Study Design: Prospective, experimental study in animals, approved by the local ethics committee for animal research.
Aims: To evaluate and compare the histological changes in myeloradicular structures and paravertebral tissue induced by contact with acrylic cement with and without methotrexate in vertebroplasty in pigs.
Material and Methods: Ten female pigs of the Large White¿Landrace breed, weighing 30 kg and divided into two groups: control group, containing five pigs that underwent vertebroplasty with acrylic cement, and methotrexate group, with five pigs that underwent vertebroplasty using cement combined with 1 g of methotrexate. A standard fluoroscopy-guide transpedicular vertebroplasty technique was performed with an 11-G trocar. Cement leak to the prevertebral and epidural muscle tissue was induced in two different lumbar vertebrae; 1 cc of cement was injected per vertebra. Animals were sacrificed at 3 weeks. Spines were removed, the section where tissues were in contact with cement was isolated by dissection, the surface in direct contact with cement was marked with India ink, and specimens were processed by fixation and hematoxylin eosin staining for pos-terior microscopic study.
Results: Macroscopic results: In both groups, the cement was distributed in layers surrounding the dural sac. Histological results: In the control group, leakage to the prevertebral musculature with atrophy of muscle fibers, inflammatory infiltrate in areas in contact with cement, epithelial dysplasia, and foreign body reaction in relation to cement particles. In addition, epidural leak with dural thickening and inflammatory reaction only in areas of the dura mater in contact with cement. In the methotrexate group, the same changes as in the control group were observed.
Clinical results: Neurological lesion due to cement leak was not produced any of the ten pigs.
Conclusions:The tube-like laminar distribution of the cement may explain the fact that there was an absence of paraplegia in the study animals. Contact of the muscle and dura with cement seemed to induce an inflammatory reaction, with cell death, and atrophy and thickening of membranes in some cases. Addition of methotrexate to acrylic cement did not seem to increase the local toxicity of cement alone.