Imaging Study On The Morphology And The Pedicle Screw Placement Of First And Second Sacral In Children

BackgroundThe incidence of congenital lumbosacral spine deformity in children is low,and difficult to diagnosis early.The lack of a mobile spine below the deformity results in early truncal decompensation frequently and a long compensatory curve above,which may progress with time.Pedicle screw fixation is a recognized and effective method to treat such disease.The pediatric sacrum is in the developmental stage,the vertebral pedicle is small,the epiphysis is not completely closed,and the individual difference is large,and anatomic characteristics is special,adjacent to the important structure,such as cauda equina,the great vessels of the abdominal cavity and the nerve root,and so on.The difficulty and risk of pedicle screw fixation are more serious.The morphological study of thoracic vertebral pedicle with age at home and abroad is still in its infancy at home and abroad,and the research method is single.At present,the research on the morphology and pedicle screw fixation of children’s thoracic and lumbar vertebrae is still at the initial stage at home and abroad.And there is little research on S1 and S2 in children,especially in young children.ObjectiveExplore the morphological characteristics and developmental regularity of the first and second sacral vertebrae(S1,S2)in children,and the minimum age,the way of nail placement and the safety angle of the pedicle screws via Computed Tomography(CT),so as to provide a theoretical basis and reference for the clinical application of S1 and S2 screw fixation techniques.Materials and methodsThe data of lumbosacral CT scan of children aged 1 ~ 4 years from June 2017 to December 2017 in the Third Affiliated Hospital of Zhengzhou University were collected,a total of 120 healthy children were divided into three groups,Group A: > 1,≤ 2 years;Group B: > 2,≤ 3 years;Group C: > 3,≤ 4 years;40 cases per group,half of men and women.The original data were entered into the Syngo.via to reconstruct the three-dimensional image of the sacral CT from the sagittal,coronal,axis three level and obtaining morphology data,such as Vertebral Mediolateral dimension(VM),Vertebral Superoinferior dimension(VS),Vertebral Anteroposterior dimension(VA),Spinal canal Mediolateral dimension(SM),Spinal canal Anteroposterior dimension(SA),Vertebral maximum anteroposterior dimension(VMA)、Vertebral Plate Length(VPL),Vertebral Plate Width(VPW),Sacrum and iliac distance(SI).In software,putting in pedicle screw on S1 and S2,compare the anterior vertebral body direction bony channel length(L1),mass body direction bony channel length(L2),S1 mass direction bony channel length from S2(L3),Sacral Hole Distance(SH)with the pedicle screw of 25 mm length,3.5mm diameter.Explore the developmental characteristics of S1,S2 and the minimum age,safety method and point of view of the pedicle screw placement.The angles of the bony channel and the sagittal plane of the sacrum,the upper and lower end plates of the vertebral body were measured and recorded.Results1.There was no significant difference between the sex and the left and right sides of the S1,S2 vertebral morphological parameters and the measured data of the pedicle screw related to the simulated implantation of 1~4 year old children(P>0.05).2.After statistical processing,VM、VS、VA、L1、L2、L3 and SH generally showed a rising trend with advancing age(P<0.05).3.The entry point of S1 screw located at outside the lower edge of articular process.The S1 vertebral body anterior direction bony channel length(L1)of group A(27.74±1.94)mm,mass body direction bony channel length(L2)of group C(30.37±1.95)mm,both average value were statistically significant greater than 25 mm.4.The entry point of S2 screw located at the midpoint of the posterior sacral hole line of S1 and S2.The S1 mass direction bony channel length(L3)of group B(27.22±2.71)mm,S2 vertebral body anterior direction bony channel length(L1)and mass direction bony channel length(L2)of group C(26.54±1.68)mm,(25.74±1.01)mm,all average value were statistically significant greater than 25 mm.5.The minimum distance between the lower margin of the first sacral posterior foramen and the upper margin of the second sacral foramen,defined as Sacral Hole Distance(SH),which is the reference value of the width of the pedicle.The SH of all 3 group are(7.36±3.54)mm,(8.25±2.87)mm,(9.14±4.12)mm,the difference between the three groups was statistically significant.Using single sample t test to compare the difference between SH and 3.5mm,all average value were statistically significant greater than 3.5mm.ConclusionThe growth and development of spine in children aged 1-4 years,morphological development varies greatly among various age groups,the overall trend is increasing year by year.It is feasible to insert a pedicle screw with a diameter of 25 mm length,3.5mm diameter into S1 of 1 year old or older and S2 of 2 year old or older.