Primary stability of tibial plateaus under dynamic compression-shear loading in human tibiae – Influence of keel length, cementation area and tibial stem

Abstract

The objective of our study was to evaluate the impact of the tibial keel & stem length in surface cementation, of a full cemented keel and of an additional tibial stem on the primary stability of a posterior stabilised tibial plateau (VEGA® System Aesculap Tuttlingen, Germany) under dynamic compression-shear loading conditions in human tibiae.We performed the cemented tibial plateau implantations on 24 fresh-frozen human tibiae of a mean donor age of 70.7years (range 47–97). The tibiae were divided into four groups of matched pairs based on comparable trabecular bone mineral density. To assess the primary stability under dynamic compression shear conditions, a 3D migration analysis of the tibial component relative to the bone based on displacements and deformations and an evaluation of the cement layer including penetration was performed by CT-based 3D segmentation.Within the tested implant fixation principles the mean load to failure of a 28mm keel and a 12mm stem (40mm) was 4700±1149N and of a 28mm keel length was 4560±1429N (p=0.996), whereas the mean load to failure was 4920±691N in full cementation (p=0.986) and 5580±502N with additional stem (p=0.537), with no significant differences regarding the dynamic primary stability under dynamic compression-shear test conditions.From our observations, we conclude that there is no significant difference between a 40mm and a 28mm tibial keel & stem length and also between a surface and a full cementation in the effect on the primary stability of a posterior stabilised tibial plateau, in terms of failure load, migration characteristics and cement layer thickness including the penetration into the trabecular bone.