Hypothesis: Navigation can improve accuracy of placement of the glenoid component in reversed shoulder arthroplasty.
Material and methods: A glenoid component of a reversed shoulder prosthesis was implanted in 14 paired scapulohumeral cadaver specimens. Seven procedures with standard instrumentation were compared with 7 procedures using navigation. The intraoperative goal was to place the component centrally in the glenoid in the axial plane and 10 degrees inferiorly tilted in the frontal plane. Glenoid component version and tilt and screw placement were studied using CT scan and macroscopic dissection.
Results: The mean version of the glenoid component in the standard instrumentation group was 8.7 degrees of anteversion, compared with 3.1 degrees of anteversion in the navigated group. The mean tilt of the glenoid component was 0.9 degrees in the standard group and 5.4 degrees of inferior tilt in the navigated group. Using navigation, the range of error for version was 8 degrees (SD 3.3 degrees) compared to 12 degrees (SD 4.1 degrees) in controls. For tilt, the range of error was 8 degrees (SD 3.6 degrees) in navigated specimens and 16 degrees (SD 6.0 degrees) for controls. In the control group, there were no perforations of the central peg, but 1 inferior screw and 4 superior screws were malpositioned. In the navigation group, no central peg perforated, all inferior screws were correctly positioned, and 2 superior screws were malpositioned.
Conclusion: Computer navigation was more accurate and more precise than standard instrumentation in its placement of the glenoid component in reversed shoulder arthroplasty.
Level of evidence: Basic Science Study. (C) 2011 Journal of Shoulder and Elbow Surgery Board of Trustees.