| There are some complications of anterior spinal interbody fusion, such as subsidence and non-union of the grafts, which impact the clinic effects greatly. The surgery involving the endplate preserved completely or near completelv.in which cuts the endplate partly until punctate bleeding can be obtained, has the advantage of better biomechanics and can maintain the height of interbodv space. It can also diminish the occurrence of graft subsiding into the vertebra. which may incur kyphosis. But whether the endplate would influence the healing of graft has not been reported.Jn this study, a group of 15 adult dogs was divided into 3 groups with 5 dogs in every group according to different postoperative period. Two procedures of anterior lumbar fusion with (group I )or without (group II )endplate preserved were performed in two different lumbar disc spaces in every dog. Which space is chosen to perform either of the two procedures was randomized. Then the healing quality of the grafts applying two different techniques was compared by different methods: 1 Roentgenography of the lumbar spine of 4 weeks, 8 weeks and 12 weeks after surgery. 2. Histology of the specimens of different post-operative period. 3. Immunostaining using an anti-von Willebrand Factor (vWF) antibody to mark the blood vessels in order to display the distribution of the newly born vessels in the grafting region. 4. The biomechanics of axial torsion of the specimen of 4 weeks, 8 weeks and 12 weeks after surgery and the biomechanics of axial compression of two artificial surgical models in vitro. Results: 1. Roentgenographically ,group I showed almost the same results as group II in 4 weeks, 8weeks and 12 weeks after surgery. 2. Histologically, both of the newly born tissues in the two groups are fibrous callus in 4 weeks after surgery, but there are less newly born matrix and blood vessels in group I than those in group II. In 8 weeks after surgery, both of them showed newly born bone tissues, but there was more cartilage tissue in group I than that in group II. Both of the grafts showed bony fusion in the two group in 12 weeks after surgery. 3. Through the immunostaining, both of the grafting area in the two group had some newly born blood vessels in 4 weeks after surgery, but the density of the vessel was more intensive in group II than that in group I The density of the vessel in the two groups trended to equalization in 8 weeks after surgery, 8nd there had no transparent difference between the two groups in 12 weeks after the surgery. 4. The biomechanical strength of axial torsion of the functional spinal units after 4 weeks in group H is greater than those in group I (P<0.05) under different twisting angles, and the maximal torque of group II (746.2 5.5Nm) was bigger than that of group I (612.3 4.1N.mm).It had no difference statistically between the two groups in 8 weeks under different twisting angles and the value of maximal torque was 722.3d70.1N.mm( group I )and 852.5.2 20Nm (group II )respectively. In 12 weeks after surgery, the torques in different angles and the maximal torque of group I were almost the same as those of group II. 5. The biomechanical strength of axial compression in group I is greater than group II (P<0.05) with the stress causing the graft of 1mm migration being 150.92 2.26N (in group I) and 117.21 1.88N (in group I) respectively. Conclusion: In early period after anterior spinal fusion with endplate preserved, there are less vessels in the grafting area and the stiffness of fusion unit is lower than t... |
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