The effects of tubular structure on biomaterial aided bone regeneration in distraction osteogenesis

Abstract

Background: Long duration of bone consolidation in distraction osteogenesis (DO) has been regarded as a major disadvantage. Porous bone substitutes have been long used in aiding bone formation. However the effects of geometric tubular structure of the porous scaffolds on bone formation in DO remains unknown. This study investigated the effects of porous scaffolds with three different geometric structures on bone regeneration in a rabbit DO model. Methods: β-tricalcium phosphate (β-TCP) was fabricated into no tubular, single tubular, or multi-tubular structure constructs. The microstructure of the three types of β-TCP constructs was determined by scanning electron microscope (SEM). Unilateral tibial osteotomy was made at the midshaft with 1 cm tibial shaft removed, fixed with an external lengthener in adulkt New Zealand white rabbits. After acute tibial shortening of 0.5 cm, the remaining 0.5 cm defect was implanted with β-TCP constructs with no tubular, single tubular, or multi-tubular structure. Five days after surgery, the tibia was lengthened at 0.5 mm/12 h for 5 days. After further 28 days of consolidation, the animals were terminated. Bilateral tibial specimens were collected for X-ray, micro-computed tomography examination, four-point bending mechanical test and histological analysis. Results: SEM results showed that pore sizes and pore interconnectivity in all three types of β-TCP constructs were identical. 38 days after surgery (4 weeks after lengthening), the new bone formation and mechanical properties were significantly enhanced in the groups implanted with multi-tubular and single tubular constructs, comparing to the group implanted with no tubular constructs. Furthermore, the group implanted with multi-tubular constructs had significantly better mechanical properties comparing to the group implanted with single tubular constructs. Histological results confirmed that group implanted with multi-tubular constructs had the most advanced bone formation and remodelling in the defect gap. Conclusion: The current study confirmed that β-TCP constructs with multi-tubular structure was the best choice as scaffold aid for bone regeneration in DO, indicating a novel fabrication approach of multi-tubular constructs for rapid bone formation together with DO procedure. The translational potential of this article: Porous β-TCP scaffold with a multi-tubular structure used in combination with DO procedure can significantly shorten the bone consolidation duration. The tubular shaped porous β-TCP scaffold may be used to fill bone defect and to aid bone formation, consolidaiton and remodelling in DO.