The Experimental Study Of Adjacent Segment Disc Degeneration After Spinal Fusion In Osteoporosis Rats

Objectives The purpose of the experiment is to explore whether osteoporosis aggravate adjacent segment disc degeneration after spinal fusion in the osteoporosis rat model and spinal fusion model.Methods 3- month-old healthy female Sprague Dawley rats(SPF) 80,No. Adaptive feeding after a week, they were randomly divided into four groups : Normal control group(Sham) 20; O vary resection group(OVX) 20, given bilateral ovaries removed when starting; Spinal fusion group(PLF) 20, did not do any processing when starting, normal feeding to 4 weeks to give the posterolateral fusion of the spine( Bilateral L4-L5 intertransverse fusion with autogenous bone grafts + L4-L5 spinous process wire winding fixed); Ovary resection plus Spinal fusion group(OVX + PLF) 20, given bilateral ovaries removed when starting, feeding to 4 weeks to give the posterolateral fusion of the spine(Bilateral L4-L5 intertransverse fusion with autogenous bone grafts + L4-L5 spinous process wire winding fixed). When breeding to 12 weeks, the Sham group and OVX group were killed immediately, while the PLF group and OVX plus PLF group were killed after DR- X-ray photography of the spine. After death, all experimental animals were to return L3-L6 segment to evaluate methods of fusion segment. After the assessment of fusion segment, 10 specimens were taken out from each group randomly for VG staining of intervertebral disc of L5-L6 segments. Observing the dyeing images of intervertebral disc to obtain histological score of intervertebral disc and the measurement of intervertebral height, the thickness of the endplate and the endplate calcification area and endplate area ratio; Micro-CT scanning of the L6 vertebral o f remained specimen to measure bone mineral density, bone volume fraction, bone trabecular thickness, number of trabecular bone, bone trabecular separation degree and index structure model, and to observe the changes of vertebral body bone mass and bone microstructure.Results 1 Results of fusion evaluation: ① Radiological assessment score results show that compared with the PLF group, radiology score of fusion segments of OVX+PLF group has a reducing trend, but not statistically significant; ② Methods assessment results show that the activity of L4-L5 segment of Sham group and O VX group was normal, while the activity of L4-L5 segment of PLF group and OVX+PLF group was disappeared, there was bone formation between transverse process, determined the stability of L4-L5 segmental was good, and the bone fusion was successful. 2 Results of Micro-CT scanning of the L6 vertebral bone show that the bone mineral density(BMD), bone volume fraction(BV/TV), bone trabecular thickness(Tb. Th) and bone trabecular number(Tb. N) of L6 vertebral bone of OVX group and OVX+PLF group were significantly lower than Shamgroup(P < 0.05), while the trabecular bone separating degree(Tb. Sp) and bone structure model index(SMI) were significantly higher than Sham group(P < 0.05); The bone mineral density(BMD), bone volume fraction(BV/TV), bone trabecular thickness(Tb. Th) and bone trabecular number(Tb. N) of L6 vertebral bone of OVX+PLF group were significantly lower than PLF group(P < 0.05), while the trabecular bone separating degree(Tb. Sp) and bone structure model index(SMI) were significantly higher than PLF group(P < 0.05). 3 Intervertebral disc VG staining observation results show that compared with the Sham group, intervertebral disc of the other three groups have a different degree of degeneration, and the OVX+PLF group intervertebral disc degeneration is the most serious. 4 Intervertebral disc histological score results show that intervertebral disc histological score of OVX group, PLF group and OVX+PLF group was significantly higher than Sham group(P < 0.05); Intervertebral disc histological score of OVX+PLF group was significantly higher than OVX group and PLF group(P < 0.05). 5 ① Intervertebral height measurement results show that the intervertebral height of the OVX group, PLF group and OVX+PLF group was significantly lower than Sham group(P < 0.05); The intervertebral height of OVX+PLF group was significantly lower than OVX group and PLF group(P < 0.05). ② End plate thickness measurement results show that the end plate thickness of OVX group, PLF group and OVX+PLF group was significantly higher than Sham group(P < 0.05); The end plate thickness of O VX+PLF group was significantly higher than OVX group and PLF group(P < 0.05). ③ Endplate calcification and endplate area ratio measurement results show that the endplate calcification and endplate area ratio of OVX group,PLF group and OVX+PLF group was significantly higher than Sham group(P < 0.05); The endplate calcification and endplate area ratio of OVX+PLF group was significantly higher than OVX group and PLF group(P < 0.05).Conclusions 1 Bilateral ovaries resection and posterolateral fusion of the spine(Bilateral L4-L5 intertransverse fusion with autogenous bone grafts + L4-L5 spinous process wire winding fixed) in rats is a true and correct model to imitate the osteoporosis and spinal fusion in postmenopausal women. 2 Osteoporosis can aggravate adjacent segment disc degeneration after spinal fusion.