This RSA study compared early migration of cemented and uncemented tibial components in 360 primary TKAs. The central question: should the same migration thresholds apply to both fixation types when predicting long-term loosening?
The two benchmarks every resident should know for tibial component RSA migration — Ryd's 0.2 mm change threshold and Pijls' 0.5 mm 1-year threshold — were both derived from datasets that mixed cemented and uncemented implants together.
This study shows that applying the 1-year threshold uniformly is problematic: uncemented components consistently exceed 0.5 mm at 1 year, yet stabilize at the same rate as cemented components thereafter. Labeling every uncemented design 'at risk' based on 1-year data alone overstates early failure risk and could inappropriately discourage use in young, active patients where durability matters most.
The 1-to-2-year change metric, by contrast, held up equally well for both fixation types and remains the more reliable predictor.
Within the uncemented group, implant design matters: the TM Modular performed substantially worse than the TM Monoblock, and this distinction has clinical consequences — a similar trabecular metal modular tibial plate was recalled by the FDA in 2015 for increased loosening complaints.
This RSA study compared early migration of cemented and uncemented tibial components in 360 primary TKAs. The central question: should the same migration thresholds apply to both fixation types when predicting long-term loosening?
The two benchmarks every resident should know for tibial component RSA migration — Ryd's 0.2 mm change threshold and Pijls' 0.5 mm 1-year threshold — were both derived from datasets that mixed cemented and uncemented implants together.
This study shows that applying the 1-year threshold uniformly is problematic: uncemented components consistently exceed 0.5 mm at 1 year, yet stabilize at the same rate as cemented components thereafter. Labeling every uncemented design 'at risk' based on 1-year data alone overstates early failure risk and could inappropriately discourage use in young, active patients where durability matters most.
The 1-to-2-year change metric, by contrast, held up equally well for both fixation types and remains the more reliable predictor.
Within the uncemented group, implant design matters: the TM Modular performed substantially worse than the TM Monoblock, and this distinction has clinical consequences — a similar trabecular metal modular tibial plate was recalled by the FDA in 2015 for increased loosening complaints.