Repair of critical-sized bone defects of the femoral condyle with nano-hydroxyapatite/chitosan composites in rabbits

Abstract

Objective To investigate the bone regeneration potential of nano-hydroxyapatite/chitosan composite scaffolds when implanted into critical-sized bone defects in rabbit femoral condyles.Methods Critical-sized bone defects (6 mm in diameter and 10 mm in depth) were created in the left femoral condyles of 44 adult New Zealand white rabbits.All the rabbits were randomly divided into 3 groups according to bone grafts.Nano-hydroxyapatite/chitosan compositions were implanted into the defects in the experimental group (n =20),pure chitosan in the control group (n =20),and nothing in the blank group (n =4).New bone formation was detected and compared among the 3 groups by gross observation,plain radiography,quantitative computer tomography (CT) and histological examination at 8 and 12 weeks after surgery.Results Plain radiography at 12 weeks after surgery showed that bone defects were being repaired well and cortical bone union was observed in the experimental group,and that the depth of defect diminished but bony connection was not achieved in the control group,and that there was no new bone formation in the blank group.The Lane-Sandhu X-ray scores were 10.18 ±0.98 in the experimental group and 8.90 ±0.99 in the control group,with a significant difference between the 2 groups (t =6.858,P =0.000).At 12 weeks,CT showed that the defects were almost filled with new osteoid tissue and the bone contour remodeled smoothly in the experimental group; most of the defects were filled with new osteoid tissue but still visible in the control group; bony union was not achieved and the defects were still very obvious in the blank group.The CT scores were 256.1 ± 26.8 Hu in the experimental group and 169.2 ± 25.4 Hu in the control group,with a significant difference (t =4.711,P =0.003).The histological observation showed a lot of trabecular bone in the bone defects at 12 weeks in the experimental group,with no visible boundary between newly formed bone tissue and native bone.In the control group,the bone defects were full of the remnant material and fibrous tissue at 12 weeks.In the blank group,the bone defects were filled with a little fibrous tissue at 12 weeks but no new bone formed.Conclusion Since nano-hydroxyapatite/chitosan composite scaffolds may have better performance than pure chitosan in repair of bone defects,it is a sort of promising candidate material for regeneration of bone loss. Key words: Femur;  Hydroxyapatites;  Chitosan;  Nano-composites;  Bone defect