Basic And Clinical Research Of "Within Ring"-based Screw-rod System For Pelvic Ring Injury

OBJECTIVEThis project intends to develop and design a new type of pelvic internal fixator system for Chinese through the study of normal pelvic anatomy.Analyze its mechanical stability.To explore the clinical efficacy of "within ring"-based screw-rod system for pelvic ring injury.And to explore some new fixation models in posterior pelvic ring injury,so as to provide a novel perspective on the clinical practice.METHODSThe anatomical data of normal pelvis were measured,and the pelvic internal fixator was designed and prepared.The pelvic fracture model was fixed by four methods:plate plus iliosacral screw,anterior Infix plus iliosacral screw,Infix plus TIFI and Annular Internal Fixator.The stress-strain distribution and the stability of the fixation were evaluated by the finite element method.A novel technique of iliosacral triangular osteosynthesis(ITO)based on "within ring"-based concept was proposed,and the applicable safety and screw compatibility of ITO were analyzed on pelvic digital model.In the finite element model,the posterior pelvic ring was fixed with two transsacral screws(TTS),triangular osteosynthesis(TOS)and ITO,respectively.The stress-strain distribution and the stability of the fixations were evaluated by the finite element method.The clinical retrospective analysis was performed to compare the novel ITO group and the traditional iliosacral screw group.The operation time,intraoperative blood loss,intraoperative fluoroscopy,fracture healing time,reduction quality and Majeed functional score were compared between the two groups.The clinical data of 18 patients with unstable posterior pelvic ring injury using S2AI screw fixation technique were retrospectively analyzed.To evaluate the accuracy,complications,and clinical effects of screw placement for S2AI placement.RESULTSA new pelvic internal fixator was designed.By finite element analysis,the stress distribution of the Annular internal fixator is evenly distributed,and it has good static mechanical stability.The theoretical compatibility rate of S2AI screw and S2 iliosacral screw in S2 segment was 94%.In the finite element model,in terms of overall relative displacement,TTS group showed the smallest relative displacement,the ITO group showed the second smallest,and the TOS group the largest relative displacement.A total of 35 sacral fractures were included in the study.At the last follow-up,there was no statistical difference between the ITO fixation group(15 cases)and the sacroiliac screw group(20 cases)in fracture healing,fracture reduction quality,and functional scores.The iliosacral screw group was superior to the ITO group in terms of operation time,blood loss,and times of fluoroscopy.18 patients using S2AI screw fixation technique were followed up.A total of 21 S2AI screws were implanted in 18 patients without intraoperative neurovascular injury.Postoperative CT found in 2 cases S2AI had perforation of the iliac cortex.According to the Matta standard,excellent in 9 cases,good in 7 cases and fair in 2 cases.2 cases had surgical site infection.No cases showed prominent,break or loosen.CONCLUSIONSuccessfully developed and designed a new pelvic internal fixator.Through the finite element analysis,the stress distribution of the Annular Internal Fixator is relatively well distributed and has good static mechanical stability,which can effectively repair the Tile C1.3 pelvic fracture.The simultaneous placement of S2AI screw and S2 sacroiliac screw in the S2 segment is theoretically safe.Although the biomechanical stability of ITO is slightly lower than TTS,it is better than TO,and can be used as a new method for the treatment of posterior pelvic ring injuries.The new ITO fixation without interference with lumbosacral motion has achieved good clinical effect and imaging results.It has the advantages of less trauma,good biomechanical stability and early weight-bearing,which is an effective treatment schemes for unilateral vertical unstable sacral fractures.The S2AI screw fixation technology can be flexibly applied to various types of posterior pelvic ring injuries,and can provide rigid fixation to the pelvic ring and the lumbosacral junction,with a low complication rate.