Bone regeneration using an injectable calcium phosphate/autologous iliac crest bone composites for segmental ulnar defects in rabbits.

BACKGROUND: Treatment of segmental bone loss remains a challenge in skeletal repair. A major therapeutic goal is the development of implantable materials that will promote bone regeneration.
OBJECTIVE: We evaluate bone regeneration in grafts containing different concentrations autologous iliac crest bone (ACB) particles, carried in a new injectable calcium phosphate cement (CPC), in ulnar bone defects in rabbits.
METHODS: Large upper-mid-diaphyseal defects (10 mm) were created in the left ulnae of 60 skeletally mature New Zealand white rabbits. ACB concentrations of 0, 25, 50, 75, and 100% (by volume) in CPC were used to fill operated sites. Defect bridging was monitored by serial radiography at 4, 8, and 12 weeks post-operation. Samples were then examined histologically and by manual palpation to determine the extent of new bone formation.
RESULTS: At 4 weeks, we observed more elaborate structures and extensive absorption in ulnae treated with mixtures containing low concentrations of ACB (such as 0% and 25% volume of ACB/CPC), compared with those treated with mixtures containing high concentrations of ACB (such as 75% and 100% volume of ACB/CPC). At 8 weeks, histomorphometry revealed increased trabecular area and volume in the group treated with high ACB concentrations compared with those treated with low ACB concentrations. At 12 weeks, complete cortical bridging and regeneration of marrow space were detected in groups treated with high concentrations of ACB, and the amount of new bone regeneration was greater in these groups than in those treated with low ACB concentrations.
CONCLUSIONS: Treatment of rabbit ulnar defects with injectable CPC carrying an optimized concentration of ACB particles can lead to cortical bridging and bone marrow regeneration within 12 weeks.