Abstract
Background: Glenoid inclination influences glenohumeral biomechanics. Superior inclination has been associated with superior humeral head migration and the rocking-horse phenomenon in anatomic total shoulder arthroplasty (aTSA). While surgical correction of glenoid inclination has been extensively investigated, it remains unknown whether commercially available glenoid components incorporate intrinsic inclination as a design characteristic.
Purpose: To quantify the intrinsic inclination of contemporary glenoid components used in aTSA.
Methods: A cross-sectional three-dimensional geometric analysis was performed using a manufacturer-independent preoperative planning platform. All commercially available anatomic glenoid components contained within the mediCAD® 3D Shoulder implant library were evaluated. Glenoid component inclination was measured in the central coronal plane as the angle between the articular surface and the vertical reference plane of the virtual three-dimensional environment using a standardized measurement protocol. Additionally, implant height was measured for the available sizes of each system. Measurements were performed independently by two observers, and intra- and interobserver reliability was assessed using the intraclass correlation coefficient (ICC).
Results: A total of 111 glenoid components representing 26 implant systems from 14 manufacturers were analyzed. The intra- and interobserver reliability for the inclination parameter was excellent (ICC = 0.89–0.99). Twenty of the 26 systems (76.9%) demonstrated neutral intrinsic inclination (0°), whereas six systems (23.1%) exhibited non-neutral inclination ranging from +1.9° (superior inclination) to −4.4° (inferior inclination). Within individual implant systems, inclination showed only minor variation across component sizes.
Conclusion: Contemporary glenoid component designs differ only slightly in intrinsic inclination, as most systems exhibit a neutral (0°) inclination. Given the usual superior native glenoid inclination in osteoarthritic shoulders, neutral implant geometry alone may not always achieve the desired postoperative orientation without corrective reaming.