Fasetektomi Uygulanmış Lomber Bölgede Kullanılan Dinamik Pedikül Vida – Rod Sisteminin Sem Analizi
Fasetektomi Uygulanmış Lomber Bölgede Kullanılan Dinamik Pedikül Vida – Rod Sisteminin Sem Analizi
Dosyalar
Tarih
2013-09-13
Yazarlar
Doğru, Suzan Cansel
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Institute of Science and Technology
Institute of Science and Technology
Özet
Fasetektomi, omurgadan fasetlerin alınmasıdır. Omurilik kanal darlığı, disk hernileri, v.b hastalıkların tedavilerinde omurlara fasetektomi uygulanmaktadır. Fasetler, omurga hareketi sırasında stabiliteyi sağladıkları için; fasetektomi sonrası omurgada instabilite oluşmaktadır. İnstabiliteyi engellemek için rijit pedikül vida-rod sistemi kullanılmaktadır. Rijit sistem, uygulandığı omurların çevresinde yüksek gerilmelere neden olmaktadır. Dinamik pedikül vida-rod sistemi kullanılarak omurganın hareketini fizyolojik sınırlarda yapması sağlanır. Tez kapsamında, tek taraflı fasetektomi yapılmış lomber bölgenin stabilizasyonunu sağlamak amaçlanmıştır. Omurganın stabilizasyonunu sağlarken ise fizyolojik hareket aralığı dahilinde hareket etmesi beklenmiştir. Fasetektomi uygulanmış fonksiyonel omurga ünitesinde (FSU) instabilite oluşmaktadır. Fonksiyonel omurga ünitesi (fuctional spinal unit, FSU), birbirine komşu iki omur ve buna bağlı kıkırdak, bağ, kas dokularının bütününe denir. Sağlıklı (intact) FSU’da ve dinamik pedikül vida-rod sistemi uygulanmış FSU’da sonlu elemanlar metodu (SEM) ile analiz yapılmıştır. Sonlu elemanlar analizinde; sağlam (intact) fonsiyonel omurga ünitenin (FSU) ve pedikül vida-rod sistemi uygulanmış fonsiyonel omurga ünitesinin şekil değişimi miktarı, hareket aralığı ve gerilme değerleri hesaplanmıştır. Modeller, yüksek hızlı bilgisayarda sonlu elemanlar paket programı ile analiz edilmiştir. Modelleme aşamasında, yapay omurlar lazer sistemiyle taranarak üç boyutlu görüntüleri elde edilmiştir. Bunun yanı sıra literatür bilgileri ile diğer dokular modellenmiştir. Morfolojik değerleri kontrol edilen model analize hazır hale gelmiştir. Model doğrulama için yükleme ile oluşan mekanik cevap mekanizmasının kontrolü yapılmıştır. Bu kontrol analiz sonuçları ile literatürden alınan fizyolojik hareket değerlerinin karşılaştırılmasıdır. Analiz aşamasında; omurların, fasetlerin, omurlar arası disk dokunun, sinoviyal sıvıların ligamentlerin, vida rod sisteminin malzeme değerleri literatürden bulunmuştur. Sonlu elemanlar methodu ile analizi yapılan dinamik pedikül vida rod sisteminin, rijit sistemlere kıyasla omurgada fizyolojik hareket miktarını arttırması beklenmiştir. Ayrıca gerilme ve şekil değiştirme açısından da yeterince dayanıklı olması beklenmiştir. Sonlu elemanlar analizi sonucunda beklenen üzere fasetektomi sonrası omurga hareketi fizyolojik sınırları aşmıştır. dinamik pedikül vida-rod sistemi uygulanmış fonksiyonel omurga ünitesine, günlük hareketlerin oluşturduğu moment xviii uygulanmıştır. Model, literatürdeki deneysel verilerden elde edilen uygun fizyolojik hareket aralığında kalmıştır.
The aim of this thesis is to decrease the instability in the one side facetectomy applied functional spinal unit and generate the motion limitations of spine by the new designed dynamic pedicle screw – rod assembly. Facetectomy removes the facets from the vertebral bone and also is a decompression method. Decompression is a pressure decreasing process. An instability occurs in the facetectomy applied FSU. Functional spinal unit can be determined as a whole of two adjacent vertebra also cartilage, ligament and muscle tissues related them. Facetectomy is practiced in the treatment of some diseases such as spinal stenosis, dischernia etc. Due to the stability of the spine motion by the facets, an instability occurs in the spine after facetectomy. A rigid pedicle screw – rod system is used to restrain this instability. The rigid assembly causes stres concentration around the vertebra. Therefore a limited physiological motion of spine is carried out by dynamic pedicle screw – rod assembly. It was expected that dynamic design would allow the physiological motion and being stress under the yield point. The healing process could be more effective because of designing the dynamic pedicle screw – rod assembly considering troubles at treatment stage nowadays. Intact FSU and also FSU including new designed dynamic pedicle screw – rod assembly model, finite elements method (FEM) analysis has been carried out. The range of motion and stress values of the models have been calculated in these analysis. The models were analysed in the finite element package software by high speed PCs. At the stage of modelling, the 3D views of sawbone vertebras could be obtained by the the scanning of laser system. Besides, other tissues were modelled with the help of literature information. After the control of morphologic values, the model got ready to be analysed. The model, that doesn’t have valid material properties and geometry features, could not be proceed in estimated physiological motion limits. The material properties were obtained from the literature. The vertebras were assumed as an isotropic and linear elastic model with the values of 10 GPa elasticity module and 0,3 Poisson Ratio. The pedicle screw – rod assembly was modelled as an isotropic and linear elastic titanium with the values of 210 GPa elasticity module and 0,3 Poisson Ratio. xx The zygapophysial joint were modelled as linear isotropic elastic material with the values of 18 MPa elasticity module and 0,4 Poisson Ratio. The nucleus pulpozus was defined as an elastic material. Elasticity module was assumed as 4 MPa and also Poisson Ratio as 0,499. The nuclues pulpozus and facets in the synovial fluid were modelled as a fluid element. This fluid was surrounded by shell structure. The fluid in the shell gave it incompressible feature. The tensile stress of all ligaments was determined by 1 – D tensile tests. Test results were acquired from the literature data of Chazal et al. The mechanical response mechanism was controlled to validate the model. This control is a comprasion of physiological motion values of literature and analysis results. In functional spinal unit; flexion, extension, lateral bending and axial rotation were applied into a contact surface between L3 vertebra and L2 – L3 disc. Moment was applied to L3 as 7,5 Nm. The motion was limited to translation and rotation from the contact surface of lomber 4 vertebra and L4 – L5 disc. It is necessary to define the valid material properties to carry out the finite element model. Otherwise, according to the result of loading and boundary conditions to the assembly, the expected physiological motion doesn’t occur and result is deceptive. The results of loading to the assembly were compared to the values of physiological range of motion obtained from literature as experimental. Besides, the attempts to reach the steady result with element number alteration confirmed the finite element model. To solve the analysis in an optimum duration, the number of element and step number were simplified also singular loading was applied. Besides, material properties were simplified and frictions between the assembly were neglected. The cortical and cancellous in the vertebra structure were modelled by the same material property as cortical. The fibers in annulus fibrozus was neglected. With regards to the analysis results, the stres of the assembly is under the limitations of yield point. During the flexion and extension, the stres was 130 MPa, for lateral bending 143 MPa and also axial rotation 143 MPa on the pedicle screw – rod assembly. These values are under the yield point (940 MPa) of titanium. It was expected that dynamic design permitted to the physiological motions and also occured the stress in yield point. Various lomber level values were measured due to the study of Panjabi considering the range of motion in the lomber spine. As far as this study; during the L1 – L2 level flexion and extension 5° – 16° motion ranges, for lateral bending 3° – 8° ranges and also axial rotation 1° – 3° ranges were measured. During the L2 – L3 level flexion and extension 8° – 18° motion ranges, for lateral bending 3° – 10° ranges and also axial rotation 1° – 3° ranges were measured. During the L3 – L4 level flexion and extension 6°– 17° motion ranges, for lateral bending 4° – 12° ranges and also axial rotation 1° – 3° ranges were measured. During the L4 – L5 level flexion and extension 9° – 21° motion ranges, for lateral bending 3° – 9° ranges and also axial rotation 1° – 3° ranges were measured. During the L5 – S1 level flexion and extension 10° – 24° motion ranges, for lateral bending 2° – 6° ranges and also axial rotation 0° – 2° ranges were measured.xxi Considering the results of analysis; during the flexion in the L3 – L4 level FSU of new designed dynamic pedicle screw –rod assembly, 6° level range of motion was obtained also for extension 5,7°, for right side lateral bending 6,8° lateral bending to the facetectomy implemented region 8°, for axial rotation 3,3°.
The aim of this thesis is to decrease the instability in the one side facetectomy applied functional spinal unit and generate the motion limitations of spine by the new designed dynamic pedicle screw – rod assembly. Facetectomy removes the facets from the vertebral bone and also is a decompression method. Decompression is a pressure decreasing process. An instability occurs in the facetectomy applied FSU. Functional spinal unit can be determined as a whole of two adjacent vertebra also cartilage, ligament and muscle tissues related them. Facetectomy is practiced in the treatment of some diseases such as spinal stenosis, dischernia etc. Due to the stability of the spine motion by the facets, an instability occurs in the spine after facetectomy. A rigid pedicle screw – rod system is used to restrain this instability. The rigid assembly causes stres concentration around the vertebra. Therefore a limited physiological motion of spine is carried out by dynamic pedicle screw – rod assembly. It was expected that dynamic design would allow the physiological motion and being stress under the yield point. The healing process could be more effective because of designing the dynamic pedicle screw – rod assembly considering troubles at treatment stage nowadays. Intact FSU and also FSU including new designed dynamic pedicle screw – rod assembly model, finite elements method (FEM) analysis has been carried out. The range of motion and stress values of the models have been calculated in these analysis. The models were analysed in the finite element package software by high speed PCs. At the stage of modelling, the 3D views of sawbone vertebras could be obtained by the the scanning of laser system. Besides, other tissues were modelled with the help of literature information. After the control of morphologic values, the model got ready to be analysed. The model, that doesn’t have valid material properties and geometry features, could not be proceed in estimated physiological motion limits. The material properties were obtained from the literature. The vertebras were assumed as an isotropic and linear elastic model with the values of 10 GPa elasticity module and 0,3 Poisson Ratio. The pedicle screw – rod assembly was modelled as an isotropic and linear elastic titanium with the values of 210 GPa elasticity module and 0,3 Poisson Ratio. xx The zygapophysial joint were modelled as linear isotropic elastic material with the values of 18 MPa elasticity module and 0,4 Poisson Ratio. The nucleus pulpozus was defined as an elastic material. Elasticity module was assumed as 4 MPa and also Poisson Ratio as 0,499. The nuclues pulpozus and facets in the synovial fluid were modelled as a fluid element. This fluid was surrounded by shell structure. The fluid in the shell gave it incompressible feature. The tensile stress of all ligaments was determined by 1 – D tensile tests. Test results were acquired from the literature data of Chazal et al. The mechanical response mechanism was controlled to validate the model. This control is a comprasion of physiological motion values of literature and analysis results. In functional spinal unit; flexion, extension, lateral bending and axial rotation were applied into a contact surface between L3 vertebra and L2 – L3 disc. Moment was applied to L3 as 7,5 Nm. The motion was limited to translation and rotation from the contact surface of lomber 4 vertebra and L4 – L5 disc. It is necessary to define the valid material properties to carry out the finite element model. Otherwise, according to the result of loading and boundary conditions to the assembly, the expected physiological motion doesn’t occur and result is deceptive. The results of loading to the assembly were compared to the values of physiological range of motion obtained from literature as experimental. Besides, the attempts to reach the steady result with element number alteration confirmed the finite element model. To solve the analysis in an optimum duration, the number of element and step number were simplified also singular loading was applied. Besides, material properties were simplified and frictions between the assembly were neglected. The cortical and cancellous in the vertebra structure were modelled by the same material property as cortical. The fibers in annulus fibrozus was neglected. With regards to the analysis results, the stres of the assembly is under the limitations of yield point. During the flexion and extension, the stres was 130 MPa, for lateral bending 143 MPa and also axial rotation 143 MPa on the pedicle screw – rod assembly. These values are under the yield point (940 MPa) of titanium. It was expected that dynamic design permitted to the physiological motions and also occured the stress in yield point. Various lomber level values were measured due to the study of Panjabi considering the range of motion in the lomber spine. As far as this study; during the L1 – L2 level flexion and extension 5° – 16° motion ranges, for lateral bending 3° – 8° ranges and also axial rotation 1° – 3° ranges were measured. During the L2 – L3 level flexion and extension 8° – 18° motion ranges, for lateral bending 3° – 10° ranges and also axial rotation 1° – 3° ranges were measured. During the L3 – L4 level flexion and extension 6°– 17° motion ranges, for lateral bending 4° – 12° ranges and also axial rotation 1° – 3° ranges were measured. During the L4 – L5 level flexion and extension 9° – 21° motion ranges, for lateral bending 3° – 9° ranges and also axial rotation 1° – 3° ranges were measured. During the L5 – S1 level flexion and extension 10° – 24° motion ranges, for lateral bending 2° – 6° ranges and also axial rotation 0° – 2° ranges were measured.xxi Considering the results of analysis; during the flexion in the L3 – L4 level FSU of new designed dynamic pedicle screw –rod assembly, 6° level range of motion was obtained also for extension 5,7°, for right side lateral bending 6,8° lateral bending to the facetectomy implemented region 8°, for axial rotation 3,3°.
Açıklama
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2013
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2013
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2013
Anahtar kelimeler
mekanik,
biyomekanik,
modelleme,
sonlu elemanlar analizi,
mechanic,
biomechanic,
modelling,
finite element analysis