Comparison of periprosthetic radiographic bone density between cruciate-retaining and posterior-stabilized designs in cementless total knee arthroplasty

Purpose: Cementless total knee arthroplasty (TKA) avoids cement-related complications and has demonstrated high implant survival rates. However, post-operative periprosthetic bone resorption may increase the risk of implant migration. The aim of this study was to compare periprosthetic radiographic bone density changes between cruciate-retaining (CR) and posterior-stabilized (PS) cementless TKA. Methods: A total of 62 knees that underwent cementless TKA between June 2017 and December 2023 were retrospectively analyzed. Post-operative range of motion (ROM) and 2011 Knee Society Score (KSS) were evaluated and compared between the CR and PS groups. Periprosthetic radiographic bone density around the tibial component was assessed by measuring the intensity of five predefined regions of interest (ROIs) on radiographic images using ImageJ software immediately after surgery and at 6 and 12 months post-operatively. Results: Of the 62 knees, 32 received the CR design and 30 received the PS design. There were no significant differences in post-operative ROM or 2011 KSS between the CR and PS groups. At 12 months, the PS group had significantly lower relative brightness values in all ROIs compared with the CR group (p < 0.05). Multiple regression analysis revealed that only implant design influenced periprosthetic radiographic bone density loss across all ROIs. Conclusion: Compared with CR cementless TKA, PS cementless TKA was associated with greater periprosthetic radiographic bone density loss. These findings suggest that careful pre-operative assessment of bone mineral density and long-term monitoring may be particularly important when considering cementless PS fixation.