Effect of activity level after a posterior-stabilized TKA on the relative bone mineral density measured on standard radiographs in periprosthetic tibial bone: a five-year follow-up study

Abstract

Background: The aim of this study was to evaluate the effect of activity level after a posterior-stabilized TKA on the relative bone mineral density measured on standard radiographs in periprosthetic tibial bone. Methods: A retrospective review identified 121 patients (121 knees，19 men/102 women) that underwent PS TKA with 5-year follow-up. Patients activity level was evaluated by University of California Los Angeles (UCLA) activity score, and the relative BMD in periprosthetic tibial bone was measured by ImageJ software on anteroposterior X-ray images. Clinical assessments included Western Ontario and McMaster Universities (WOMAC), Knee Society, VAS score and UCLA activity score. Nonlinear regression analysis was used to assess the impact of activity levels on periprosthesis bone density.Results: Activity level significantly affected rBMD in the proximal tibia, with the smallest reduction in rBMD observed with moderate activity. The difference in rBMD% between the lateral and medial metaphysis was significant. The regions with a significant difference in rBMD% between the lateral and medial metaphysis were closest to the base plate of the prosthesis. The lateral and medial regions closest to the stem of the prosthesis showed no significant difference in rBMD%.Conclusions: We found that activity level had a significant effect on radiographic measurements of BMD at 1 and 3 years but not at 5 years and moderate activity was associated with a minimal reduction in proximal tibial BMD.