Central cone design demonstrates greater micromotion compared to keel design in cementless tibial baseplates: A biomechanical analysis

Abstract

PurposeThe purpose of this study was to compare micromotion of two new cementless tibial baseplates to a cementless design with well‐published clinical success.MethodsThree cementless tibial baseplate designs (fixed‐bearing [FB] with keel and cruciform pegs, rotating‐platform with porous central cone and pegs, FB with cruciform keel and scalloped pegs) were evaluated on sawbone models. Loading was applied to the baseplate at a rate of 1 Hz for 10,000 cycles, which represents 6–8 weeks of stair descent. This time frame also represents the approximate time length for the induction of biologic fixation of cementless implants. Compressive and shear micromotion at the sawbone–implant interface were measured.ResultsAt the end of the loading protocol, the central cone rotating‐platform design exhibited greater micromotion at the anterior (p < 0.001), posterior (p < 0.001) and medial locations (p = 0.049) compared to the other two implants. The central cone design also exhibited greater translational micromotion in the sagittal plane at the medial (p = 0.001) and lateral locations (p = 0.034) and in the coronal plane anteriorly (p = 0.007).ConclusionThe cementless central cone rotating‐platform baseplate demonstrated greater vertical and translational micromotion compared to the two FB baseplates with a keel underloading. This may indicate lower initial mechanical stability in implants without a keel, which possibly affects osseointegration. The implication of this is yet unknown and requires further long‐term clinical follow‐up to correlate these laboratory findings.Level of EvidenceV (biomechanical study).