Attachment of PMMA cement to bone: force measurements in rats

The attachment of an implant material to bone relates to surface roughness and surface chemistry. There is a relatively low chemical bonding strength of so-called bioactive surfaces. Hydroxyapatite interfaces typically have a n interfacial tensile strength of 0.1-1.5 MPa. An attachment force similar to that of bioactive surfaces might also be reached through mechanical inte rlock with ordinary bone cement. This study measured bone-cement interfacia l tensile strength for polished (R-a 0.5 mu m) and regular (R-a 4.8 mu m) v acuum mixed PMMA bone cement. Bone bonding was evaluated by a detachment te st. We used unloaded cement surfaces, which could be detached from the bone . Titanium plates were developed such that a cement fill was contained with in a plate, which was contained within a titanium holder. The cement surfac e came into contact with traumatized bone only, and the rest of the plate h ad no contact with tissue. The cement surface was either polished or left u ntreated after conventional preparation. Four weeks later, the plates were detached from the bone by a perpendicular force. The detaching load of the polished cement surface never exceeded 0.07 MPa, whereas for unpolished cem ent there was a load up to 0.9 MPa. The results suggest that surface irregu larities and microinterlock enable an attachment that can resist tension be tween bone and a cement surface. (C) 1999 Elsevier Science Ltd. All rights reserved.