgical performance and that system accuracy was 2.6 degrees +/- 2.5 degrees. In the clinical series, the navigation system reported the anatomic humeral neck measurements (retroversion 30.0 degrees +/- 16.0 degrees; inclination 137.0 degrees +/- 11.7 degrees), the humeral head diameters (major axis 46.2 mm +/- 4.8 mm; minor axis 43.2 mm +/- 3.8 mm), the humeral neck resection angles (retroversion 29.9 degrees +/- 15.1 degrees and inclination 135.6 degrees +/- 9.1 degrees), and glenoid reaming orientation relative to the native glenoid (+3.0 degrees +/- 6.3 degrees of version; -6.7 degrees +/- 4.4 degrees of inclination). This initial clinical experience with computer-aided shoulder navigation demonstrates that the procedure is safe and can provide valuable intraoperative measurements. With an anatomic humeral implant system, the navigation system provides real-time feedback on the humeral resection as it relates to anatomic neck geometry. The system also provides realtime angulation of the glenoid reamer relative to preoperative glenoid deformity.