| Objective1.Measured the C1 posterior arch bone specimens and CT data,then analyzed the difference for bone specimens and CT data.2.Analyzed the C1 anatomic characteristics to provide the anatomic basis for the design of novel C1 posterior arch plate.3.Designed a novel C1 posterior arch plate based on anatomical data and analyzed its feasibility.4.Did biomechanical evaluation for novel C1 posterior arch plate by finite element method.Methods1.Measured 30 cases C1 posterior arch bone specimens and 100 cases(50 male & 50 female)C1 posterior arch CT data.Measured the height and thickness of C1 posterior arch,the distances from C1 posterior midline to both sides of vertebral artery groove(inner side & outer side)and the two angles of C1 posterior arch(inner & outer)for bone specimens.Measured the height of C1 posterior arch on CT sagittal plane,measured the thickness of C1 posterior arch,posterior arch chord length and the distance from posterior midline to the chord length,the distances from posterior midline to the left & right vertebral artery groove(inner side & outer side)and the left & right posterior arch angles on CT horizontal plane,then compared and analyzed the data differences among bone specimens and CT data.2.Observed the C1 posterior arch morphological structure and analyzed the C1 posterior arch anatomic characters,then designed a novel C1 posterior arch plate which conformed to the C1 posterior arch anatomic structure according to measured C1 posterior arch anatomic parameters,and finally analyzed its feasibility.3.Established normal upper cervical spine finite element model,atlantoaxial instability finite element model,atlantoaxial pedicle screw finite element model and novel C1 posterior arch plate finite element model,then analyzed the ROM & stress for each kind model by finite element method;the stress of model showed by stress nephogram and compared the novel C1 posterior arch plate finite element model with the atlantoaxial pedicle screw finite element model,then compared and analyzed the ROM and stress among each model.Results1.After measuring 30 cases C1 bone specimens,the C1 posterior midline height and thickness were 10.75±1.38 m and 8.55±1.77mm;C1 posterior arch inner angle on horizontal plane was 141.00±3.43° and outer angle was 134.67±2.87°;the distances from C1 posterior midline to both sides of vertebral artery groove were 13.45±0.73mm(inner side)and 20.28±2.20mm(outer side).Measuring result for 100 cases C1 CT,C1 posterior arch outer edge radius was 26.77±2.14mm;C1 posterior midline height was 10.45±1.61 mm,thickness was 8.12±1.57mm;C1 posterior arch inner angle on horizontal plane was 141.23±9.64°,outer side angle was 135.47±9.02°;the distance from C1 posterior midline to inner side of vertebral artery groove was 13.60±1.26 mm,the distance to outer side was 20.48±2.05 mm.There was no statistical significance for both sides measuring data difference of bone specimens and CT data and there was no statistical significance for the measuring data of bone specimens and CT data.2.According to the analysis of the measured C1 posterior arch anatomic parameters,designed the arc-shaped C1 posterior arch plate.The length of plate was 30 mm.The plate was bilateral symmetry and gets narrower symmetrically along posterior midline as the center.The thickness of plate was 2mm and the radius was 27 mm.On the plate,there were two 3.5mm locking screw holes,2 bilateral symmetry and multiaxial U-shaped grooves and 4 posterior arch hooks.The C1 posterior arch screw was locking screw and its diameter was 3.5mm and length was 12~14mm.The novel C1 posterior arch plate designed based on the C1 posterior arch anatomic characters and conformed to the C1 anatomic characters.3.Compared with the published literature,normal upper cervical spine finite element model,we established,was effective.Compared with normal upper cervical vertebra finite element model,under each status,the implanted segment ROM of the novel C1 posterior arch plate finite element model decreased obviously.For the flexion & extension ROM of adjacent segments which were next to the implanted segment,C0-1 increased slightly but C2-3 decreased slightly.For the lateral bending ROM of adjacent segments,both of them decreased obviously,but for the rotation ROM,both increased slightly.Through finite element analysis,the C1-2 segment ROM for novel C1 posterior arch plate finite element model was 1.10°,0.49°and 0.59° under flexion & extension,lateral bending and rotation and the data was closed to the ROM of atlantoaxial pedicle screw finite element model.The novel C1 posterior arch plate almost had no influence to C2-3 intervertebral disc stress.The stress of novel atlantoaxial posterior internal fixation system mainly concentrated on the joint that the U-shaped grove of novel C1 posterior arch plate connects to the plate,the pedicle screw root and the connecting rod.Conclusion1.Through the comparison between bone specimens and CT data,CT data can better reflect the anatomical parameter of bone specimens.2.Through the measurement and analysis of C1 anatomical structure,the C1 anatomical measurement can provide the anatomical basis to the design of novel C1 posterior arch plate.3.The study of C1 posterior arch anatomy showed that the novel C1 posterior arch plate was feasible in anatomy and the plate provided a new fixed mode to C1 posterior arch internal fixation.4.Through the finite element analysis,the novel C1 posterior arch plate owned great biomechanical stability and it can be a remedy for atlantoaxial instability internal fixation. |
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