The Study On Filling Rate Of Bone Cement In The Treatment Of Spine Metastases With Percutaneous Kyphoplasty

Background: Eventually about 30% of cancer patients will develop spinal metastases.The mechanism of PKP is not yet clear,but most scholars believe that the technology can relieve pain,stabilize the spine,and avoid the spinal cord and nerve root compression.Nowadays most of studies focus on the effect of amount of bone cement on the clinical outcomes.However,the the amount of bone cement are absolute values,which are different along with the difference of the vertebral body and individual difference.It is not enough simply using the amount of bone cement as an indicator of clinical outcomes.Objective: To establish a new evaluation indicator,which is named the filling rate of bone cement.And to study how this indicator works in evaluating the clinical outcomes of spinal metastases with percutaneous vertebroplasty.Materials and Methods: A retrospective study of clinical outcomes and prognosis of the patients with spinal metastasis from January 2012 to December 2016,all patients received PKP treatment.In the retrospective 3-month follow-up,the clinical and radiological data were documented pre and postoperatively at 1 day,7 day,and 3 months.The clinical data include Visual Analog Scale(VAS)and Oswestry Disability Score(ODI).The radiological data include: anterior vertebral height(AVH),posterior vertebral height(PVH),vertebral kyphosis angle(VKA)and segmental kyphosis angle(SKA).The filling rate of bone cement was measured by the Mimics software.The correlation between the filling rate of bone cement and the existing indicators was analyzed.The data were analyzed using the t tests and Pearson tests.Results: We performed PKP for 32 patients(male 14,female 18)with 62 affected vertebral bodies.Average age was 66.5(33-88)years old.The average filling rate of bone cement was 40.27±15.84%.The preoperative VAS was 8.6±0.7.At 24 h,1M,3M after surgery,the VAS score were 3.9±1.2(p<0.05),2.5±0.9(p<0.05)and 3.5±0.8(p<0.05).We use the difference between the preoperative VAS and the VAS of 24 h after surgery as the indicator of pain alleviation,the correlation coefficient between the filling rate of bone cement and pain alleviation was-0.001(p=0.995).The preoperative ODI was 76.4±11.1%.At 24 h,1M,3M after surgery,the ODI scores were 34.6±8.6%(p<0.05),32.6±10.2%(p<0.05)and 33.9±12.4%(p<0.05).The correlation coefficient between the filling rate of bone cement and the difference of ODI(preoperative vs 24 h after surgery)was-0.107(p=0.410).The preoperative Cobb angles of affected vertebrae were 17.2±2.6°.At 24 h,1M,3M after surgery,the Cobb angles were 14.2±3.4°(p<0.05),14.3±3.5°(p<0.05)and 14.2±4.3°(p<0.05).24 h after surgery,the Cobb angle was averagely rectified by 3.0±1.1°.The correlation coefficient between the filling rate of bone cement and rectified angle was 0.713°(p<0.01).The heights of anterior vertebral body in postoperative rose from 2.12±0.38 cm to 2.64±0.35 cm(p<0.05).Rectified height was 0.52±0.12 cm.The last follow up of heights of anterior vertebral body showed 2.59±0.41cm(p<0.05).The correlation coefficient between the filling rate of bone cement and the rectified height was 0.694(p<0.01).The postoperative height of posterior vertebral body was 3.16±0.38 cm,which was rectified with 0.11±0.03 cm after surgery.The last follow up of heights of posterior vertebral body showed 3.25±0.41 cm(p<0.05).The correlation coefficient between the filling rate of bone cement and the rectified height was 0.127(p=0.324).The VKA of affected vertebral body decreasing from 17.20±3.42° to 8.01±3.38°(p<0.05)24h after surgery,being rectified by 9.19±2.23°.At 1M and 3M,the VKA were 8.51±3.27°(p<0.05)and 9.12±3.42°(p<0.05).The correlation coefficient between the filling rate of bone cement and the rectified VKA was 0.478(p<0.01).Conclusion: 1.In the treatment of spinal metastases with PKP,we can receive satisfactory clinical outcomes and avoid serious complications at the same time when the filling rate of bone cement comes to 40.27±15.84%.The filling rate of bone cement could act as a effective indicator to evaluating the clinical outcomes of spinal metastases with PKP;2.PKP in the treatment of spinal metastases without nervous symptoms can relieve the pain and improve the activities of daily life,however,neither of the two symptoms has a linear correlation with the filling rate of bone cement;3.PKP can help restoring the Cobb angle and VKA,and both of them have a linear correlation with the filling rate of bone cement;4.PKP can restore the heights of the affected vertebral body of the spinal metastases,not like heights of anterior vertebral body,the heights of posterior vertebral body has a linear correlation with the filling rate of bone cement.