Similar survival rate but lower functional outcomes following TKA in the elderly people compared to younger patients: analysis of a posterior stabilised implant with minimum 5-year follow-up

Background Literature regarding outcomes in patients over 80 years old after total knee arthroplasty (TKA) is inconsistent. We aimed to compare implant survivorship and functional outcomes between elderly patients (>= 80 years) and younger patients (< 80 years) following TKA, using a single modern posterior-stabilized (PS) prosthetic design. Methods This is a retrospective cohort study of 80 patients over 80 years old who underwent TKA between January 2015 and December 2016, who were compared with younger patients (60-75 years old) operated during the same period. Patients were matched with a ratio of 1:3 based on logistic regression analysis of gender and body mass index. All patients received the same cemented PS prosthesis with a fixed bearing polyethylene insert, with or without patellar resurfacing. Implant survival and patient-reported outcome measurements were compared between the two groups. At last follow-up, data were available for 41 knees in the elderly group (including 17 patients who died before 5-year follow-up) and 123 knees in the younger group. Results Functional results were better at final follow-up in the group < 80 years with a significantly higher Knee Society Function Subscore (88.6 +/- 16.9 vs 79.4 +/- 22.1, p < 0.01), but no significant differences in Knee Subscore and global Knee Society Score (p > 0.05), nor regarding maximum flexion (121 degrees +/- 12 and 117 degrees +/- 13, p = 0.08). The implant survivorship was 100.0% after a mean 64.4-month follow-up (range 60-78), without revision requiring removal of the implant in any group. The survival rate without any reoperation was 97.6% (95% CI 93.0-100.0) in the elderly group and 95.9% (95% CI 92.5-99.5) in the younger group (p = 0.64). Conclusion At a minimum of 5-year follow-up, there was no revision surgery and a very low rate of complications requiring reoperations both in the group over 80 years of age and in the younger population, with the use of a PS prosthesis. The functional results were slightly lower for elderly patients and correlate with the lower functional demands of this population. The indication for TKA, especially with a PS implant, may be encouraged in appropriately selected elderly patients.