Digital Anatomic Basis Of Parallel Double Screw In The Posterior Column Of The Acetabulum

Backgrounds:Acetabular fracture is a serious trauma usually caused by high violence injury,because of its deep anatomical location and hard to exposure and reduction,on the other hand,lots of blood vessels and nerve in the vicinity,so it will lead to serious consequences if you lose your attention.Therefore,the treatment of acetabular fractures has been a difficult problem in orthopedics.Conservative treatment is the main treatment for acetabular fractures in the past.But now,with the development of technology and orthopaedics,the acetabular fractures in young patients are mainly treated with open reduction and internal fixation,while the acetabular fractures in elderly patients are treated with open reduction and internal fixation and arthroplasty.Acetabular fractures caused by high violence injury will lead to soft tissue,other organs and multiple injury.Such as the anorectal,urethra and lumbosacral nerve injury.So the treatment plan is very important to minimize intraoperative trauma.Small incision or percutaneous screw placement technique can minimize the trauma of the patients who have slight displacement fracture,relative stability of fracture,the fracture line was located in the non weight-bearing area and femoral head and acetabulum match well.Generally,the percutaneous screw technique in the acetabular region is used as a single screw system.But in the patients with anterior and posterior column separation,such as both-column,T-sharped and the anterior column and posterior hemitransverse fractures,the single screw system can not control the rotation of the bone fragments,while the double screw is a good solution to this problem.The double screw placement is not as easy as the single screw and it is a serious challenge for surgeons.Our research in this area is to solve this problem and to provide some reliable clinical data for the Surgeons when they treated acetabular fractures patients with percutaneous double screw placement.Purpose:The objective of this study was to provide a safe zone for double screws in the posterior column and to calculate and measure the length and radius of each of the two screws,and the distance between the screws and the anatomical landmarks.Methods:48 cases of pelvic CT data,including 23 male cases and 25 female cases,are from the radiology department of Provincial Hospital Affiliated to Shandong University.with the help of Mimics software(15.0),we implanted the two cylinders(instead of screws)parallel to the posterior column of the right side acetabulum,in the confirmation that cylinders were not inserted into the medial,lateral and posterior cortex of the acetabulum and then Measure the length and radius of the two cylinders,the distance from the anatomical landmarks and the direction of the screw.Finally,the data were collected and analyzed statistically.Results:1.The Average length:the average length of the posterior cylinder(L1)was 130.88±6.11mm in males and 121.47±5.23mm in females.The average length of the anterior cylinder(L2)was 125.25±5.49mm in males and 116.37±4.83mm in females.2.The average distance to the linea terminalis of the pelvic:The average distance(Dl)between the posterior cylinder and the linea terminalis was 19.65±2.45mm in males and 17.89±2.00mm in females.The average distance(D2)between the anterior cylinder and the linea terminalis was 13.21±1.89mm in males and 11.62±1.39mm in females.3.The average distance to the junction between the anterior border of the iliosacral articulation and the linea terminalis of the pelvis:The average distance(S1)between the posterior cylinder and the junction between the anterior border of the iliosacral articulation and the linea terminalis of the pelvis was 23.71±2.61mm in males and 25.77±3.11 mm in females.The average distance(S2)between the anterior cylinder and the junction between the anterior border of the iliosacral articulation and the linea terminalis of the pelvis was 24.36±3.95mm in males and 28.15±4.70mm in females.4.The direction of the cylinders:The average angle(a)between the cylinders and the horizontal plane was 66.18±4.40°in maales and 69.01±5.25°in females.The average angle(?)between the cylinders and the sagittal plane was 10.40±2.48° in males and 5.60±2.56° in females.The average angle(?)between the cylinders and the coronal plane was 20.89±5.05°in males and 19.91±5.58°in females.5.The radius of the cylinder:4.00mm for 5cases,4.50mm for 5 cases,5.00mm for 5 cases,5.50mm for 5 cases and 6.00mm for 3 cases in males.3.00mm for 1 case,3.50 for 2 cases,4.00 for 6 cases,4.50 for 8 cases and 5.00mm for 8 cases.Conclusion:The present study showed that there is sufficient space for two parallel cylinders with the same diameter in the posterior column of the acetabulum,the maximum radius of the cylinders was 6mm.