Does Relative Femoral and Tibial Component Size Influence Revision Risk Following Primary Total Knee Arthroplasty?

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Arthroplasty Research

Background:

• Total knee arthroplasty (TKA) component sizing recommendations are common.
• Limited research exists on the impact of relative femoral and tibial component size on TKA revision rates.

Purpose of the Study:

• To investigate the association between matched and unmatched femoral and tibial component sizes and revision rates in primary TKA.
• To determine specific revision reasons (infection, loosening, instability, etc.) linked to component size mismatch.

Main Methods:

• Analysis of 86,584 primary, cruciate-retaining TKA procedures from the Australian Orthopaedic Association National Joint Replacement Registry.
• Comparison of all-cause revision rates between matched (femur size = tibia size) and unmatched (femur size ≠ tibia size) component combinations.
• Sub-analysis of unmatched procedures based on whether femoral size was greater than or less than tibial size.

Main Results:

• Unmatched component combinations showed a higher rate of all-cause revision (HR 1.15) compared to matched combinations.
• Higher revision rates for loosening (HR 1.38) and instability (HR 1.38) were observed in the unmatched group.
• Procedures with femoral size > tibial size had significantly higher rates of all-cause revision (HR 1.52), loosening (HR 3.64), and instability (HR 1.35) compared to matched components.

Conclusions:

• Femoral size greater than tibial size in TKA is associated with increased revision rates for loosening and instability.
• Surgeons must carefully consider relative component sizing during TKA to mitigate revision risks.
• Findings highlight the importance of precise component selection in total knee arthroplasty.