Modern Total Knee Arthroplasty Designs: Are we Improving Outcomes?

Total knee arthroplasty (TKA) continues to be very effective in providing pain relief and improved function since the early 1970s when Insall and Coventry introduced the total condylar prosthesis. In this timeframe, the number of primary total knee replacements performed in the United States outside from Federal Hospitals reached 719,000 in 2010 [1]. If the number of TKA performed continues to growth at the current rate, the demand for primary TKA is projected to reach 3.48 million procedures by 2030 [2]. Although the results of classic TKA designs have been previously reported as excellent with a 93% survival rate at 15 years [3], recent studies focusing on patient satisfaction as the primary outcome measure have been less encouraging, with the Ontario Joint Registry showing that only 70% of patients met their expectations one year after TKA [4]. This “un-satisfaction” rate is also higher in younger individuals requiring early intervention because of severe knee osteoarthritis: Parvizi et al. [5] reported only 66% of young patients (< 60 years) indicating their knees feeling normal at 1 to 4 years after primary TKA. Because of these reports, in recent years, several manufacturers have implemented specific design modifications in the attempt to improve patient outcomes: between those modifications, highflexion femoral components and increased modularity (femoral, tibial, polyethylene thickness and patellar sizes) have captured particular attentions by many designers. In this editorial note, we evaluate the evidence concerning the introduction of these two device technologies (high-flexion femoral components and increased implants modularity) in primary TKA. High-Flexion Designs