Computed tomography quantification of bone density adjacent to cemented pegged polyethylene glenoid components in shoulder arthroplasty.

BACKGROUND: Cemented polyethylene devices are the prostheses implanted more frequently, but there is no agreement on the optimal glenoid component design. In this study, bone mineral density (BMD) adjacent to cemented all-polyethylene glenoid components was assessed to gain insights into the characteristics of glenoid bone as a potential risk factor implicated in the failure of shoulder arthroplasty. PATIENTS AND METHODS: Twenty-two subjects were examined at an average follow-up of 31 months using the Constant-Murley score (CS) and multi-detector computed tomography. BMD was measured in 5 regions of interest (ROIs) at the sites where radiolucent lines are usually detected. BMD differences among the ROIs were tested. The relationship between BMD and a number of variables (CS subscores, age, gender, follow-up duration) was explored.
RESULTS: There was a significant increase in CS scores (p<0.05). Significantly different BMD (p=0.0039) was found in the 5 ROIs, especially between ROIs 2 and 5 (p=0.016, Bonferroni's test) and between ROIs 3 and 5 (p=0.005, Bonferroni's test). BMD was lower in ROI 1 than ROI 3 and in ROI 2 than ROI 4, but the difference was not significant. DISCUSSION: The heterogeneous BMD distribution may be related to: (1) an interindividual variability in glenoid BMD; (2) the fixation technique; or (3) the different bone response to eccentric loading of the prosthetic head on the glenoid component.
CONCLUSIONS: BMD analysis may contribute to extent our knowledge on glenoid component loosening and encourage further techniques of glenoid fixation.