The influence of a bisphosphonate on bone generation determined using a chick-femur model

To determine the direct influence of a bisphosphonate (pamidronate) delivered by one of two carriers, on bone generation in chick-femurs supported by chick egg chorio-allantoic membranes.

Twenty chick femurs freshly harvested from fertilized eggs were randomly allocated to two groups: (i) Affi-Gel blue bead carrier (n=10); and (ii) hydroxyapatite bead carrier (n=10). The femurs in each group were further randomly divided into control (n=4) and experimental (n=6) subgroups. Carriers charged with PBS solution or 0.1 M pamidronate were delivered into the bone marrow of each femur at its mid-portion through a needle puncture. Each femur was then grafted onto the chorio-allantoic membrane of a chick egg and incubated for 7 days. Each experimental and control subgroup femur yielded four histological sections at the puncture site, constituting the test and inter-bone controls. In addition, two histological sections were also obtained from 400 to 450 μm away from each end of the experimental puncture site to act as the intra-bone controls. Bone generation was quantified and the ratio of cross-sectional area of bone marrow to circumference of bone (outcome measure) was determined using a software package, Image-Pro(®) Plus. The data were analysed using Mann-Whitney tests and Wilcoxon signed rank tests.

The outcome ratio in the test group was significantly (P<0.001) smaller than both the inter-bone and intra-bone control groups. There was evidence of increased bone formation directly over the pamidronate-charged carriers.

The test model established that pamidronate had a positive effect on bone generation over a period of 7 days, regardless of the carrier type.