Bone Abstracts

Hip osteoarthritis is a cause of significant morbidity to people and their canine companions. Medical management is frequently insufficient, leading to surgery to relieve pain and regain mobility. Hip replacements are not without potential complications, including loosening and infection. Currently, there is a focus on uncemented implants to decrease these problems, however these rely on the biology of the femur for osseointegration and long-term stability. It has been previously shown in humans that osteoblasts from different types of bone from the same anatomical region have inherent programmed diversity in what concerns growth and differentiation. Our main goal was to determine if we can find the same differences in canine femoral samples due to potential importance for osseointegration of hip replacement implants.

Femoral heads from three canine hip replacement surgeries were collected. Fragments of bone from subchondral, trabecular and cortical areas of the femoral epiphysis were collected and washed in PBS+AB/AM, trypsin-digested and incubated in 0.2% collagenase. The fragments were seeded in DMEM+10% FCS+AB/AM at 37 °C, 5% CO₂, grown until confluence and the cells seeded (n=6) at a density of 1.3×10⁴ cells/cm². We determined cell proliferation after 4 days with crystal violet staining and basal alkaline phosphatase activity 24 h post-confluence.

No significant differences were found in cell proliferation or doubling time among bone types, however basal alkaline phosphatase activity was higher in trabecular than in subchondral (P<0.05) or cortical (P<0.001) bone cells. We are now optimising culture conditions to stimulate matrix mineralisation activity.

Our preliminary data indicates that canine osteoblast activity differs between trabecular, subchondral and cortical bone types. This could have significant implications for future design of implants that osseointegrate leading to improved longevity and faster recovery from hip replacement surgery.