Different Bone Graft Materials Induced Rabbit Lumbar Intertransverse Process Fusion

Objective:Spinal fusion is the surgical treatment of spinal instability, which is one of the most commonly used operation methods. In recent years, instability of the lumbar spine attracts people’s attention. There are reports of nearly1/3of patients with low back pain caused by lumbar instability, so, autologous bone with good bone conduction, bone induced and bone formation, is still the gold standard for bone grafting fusion. However, autogenous bone graft for bone mass has limits, such as long operation time, excessive loss of intraoperative blood and long-term pain for donor site, fracture of ilium, deep infection, complications such as abdominal hernia. Therefore, the search for an ideal substitute material of artificial bone graft has become the hotspot of Material science, medicine and biology. To solve the shortage of clinical bone graft materials, various bone graft substitute materials have been used in spinal surgery in basic research and clinical research. The experimental use of rabbit lumbar intertransverse fusion model was to evaluate the effects of different bone graft materials for lumbar intertransverse fusion in rabbits, and to investigate the effects of different bone graft materials in the alternative to autogenous bone for lumbar intertransverse process fusion feasibility. Methods:Twenty eighth healthy adult male New Zealand white rabbits (average of3.1kg) were divided into four groups (n=7), A group of chitosan/calcium silicate (CS/CaSiO3), B group of calcium silicate (CaSiO3), C group of chitosan (CS), D group of ilium. According to Boden describing a method for making animal model, fabrication of L4/5intertransverse fusion model, respectively after posterolateral lumbar intertransverse process spine arthrodesis, artificial bone were implanted into the sides of the L4/5between the transverse process. Using0.7%pentobarbital sodium auricular vein anaesthesia, preoperative skin preparation, the prone position is fixed, compound iodophor disinfectant, shop asepsis hole towel, strict aseptic operation, In L4/5as the center of dorsal midline incision, About5cm. Cut back on both sides of the fascia, since the multifidus muscles and muscle between blunt separation into, layer-by-layer separation of tissue, Revealed bilateral transverse root, the removal of the soft tissue, drill grinding removal with transverse process to reveal cortical cancellous bone, take care not to wound around the blood vessels and nerves. Will both sides were implanted into the prepared artificial bone materials about2.5g, hemostasis after chase a suture, sterile gauze bandage, each process only4transverse process. As for Autogenous iliac bone group, preparation of the operation is same as above. Take the anterior superior iliac spine as the center median incision, about3cm, blunt separation into, layer-by-layer separation of tissue, the removal of the soft tissue and muscle, full exposure of the ilium, using forceps biting of the ilium (approx.10mm×7mm×3mm), hemostasis after chase a suture, median incision ibidem,using forceps removed iliac crush, on the L4/5transverse process between. After12weeks of gross observation, imaging observation, histological observation, manipulation detection and biomechanical testing, to observe the artificial bone formation. Result:In general, four groups of rabbits were survived without abnormal death, the cuts were healed well, artificial bone and soft tissue were no inflammation phenomenon, no skin irritation without fester. After12weeks, A, B, C groups callus only intertransverse region, each artificial bone and soft tissue without inflammatory cell infiltration, no outside the bone, postoperative X examination without artificial bone loss shift phenomenon. Gross observation and manual detection intertransverse process fusion, each callus only intertransverse region, no outside the bone, autogenous iliac bone group, CaSiO3group and CS group in the fusion rate difference does not have statistical significance (fusion rates were71.4%,57.1%,57.1%); CS/CaSiO3implant site not only has the obvious osteogenesis phenomenon, but achieve solid fusion, dorsal extension, flexion, lateral bending and axial rotation without any activity, CS/CaSiO3fusion rate (100%) and iliac bone autograft group had no difference, Higher than the other groups (P=0.046). Imaging observation of intertransverse process fusion, after12weeks, lateral X ray films showed, autogenous iliac bone group showed bony fusion, transverse process with continuous trabecular bone formation, the end plate and bone grafting between surfaces without gaps and lucent zone, but the fusion of bone block smaller; the CaSiO3group showed no vertebral edge clearance, no graft settling, moderate continuous bone bridge formation, cartilage structure; CS group with a medium amount of new bone formation, with osteogenic performance, scattered punctate high density shadow disappearance; CS/CaSiO3group and solid bony fusion fusion,two transverse process between continuous trabecular bone formation, implants and transverse process together, maintain the normal transverse gap height. Tensile strength test results, all specimens were nondestructive biomechanical testing, iliac crest autograft group and CaSiO3group and CS group were not statistically significant difference (P>0.05); CS/CaSiO3group of the maximum tensile strength, its biomechanical strength higher than other groups (P<0.05). Histological observation, manipulation detection after each take2samples for histological examination, CS/CaSiO3group after12weeks of small amount of cartilage and substantially continuous trabecular bone formation, large number of woven bone formation, around the trabecular bone surrounding structure for cortical bone, cartilage structure, cartilage bone, bone metabolic activity was close to normal, implant implantation site had achieved bone fusion; autogenous iliac bone group started12weeks postoperatively with new bone formation, visible irregular woven bone and new trabecular bone formation, visible bone continuity, a component of cartilage, bone matrix bone cells, but their osteogenic ability is inferior to that of the CS/CaSiO3group; CaSiO3group fusion block transverse process between irregular trabecular bone formation, visible medium large woven bone formation; CS group around the class of aggregation and cartilage cells, with osteogenic performance, maturity of less than CS/CaSiO3group. Conclusion:Three materials can replace the autologous bone on lumbar intertransverse fusion, CS/CaSiO3can promote the process and improve the biomechanical strength, which is expected to be a new ideal substitute material of intertransverse spinal fusion bone graft.