Bone Cell Adhesion: An Important Aspect Of Cell Biomechanics In The Development Of Surface Modifications For Orthopaedic Implants

Most revisions of total joint replacements are due to implant loosening, which is mainly caused by wear particles ("wear disease") and inadequate primary implant stability. The optimised integration of cementless total hip and knee endoprostheses into the bone stock is the most adequate approach to achieve secondary implant stability and to prevent implant loosening. Secondary stability is characterized by bone ingrowth of the implant and decreases the amount of relative implant motion between the implant and bone stock. It has also been suggested that prostheses which are fully occupied by bone cells are less susceptible to infection. The economic impact of implant loosening is immense, hence orthopaedic implant manufactures refine their products continuously.Many technical developments have improved the survival rate of endoprosthetic implants. Modem materials and surface modifications such as coatings help to reduce wear rates, promote cell ongrowth or prevent infections. The cell adhesion of bone cells onto implant surfaces has not been thoroughly investigated so far. However, different methods to measure cell adhesion have been described. Some workgroups investigate short-term adhesion or proliferation of bone cells on implant materials in-vitro, but little is known about the long-term adhesion. Proliferation or short-term adhesion cannot predict how strong the bonding between bone and implant will be. In most cases, cost intensive animal studies have to be performed in order to gain expressive data. Hence, it is important to assess the bone cell adhesion forces in an adequate experimental setup in-vitro.The exploration of bone cell adhesion on surfaces of orthopaedic implants encourages the development of bio-compatible, bio-active and anti-infectious surfaces. We have developed a test device, based on the spinning disc principle, which allows quantitative measurements of osteoblastic cells on implant surfaces. First results show differences in adhesion forces depending on the substrate. In future assessments different bio-active and anti-infectious surface modifications will be analyzed regarding bone cell adhesion prior to animal studies.