Tesis

Perbandingan expandable cage tipe tiga dimensi dan tipe lurus pada Fusi interbody transforaminal pada Lumbal – studi finite element = Biomechanical study of intraoperative subsidence in expandable cage transforaminal lumbar interbody fusion -finite element analysis.

Latar Belakang: Intraoperative cage subsidence pada penggunaan expandable cage TLIF cukup tinggi yaitu 29% dan 2.73X lebih tinggi dibandingkan dengan static cage TLIF. Beberapa faktor yang mempengaruhi antara lain ketinggian expandable cage, luas penampang cage dan densitas tulang pasien. Penelitian ini bertujuan untuk melihat biomekanika pada expandable cage TLIF yang diekspansikan insitu pada expandable cage TLIf tipe lurus dan tipe 3D pada densitas tulang normal dan osteoporosis dengan menggunakan finite element analysis. Metode: Penelitian ini terdiri dari tiga tahap yaitu pembuatan modelling Lumbal 3-5, pembuatan modeling expandable cage tipe lurus dan tipe 3D pada solidwork, kemudian model lumbal dan expandable cage TLIF digabungkan. Pada model lumbal dibuat model osteoporosis dan normal. Terdapat 4 model yaitu expandable cage tipe lurus pada densitas tulang normal dan osteoporosis, expandable cage tipe 3D pada densitas tulang normal dan osteoporosis. Keempat jenis model dilakukan pengukuran peak stress pada endplate superior dari L5 dan inferior endplate L4. Pembebanan dilakukan pada Lumbal III sebesar 300N untuk mensimulasikan pasien berbaring, pada inferior lumbal V dijadikan batasan tetap. Ekspansi expandable cage di 1,2,3,4.5 mm dilakukan dengan menambahkan gaya reaksi pada expandable cage selain pembebanan 300N pada lumbal III kemudian diukur peak stress pada endplate superior lumbal 5 dan endplate inferior lumbal 4. Nilai peak stress yang terjadi di tiap model kemudian diukur dan dibandingkan. Hasil: Simulasi pembebanan pada saat pasien berbaring yaitu dengan pemberian beban 300N pada superior endplate Lumbal 3 ekspansi expandable cage dari 0 mm hingga 4,5 mm terjadi peningkatan peak stress pada endplate superior L5 dan inferior lumbal 4 masing-masing model yaitu expandable cage tipe lurus dengan densitas normal L5 1.36-3.37 MPa, L4 1.36-1.82 MPa pada expandable cage tipe lurus densitas osteoporosis L5 1.56-8.59MPa dan L4 1.44-1.75MPa, expandable cage tipe 3D densitas normal L5 1.84-3.19 MPa, L4 1.49-2.36 MPa dan expandable cage tipe 3D densitas osteoporosis L5 2.66-4.18 MPa dan L4 2.49-3.34 MPa. Kesimpulan: terjadi peningkatan peak stress pada masing masing model sesuai dengan peningkatan ekspansi cage, peningkatan peak stress pada densitas osteoporosis lebih tinggi dibandingkan dengan densitas normal pada kedua jenis expandable cage hal ini karena adanya peningkatan perbedaan modulus young pada expandable cage dengan lumbal, peningkatan peak stress pada expandable cage tipe lurus lebih besar dibandingkan tipe 3D pada densitas tulang normal maupun densitas tulang osteoporosis, peak stress pada expandable cage tipe lurus lebih tinggi karena luas penampang pada expandable cage yang bersentuhan dengan endplate lebih kecil dibandingkan dengan expandable cage tipe 3D, sehingga pada expandable cage tipe 3D distribusi stress yang terjadi lebih merata dan menurunkan peak stress pada endplate superior lumbal 5 maupun endplate inferior L4.
Kata kunci: Expandable cage, TLIF, peak stress, Finite element analysis


Introduction: Intraoperative cage subsidence due to endplate violence in expandable cage TLIF is quite high, approxymately 29% and 2.73X higher than with static cage TLIF. Several influencing factors include the height of the expandable cage, the cross-sectional area of the cage and the patient's bone density. This study aims to look at the biomechanics of the TLIF expandable cage which was expanded in situ on straight type and 3D type TLIf expandable cages for normal bone density and osteoporosis using finite element analysis. Method: This study comprises three stages: modeling of Lumbar III-V, modeling of expandable cage straight type and 3D type on SolidWork, and finally combining the lumbar model and expandable cage TLIF. In the lumbar model, two models are made: osteoporosis and normal. There are four models in total, which include the straight-type expandable cage for normal bone density and osteoporosis, and the 3D-type expandable cage for normal bone density and osteoporosis. Peak stress measurements were carried out on the superior endplate of L5 and the inferior endplate of L4 for all four types of models. The load of 300N was applied to Lumbar III to simulate a lying patient, and the inferior lumbar V was used as a fixed constraint. The simulation of expanding the cage at 1,2,3,4.5 mm was carried out by adding a reaction force to the cage in addition to the 300N load on Lumbar III. The peak stress on the superior endplate of Lumbar 5 and the inferior endplate of Lumbar 4 was measured after expanding the cage. The peak stress value that occurred in each model was then calculated and compared. Results: to simulate lying down patient, a load of 300N was applied to the superior endplate of Lumbar III, and the expandable cage was expanded from 0mm to 4.5 mm. This led to an increase in peak stress on the superior endplate of L5 and inferior lumbar 4 in each model. The straight-type expandable cage with normal L5 density had a peak stress range of 1.36-3.37 MPa and L4 had a 1.36-1.82 MPa peak stress range. In the straight-type expandable cage with osteoporosis density, L5 had a peak stress range of 1.56-8.59 MPa, and L4 had a 1.44-1.75 MPa peak stress range.In the 3D-type expandable cage with normal density, L5 had a stress range of 1.84-3.19 MPa, and L4 had a 1.49-2.36 MPa stress range. Lastly, the 3D-type expandable cage with osteoporosis density had a stress range of 2.66-4.18 MPa for L5 and 2.49-3.34 MPa for L4. Conclusion: There is an increase in peak stress in each model when the expandable cage expanded. Furthermore, the increase in peak stress in the osteoporosis density is higher compared to the normal density in both types of expandable cages. This is due to an increase in the difference in Young's modulus in the expandable cage and the lumbar. The increase in peak stress in the straight-type expandable cage is greater than the 3D type in both normal bone density and osteoporotic bone density. The reason behind this is that the cross-sectional area of the expandable cage in contact with the endplate is smaller compared to the 3D-type expandable cage, which results in higher peak stress in the straight-type expandable cage. The 3D-type expandable cage distributes stress more evenly, which reduces peak stress on the superior endplate of lumbar 5 and the inferior endplate of L4.
Keywords: Expandable cage, TLIF, peak stress, Finite element analysis