Analysis Of The Therapeutic Effects And Finite Element Of Vertebral Body Stenting System On Osteoporotic Vertebral Compression Fractures

ObjectiveThis study aims to analyze the clinical efficacy of vertebral body stenting system and balloon kyphoplasty in the treatment of osteoporotic vertebral compression fractures and severe vertebral compression fractures,and to compare the influence of different vertebral augmentation about stress distribution of the fractured vertebral and the adjacent segment through finite element analysis,Methods(1)Patients who diagnosed as osteoporotic vertebral compression fractures(OVCF)were included in the study,and the TCM syndrome was diagnosed according to the standard of syndrome.(2)Retrospective analysis.Patients with the diagnoses of OVCF were divided into2 groups according to the surgical methods performed by the patients: VBS group and BKP group.The basic surgical conditions(operative blood loss,operation duration,bone cement),postoperative and follow-up clinical efficacy(VAS score)and imaging parameters(anterior vertebral height,middle vertebral height,vertebral height improvement,vertebral height recovery ratio,vertebral compression Cobb angle,and local Cobb angle)were included in the study.(3)From the patients above,the patients with severe osteoporotic vertebral compression fractures(s OVCF)were screened out and divided into 2 groups: VBS subgroup and BKP subgroup,and the difference of therapeutic effects was further analyzed.(4)To establish a T12-L2 spine segment model to simulate the L1 osteoporotic vertebral fractures,and further establish different cement-augmented models as vertebroplasty(PVP)and vertebral body stenting system(VBS).The VBS group included VBS-A group with cement connected and VBS-B group with cement not connected.To analyze the mobility of the fractured vertebral(L1),the stress distribution of the fractured vertebral,adjacent vertebral(T12,L2)and bone cement surrounding under ther simulation of different motion states as flexion,extension,lateral flexion and rotation.Results(1)A total of 54 patients with OVCF were included in the study on the analysis of the TCM syndrome.And 17 patients were diagnosised as liver and kidney yin deficiency,21 patients were diagnosised as spleen and kidney yang deficiency,9patients were diagnosised as qi and blood deficiency and 7 patients were diagnosised as qi stagnation and blood stasis syndrome.Among the 29 patients with s OVCF,10 patients presented with liver and kidney yin deficiency,13 patients presented with spleen and kidney yang deficiency,5 patients presented with qi and blood deficiency,and 1 patient presented with qi stagnation and blood stasis.(2)(1)A total of 54 patients with OVCF were enrolled in this study,including 29 in the VBS group,with an average age of(73.86±10.51)years and follow-up time of(8.26±8.45)months,and 25 cases in the BKP group,with an average age of(72.84±7.52)years and follow-up time of(6.32±4.43)months.(2)In terms of surgical conditions,compared with the BKP group,the VBS group had more operative blood loss and longer operation duration(P<0.05),but there was no significant difference in the amount of bone cement applied(P>0.05).(3)In terms of clinical efficacy and complications,pain was significantly relieved in both group postoperatively,but there was no significant difference between the groups(P> 0.05);the bone cement leakage rates of the VBS group and BKP group were 31% and 24% respectively,and the re-collapse rates of the vertebral were 10.3% and 12.0%,with no significant difference between the groups(P>0.05).(4)In the evaluation of imaging parameters,postoperatively,the anterior vertebral height,middle vertebral height,and compression Cobb angle in both group were significantly improved.The local Cobb angle of the VBS group was significantly decreased while no significant improvement in the BKP group.In comparison between two groups,preoperatively the anterior and middle vertebral height in the VBS group was significantly lower than that of the BKP group(P=0.011;P=0.026),which meaned the degree of compression was more serious.Postoperatively,there was no significant difference in anterior and middle vertebral height,compression Cobb angle,and local Cobb angle between the groups(P>0.05).In terms of height recovery,the VBS group had higher vertebral height improvement and higher vertebral height recovery ratio than the BKP group,though the difference was not statistically significant(P=0.083;P=0.085).At the last time follow-up,the Cobb angle of vertebral compression in the VBS group was significantly lower than that in the BKP group(P=0.030),and there was no significant difference among other index groups.(3)(1)From 54 patients above with OVCF,29 patients with severe vertebral compression fractures were screened out,including 12 patients in the VBS severe compression group and 17 patients in the BKP severe compression group.(2)In terms of surgical conditions,the duration of surgery in the VBS subgroup was longer,but there was no significant difference between the two groups in terms of intraoperative blood loss and bone cement injected(P> 0.05).(3)In terms of clinical efficacy and complications,pain was significantly relieved in both subgroup with no significant difference between the groups(P> 0.05).The bone cement leakage rate of the VBS subgroup and the BKP subgroup was 41.7% and 23.5% respectively,the recollapse rate was 16.7% and 5.9%,there was no significant difference between two groups(P> 0.05).(4)In imaging evaluation,there was no significant difference between two group preoperatively.After the operation,the anterior vertebral height,the middle height and the compresssion Cobb angle of the VBS subgroup and BKP subgroup were significantly improved(P<0.05),with no significant improvement of the local Cobb angle in both group(P> 0.05).But at the last follow-up,the local Cobb angle of the VBS subgroup was significantly improved compared with that of the postoperative period(P<0.05).In comparison between the groups,there was no significant difference between the two groups in terms of height recovery and correction of kyphosis after operation and at the last follow-up.(4)(1)In terms of vertebral mobility,the OVCF model had the highest mobility in various motion states,among which the mobility in the forward flexion state was the highest.While,the mobility of the other three surgical models was significantly reduced,among which the mobility in the stretched state was the highest.(2)In terms of the stress of the fractured vertebral,the stress of the OVCF model was significantly higher than that of the other groups under various conditions.The stress in the anterior flexion position was the highest,while that of the other models was significantly reduced.In the other surgical models,the stress of the VBS-B group was slightly higher than that of the VBS-A group.(3)In terms of the stress of upper vertebral,it was significantly higher than that of the lower vertebral body in the four models in the any motion state.In the OVCF model,the upper vertebral had the highest stress during rotation,which was decreased significantly in the other three surgical models,but there was no significant difference in the other positions.(4)In the stress of the lower vertebral,in the forward flexion motion,the stress in the PVP group was slightly lower than that in the OVCF group,but there was no significant difference among the groups in other states.(5)In the stress analysis around the cement,in the PVP group,the stress was highest in the flexion position.Under various motion states,the stress of the VBS groups was higher than that of the PVP group.In the VBS-B group,the stress in the anterior flexion,posterior extension and rotation motions was higher than that of the VBS-A group,and the increase in the previous flexion was the most obvious.Conclusions(1)Most of the patients with OVCF presented with liver and kidney yin deficiency and spleen and kidney yang deficiency.(2)Vertebral body stenting system and balloon kyphoplasty both have significant therapeutic effects in the treatment of OVCF and s OVCF on pain relieve,height restoration and correction of kyphosis.To some extent,VBS may have advantages in correcting and maintaining the local segment sequence of the spine.(3)The implantation of the VBS stent increases the stress around the bone cement especially when the cement diffusion is unsatisfactory,which may increase the risk of re-collapse of the surgical vertebra.