Precision of Periprosthetic Bone Mineral Density Around Total Ankle Replacement Using Dual-Energy X-ray Absorptiometry

Purpose: Joint prosthesis survival is associated with the quality of surrounding bone. Dual-energy X-ray absorptiometry (DXA) is capable of evaluating areal bone mineral density (BMD) around different prosthetic implants, but no studies have evaluated periprosthetic bone around total ankle replacement (TAR). Our aim was to determine the precision of DXA periprosthetic BMD around TAR.

Methods and Materials: Short-term precision was evaluated on 15 consecutive patients. Each ankle was scanned three times both in the anteroposterior (AP) and mediolateral (ML) views with a dedicated patient-positioning protocol. Up to four squared regions of interest (ROIs) were placed in the periprosthetic bone around tibial and talar implants, with an additional ROI to include the calcaneal body in the ML scan. Coefficient of variation (CoV%) and least significant change (LSC) were calculated according to the International Society for Clinical Densitometry.

Results: The ML projection showed lower mean CoV values compared with the AP projection, with an average precision error of 2.21% (ML scan) compared with 3.34% (AP scan). Overall, the lowest precision error was found at both “global” ROIs (CoV: 1.25% on AP; CoV: 1.3% on ML). The highest CoV value on AP was found at the medial aspect of the talar side (ROI: 3; CoV: 4.89%); on ML the highest CoV value was found on the posterior aspect of the talar side (ROI: 2; CoV: 2.99%).

Conclusion: We found very good reproducibility BMD values of periprosthetic bone around TAR that were comparable or even better compared with other studies that evaluated periprosthetic BMD around different prosthetic implants. DXA can be used to precisely monitor bone density around ankle prostheses. Further long-term longitudinal studies are required to assess the clinical utility of such measurements.