Experimental Study Of Intervertebral Fusion Cage Made By Nano-Hydroxyapatite/Polyamide 66

Spinal fusion is the most commonly surgical treatment in the spinal surgery, but the incidence of the failure of fusion and pseudarthrosis is high. Today the spine will be fixed more firmly with the method of surgery, but the failure of spinal fusion can not be completely avoided. So the scholars are looking for some ways to improve the performance of the substitute materials of bone grafts, maybe it enhanced the rate of spinal fusion. The ideal substitute materials of bone grafts with the following characteristics : non-toxic and without side effects, facility obtain, low prices, with biological activity of bone formation, bone conduction and bone-induced. The material is used in spinal fusion with autologous bone, heterologous bone and autologous bone, artificial bone . Autologous bone transplantation is the gold standard in spinal fusion because it is ability of bone induction ,bone formation and bone conduction. But it must be require additional surgery to obtain autologous bone ,the process maybe bring some complications in the region. If the patient is a child or the patient whose autologous bone have be taken before, there is not enough autologous bone, and we must take other substitute materials . Although the allograft bone and xenogeneic bone will be taken easily, but it has many problems as grafts, including the lack of bone morphogenetic protein, high absorption rate, infectious and immune rejection. The metal cage implants has been widely applied because it is high intensity can provide early stability, but in the body the metal cage will be electrolyzed and foreign body reaction will be taken place .Furthermore, metallic cages lead to artifacts during computed tomography (CT) and magnetic resonance imaging (MRI), complicating early detection of a metastatic recurrence and the evaluation of interbody fusion.Because of their high axial compression stiffness, metallic cages may lead to stress shielding of the cancellous bone grafts inside the cage, resulting in a decreased interbody bone matrix formation or nonunion.With the BMP and other biological activity factors be found and used in the spinal fusion ,spine fusion will be more rapid and strong ,the autologous bone as a gold standard in spinal fusion will be challenged.Objective :The purpose of our study is to evaluate the characteristics of the interbody cage made by nano hydroxyapatite / polyamide 66 (n-HA/PA66) composite in vivo and discuss the feasibility of it.The study has three separate parts :1. Nano-hydroxyapatite / polyamide 66 interbody fusion experimental study. 2. Nano-hydroxyapatite/polyamide 66 interbody with rhBMP-2 fusion experimental study.3. Nano-hydroxyapatite/polyamide 66 interbody fusion devices preliminary clinical application.Method :1. Nano-hydroxyapatite / polyamide 66 interbody fusion experimental study.Thirty adult female goats underwent c3-4 discectomy and interverbral fusion performed with n-HA/PA66interbody cage(n=15)or autogenous iliac crest bone graft(n=15).CT scans was carried out at 4,12 and 24 weeks after surgery to evaluate fusion quality. The goats were killed respectively on the 12th and 24th weeks. Nondestructive biomechanical testing for stiffness, un-decalcified histology was performed.2. Nano-hydroxyapatite/polyamide 66 interbody with rhBMP-2 fusion experimental study.Thirty adult female goats underwent c3～4 discectomy and interverbral fusion performed with nHA/PA66 interbody cage without rhBMP-2 (n=10),nHA/PA66 interbody cage with rhBMP-2(n=10),autogenous iliac crest bone graft(n=10).X ray was carried out at 4 and12 weeks after surgery to evaluate fusion quality. The goats were killed respectively on the 12th week. Nondestructive biomechanical testing for stiffness, un-decalcified histology was performed. 3,Nano-hydroxyapatite / polyamide 66 interbody fusion devices preliminary clinical application.Randomly selected 10 patients with cervical spondylotic myelopathy. Surgical excision anterior spinal decompression and implantation n-A/PA66 interbody fusion cage. Follow-up imaging and clinical results for 3-12 months. Observate the improvement of the symptoms and the compatibility of the materials. Take X-ray to observate its stability, the fusion of the vertebrae interface and intervertebral height changes.Results :1. Nano-hydroxyapatite / polyamide 66 interbody fusion experimental study .The goats in the n-HA/PA66 group and the autograft group all showed complete fusion at 24th week. There was no statistically significant difference between the n-HA/PA66 group and the autograft group upon biomechanics, radiography and histomorphology.2. Nano-hydroxyapatite/polyamide 66 interbody with rhBMP-2 fusion experimental study. The goats in the n-HA/PA66 with rhBMP-2 group and the autograft group all showed complete fusion at 12th week. there was no statistically significant difference between the n-HA/PA66 with rhBMP-2 group and the autograft group upon biomechanics, radiography and histomorphology.3. Nano-hydroxyapatite / polyamide 66 interbody fusion devices preliminary clinical application.Spinal cord functions of all patients have been improved. Symptoms were no recurrence, and X-ray examination revealed that all patients were fusion. Cervical stability has been maintained well and without internal fixation screw loosening .The cage is not moved. Conclusion :N-HA/PA66 interbody fusion cage has excellent biocompatibility, and the biomechanical properties. The spinal fusion can be more rapid if we implant the n-HA/PA66 interbody fusion cage with rhBMP-2. Safe, good fusion, height of the vertebral body can maintain stability, this is we observed in 10 patients used n-HA/PA66 interbody fusion cage. Its composition and structure similar to human bone, it will be an ideal interbody fusion device and to avoid the use of autologous bone.