KSSTA - 2026-08-17 - Journal Article
A new cementless tibial baseplate in kinematically aligned total knee arthroplasty has low migration and stabilizes at 3 months: A cohort study using radiostereometric analysis.
Monteiro R, Mohammadi A, Nedopil AJ, Howell SM, Hull ML
Topics
Key Takeaway
A new cementless tibial baseplate in KA-TKA achieved mean 6-month MTPM of 0.93 mm, significantly below the 1.15 mm RSA stability threshold predictive of low long-term loosening risk (p=0.015), with stabilization by 3 months.
Summary Depth
Choose how much analysis to show on this article page.
Summary
This study evaluated early fixation stability of a new cementless tibial baseplate in KA-TKA using model-based RSA in 45 patients, 38% of whom required a tibial recut. Mean 6-month MTPM was 0.93 mm, significantly below the validated 1.15 mm threshold (p=0.015), with equivalence analysis confirming stability by 3 months. Varus tibial alignment (MPTA), limb alignment (HKAA), and tibial recut status showed no significant correlation with migration.
Key Limitation
Six-month RSA follow-up is insufficient to confirm long-term implant survival; the validated 1.15 mm threshold predicts but does not guarantee freedom from late aseptic loosening.
Original Abstract
PURPOSE
Introduction of new components in total knee arthroplasty (TKA) should be assessed for long-term stability. The primary objective was to determine whether migration of a new cementless tibial baseplate in kinematically aligned (KA) TKA is below the 6-month threshold where baseplates have a low incidence of long-term loosening. Other objectives were to determine when stability occurred, whether stability was associated with varus angles in knee and limb alignments, and whether a recut of the tibia affected migration.
METHODS
New cementless components were implanted in 45 patients, of which 38% had a tibial recut. Baseplate migration was assessed using model-based radiostereometric analysis with radiographs obtained post-operatively and at 6 weeks, 3 months and 6 months. Mean maximum total point motion (MTPM) at 6 months was compared to a 6-month threshold where baseplates have low incidence of long-term loosening. An equivalence analysis determined when stability occurred. Correlation analyses related MTPM at 6 months to the medial proximal tibial angle (MPTA) and the hip-knee-ankle angle (HKAA). A two-sample t test determined whether mean MTPM differed between recut and non-recut groups.
RESULTS
Mean 6-month MTPM of 0.93 mm was significantly below the 6-month stability threshold of 1.15 mm (p = 0.015), and stability was achieved by 3 months. There was no significant relationship between MTPM and MPTA (ρ = 0.050, p = 0.77) or HKAA (ρ = 0.060, p = 0.72). Mean MTPM did not differ between recut (0.85 ± 0.56 mm) and non-recut (0.97 ± 0.64 mm) groups (p = 0.57).
CONCLUSION
The new cementless tibial baseplate has migration significantly below the 6-month threshold where baseplates have a low incidence of long-term loosening and migration stabilizes early at 3 months. Varus alignment of the baseplate and the limb as well as tibial recuts were not associated with increased migration.
LEVEL OF EVIDENCE
N/A.