Morphology analysis of nano hydroxyapatite/biphasic calcium phosphate for posterlateral lumbar fusion after combined magnetic field-an experimental study in rabbit

Abstract

Objective To analyze morphology of nano hydroxyapatite (nano-HA) coating and combined magnetic field (CMF) treatment on rabbits posterlateral lumbar fusion (PLF). Methods 48 adult rabbits undergone bilateral intertransverse processes fusion at the level of L5-6 were randomly divided into six groups G1, G2, G3, G4, G5 and G6 according to grafts used and CMF treatment. Group G1 received autologous iliac bone graft (AIBG) and CMF treatment; Group G2, nano-HA/biphasic calcium phosphate (BCP)+ CMF; Group G3, BCP+ CMF; Group G4, AIBG + placebo; Group G5, nano-HA/BCP + placebo; Group G6, BCP+ placebo. CMF treatments began at postoperative 1 week for 8 weeks, 30 minutes a day. The animals were euthanized at postoperative 9 weeks. Analyses included Field Emission Transmission Electron Microscope (FESEM), bone morphogenetic protein-2 (BMP-2) and transforming growth factor-β1 (TGF-β1) expression by immunohistochemistry and histological analysis. Results The biological scaffold were covered with new bone callus and bone ingrowth. Continuous bone bridge formed between the L5 and L6 transverse process in some specimens.The histological fusion score in G1-G6 group was 7.25±1.16, 5.00±0.76, 5.88±1.64, 5.87±1.25, 6.50±1.60 and 5.25±1.91. CMF and nano-HA coating significantly improved the spinal fusion rate, fusion score (P 0.05). Conclusion Both CMF and nano-HA coating can promote new bone formation and osseointegration, improve the spinal fusion rate in this rabbit PLF model. CMF combined with nano-HA/BCP for PLF can be used as a new spinal fusion method. Key words: Nano hydroxyapatite coating; Combined magnetic field; Biphasic calcium phosphate; Posterlateral lumbar fusion