Patient mortality exceeds implant revision risk with equivalent survival following unicompartmental versus total knee arthroplasty in octogenarians

Background: While traditional surgical decision-making emphasizes long-term implant survivorship for octogenarians knee reconstruction, this paradigm may be inappropriate when patient mortality risk substantially exceeds revision risk. This study compared mid-term mortality between unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) in octogenarians, hypothesizing that implant type would not significantly influence patient survival. Methods: A retrospective cohort study was conducted on 238 consecutive octogenarian patients (age ≥ 80 years) who underwent primary knee arthroplasty at a single tertiary orthopaedic center between January 2018 and December 2020. Patients with revision arthroplasty, fracture, tumor, inflammatory arthropathy, or incomplete data were excluded. The primary outcome was all-cause mortality at minimum 5-year follow-up. Secondary outcomes included age-stratified mortality (80-84, 85-89, ≥ 90 years) and identification of independent mortality predictors. Statistical analyses included independent t-tests, chi-square/Fisher's exact tests, standardized mean differences, and multivariable logistic regression adjusting for age, follow-up duration, and registry year. Results: Of 238 patients, 185 (77.7%) underwent TKA and 53 (22.3%) underwent UKA. Overall mortality was 35.3% (84/238): 33.5% in TKA versus 41.5% in UKA (OR = 1.41, 95% CI: 0.75-2.63, p = 0.329). Age-stratified mortality showed no significant differences: 80-84 years (31.2% TKA vs. 37.2% UKA, p = 0.467), 85-89 years (42.3% vs. 50.0%, p = 1.000). Multivariable analysis identified age as the only significant mortality predictor (adjusted OR = 1.16 per year, 95% CI: 1.03-1.32, p = 0.013), while implant type was not associated with mortality (adjusted OR = 1.40, 95% CI: 0.72-2.73, p = 0.319). Patient mortality exceeded registry-reported revision rates 3-5 fold. Conclusions: In octogenarians, patient mortality substantially exceeds implant revision risk, with no significant difference between UKA and TKA. Surgeons should prioritize patient-specific clinical indications over theoretical implant durability concerns when selecting procedures in this population. Level of evidence: III.