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Objective To investigate the effects from head angle and locking times of locking screws on mechanical properties of the screw-plate system, so as to provide a theoretical basis for doctors to select appropriate locking screws and master the locking times in clinical surgical procedure. Methods Locking screws with different head angles were selected to match with locking compression plates in the case of different locking times, and cantilever bending method was used to compare the differences of mechanical properties in each group. Results There were significant differences in failure load and bending stiffness between locking compression plate and locking screw with different head angles (P0-05). The failure modes of locking screw with different head angles and different locking times were different, and the failure mode of locking screw had a positive correlation with its head angle and locking times. Conclusions The differences in mechanical properties between locking screw with different head angles and locking compression plate cannot be neglected. It is suggested that doctors should choose locking screw and locking compression plate with the best locking degree in clinical procedure, and choose the right torque wrench to lock in multiple times if necessary, thus to prevent screw loosening from affecting recovery of the patients.
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Objective To discuss the clinical effect and safety of the unilateral C2 pedicle screw-plate(C2PSP)combined with contralateral C2 laminar screw-rod(C2LSR)for atlanto-axial joint and occipital cervical fixation.Methods 11 patients were treated by internal fixation with pedicle screw plate system combined with contralateral C2 laminar screw rod system.The cause of atlantoaxial instability was fresh type Ⅱ odontoid fracture in 5 patients,old odontoid fracture in 3 patients,occipitalization mal-formation in 2 patients,atlantoaxial instability in 2 patients.6 patients had small pedicle of the vertebral arch,2 patients had a high-riding vertebral artery(VA),2 patients had an asymmetrical VA,1 patient re-ceived a revision operation.9 patients performed C1-2 fixation,2 patients performed occipito-cervical fixa-tion.1 patient of irreducible atlantoaxial dislocation also performed anterior atlantoaxial joint release before posterior Fixation.All patients performed bone grafting to achieve a further occipito-cervical fusion or at-lantoaxial fusion.Before and after the operation,the neurologic function was scored according JOA scale. The X-ray and CT-scan also performed at regular intervals to evaluate cervical alignment and the fusion. Results All cases were complete reposition without vertebral artery,spinal cord or never root injuried.All patients were followed up for 6-32 months ( mean 16 months ),clinical symptom were improved visibly. The mean postoperative JOA scores was 14.9(13-16).The postoperative JOA score improvement rate was 76%-92%,and its mean value was 83%.All patients achieved bone fusion approved by CT scan after six months of operation.The reduction maintained well and the internal fixation was well positioned.Conclu-sion It will be an effective and safe way to achieve atlantoaxial fusion by posterior unilateral C2 pedicle screwing combined with contralateral C2 laminar screwing,but this study had not including clinical com-parative study.
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Objective To explore the clinical effect of the atlanto-axial pedicle screw internal fixation to reconstruct upper cervical spine instability. Methods Using atlanto-axial pedicle screw and internal fixation system combined with autogenous iliac bone graft to treat 21 patients with upper cervical spine instability. Type Ⅱ odontoid process old fracture was 13 patients, odontoid process nonunion was 5 patients, injury of the transverse ligament was 3 patients. They were placed in 84 atlanto-axial pedicle screws, autogenous bones were placed in the posterior arch of atlas and axis to fusion, so that atlanto-axial complex got stabilized. Results The left lateral cortical bone of atlas vertebral pedicle was broken by screws in 2 patients, but the spinal cord and vertebral artery was intact. X-ray film showed the atlas and the fracture of dens of axis was completely replaced in all patients. The position of screw and vertebral artery or spinal cord was good in CT image. According to JOA score standard, 15 cases of all were excellent, 3 cases were good,2 cases were common,1 case was bad, and the rate of excellent and good was 85.71%(18/21).Seventeen cases were followed up for 12-26 (12.83 ± 4.23) months, all patients had acquired bone fusion and found no screw and plate fracture. Conclusions Atlanto-axial pedicle screw combined with screw-plate system fixation to treat upper cervical spine instability, can significantly enhance the biomechanical stability of the atlanto-axial interbody, bone grafting fusion rate is higher, the application value of the atlanto-axialfusion is higher.
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[Objective]To investigate the effect of atlanto-axial pedicle screw plate and fusion in treatment of upper cervical injuries. [Methods]Fifty-six cases of upper cervical spine injuries were treated with atlanto-axial pedicle screw plate and internal fixation,with total 200 screws,from March 2000 to September 2007.There were 36 males and 14 females,with an average age of 41.52 years(ranged,20~65 years).There were 23 cases of type II odontoid process fracture,12 cases of odontoid process nonunion,15 cases of transverse ligament injury.[Results]Greater occipital nerve pain occurred in 4 cases postoperatively and fully recovered after treatment 1 month later.The lateral cortical bone was penetrated by screws in 2 cases,without spinal cord or vertebral artery injury.Forty-eight cases were followed up for an average of 27.56 months(ranged,25~60 months).Bone fusion was achieved in all cases,without plate or screw broken.X-ray showed complete replacement of atlas and odontoid process of axis fracture.CT showed good position relation between screw and vertebral artery or spinal cord.According to JOA classification,excellent result was achieved in 34 cases,good in 13 cases,fair in 2 cases,poor in 1 case,with the good-to-excellent rate of 94.00%.[Conclusion]Atlanto-axial pedicle screw combined with plate fixation system is effective in treatment of upper cervical injuries.It can significantly improve the biomechanical stability of atlantoaxial joint,with high bone graft fusion rate.
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[Objective]To discuss the perioperative management of thoracolumbar fractures fixed with latero-anterior screw-plate system.[Method]The entry point and direction of screw on 30 thoracic and lumbar vertebra specimens were marked based on the principle and demand of implantation of latero-anterior screw-plate system and were determined exactly by anatomic landmarks in order to make reference for operation.Sixty patients with thoracolumbar fractures were treated with anterior decompression,bone grafting and internal fixation from January 2000 to June 2007.Reference data such as the length of vertebral body screw and plate and the height of bracing gotten from the patients'X-ray and CT findings before operation were compared with practical data measured during operation.The entry point and the direction of screw were determined exactly by anatomic landmarks of thoraco lumbar vertebrae and were checked by X-ray during operation.[Result]The judgement of the entry point and the direction of screw was easy and accurate during operation and the reference data were in coincidence with practical data.The effects of operation were satisfactory.[Conclusion]The perioperative management is both scientific and practical.The surgical complications can be reduced in this way.
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[Objective]Design the Static Three Dimensional Screw-Plate system(STDSP), bring a new instrument for the treatment of femoral neck fractures, which has good biome chanical features of axial loading and rotation stability and can reestablish the loss of support of the posterior neck of fracture with posterior comminution. [Method]Design the STDSP. To the fracture group,one femur of each pair was randomly selected to be stabilized by STDSP, and the other was fixed by the three cancellous lag screws(TCS). Then the constructions were tested with axial loading or rotation to failure. The intact group were fixed and then taken out with the two methods, then tested with axial loading. [Result] (1)Rotation test: Compare the loads of the same rotation angle and the loads of the same width the anterior gap of the osteotomy open, STDS group is bigger than TCS group(PTCS group (P