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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Determination of the biomechanical effect of an interspinous process device on implanted and adjacent lumbar spinal segments using a hybrid testing protocol: a finite-element study(Amer Assoc Neurological Surgeons, 2015) N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Erbulut, Deniz Ufuk; Zafarparandeh, Iman; Hassan, Chaudhry Raza; Lazoğlu, İsmail; Özer, Ali Fahir; Researcher; PhD Student; Master Student; Faculty Member; Faculty Member; Department of Mechanical Engineering; School of Medicine; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; 37661; N/A; N/A; 179391; 1022OBJECT The authors evaluated the biomechanical effects of an interspinous process (ISP) device on kinematics and load sharing at the implanted and adjacent segments. METHODS A 3D finite-element (FE) model of the lumbar spine (L1-5) was developed and validated through comparison with published in vitro study data. Specifically, validation was achieved by a flexible (load-control) approach in 3 main planes under a pure moment of 10 Nm and a compressive follower load of 400 N. The ISP device was inserted between the L-3 and L-4 processes. Intact and implanted cases were simulated using the hybrid protocol in all motion directions. The resultant motion, facet load, and intradiscal pressure after implantation were investigated at the index and adjacent levels. In addition, stress at the bone-implant interface was predicted. RESULTS The hybrid approach, shown to be appropriate for adjacent-level investigations, predicted that the ISP device would decrease the range of motion, facet load, and intradiscal pressure at the index level relative to the corresponding values for the intact spine in extension. Specifically, the intradiscal pressure induced after implantation at adjacent segments increased by 39.7% and by 6.6% at L2-3 and L4-5, respectively. Similarly, facet loads at adjacent segments after implantation increased up to 60% relative to the loads in the intact case. Further, the stress at the bone-implant interface increased significantly. The influence of the ISP device on load sharing parameters in motion directions other than extension was negligible. CONCLUSIONS Although ISP devices apply a distraction force on the processes and prevent further extension of the index segment, their implantation may cause changes in biomechanical parameters such as facet load, intradiscal pressure, and range of motion at adjacent levels in extension.Publication Metadata only The safety and accuracy of the fluoroscopic imaging during proximal femoral fixation: a computerized 3D reappraisal of the joint penetration risk(Elsevier Sci Ltd, 2021) N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Aslan, Lercan; Subaşı, Ömer; Demirhan, Mehmet; Seyahi, Aksel; Lazoğlu, İsmail; Faculty Member; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Mechanical Engineering; School of Medicine; Graduate School of Sciences and Engineering; School of Medicine; School of Medicine; College of Engineering; 145301; N/A; 9882; 52082; 179391Background: To assess the success of proximal cephalomedullary nailing operations for treating trochanteric fractures, surgeons utilize 2D fluoroscopy to observe the relative positions of the femoral head and the implant. One distance-based risk parameter, observed from the AP and Lateral projections, is the Tip-Surface Distance(TSD) that dictates how close to the outer cortex should the implant tip be residing to avoid post-surgical complications such as cut-out or joint penetration. In this study, the safety and the accuracy of the orthogonal fluoroscopic imaging were evaluated. Methods: A femoral head model was created and the risk zone was defined as a hemispherical shell of 5 mm thickness beneath the subchondral cortex, which should not be violated during screw insertion. The remaining hemisphere beneath the risk zone was designated as the safe zone. To assess the effect of head size, each simulation was conducted for 34, 47, and 60 mm diameter(Dfemur) femoral heads. The rate of safe zone violation was calculated for all possible screw endpoints with a TSD of at least 5 mm on fluoroscopic orthogonal views (TSDAP and TSDLat). Results: The minimum risk of joint penetration was achieved when the TSDAP/TSDLat ratio was 1. For Dfemur of 34 mm there was a risk of 91.7% of the safe zone violation when each TSDAP and TSDLat were 5 mm and 0% for 9 mm. For Dfemur of 47 mm, the risk was 92.2% for 5 mm and 0% for 11 mm. For Dfemur of 60 mm, the risk was 92.3% for 5 mm and 0% for 13 mm. Safety maps were constructed for all possible TSD combinations for 34, 47, and 60 mm femoral heads. Conclusions: Depending solely on the orthogonal fluoroscopic images is not a safe and accurate technique for assessing joint penetration risk during proximal femoral fixation due to the spherical geometry of the femoral head. The screw tip can lie completely outside of the femoral head even when it appears inside, in both orthogonal fluoroscopic views. Evidently, when using TSD, more stringent distance limits should be chosen, contrary to the recommended 5 mm limit. Our safety maps for TSD combinations may be used to check the security of the implantation. (C) 2020 Elsevier Ltd. All rights reserved.Publication Metadata only A robotic indenter for minimally invasive characterization of soft tissues(Elsevier Science Bv, 2005) Avtan, Levent; Düzgün, Oktay; N/A; N/A; Department of Mechanical Engineering; Samur, Evren; Sedef, Mert; Başdoğan, Çağatay; Master Student; Master Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering College of Engineering; 192890; N/A; 125489We have developed a robotic indenter for minimally invasive measurement of tissue properties during a laparoscopic surgery. Using the indenter, we conducted animal experiments in situ and successfully measured the force versus displacement response of pig liver under static and dynamic loading conditions. Using the small deformation assumption, we estimated the effective Young's modulus of pig liver around 15 kPa from the force-displacement data of static indentations. We also obtained the relaxation function, describing the variation of force response with respect to time, from the data of stress relaxation experiments. We observed that pig liver shows linear viscoelastic behavior.Publication Metadata only A novel adjustable locking plate (ALP) for segmental bone fracture treatment(Elsevier Sci Ltd, 2019) N/A; N/A; Department of Mechanical Engineering; Subaşı, Ömer; Oral, Atacan; Lazoğlu, İsmail; PhD Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 179391A novel Ti6Al4V adjustable locking plate (ALP) is designed to provide enhanced bone stability for segmental bone fractures and to allow precise positioning of disconnected segments. The design incorporates an adjustable rack and pinion mechanism to perform compression, distraction and segment transfer during plate fixation surgery. The aim of this study is to introduce the advantages of the added feature and computationally characterize the biomechanical performance of the proposed design. Structural strength of the novel plate is analyzed using numerical methods for 4-point bending and fatigue properties, following ASTM standards. An additional mechanical failure finite element test is also conducted on the rack and pinion to reveal how much torque can be safely applied to the mechanism by the surgeon. Simulation results predict that the new design is sufficiently strong to not fail under regular anatomical loading scenarios with close bending strength and fatigue life properties to clinically used locking compression plates. The novel ALP design is expected to be a good candidate for addressing problems regarding fixation of multi-fragmentary bone fractures.Publication Metadata only In vitro validation of a self-driving aortic-turbine venous-assist device for fontan patients(Elsevier, 2018) Türköz, Rıza; Department of Mechanical Engineering; N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Pekkan, Kerem; Aka, İbrahim Başar; Tutsak, Ece; Ermek, Erhan; Balım, Haldun; Lazoğlu, İsmail; Faculty Member; PhD Student; Master Student; Other; Master Student; Faculty Member; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; Graduate School of Sciences and Engineering; College of Engineering; 161845; N/A; N/A; N/A; N/A; 179391Background: Palliative repair of single ventricle defects involve a series of open-heart surgeries where a single-ventricle (Fontan) circulation is established. As the patient ages, this paradoxical circulation gradually fails, because of its high venous pressure levels. Reversal of the Fontan paradox requires an extra subpulmonic energy that can be provided through mechanical assist devices. The objective of this study was to evaluate the hemodynamic performance of a totally implantable integrated aortic-turbine venous-assist (iATVA) system, which does not need an external drive power and maintains low venous pressure chronically, for the Fontan circulation. Methods: Blade designs of the co-rotating turbine and pump impellers were developed and 3 prototypes were manufactured. After verifying the single-ventricle physiology at a pulsatile in vitro circuit, the hemodynamic performance of the iATVA system was measured for pediatric and adult physiology, varying the aortic steal percentage and circuit configurations. The iATVA system was also tested at clinical off-design scenarios. Results: The prototype iATVA devices operate at approximately 800 revolutions per minute and extract up to 10% systemic blood from the aorta to use this hydrodynamic energy to drive a blood turbine, which in turn drives a mixed-flow venous pump passively. By transferring part of the available energy from the single-ventricle outlet to the venous side, the iATVA system is able to generate up to approximately 5 mm Hg venous recovery while supplying the entire caval flow. Conclusions: Our experiments show that a totally implantable iATVA system is feasible, which will eliminate the need for external power for Fontan mechanical venous assist and combat gradual postoperative venous remodeling and Fontan failure.Publication Metadata only Comparison of the morphologic and mechanical features of human cranial dura and other graft materials used for duraplasty(Elsevier Science Inc, 2022) Ozkan, Mazhar; N/A; N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Çavdar, Safiye; Sürücü, Hüseyin Selçuk; Malik, Anjum Naeem; Tanış, Özgül; Lazoğlu, İsmail; Faculty Member; Faculty Member; PhD Student; PhD Student; Undergraduate Student; Faculty Member; Department of Mechanical Engineering; School of Medicine; School of Medicine; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; School of Medicine; College of Engineering; 1995; 21780; N/A; N/A; N/A; 179391Objective: This study aimed to compare the thickness and mechanical properties of the frontal; parietal; temporal; occipital human dura; autogenous grafts (facia lata, temporal fascia, galea aponeurotica); and artificial dura. Methods: Sagittal and transverse dura samples were obtained from standard regions of the cranial dura from 30 autopsies for histologic and mechanical property measurements. Identical measurements were made for the autogenous grafts artificial dura, and the results were statistically analyzed. Results: The thickness of the temporal (0.35 +/- 0.11 mm), parietal (0.44 +/- 0.13 mm), frontal (0.38 +/- 0.12 mm), and occipital (0.46 +/- 0.18 mm) dura showed regional variations. The parietal and occipital dura were significantly thicker than the temporal dura. The occipital dura was considerably thicker than the frontal dura. The frontal and temporal dura of males were significantly thicker than females. The sagittal maximum tensile force measurements were significantly greater than transverse, for the frontal, temporal, and occipital dura. The stiffness measurements in sagittal direction were greater than the measurements in transverse direction for the frontal dura. The mechanical properties and thickness of the autogenous and artificial dura were not similar to the human dura. Consclusions: The thickness and mechanical properties of the regional cranial dura should be taken into consideration for a better cure and fewer complications. The mechanical properties of sagittal and transverse dura should be kept in mind for the preference of dura material. The present study's data can pave the way to produce artificial regional dura by mimicking the thickness and mechanical properties of the human dura.Publication Metadata only Computer modeling for the prediction of thoracic aortic stent graft collapse(Mosby-Elsevier, 2013) Pasta, Salvatore; Cho, Jae-Sung; Dur, Onur; Vorp, David A.; Department of Mechanical Engineering; Pekkan, Kerem; Faculty Member; Department of Mechanical Engineering; College of Engineering; 161845Objective: To assess the biomechanical implications of excessive stent protrusion into the aortic arch in relation to thoracic aortic stent graft (TASG) collapse by simulating the structural load and quantifying the fluid dynamics on the TASG wall protrusion extended into a model arch. Methods: One-way coupled fluid-solid interaction analyses were performed to investigate the flow-induced hemodynamic and structural loads exerted on the proximal protrusion of the TASG and aortic wall reconstructed from a patient who underwent traumatic thoracic aortic injury repair. Mechanical properties of a Gore TAG thoracic endoprosthesis (W. L. Gore and Assoc, Flagstaff, Ariz) were assessed via experimental radial compression testing and incorporated into the computational modeling. The TASG wall protrusion geometry was characterized by the protrusion extension (PE) and by the angle (q) between the TASG and the lesser curvature of the aorta. The effect of q was explored with the following four models with PE fixed at 1.1 cm: q [ 10 degrees, 20 degrees, 30 degrees, and 40 degrees. The effect of PE was evaluated with the following four models with q fixed at 10 degrees: PE [ 1.1 cm, 1.4 cm, 1.7 cm and 2.0 cm. Results: The presence of TASG wall protrusion into the aortic arch resulted in the formation of swirling, complex flow regions in the proximal luminal surface of the endograft. High PE values (PE [ 2.0 cm) led to a markedly reduced left subclavian flow rate (0.27 L/min), low systolic perfusion pressure (98 mm Hg), and peak systolic TASG diameter reduction (2 mm). The transmural pressure load across the TASG was maximum for the model with the highest PE and q, 15.2 mm Hg for the model with PE [ 2.0 cm and q [ 10 degrees, and 11.6 mm Hg for PE [ 1.1 cm and q [ 40 degrees. Conclusions: The findings of this study suggest that increased PE imparts an apparent risk of distal end-organ malperfusion and proximal hypertension and that both increased PE and q lead to a markedly increased transmural pressure across the TASG wall, a load that would portend TASG collapse. Patient-specific computational modeling may allow for identification of patients with high risk of TASG collapse and guide preventive intervention.Publication Metadata only Defining a new variable that may impact long-term postoperative nasal tip support the biomechanical properties of the columellar strut graft(Lippincott Williams and Wilkins (LWW), 2019) Layegh, Ehsan; N/A; N/A; Department of Mechanical Engineering; N/A; N/A; N/A; N/A; Sezgin, Billur; Güney, Kırdar; Lazoğlu, İsmail; Tatar, Sedat; Özel, Melis; Özmen, Selahattin; Yavuzer, Cahit Reha; Faculty Member; Doctor; Faculty Member; N/A; Undergraduate Student; Faculty Member; Other; Department of Mechanical Engineering; School of Medicine; N/A; College of Engineering; School of Medicine; School of Medicine; School of Medicine; School of Medicine; 133762; N/A; 179391; N/A; N/A; 125951; N/ABackground: Although columellar strut grafts (CSGs) are considered among the fundamental steps for providing nasal tip support, a downward rotation of the nasal tip in patients with strut grafts can still be encountered. Patient-related factors such as nasal skin thickness can allow the plastic surgeon to anticipate certain drawbacks that can be encountered in the healing phase, but patient-based differences of nasal cartilage and the resulting impact have yet to be investigated. The purpose of this study was to evaluate the effect of the biomechanical properties of CSGs on late postoperative nasal tip position and support. Methods: The study was undertaken with the participation of 20 patients undergoing closed-technique primary rhinoplasty with CSGs. Each cartilage specimen was biomechanically analyzed to calculate the modulus of elasticity. Preoperative and postoperative images were obtained to determine nasal tip position and rotation with quantitative measurements. Postoperative 3- and 12-month measurements were evaluated according to their relationship with the elasticity modulus of the utilized cartilages. Results The evaluation demonstrated that the elasticity modulus can impact the long-term support of the nasolabial angle in which an increase in the coefficient of elasticity can result in a decrease in long-term nasal tip support. Conclusion: The results of the study reveal a new objective variable that can impact nasal tip dynamics and patient-related differences following rhinoplasty. This study not only brings forth a different perspective in the evaluation of nasal tip dynamics but can also provide data for determining ideal values for cartilage prefabrication.