Retrospective study of 3,152 AGC total knee arthroplasties using a nonmodular metal-backed cemented tibial component. Analyzed 41 tibial revisions (1.3%) to identify what failure mechanisms arise when polyethylene wear is effectively eliminated by implant design. The central question: if PE wear is not the failure mode, what actually causes these knees to fail?
The tibial cut is the most controllable variable in TKA longevity, and this paper puts hard numbers on why it matters. Varus beyond 3° doesn't linearly increase risk — it multiplies it 17-fold. In an obese patient, the same malalignment becomes a 168-fold increase in failure odds.
When you plan a TKA, let the preoperative deformity tell you which failure mode to guard against. A varus knee demands a precise neutral tibial cut above all else. Medial cancellous overload is the threat. A valgus knee (especially >10-14°) demands aggressive soft-tissue balancing and should make you think about added constraint, because posterolateral subluxation. Not bone collapse. Is what will bring that patient back for revision.
The finding that BMI alone does not predict failure reframes the obesity conversation. The obese patient is not inherently at higher risk. The obese patient with a malpositioned tibial component is. Nail the alignment and the BMI stops mattering.
One nuance worth knowing: correcting overall limb alignment through added femoral valgus partially mitigates tibial varus risk but does not eliminate it. The tibial cut itself must be neutral. Compensatory femoral adjustments are a partial rescue, not a solution.
Retrospective study of 3,152 AGC total knee arthroplasties using a nonmodular metal-backed cemented tibial component. Analyzed 41 tibial revisions (1.3%) to identify what failure mechanisms arise when polyethylene wear is effectively eliminated by implant design. The central question: if PE wear is not the failure mode, what actually causes these knees to fail?
The tibial cut is the most controllable variable in TKA longevity, and this paper puts hard numbers on why it matters. Varus beyond 3° doesn't linearly increase risk — it multiplies it 17-fold. In an obese patient, the same malalignment becomes a 168-fold increase in failure odds.
When you plan a TKA, let the preoperative deformity tell you which failure mode to guard against. A varus knee demands a precise neutral tibial cut above all else. Medial cancellous overload is the threat. A valgus knee (especially >10-14°) demands aggressive soft-tissue balancing and should make you think about added constraint, because posterolateral subluxation. Not bone collapse. Is what will bring that patient back for revision.
The finding that BMI alone does not predict failure reframes the obesity conversation. The obese patient is not inherently at higher risk. The obese patient with a malpositioned tibial component is. Nail the alignment and the BMI stops mattering.
One nuance worth knowing: correcting overall limb alignment through added femoral valgus partially mitigates tibial varus risk but does not eliminate it. The tibial cut itself must be neutral. Compensatory femoral adjustments are a partial rescue, not a solution.