| Objective:The purpose of this experiment is to develop a minimally invasive percutaneous bone graft that can connect the defect area around the graft through the skin and implant the graft;establish the vertebral compression fracture model and then the bone graft is used to evaluate the effect of bone graft.Methods:1.Development of a minimally invasive percutaneous bone graft device:(1)Measurement of main parameters:Vertebral body related parameters of 32 patients with thoracolumbar vertebral compression fracture(T11-L2)were measured,including the transverse diameter and sagittal diameter of the narrowest region of the pedicle;On the median horizontal cross-section of the pedicle,the cross-section of the vertebral body was divided into four equal parts on the left and right by three bisectors,and the front and back of the vertebral body were divided into four equal parts by three parallel lines.The intersection of the left and right bisectors of the vertebral body close to one side and the parallel lines close to the posterior edge of the vertebral body was taken as the posterior 3/4midpoint of the vertebral body.The distance from the posterior 3/4 midpoint of the vertebral body to the center of the narrowest area of the pedicle and the distance extended to the skin were measured.(2)Proposed the design idea:According to the above main parameters,designed a rod-shaped bone graft,which could be connected to the stent of the vertebral body through the narrowest area of the pedicle and the bone defect area of the stent.According to the design drawings,it was entrusted to the company.2.Evaluation of the effect of bone graft:(1)Prepared the vertebral compression fracture model:20 single vertebral specimens were made in 5 human dead body specimens with T11～L2 vertebral specimens.A microcomputer controlled material tester placed the vertebral body between plates and continuously preloaded for 2min at 200N,then in displacement control mode,which compressed the vertebral front edge to 1/4 of the average height of the original vertebral body.(2)Supported bone graft:Established a 6.0mm diameter channel from the pedicle to the vertebral body.Through this channel,the stent was placed into the anterior and middle column position of the vertebral body.The auxiliary pipe could be connected to the bracket by using the positioning rod.Bone graft was performed with a 1.2mm bone particle.Recorded the amount of bone graft;(3)Evaluation index:X scan before and after vertebral compression and bone graf.Measured the height of the vertebral body front edge;A CT scan was performed on the vertebrae to observe the bone graft filling condition.The area of the defect before bone graft and that of after bone graft were measured by SURGIMAP;Measured the CT values at 3mm within the stent boundary.Differences in CT values were compared before and after bone graft.Results:(1)The transverse diameter of the narrowest part of T11～L2 pedicle was(6.37±1.61)mm～(7.34±1.21)mm.The sagittal diameter was(12.50±1.54)mm～(14.81±1.72)mm.The distance from the posterior 3/4 of vertebral body to the narrowest area of pedicle was(13.40±2.35)mm～(14.10±1.49)mm,and the distance from the posterior3/4 of vertebral body to the skin was(61.77±5.80)mm～(71.22±6.99)mm.(2)The developed bone graft device was made of medical stainless steel,including auxiliary tube,bone graft tube,bone graft rod and positioning rod.The diameter of auxiliary tube was6.0mm,and the inner diameter of bone graft tube was 1.8mm.(3)The amount of bone graft per scaffold was 2.05g±0.03g.(4)The original height of vertebral body was(29.48±1.33)mm;The height of the anterior edge of the vertebral body decreased by 1/4 to(22.34±1.05)mm after the establishment of the compression fracture model;The height of vertebral body after supporting bone grafting was(29.27±1.25)mm,which was significantly higher than that after compression(P<0.05).(5)The area of bone defect before bone graft was(65.90±2.68)mm~2,and the area of bone graft was(64.85±2.81)mm~2.The percentage of the area of bone graft and the area of bone defect before bone graft was 98.4%.(6)The CT value before and after bone graft was(-170.19±16.18)HU and(560.50±28.45)HU respectively.There was significant difference between the CT values before and after bone graft(P<0.01).Conclusion:1.The percutaneous minimally invasive bone graft can be accurately connected through the pedicle channel and the stent through the positioning rod,and the bone graft tube can be sufficient for bone graft in the stent defect area through the tilt channel in the auxiliary tube.2.The minimally invasive bone graft is matched with the stent,and can be used by minimally invasive surgery to graft the stent space successively through the pedicle channel,which can achieve good bone graft effect. |
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