Increasing hydroxyapatite incorporation into poly(methylmethacrylate) cement increases osteoblast adhesion and response

Poly(methylmethacrylate) (PMMA) is the current standard for cement held prostheses. It forms a strong bond with the implant, but the bond between the cement and the bone is considered to be weak, with fibroblastic cells observed at the implant site, rather than direct bone contact, a contributing factor leading to implant failure. Incorporation of hydroxyapatite (HA) increases the biological response to the cement from tissue around the implant site, thus giving increased bone apposition. In this study, PMMA discs with 0, 4.6 and 8.8 vol% HA were examined. Primary human osteoblast-like cells (HOBs) were used for the biological evaluation of the response to the cements in vitro. Morphology was observed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Measurement of tritiated thymidine (3H-TdR) incorporation and alkaline phosphatase (ALP) activity were used to assess proliferation and differentiation. A synergy between increasing focal contact formation, cytoskeletal organisation, cell proliferation and expression of phenotype was observed with increasing HA volume. Preferential anchorage of HOBs to HA rather than PMMA was a prominent observation.