ABSTRACT
Objective To compare the biomechanical pull-out strength (POS) of three different fixations in upper thoracic vertebras using translaminar screws (TLS), translaminar facet screws (TLFS), and transpedicle screws (TPS), respectively. Methods Nine fresh human cadaveric cervicothoracic junction spines specimens which including T1-T3 vertebras were harvested. The vertebras specimens were scanned using dual-energy radiograph absorptiometry for bone mineral density. Both of screw insertion techniques at each vertebrae was randomized. All the screw insertions were based on direct observation and the CT scan on the pedicles. The peak of insertional torque (IT) was recorded and axial pull-out testing was performed to simulate intraoperative failure of fixation. Results The mean peak IT of the TFLS, TPS and TLS were (0.43±0.01), (0.40±0.01), (0.35±).01) N·m, respectively. There was no statistically significant difference between the TFLS and TPS, and between the TPS and TLS was same. But the TFLS generated statistically greater peak 1T in comparison with the TLS(t=-13.86, P＜0.05). The mean POS of TLFS was (771±106) N,which had no statistically significant difference in comparison with the TPS(733±65) N. And the TLS (663±86) N was same. But the TFLS generated statistically greater POS in comparison with the TLS (t=9.907, P＜0.05). The peak IT showed a strong positive correlation with POS in three screw techniques. Bone mineral density correlation with POS in all methods of fixation. Conclusion It was not a significant difference to compare POS of TLS and TLFS to that of TPS respectively. TLS and TLFS appear to be a biomechanically sound alternative in the upper thoracic spine, and appear to be a safe and effective technique for instrumenting the upper thoracic spine.
ABSTRACT
Objective To study the effect of sodium hyaluronate on the expression of transforming growth factor-β3(TGF-β3) and Smad 6 of the epidural scar tissue. Method Totally 60 male SD rats were randomly divided into two groups:the control group(A, n = 30), sodium hyaluronate group(B, n = 30). 0.25 × 1 cm2 dura mater uncovered area laminectomy was performed at L4 and L5, covered with 0.3 ml sodium hyaluronate in group B, covered with same amount of saline in group A. The animals were sacrificed at 2, 4 and 8 weeks after operation. The specimens were prepared for determination of the expression of TGF-β3 and Smad 6 at scar tissue and the degree of scar adhesion according to Rydell method, and observed the ultrastructure changes of scar tissue with transmission electron microscope. Results At 2 weeks after operation, the expression of TGF-β3 mRNA of two groups were 0.22 and 0.257 ( P = 0.027), respectively. At 4 weeks, group B was was increased significantly, and the mean numbers were 0.362 and 0.411 (P = 0.006). At 8 weeks, the expression of TGF-β3 mRNA of group A was increased significantly, too, but the difference between two groups was significantly, they were 0.427 and 0.470 (P =0.015), respectively. The trend of the expression of TGF-β3 and Smad 6 mRNA was similar. At 2, 4, 8, weeks, the expression was 0.169 and 0.205 (P = 0.089), 0.294 and 0.351 (P = 0.031), and 0.469 and 0.543 (P = 0.021), respectively.In group B the duramater adhesion was decreased (P ＜ 0.05), the proliferation of fibroblasts and fihroblastic function were inhibited (P ＜ 0.05). Conclusions Sodium hyaluronate up-regulated the expression of TGF-β3 and Smad6 and reduced the proliferation and collagen synthesis in fibroblast culture in the scar tissue.