|Beitragstitel||Comparative analysis of Friedman's and the Vault measurement methods for glenoid version according to CT scan slice height and angulation|
Introduction: Most glenoid version measurement methods have been validated on 3D-corrected axial CT slices at the mid-glenoid. This is not necessarly applicable for reverse arthroplasty where the baseplate is usually aligned with the lower-glenoid, and no study has yet analysed variation of the vault according to slice height and angulation. The aim of this study was to analyse variation of glenoid vault compared to Friedman’s angle according to different CT scan slice height and angulation.
Methods: 60 consecutive right shoulder CT scans were retrieved from a hospital imaging database and were reconstructed in the plane of the scapula. 7 axial slices of different height (mid-, lower-, upper-glenoid), and coronal angulation (-20 to +20°) were then selected, and measures were carried out by 3 observers. Intra- and inter-observer reliability was checked with Bland-Altman.
Results: Mid-glenoid mean version was -7.9° (±5,0, range -9.2 to -6.6) and -2.0° (±4.7, range -3.2 to -0.8) according to the vault and Friedman’s angle, respectively. For both methods, decreasing slice height or angulation didn't affect version. The vault was however significantly more anteverted when increasing slice height (+12.1°, range 10.5 to 13.6, p<0.001), or angulation (+10.3°, range 8.98 to 11.7, p<0.001). Both intra- and inter-observer reliability were higher using Friedman’s angle (P<0.008).
Conclusion: Version at the mid- and lower- glenoid are similar using either method. However, version relative to the vault shows less reliability and more variability to slice height or angulation. Yet, as it significantly differs from Friedman's angle, it should still be used in situations where maximum bone purchase is sought with glenoid implants. For any other situation, Friedman's method remains recommended.