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    Finite element analysis of lattice designed lumbar interbody cage based on the additive manufacturing
    (Sage Publications Ltd, 2023) Bozyigit, Bulent; Oymak, Mehmet Akif; Bahce, Erkan; Uzunyol, Omer Faruk
    Additive manufacturing (AM) methods, which facilitate the production of complex structures with different geometries, have been used in producing interbody cages in recent years. In this study, the effects of Ti6Al4V alloy interbody lattice designed fusion cages between the third and fourth lumbar vertebrae where degenerative disc diseases occur were investigated using the finite element method. Face centered cubic (FCC), body centered cubic (BCC), and diamond structures were selected as the lattice structure suitable for the interbody cage. A kidney shaped interbody lumbar cage was designed. The designated lattice structures were selected by adjusting the cell sizes suitable for the designed geometry, and the mesh configuration was made by the lumbar lattice structure. 400N Axial force and 7.5 N.m moments were applied to the spine according to lateral bending, flexion, and torsion. 400N axial force and 7.5 N.m flexion moment is shown high strain and total deformation then lateral bending and torsion on BCC FCC and diamond lattice structured interbody cages. In addition, the effects of lattice structures under high compression forces were investigated by applying 1000N force to the lattice structures. When von Mises stresses were examined, lower von Mises stress and strains were observed in the BCC structure. However, a lower total deformation was observed in the FCC. Due to the design of the BCC and the diamond structure, it is assumed that bone implant adhesion will increase. In the finite element analysis (FEA), the best results were shown in BCC structures.
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    Microendoscopic Discectomy for Lumbar Disc Herniations: A Series of 389 Cases
    (Galenos Publ House, 2023) Bozyigit, Bulent; Abbasoglu, Bilal; Unluer, Caner; Ulku, Goktug; Tacyildiz, Abdullah Emre; Kertmen, Huseyin Hayri
    Objective: Lumbar disc herniation is one of the discogenic causes of lower back pain. Patients with severe nerve root compression or progressive neurologic deficit who do not respond to conventional treatments require surgical intervention. These surgical treatments include minimally invasive and traditional methods. In this study, we have presented the clinical data of patients who underwent microendoscopic discectomy (MED)-a minimally invasive method.Methods: The surgical and clinical data of 389 adult patients who were operated through MED by a single surgeon between 2017 and 2022 were retrospectively evaluated. Parameters such as per-oppostop visual analog scale (VAS), follow-up time, duration of hospitalization, and amount of intraoperative blood loss were examined.Results: Of the 389 patients included in our study, 169 were female and 220 were male, and their mean age was 42.78 years. L4-L5 (n=205, 51.6%), L5-S1 (n=185, 46.8%), L3-L4 (n=4, 1%), and L2-L3 (n=2, 0%) were the most frequently operated levels, showing a sequentially decreasing frequency. Bilateral surgery was performed in two patients. Recurrence was observed in 11 patients (2.8%). Cerebrospinal fluid was detected in 2 (0.5%) patients. The mean pre-and post-op VAS scores were calculated as 7.45 and 1.14, with a significant difference of p<0.001. The mean blood loss during surgery was calculated as 9.6 +/- 5.8 mL, and the postoperative hospital stay was 17.2 +/- 8.5 hours.Conclusion: MED was comparable to conventional methods in terms of symptom relief, recurrence rate, recovery time after surgery, and intraoperative blood loss.
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    Patient-Specific Lattice Cage Design for Cervical Spinal Fusion
    (Turkish Neurosurgical Soc, 2026) Bozyigit, Bulent; Oymak, Mehmet Akif; Bahce, Erkan; Singh, Gurminder
    AIM: To propose a patient-specific interbody cage with graded stiffness distributions analogous to the Young's modulus of the cervical spinal bone interface in order to improve mechanical compatibility, promote physiological load sharing, and enhance osseointegration. MATERIAL and METHODS: A synthetic database of spinal bone Young modulus values was used, incorporating anatomical regions (cervical, thoracic, lumbar) and patient-specific factors (age, bone density, health status). A parametric generative design approach allowed dynamic modification of lattice unit cell geometry to achieve target stiffness values (200-3000 MPa) while preserving structural integrity. RESULTS: Finite element endplate analysis demonstrated a 30%-50% reduction in stress shielding compared with conventional solid or homogeneous mesh lattices. Additively manufactured prototypes showed tunable stiffness-porosity trade-offs, achieving yield strength >= 150 MPa while supporting osseointegration. CONCLUSION: This study demonstrates improved load distribution and reduced risk of cage collapse compared with cadaveric spine data. Integrating computational design, biomechanical compatibility, and additive manufacturing may facilitate the development of patient-specific spinal implants with superior mechanical and biological performance.