What mechanisms are associated with tibial component failure after kinematically-aligned total knee arthroplasty?

Purpose Eight patients treated with kinematically-aligned (KA) total knee arthroplasty (TKA) presented with tibial component failure. We determined whether radiographic measurements and clinical characteristics are different between patients with and without tibial component failure to identify mechanisms of failure and strategies to reduce the risk. Methods Out of 3,212 primary TKAs (2,725 TKAs with a two-year minimum follow up), of which all were performed with KA, eight patients presented with tibial component failure. Radiographic measurements, clinical characteristics (e.g. age, gender, BMI, etc.), revision surgical records, and Oxford knee scores were compared to control cohort patients matched 1:3. Results Tibial component failure presented at an average of 28 +/- 15 months after primary TKA. Patients with tibial component failure had a 6 kg/m(2) greater body mass index (p = 0.034) and 5A degrees greater posterior slope of the tibia component (p = 0.002) than controls. Final follow-up averaged 56 +/- 19 months after the primary TKA and 28 +/- 24 months after the revision TKA. The final Oxford knee score was 39 +/- 4.6 for patients with tibial component failure and 44 +/- 6.5 for the controls (p = 0.005). Conclusions The incidence of tibial component failure after KA TKA was 0.3% and was caused by posterior subsidence or posterior edge wear and not varus subsidence. The strategy for lowering the risk of tibial component failure when performing KA is to set the tibial component parallel to the flexion-extension plane (slope) and varus-valgus plane of the native joint line.