Effect Of Vertebroplasty On The Adjacent Intervertebral Disc In Rabbits

Backgroud:Vertebroplasty is a newly and minimally invasive procedure in the recent decades that is optimal for the treatment of osteoporosis-induced vertebral compression factures, which owns the advantages of minor trauma, simple operation, quick pain alleviation and is widely accepted by the patients and surgeons. While disc degeneration and fractures of adjacent augmented vertebrae are frequently observed complications after VP in the following half year. To this area of research, the more concerned about biomechanical changes of intervertebral disc or vertebrae adjacent to the augmendted vertebral body at home and abroad, and usually the cadavers are used to mechanical testing by static analysis, while the research concerned on disc is rare in vivo following VP.Objective:To investigate whether vertebroplasty can lead to the degeneration of adjacent disc in rabbits, and the correlation of degeneration degree to the doses of polymethyl methacrylate (PMMA).Methods:Eighty female New Zealand white rabbits of5months old were used for the study, and sixteen of them were randomly selected for the normal control group (Group A). The other sixty four rabbits were established an osteoporosis rabbit model by bilateral ovariectomy, and then divided into four groups of16rabbits each. The fifth lumbar vertebrate (L5) was injected into nothing as experimental control group (Group B), and L5was injected with0.1ml,0.3ml and0.5ml PMMA as Group C, D and E, respectively. Four rabbits were selected randomly, then X-ray, MRI and histological observation were performed preoperatively and at the first, third, sixth month postoperatively. The DHIP (disc height index percent) and MRI index (the product of nucleus pulposus area and average signal intensity) of each disc were calculated to analyze degrees of disc degeneration. And disc degeneration was graded by Masuda’s standard of histological grading scale. The data were statistically analyzed by SPSS19.0.Results:There were no obvious changes at every time point on DHIP, MRI index and Masuda grade in Group A and B. There were also no obvious changes on DHIP, MRI index and Masuda grade preoperatively and at the first month postoperatively in Group C, D and E compared to Group A and B. However, at the third month, the DHIP and MRI index decreased in Group E compared with the A, B, C and D groups. And there were significant differences of MRI index and Masuda grade between Group E and Group A, B (P<0.05). At the sixth month, there were significant differences of DHIP, MRI index and Masuda grade in Group D and E between the preoperative and1-month as well as3-month postoperative surgery (P<0.05). And the DHIP and MRI index in Group E were statistically significantly lower than those of in Group A, B, C and D. The Masuda grade in Group E was also statistically significantly higher than those of in Group A, B, C and D.Conclusions:Vertebroplasty can lead to the degeneration of adjacent disc in rabbits, and intervertebral disc degeneration degree is correlative to the doses of PMMA.