Obesity and Total Knee Arthroplasty Revisited: Minimal Impact on Loosening and Mechanical Failure in the Modern Era.
Academic Article
Overview
abstract
INTRODUCTION: Obesity has historically been considered a risk factor for mechanical failure after total knee arthroplasty (TKA), particularly tibial aseptic loosening. However, advances in implant design, fixation strategies, and perioperative practices may have mitigated these risks. This study evaluated the association between obesity severity and mechanical failure in a contemporary TKA cohort, while examining implant- and patient-related factors associated with loosening and revision. METHODS: We retrospectively reviewed all primary TKAs performed in patients who had a body mass index (BMI) ≥ 30 at a single high-volume tertiary center from 2016 to 2022. Postoperative events were captured through 2024, providing 2.5 to nine years of potential follow-up. The primary outcomes were aseptic mechanical loosening of any component and tibial aseptic loosening specifically. Among 7,372 TKAs, 185 revisions occurred (2.5%), including 139 for aseptic mechanical loosening (1.9%) and 21 for tibial loosening (0.3%). Multivariable Cox proportional hazards models assessed associations between World Health Organization (WHO) obesity class and each endpoint, adjusting for age, sex, fixation method, tibial baseplate size, stem extension use, and recalled implant status. RESULTS: Obesity class was not associated with increased risk of revision, overall aseptic loosening, or tibial loosening. Increasing age was associated with lower risk of revision (hazard ratio (HR) 0.97/year, P = 0.006) and tibial loosening (HR 0.95/year, P = 0.031). A larger tibial baseplate size was associated with reduced risk of tibial loosening (HR 0.58 per unit increase in normalized size, P = 0.043). Fixation method, stem use, and recalled implant status were not independently associated with loosening. CONCLUSION: In this large contemporary cohort of obese TKA patients, obesity class was not associated with increased risk of mechanical loosening or revision, and tibial failures were uniformly rare. These findings suggest modern surgical practices and implant designs may have mitigated traditional obesity-related risks and that fixation and implant decisions should be guided by patient- and implant-specific factors rather than BMI alone.
