Better survival of total knee replacement in patients older than 70 years: a prospective study with 8 to 12 years follow-up.

Background: Modern knee designs have popularized its use in younger patients due to its better performance. There remains uncertainty whether higher demands of these patients can affect implant survivorship.
Purpose: To assess whether modern knee designs have provided similar results in patients younger than 70 years versus older patients.
Methods: We included 203 consecutive patients (236 knees) who underwent knee replacement for osteoarthritis with a mean follow-up of 11.4 years (range: 8.8 to 12). The mean age was 70 years (range: 31 to 85). Knee replacements were stratified into two groups: 109 were younger than 70 years and 127 were older than 70 years (70 years of age is the mandatory retirement age).
Results: There were no significant pre-operative differences between groups with regards to knee alignment, alpha or beta angles, knee score or function score. Fourteen implants were radiographically loose at last follow up visit. Groups were matched in terms of demographic data. We found that patients older than 70 years had significantly better mean survivorship at 12 years. (97% vs. 88%; P=0.010). Patients under 70 years presented with a higher rate of polyethylene wear which was further associated with radiolucent lines in the femur and tibia as well as the presence of osteolysis. There was also an association between migration and presence of osteolysis.
Conclusions: Patients over 70 years old undergoing cemented total knee replacement for osteoarthritis showed better implant survivorship versus patients under 70 years old.