Stress shielding in total knee replacements: Comparative analysis between titanium and all-polyethylene bases at 10 years follow-up.

Objective: The aim of this retrospective study was to assess bone resorption due to stress shielding in total knee replacement (TKR), comparing titanium bases (TiB) versus all polyethylene bases (APB), analyzing its incidence, progression and mechanical consequences after 10 years of follow-up.

Methods: We evaluated two groups of patients undergoing TKR, one treated with TiB and the other with APB, operated consecutively between 2004 and 2009 with a diagnosis of idiopathic gonarthrosis and a minimum of 10 years of follow-up. Deen's radiographical method was used to assess tibial bone resorption. We assessed its incidence, progression, relationship with the femoro-tibial and prosthetic alignment, clinical outcomes and mechanical loosening.

Results: Eighty-six patients were treated with TiB and 80 with APB with a median follow-up of 11 (range 10-15) years. The bone resorption rate in TiB was 24.41% and in APB was 1.25% (p < 0.0001). The type 2 of Deen's classification was the most frequently observed. Bone resorption was strongly correlated with preoperative varus femoro-tibial alignment and varus placement of the tibial component, also showing a significant association with postoperative femoro-tibial alignment correction (p 0.009). We observed no significant differences in functional scores or revision rates due to mechanical loosening after 10 years of follow-up between the groups.

Conclusion: Titanium tibial bases in TKR showed a significantly higher incidence of medial tibia resorption compared to all-polyethylene bases. Our results suggest that bone resorption does not influence long-term mechanical loosening.