Application Of 3D Printing Technique In The Surgical Treatment Of Sacral Tumors

Chapter 1:Application of 3D printed model based on isotropic 3D-Space MRI and CT modeling in preoperative planning of sacral tumorsOBJECTIVE:To investigate the application value of 3D printed model based on 3D-Space MRI and CT modeling in preoperative planning of sacral tumors.METHODS:A retrospective analysis was performed on the cases with sacral tumor admitted between June 2015 and June 2020 in our hospital,twenty patients were divided into two groups(n=10,per group)and underwent resection of tumors and reconstruction of lumbo-pelvic stability by one-stage posterior approach.In the model group,3D printed model based on isotropic 3D-Space MRI and CT modeling was used to assist preoperative planning,while in the conventional group patients received conventional surgery.Operation time,blood loss,drainage volume and visual analogue scale(VAS)score were compared between two groups,internal fixation and clinical efficacy were also evaluated.RESULTS:The 3D printed model clearly presented bone,tumor,nerve,blood vessel and other tissue structures in the lesion area,and the surgical simulation was carried out in vitro.Compared with the conventional group,the operation time in model group was significantly decreased(P<0.05),and there were no significant differences in blood loss,drainage volume,and VAS score between two groups(P>0.05).In model group all cases had good internal fixation position and 2 cases experienced wound infection.In conventional group,1 case underwent pedicle screw failure and 2 cases experienced wound infection.All cases had urine and feces dysfunction.CONCLUSION:3D printed model based on isotropic 3D-Space MRI and CT modeling can effectively assist the preoperative planning of sacral tumor,and help to shorten operation time and improve the operation efficiency.Chapter 2:Application of personalized 3D-printed prosthesis in lumbo-pelvic stability reconstruction in patients with sacrectomyOBJECTIVE:To explore the application value of personalized 3D-printed prosthesis in lumbo-pelvic stability reconstruction in patients with sacrectomy.METHODS:A prospective study of 8 patients who underwent sacral tumor resection from April 2019 to June 2020 in our hospital.The lumbo-pelvis stability was reconstructed with personalized 3D-printed prosthesis,including 2 males and 6 females,aged 17?64 years,with an average age of(37.8± 16.6)years.There were 4 giant cell tumor cases,2 chordoma cases,I neurofibroma case,and 1 malignant solitary fibrous tumor case.The hospital stay,operation time,blood loss,drainage volume,intraoperative X-ray exposure times and postoperative complications were recorded.Visual analogue scale(VAS)and SF-36 score were recorded preoperatively,7 days after surgery,3 months after surgery,and at the last follow-up.The limb function MSTS score and neurological function MUD score were recorded 7 days after surgery,3 months after surgery,and at the last follow-up.X-ray and CT of the lumbar and pelvis were taken to measure the position of L5 and the opening distance of posterior pelvic ring,and the internal fixation was evaluated.RESULTS:Hemi-sacral prostheses were used in 3 patients and full-sacral prosthesis in 5 patients.The length of hospital stay ranged from 50 to 90 days,with an average of(60.3±14.2)days.The operation time ranged from 9?17 h,with an average of(12.8±2.8)h.The intraoperative blood loss ranged from 700?6850 mL,with an average of(3081.3±1920.2)mL;Postoperative drainage volume ranged from 1100?2800 mL,with an average of(1897.9±600.7)mL.Intraoperative X-ray exposures ranged from 4 to 7 times,with an average of(5.6±1.1)times.1 postoperative wound infection case improved after three times of debridement and suture,and 2 emergency treatment cases received endotracheal intubation.To the last follow-up,the VAS score continued to decrease significantly(P<0.05),while the SF-36 score showed no significant difference(P>0.05).From 7 days after surgery to the last follow-up,the MSTS score continued to improve,with significance difference(P<0.05).The difference of MUD total score and M,U score beteween 7 days after surgery and 3 months after surgery showed statistically significant(P<0.05).At the last follow-up M score showed significant difference compared with that of 3 months after surgery(P<0.05),total score and each item score showed significant difference compared with that of 7 days after surgery(P<0.05),the others showed no significant difference(P>0.05).There was no significant change in the position of L5 and the opening distance of posterior pelvic ring from 7 days after surgery to the last follow-up(P>0.05).CONCLUSION:Personalized 3D-printed sacral prosthesis can accurately match bone defects,reduce the difficulty of surgery,improve the intensity of reconstruction,and promote patients to stand at the early stage,which is expected to bring better long-term stability.It is a new method worthy of further observation.Chapter 3:Comparison of 3D-printed prosthesis and screw-rod system for reconstruction after total sacrectomy:A finite element analysis.OBJECTIVE:To explore the finite element analysis difference between 3D-printed prosthesis and only screw-rod system for lumbo-pelvic stability reconstruction after total sacrectomy.METHODS:A prosthesis case with total sacrectomy in the second chapter was selected to build three finite element analysis models.Model 1 was builded with double rods and double iliac screws on each side.Model 2 was builded with double rods and double iliac screws on each side and 3D-printed prosthesis,in which a iliac screw was inserted through the prosthesis.Model 3 was similar to Model 2,but the iliac screw did not penetrate the prosthesis.In finite element analysis software models were given the same material property and constraints,the prosthesis-bone surface was defined as surface-surface contact relation,the rest of the relationship were binding.Arbitrary direction freedom of bilateral acetabulum in the three-dimensional coordinates was limited,the L3 upper endplate was imposed 960 N axial stress,the average maximum stress of internal fixation system and L5 subsidence distance were recorded.RESULTS:The results of three finite element models were calculated successfully.The average maximum stress of bilateral iliac screws,rods,L3 and L5 pedicle screws and the subsidence distance of L5 in model 1 were higher than those in the other two groups significantly(P<0.05).The average maximum stress of L4 pedicle screws in Model l showed significant difference with Model 3(P<0.05),and no significant difference with Model 2(P>0.05).In Model 2 the average maximum stress of upper iliac screws and L3 pedicle screws was significantly greater than thoses in model 3(P<0.01),the average maximum stress of L4 and L5 pedicle screws,locking screws and the inner rods was significantly less than that in model 3(P<0.05),the average maximum stress of lower iliac screws and the outer rods showed no significant difference with Model 3(P>0.05);In Model 1 and Model 2,the average maximum stress of the upper iliac screws was significantly higher than that of lower iliac screws(P<0.05).In Model 3,there was no significant difference in the average maximum stress of iliac screws(P>0.05),and the average maximum stress of the inner rods was significantly higher than that of the outer rods(P>0.05).There was no significant difference in the average maximum stress of rods in Model 1 and Model 2(P>0.05).CONCLUSION:The 3D-printed prosthesis used to reconstruct lumbao-pelvic stability after total sacrectomy can reduce the average maximum stress of the internal fixation system and decrease the risk of screw-rod fracture,which is a technique worthy of promoting.However,the reconstruction relationship between prosthesis and screw-rod system needs to be further explored.