The Bilateral Oophorectomy Effects On The Posterolateral Intertransverse Process Lumbar Fusion In Female Rabbit

Objective: To investigate the method of bilateral oophorectomy in female rabbits, furtherverify the characteristics of bone metabolism in ovariectomized rabbits, and provide areference for the following experimental study in spinal fussion.Method: A total of24six-months old New Zealand white rabbits were randomly assignedto SHAM and OVX groups, the group SHAM: the sham-operated group; the group OVX:the bilateral oophorectomy group. The two group of animals E2、BALP、RANKL、OPGwere measured before operation and at the first, second, fourth and eighth week afteroperation respectively, and BMD were measured before operation and at the eighth weekafter operation.．Result: The E2、BALP、RANKL、OPG level in OVX group were not significantly differentbetween preoperative and the first week after operation. From the beginning of the secondweek, the E2level descended and BALP、RANKL、OPG elevated gradually(p<0.05).However, the E2、BALP、RANKL、OPG level of preoperative were not significantlydifferent compared with all times of postoperative in SHAM group. The bone mineraldensity (BMD) at eighth week after operation was significantly lower than preoperative inOVX group(p<0.05) and it was not significantly different in SHAM group(p>0.05).Conclusion: It could lead to the form of low-level estrogen physiological state effectively bybilateral oophorectomy. The descent of estrogen level could break the balance ofRANKL/OPG/RANK system, and then lead to reduced bone mass. Objective: To compare the fusion effect of the OVX group with SHAM group in the rabbitposterolateral intertransverse process lumbar fusion, and to investigate the effect of estrogendeficiency on spinal fusion.Method: The lumbar L5/6bilateral transverse posterolateral autograft bone fusion operationwas performed In OVX group and SHAM group. The half of the experimental animals werekilled respectively In3,6weeks after operation, and then obtain the specimens. Thespecimens testing:(1) manual measurement fusion rate, the fusional determine must beconfirmed by two or three doctors with double blind;(2) the X-ray, Micro-CT scan werecarried out respectively, coronal Plane and3D reconstruction were performed by mimics10.0software;(3) the flexion, extension and tensile were tested on the biomechanical machine,and then evaluate the fusion strength;(4) The fusion of bone after decalcification sectionsstained by HE, and observe the histological morphology.Result: Manual and imaging fusion rate determination: the fusion rate in OVX group waslower than SHAM group (p<0.05) at3week, however, the fusion rate of two groups had nosignificant difference (p>0.05) at6week; Biomechanical test: the flexion, extensiondisplacement of the OVX group at3,6week were greater than the SHAM group (p<0.05).tensile maximum stress test: the maximum stress of the OVX group at3,6week were lowerthan the SHAM group (p<0.05) in the corresponding period; Histological observationshowed that new bone in the OVX group fusion site was less than the SHAM group, and thetrabecular gap was larger, the trabecular was thin and more irregular in the OVX group tocompare with the SHAM group.Conclusion: The low-level estrogen after bilateral oophorectomy has a negative effect onbone repair and reconstruction, it can reduce the fusion rate of the posterolateralintertransverse process spine fusion, and it can decrease the biomechanical strength of spinalfusion.