Objective To find a new culture system to induce proliferation and osteodifferentiation of marrow stromal cells (MSCs) in vitro for bone tissueeng ineering． Methods There were four groups in this experiment to study effects of Passage 3 osteoblasts derived from the rat cranium and the osteogenic inductor (1 nmol/L dexamethasone，10 mmol/L beta-glycero-phosphate，50 μg/ml retin oic acid) on growth of MSCs isolated from the rat femur and the tibia． MSCs were cultured in the DMEM medium (the c ontrol group) and in the osteoinductive culture medium (the inductor group)；fur thermore, MSCs were co-cultured with the osteoblasts in the DMEM medium (the osteoblast group) and in the osteoinductive culture medium (the combined treatment group)．The cells in the four groups were counted every 2 days for 8 days and alkaline phosphatase (ALP) activity of MSCs at 10 days of cultivation was measured．The MRNA expression of osteocalcin (OC) of MSCs at 2 weeks was assayed with the reverse transcript polymase chain reaction (RT-PCR)． Results There were more cells in the osteoblast group than in the control group(31.73±3.31×104 V S. 24.33±3.04×104, Plt;0.05), but there were fewer cells in the inductor gro up(16.23±2.44×104, Plt;0.05). There was no significant difference in th e cell number between the combined treatment group (21.54±2.29×104) and th e control group（Pgt;0.05）．The ALP activity was higher in the combined trea tment group （2.01±0.56 U）than in the control group (1.27±0.43 U), in the inductor group（1.27±0.43 U）, and in the osteoblast group （0.77±0.19 U）.The osteocalcin mRNA was expressed in the three treat ment groups but was not expressed in the control group. The significantly higher leve l of the osteocalcin mRNA was expressed in the inductor group（0.783±0.094）and in the combined treatment group（0.814±0.071）than in the osteoblast group（0.302±0.026） (Plt;0.05). Conclusion The combined use of t he osteoblast and the inductor can induce marrow stromal cells. Their combined u se does not affect the normal proliferation but can obviously promote the osteodifferentiation of marrow stromal cells. This combined use can become a new culture system of the seed cells for bone tissue engineering．
Objective To compare the cl inical effects of indirect decompression versus open decompression to vertebral canal in treatment of thoracolumbar burst fractures without neurologic deficit. Methods From April 2004 to June 2008, 52 cases of thoracolumbar burst fracture without neurologic deficit underwent posterior exposition, reduction and fixation with Atlas Fixator (AF) instrumentation. There were 34 males and 18 females with an average age of 43.1 years (range, 31-63 years). The affectd locations were T11 in 5 cases, T12 in 24 cases, L1 in 16 cases, and L2 in 7 cases. The time from injury to operation was 3-8 days (4.4 days on average). All cases were devided into indirect decompression group (group A) and open decompression group (group B). There were no statistically significant differences (P gt; 0.05) in sex, age, affect site, and disease course between two groups. The operative time, blood loss were recoded. Preoperatively, immediately postoperstively and at last follow-up, the height of the fracture vertebra and the Cobb angle were obtained from X-ray pictures and were statistically analysed. Radiographic parameters on computed tomography (CT) pictures were used to get the encroachment rate of vertebral canal. Results The operative time was (87.3 ± 7.9) minutes and (125.3 ± 13.6) minutes, and the blood loss was (273.7 ± 23.4) mL and (512.6 ± 37.7) mL in groups A and B, respectively; showing statistically significant differences (P lt; 0.05). The average follow-up time was 17.4 months (range, 11-31 months) in group A and 19.9 months (range, 12-33 months) in group B. All wounds achieved primary heal ing postoperatively without deaths and spinal cord injuries. Postoperative compl ications in group B included 3 cases of screws loosening, 1 case of screw breakage, and 3 cases of low back pain, and were given symptomatic management. There were no statistically significant differences (P gt; 0.05) in the height of the fracture vertebra, the Cobb angle andthe encroachment rate of vertebral canal preoperatively or postoperstively between two groups. There were statistically significant differences (P lt; 0.05) in the above three parameters between preoperation and postoperation in two groups, but there were no statistically significant differences (P gt; 0.05) in the spinal correction between two groups. The losing-rate of spinal correction of the height of the fracture vertebra and the Cobb angle of group A was lower than group B, showing statistically significant differences (P lt; 0.05). Conclusion The short-term results of two decompression styles in treatment of thoracolumbar burst fractures without neurologic deficit were satisfactory, but indirect decompression has more merits than open decompression: shorter operative time, less blood loss, lower losing-rate of spinal correction, and better stabil ization of vertebral column.