Pedicle Screws System To Treat Vertically Unstable Pelvic Fracture By Both Biomechanical And Clinical Test

Pelvic fractures are common injuries, which not so many as the limbs and spine fractures. The incidence (about 40%) of hemorrhagic shock is more than the formers, with the common complications and high mortality. There are statistics of reported cases about pelvic fracture, of which 30% of the patients with hemorrhagic shock, a higher mortality and morbidity. With the economic development, traffic accidents and industrial accidents increased the incidence of pelvic fracture year by year. Pelvic fracture is a serious trauma with complex injury, especially the vertically unstable pelvic fracture. Unstable fractures of the pelvic fracture is the most serious type, accounting for 17% to 30%, which result in a lot of controversy in the clinical treatment and clinical results.Conservative treatment is used for the vertical unstable pelvic fractures in the past, such as traction, pelvic suspension and plaster immobilization method, while the incidence of disability is about 50%-60%. From the 1980s, Open reduction and fixation was used to treat pelvic fracture, and achieved satisfactory results. Internal fixation of unstable pelvic fractures has become the preferred treatment method in the past 20 years of clinical study. Operation can maximize the fracture reduction and fixation to restore pelvic anatomy and mechanical properties similar to a normal pelvis, improve the efficacy and improved functional status, play a positive role in overcoming the external fixation with conservative treatment, poor reduction, lack of mechanical strength, prolonged bed rest and the shortcomings of long-term complications.There are three parts of the study to treat the unstable pelvic fracture:Part one, Biomechanical Research on the Statically Determinate Pelvis under Vertical Loading.Part two, Biomechanical research on the improved pedicle screw system to treat vertically unstable pelvic fracture. Part three, Treatment of vertically unstable sacrum fracture by pedicle screws system fixation. Part one Biomechanical Research on the Statically Determinate Pelvis under Vertical LoadingObjective:To explore the normal pelvic biomechanical distribution under the vertical loading in statically determinate model and obtain the biomechanical parameters for various biomechanical tests in the pelvis fracture in future.Methods:With the strain electrometric methods, we detect the strain distributions, stiffness, displacements under the different load, then gather and compare the eight repeated strain values in different locations of pelvis under the load of 1500N in five specimens.Result:The greatest variance of strain is at the iliosacral joint, the load more than 3000N can be endured by the pelvis; after the eight-cycle loads of 1500N, the strain and stiffness do not change conspicuously.Conclusion:Iliosacral joint is a predilection site in the pelvis fracture. The ultimate failure point is more than 3000N.The load of 1500N is between the elastic interval of pelvis.Part two Biomechanical research on the improved pedicle screw system to treat vertically unstable pelvic fracture.Static position of the pelvis through biomechanical testing has established successfully the vertically unstable pelvic fractures biomechanical test model.Objective:The different types of fixation of vertical unstable pelvic fractures were performed the biomechanical testing, including the vertical load of local pelvic strain, partial separation of displacement and the overall stiffness.Methods:8 adult pelvic specimens,which has been made vertically unstable pelvic fracture model (Tile C-type); with the following internal fixation in random order of pelvic specimens:â‘ pedicle screw systems,â‘¡triangular osteosynthesis (TOS),â‘¢iliosacral screw. We test a variety of fixation of sacroiliac joint stiffness and displacement at the local separation, and compare the different fixation methods and the sacroiliac joint local strain at the arcuate line, by SPSS 13.0 for statistical comparison.Results:Improved screw-rod fixation system and surgical TOS vertically unstable pelvic fractures was no significant difference (P> 0.05),in the overall stiffness and the local separation but the data was significantly better than the sacroiliac screws that were significant differences (P<0.05). Local strain changes meet all the mechanical fixed conformation.Conclusion:The modified pedicle screw system successfully treats vertically unstable pelvic fractures biomechanically.Part three Treatment of vertically unstable sacrum fracture by pedicle screws system fixation.Objective:To evaluate the clinical properties of new technique of posterior pelvic fixation by pedicle screw system.Methods:Eighteen patients with vertically unstable sacral fracture were treated with new pedicle screws system fixation. The operation consisted of a posterior fixation in combine with a vertical and transverse fixation. The patients were followed up for a minimum time of 14 months (from 12 months to 18 months). Preoperative, postoperative and follow-up radiography were conducted to assess the reduction and union. The Majeed function assessment was performed at six month and a year follow-up.Results:Sacral fractures healed in eleven patients without loss of reduction at 3-6 months, no skin necrosis, iatrogenic neurovascular injury, shortening of lower limbs or claudication occurred. All patients presented complaints of pain at the incision sites occasionally, four patients complained electric-like pain at the frontal thigh sometimes, and two patients complained of symptoms related to the prominence of the pedicle screw tail. By considering symptom and satisfactory scores, the functional assessment revealed that eight patients had good results and three fair at six months and all had excellent results at one year. Conclusions:Pedicle screw system fixation that allowed early mobilisation and ambulation, with general applicability and definite safety, is an effective surgical technique for treating the unstable sacral fractures.