THE EFFECT OF THE MEDIAL COLLAR IN TOTAL HIP-ARTHROPLASTY WITH POROUS-COATED COMPONENTS INSERTED WITHOUT CEMENT - AN IN-VIVO CANINE STUDY

We performed an in vivo study in a canine model to compare the results of the use of a porous-coated collared femoral component with those of the use of a porous-coated collarless femoral component in total hip arthroplasties without cement. Our study focused on the comparative proximal strain pattern, bone ingrowth, and cortical porosity of the two types of prostheses. We used a trochanteric mire marker to measure subsidence. The use of the limb was assessed with gait analysis. Twelve weeks after the operation, the collarless components had significantly greater bone ingrowth proximally (p = 0.003) and were associated with significantly lower cortical porosity (p = 0.006). There were no differences between the groups with regard to either axial or hoop strain. While the group that had a collarless prosthesis had significantly less proximal-medial radiolucency (p = 0.03), there were no differences between the groups with regard to subsidence. CLINICAL RELEVANCE: The present study demonstrated greater bone ingrowth and less cortical porosity with the use of collarless prostheses. This may be related to the ability of these components to settle under repeated physiological loading during the early postoperative recovery period. In doing so, the prosthesis may maintain a more optimum fit and thus, in the long term, may exhibit less relative motion with respect to the femoral canal. The amount of this subsidence appears to be slight and should not measurably alter the position of the femoral component.