Foot and Ankle International - 2026-08-29 - Journal Article
Obesity Is Associated With Earlier Mechanical Failure Following Total Ankle Arthroplasty Independent of Tibial Stem or Keel Augmentation.
Sommi C, Thomas GM, McCahon JAS, Dowd T, Hsu A, Parekh SG, Pedowitz DI
Topics
Key Takeaway
BMI ≥30 independently doubles mechanical failure risk after TAA (HR 2.27) regardless of whether a stemmed or keeled tibial component was used.
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Summary
This study asked whether stemmed or keeled tibial implants mitigate the elevated mechanical failure risk associated with obesity in primary TAA. Among 699 TAAs stratified by BMI (<30 vs ≥30) and implant design (stem/keel vs low-profile), BMI ≥30 carried a 2.27-fold increased hazard of mechanical failure requiring metal component revision (95% CI 1.07–4.81, P=.033). Five-year survivorship was 93.7% for low-profile and 96.1% for stem/keel implants—a non-significant difference—indicating augmented tibial fixation did not offset obesity-related failure risk.
Key Limitation
The subgroup analysis stratified by both BMI and implant type was underpowered—with only 39 total mechanical failures across four subgroups, the study cannot exclude a clinically meaningful protective effect of stem/keel augmentation in obese patients.
Original Abstract
BACKGROUND
Obesity and elevated body mass have been associated with increased rates of aseptic loosening and implant failure following total ankle arthroplasty (TAA). The purpose of this study was to investigate the role for primary stemmed or keeled tibial implants as a protective factor against aseptic loosening in this patient population.
METHODS
We performed a retrospective cohort study of 699 modern primary TAAs with a minimum 2-year follow-up performed at a large academic institution between 2010 and 2023. Patients were stratified by body mass index (BMI <30 vs ≥30) and implant design (stem/keel vs low-profile). The primary outcome was mechanical failure requiring revision of metal components. Secondary outcomes included patient-reported outcomes (FAAM-ADL and VAS). Kaplan-Meier analysis and multivariable cox proportional hazards were used to assess revision risk.
RESULTS
Of 699 primary TAAs, 39 (5.6%) experienced mechanical failure at a mean follow-up of 5.6 years. After adjustment for age, implant type, and subtalar fusion, BMI ≥30 was associated with a greater than 2-fold increased hazard of mechanical failure (HR 2.27, 95% CI 1.07-4.81, P = .033). Kaplan-Meier survivorship was similar for low-profile (93.7%) and stem/keel (96.1%) implants at 5 years. When stratified by both BMI and implant type, with the numbers available, no significant difference could be detected in mechanical failure, time to revision, or patient-reported outcomes were observed ( P > .05). Obese patients had worse preoperative FAAM-ADL and VAS scores but achieved comparable postoperative outcomes.
CONCLUSION
After adjusting for age, implant design, and subtalar fusion, BMI ≥30 was independently associated with a significantly higher hazard of mechanical failure and shorter time to revision. Despite the proposed biomechanical advantages of increased tibial fixation, the stemmed or keeled implants used in this cohort were not associated with improved survivorship or patient-reported outcomes at mid-term follow-up.
LEVEL OF EVIDENCE
Level III, retrospective cohort study.