Managing bone defects in primary total knee arthroplasty: options and current trends
Abstract
A strategic algorithmic approach to tibial and femoral bone loss in primary TKA using the AORI classification. The review defines the hierarchy of reconstruction from cement augmentation to porous tantalum cones and metaphyseal sleeves.
The AORI Defect Management Algorithm
Key Finding
"Metaphyseal sleeves achieve 100% implant survival and osseointegration at mean 79-month follow-up for severe AORI Type 3 defects."
Background: Significant bone loss, particularly on the posteromedial tibial plateau, compromises the bone-implant interface in end-stage osteoarthritis. Without a structured protocol to address defects ranging from minor erosion to severe metaphyseal cavitary loss, surgeons risk component malalignment and early aseptic loosening.
Methods: The authors delineate management protocols based on the Anderson Orthopaedic Research Institute (AORI) classification (Types 1, 2A/B, and 3). Treatment modalities evaluated include cement augmentation, structural allografts, metal augments, porous tantalum cones, and titanium metaphyseal sleeves. Efficacy is stratified by patient demand (young/active vs. elderly) and defect magnitude.
Results: AORI Type 1 defects (< 10mm) are effectively managed with cement and screws; non-progressive radiolucency is common but failure is rare. For AORI Type 2 defects (10-20mm), metal augments are superior in low-demand patients, providing immediate rigid support. For severe Type 2B/3 defects (> 20mm), porous tantalum cones demonstrate excellent osseointegration (KSS 94.6 at 3.5 years). Metaphyseal sleeves utilized in post-traumatic cases yielded a 100% survival rate with significant functional improvement (KSS 29 to 78).
Conclusion: Reconstruction must be biologically matched to the patient: structural grafts are preferred for young, active patients to preserve bone stock, while metal augments and porous cones/sleeves provide definitive, durable fixation for elderly patients or massive metaphyseal deficiencies.