5?,dislocation of joint,instability of screws and plates and penetration of the screws into the joint surface.[Conclusion]Incorrect preoperative evaluation of the injury severity,incorrect judgement of the fracture type,improper operation indications,improper selection of internal fixation methods,nonstandard technique of bone graft and failure to reach anatomic reduction are the main causes of internal fixation failure.

BACKGROUND:The chemical compositions and structure of calcium phosphate bone cement are similar to those of human bone, which can fil the bone colapse caused by fracture and induce osteogenesis, but its degradation rate is slow. OBJECTIVE:To evaluate the biocompatibility of the calcium phosphate cement/fibrin glue and the feasibility of repairing radius defects. METHODS: In vitro cytotoxicity experiment: Mouse fibroblasts were cultured in the calcium phosphate bone cement/fibrin glue extracts, phenol solution, and RPMI 1640 culture medium containing 10% fetal bovine serum, respectively, to detect the cytotoxicity grade. Hemocompatibility experiment: Calcium phosphate bone cement/fibrin glue extracts, normal saline and distiled water were respectively added into the rabbit anticoagulation, to detect the hemolytic rate. Forty-five New Zealand white rabbits were enroled and modeled into bilateral radius defects, folowed by randomly alotted into three groups: blank control group without any intervention, experimental and control groups were given the implantation with calcium phosphate bone cement/fibrin glue and autologous radius, respectively. X-ray, histology, bone mineral density and biomechanical test were performed at postoperative 4, 8 and 16 weeks. RESULTS AND CONCLUSION:The toxicity grade of the calcium phosphate cement/fibrin glue was 0 to 1. The hemolytic rate of the calcium phosphate cement/fibrin glue was 3.15%. At 16 weeks postoperatively, X-ray showed that in the experimental and control groups, the fracture line disappeared completely, pulp cavity was recanalized, and in plastic completely. Histology showed that the reconstructed bone trabecular was obvious, plate layer of bone was mature, and medulary cavity recanalization appeared in the control group; there were a large number of new grid-shaped woven bone tissues growing into the material in the experimental group, with overt degradation, and degradation rate was in paralel to bone ingrowth. The bone density, the maximum load, maximum stress and failure energy in the experimental and control groups were significantly higher than those in the blank control group (P < 0.05), and al above indicators showed no significant differences between the experimental and control groups. These results manifest that the calcium phosphate bone cement/fiber protein glue composite material holding a good biocompatibility can promote bone tissue regeneration for bone defect repair, achieving similar curative effect with autologous bone transplantation.

ObjectiveTo compare the clinical effect of percutaneous iliosacral screws osteosynthesis (PISO) and open reduction internal reconstruction plate fixation in treating unstable pelvic fractures combined with sacroiliac joint dislocation,and evaluate their safety and practicality.MethodsFrom March 2004 to October 2010,37 patients with vertical unstable pelvic fractures were admitted to our department.Twenty cases were treated with percutaneous sacroiliac screw fixation and 17 cases were performed opened reduction and internal reconstruction plate fixation under C-arm X-ray's guide.The perioperative parameters and postoperative imaging indexes were compared and analyzed.ResultsAll patients were followed up for 6 months to 26 months,with an average of 15 months.There were statistical significances between the PISO group and open reduction internal fixation group in operation time,blood loss,postoperative pain,mean fever time and hospital stay.The two groups showed no significant difference on postoperative X-evaluation of reduction effect.The average healing time was 3.2 months and the difference was not statistically significant between two groups.PISO group had no complications such as infection,bent nails or broken nails.ConclusionThrough compared and analyzed the two groups in treating unstable pelvic fractures,the percutaneous sacroiliac screw fixation has been proved for a kind of ideal minimally invasive surgery method because of locating exactly,less damage and blood loss,milder pain and quicker recovery.But it demands higher operation techniques.Adequate preoperative preparation and postoperative patients' cooperation can reduce complications incidence.The second group of anterior reconstruction plate or T-shape plate to fix vertically unstable pelvic fractures at same time shows a good result of stabilization.