Initial stability of surface vs. full cemented tibial components under cyclic loading.

BACKGROUND

Total Knee Arthroplasty is a common treatment for end-stage osteoarthritis with excellent long-term survival. However, aseptic loosening of the tibial component remains a concern and may be influenced by cementing technique. Radiostereometric analysis studies indicate that early tibial migration increases the risk for later loosening. There is no consensus regarding how the tibial component should be cemented.

OBJECTIVES

To compare surface cementation (SC) and full cementation (FC) of the tibial component with respect to migration, micromotion, and bonding strength and to assess correlation between cement thickness and implant movement.

METHODS

Using a composite tibia model, we compared SC (n = 5) with FC (n = 5) of the NexGen Stemmed Option tibial baseplate. Groups underwent 20,000 loading cycles at a maximal axial load of 1780 N at a 1 Hz rate. Migration and micromotion were measured with Linear Variable Differential Transformers. Bonding strength was assessed in a push-out test. Parametric statistics were used for group comparisons.

RESULTS

Mean anterior migration was 0.7 µm (SD ± 0.8) for FC and -1.3 µm (±1.5) for SC (p = 0.03). Mean anterior micromotion was 1.1 µm (± 0.8) for FC and 12.3 µm (±7.2) for SC (p = 0.03). Posterior implant movement were similar between groups. The FC-group demonstrated higher mean bonding strength (7655 N ± 1613) compared with SC (4541 N ± 1202) (p = 0.009). Greater anterior cement thickness correlated with reduced micromotion (r = -0.7, p = 0.02).

CONCLUSION

Full cementation resulted in greater anterior stability and bonding strength compared with surface cementation. These findings suggest that full cementation reduces initial movement for NexGen Stemmed Option tibial baseplates.