The Effect Of Salmon Calcitonin On Rat Spinal Fusion Model

Objectives The aim of this study was to investigate whether salmon calcitonin(s CT) can enhance lumbar spinal fusion in a rat spinal fusion model, and to provide a research basis for the clinical application of s CT after spinal fusion.Methods Thirty 3- months-old healthy female Sprague Dawley(SD) rats were divided into three groups after a week of adaptive feeding: control group(Sham+V group, n=10), spinal fusion group(PLF+V group, n=10), spinal fusion+salmon calcitonin group(PLF+s C T group, n=10). All rats of PLF+V and PLF+s CT group accepted a spinal fusion operation(grafting autologous bone at the bilateral intertransverse process of L4–L5 with fixing the spinous processes of L4- L5 by steel wire). After operation rats were give n intramuscular injection of penicillin for 3 consecutive days to prevent infection. All rats received s CT or placebo treatment since 1 week postoperatively. The PLF+s C T group received subcutaneous injection of s C T at a dose of 16 IU/kg/2d. Meanwhile,Sham+V and PLF+V group received subcutaneous injection of the same dose of saline. After administration of 12 weeks, X-ray radiograph was taken on the whole spine of all rats, and then the fusion segments were scored. All rats were euthanized after radiographic evaluation, and the L3–L6 segments were harvested to assess spinal mobility using manual palpation. Afterwards half of spinal specimens from each group were randomly selected to proceed formalin fixation, then stained with hematoxylin eosin stain(HE) and made histological examination. The rest spinal specimens were evaluated by Micro-CT scan.Results 1 Results of radiographic examination showed the Sham+V group revealed distinct intertransverse space of bilateral L4-L5 and intact iliac crests. And PLF+V group showed vague dense shadows at bilateral L4-L5 intertransverse process with defected iliac crests. However, PLF+s CT group displayed clear dense shadows at bilateral L4-L5 intertransverse process with defected iliac crest. The fusion area of PLF+s CT group was larger when comparing to PLF+V group. Results of radiological scores indicated PLF+s CT group had higher radiological scores than PLF+V group significantly(P<0.05). 2 Results of manual palpation demonstrated the L4-L5 segments of all rats performed PLF were fused without mobility. 3 Results of micro-CT scanning evaluation showed Sham+V group revealed clear intertransverse space of L4–L5 without bone formation.There were a few fusions at the intertransverse process of L4–L5 of PLF+V group with certain intertransverse space remained, and the area and size of fusion bodies were minor. However, the PLF+s CT group had moderate fusions at the intertransverse process of L4–L5 with almost no intertransverse space remained, and the area of fusion bodies were larger. 4 Results of histological examination illustrated PLF+V group had unabsorbed bone graft with new collagenous fiber tissues formation. In the PLF+s CT group, bone graft was almost completely resorbed, collagenous fiber tissues gradually converted to cartilaginous tissues, and lots of cartilaginous tissues had formed. Results of histological scores informed PLF+s CT group had higher histological scores than PLF+V group significantly(P<0.05).Conclusions 1 The rat spinal fusion model(grafting autologous bone at the bilateral intertransverse process of L4–L5 with fixing the spinous processes of L4-L5 by steel wire) is a reliable model, which ca n advantageously simulates the healing process of spinal fusion. 2 s CT could enhance SD rats postoperative spinal fusion.