Femoral Component Loosening is the Predominant Mode of Early Failure in Contemporary Cementless Total Knee Arthroplasty

Abstract

Background: Cementless total knee arthroplasty (TKA) has seen a resurgence due to advancements in tibial implant fixation. However, most femoral components remained unchanged, typically being cobalt chromium with nonenhanced porous ingrowth surfaces. The literature is sparse concerning radiographic and clinical outcomes related to the femoral component in uncemented designs. Methods: This retrospective, single-center study included 268 cementless TKA. Radiolucent lines were evaluated using the Knee Society Radiographic Evaluation and Scoring System. Clinical outcomes were measured using the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR). Linear regression modeling was performed to analyze the relationship between KOOS JR and the presence of radiolucent lines. Results: Radiolucent lines were significantly more prevalent at the femoral bone–implant interface (177 of 268; 66.0%) compared to the tibial bone–implant interface (114 of 268; 42.5%) (P < .0001). There was no significant correlation between the presence of radiolucent lines and KOOS JR. Aseptic loosening was identified as the leading cause of revision surgery (6 of 268; 2.2%), with femoral component loosening accounting for 5 out of 6 aseptic revisions. Conclusions: Femoral radiolucent lines were common in this study. Although femoral component loosening was the most frequent cause of revision, these lines did not generally necessitate revision or correlate with poorer patient-reported outcomes. Thus, radiolucent lines do not inherently indicate clinical failure or reduced patient satisfaction. There was only one case of tibial component loosening, suggesting that the current design features achieve robust fixation, while the prevalence of femoral radiolucent lines and failures suggests that further enhancements to the femoral implant may be necessary.

Keywords

• Total knee arthroplasty
• Uncemented
• Cementless
• Femoral component
• Aseptic loosening
• Radiolucent lines