Background:
The aim of the present study was to evaluate the degradation pattern of highly porous bioceramics as well as the bone formation in presence of bone morphogenetic protein 7 (BMP-7) in an ectopic site.

Methods:
Novel calcium phosphate ceramic cylinders sintered at 1,300ºC with a total porosity of 92–94 vol%, 45 pores per inch, and sized 15 mm (Ø) × 5 mm were grafted on the musculus latissimus dorsi bilaterally in 10 Göttingen minipigs: group I (n = 5):
hydroxyapatite (HA) versus biphasic calcium phosphate (BCP), a mixture of HA and tricalcium phosphate (TCP) in a ratio of 60/40 wt%; group II (n = 5): TCP versus
BCP. A test side was supplied in situ with 250 μg BMP-7. Fluorochrome bone labeling
and computed tomography were performed in vivo. Specimens were evaluated 14
weeks after surgery by environmental scanning electron microscopy, fluorescence
microscopy, tartrate-resistant acid phosphatase, and pentachrome staining.

Results:
Bone formation was enhanced in the presence of BMP-7 in all ceramics (P = 0.001).
Small spots of newly formed bone were observed in all implants in the absence of BMP-7.
Degradation of HA and BCP was enhanced in the presence of BMP-7 (P = 0.001). In those
ceramics, osteoclasts were observed. TCP ceramics were almost completely degraded independently
of the effect of BMP-7 after 14 weeks (P = 0.76), osteoclasts were not observed.