Objective To analyse the correlative factors of secondary vertebral fracture after percutaneous kyphoplasty (PKP) in treatment of osteoporotic vertebral compression fracture (OVCF) at different levels (adjacent and/or nonadjacent levels). Methods Between December 2002 and May 2008, 84 patients with OVCF were treated with PKP, and the cl inical data were analysed retrospectively. There were 11 males and 73 females with an average age of 70.1 years (range, 55-90 years). All patients were followed up 24-96 months (mean, 38 months). Secondary vertebral fracture occurred in 12 cases at 3-52 months after PKP (secondary fracture group), no secondary fracture in 72 cases (control group) at over 24months. The preoperative bone mineral density, postoperative vertebral height compression rate, postoperative Cobb angle, amount of injected bone cement per vertebra, puncture pathway (uni- or bilateral puncture), age, gender, number of fracture segment, and cement intradiscal leakage were compared between 2 groups to find correlative factors of secondary vertebral fractures. Results There was no significant difference in preoperative bone mineral density, postoperative vertebral height compression rate, postoperative Cobb angle, amount of injected bone cement per vertebra, puncture pathway, age, gender, and number of fracture segment between 2 groups (P gt; 0.05). But the incidence of cement intradiscal leakage was much higher in secondary fracture group than in control group (χ2=5.294, P=0.032). Conclusion Cement intradiscal leakage may be the correlative factor of secondary vertebral fracture after PKP in OVCF.
To explore the histological and the hematological change of rabbits after implanting novel injectable artificial nucleus prostheses, and to evaluate the biological safety. Methods In accordance with Biological Evaluation of Medical Devices, materials of polyurethane, sil icone rubber and macromolecular polyethylene for medical use were made into short column 1 cm in length and 0.3 cm in diameter. Forty-eight SPF New Zealand white rabbits weighing 2.5-3.0 kg were used, and cavity 1 cm in depth was made in the area 2 cm away from the spinal midl ine by separating muscle.Then according to different material being implanted, the rabbits were divided into 3 groups (n=16): Group A, polyurethane; group B, sil icone rubber; group C, macromolecular polyethylene for medical use as negative control. General condition of the rabbits was observed after operation. Gross and histology observation were conducted 1, 4, 12 and 26 weeks after operation. Blood routine, biochemical function and electrolyte assays were performed 26 weeks after operation to observe pathological changes of organs. Meanwhile, physicochemical properties of the materials were detected, and the material in the same batch was used as negative control. Results All rabbits survived until the end of experiment, and all wounds healed by first intention. In each group, red swollen muscles were observed 1 week after operation and disappeared 4 weeks after operation, connective tissue around the implanted materials occurred 12 and 26 weeks after operation. At 26 weeks after operation, there were no significant differences among three groups in blood routine, biochemical function and electrolyte assays (P gt; 0.05). Organs had smooth surface without ulceration, ecchymosis, obvious swell ing, hyperemia or bleeding, and nodules. There were no significant differences among three groups in percentage weight of each organ (P gt; 0.05). Histology observation: granulation tissue prol iferation and inflammatory cell infiltration were observed in each group 1 week after operation, fibrous capsule formation around the materials and the disappearance of inflammatory cell infiltration were evident 4 weeks after operation, cyst wall grewover time and achieved stabil ity 12 weeks after operation. The inflammatory response and the fiber cyst cavity of groups A and B met the standard of GB/T 16175 and were in l ine with group C. No specific pathological changes were discovered in the organs 26 weeks after operation. For group A, no significant difference was evident between before and after material implantation in terms of weight average molecular weight, number average molecular weight, tensile strength at break and elongation at break (P gt; 0.05). For group B, no significant difference was evident between before and after material implantation in shore hardness (P gt; 0.05). Conclusion Novel injectable nucleus pulposus prostheses do not damage local tissue and function of organs, but provide good biocompatibil ity and biological safety.