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Öğe A biomechanical comparison of polymethylmethacrylate-reinforced and expansive pedicle screws in pedicle-screw revisions(Turkish Assoc Orthopaedics Traumatology, 2009) Bostan, Bora; Esenkaya, Irfan; Gunes, Taner; Erdem, Mehmet; Asci, Murat; Kelestemur, M. Halidun; Sen, CengizObjectives: Different techniques and choices exist for revision of pedicle screws, two of which are pedicle screw combined with cement augmentation and expansive pedicle screw fixation. This biomechanical study was designed to compare the pullout strengths of two different revision techniques. Methods: Fourteen lumbar vertebrae obtained from four calves (mean age 15 months) were divided into two groups equal in number. Monoaxial 6.0-mm pedicle screws were inserted into the right pedicles, and axial pullout testing was performed at a rate of 10 mm/min and failure strengths were recorded. Revision was performed with the same-sized pedicle screws reinforced with polymethylmethacrylate in group 1, and with 7.0-mm expansive pedicle screws in group 2, and pullout testing was repeated to record maximum revision pullout strengths. Results: The mean pullout strengths recorded before and after revision were significantly different in both groups, being 2,162.9 +/- 718.5 N and 2,794.3 +/- 979.2 N in group 1 (p=0.041) and 2,605.0 +/- 487.6 N and 3,327.1 +/- 640.8 N in group 2 (p=0.012), respectively. However, the mean pullout strengths recorded before and after revision did not differ significantly between the two groups (p>0.05). Conclusion: Our results showed that expansive pedicle screws 1 mm larger in diameter provide similar pullout strengths to those of same-sized, polymethylmethacrylate-reinforced screws in revision of pedicle screw fixation, suggesting that they can be preferred with the additional advantages of ease of application and avoiding risks for pedicle fracture and cement leakage.Öğe Can serum interleukin 34 levels be used as an indicator for the prediction and prognosis of COVID-19?(Public Library Science, 2024) Karahan, Dogu; Bolayir, Hasan Ata; Bolayir, Asli; Demir, Bilgehan; Otlu, Oender; Erdem, Mehmet; Perera, NilankaObjective Interleukin 34 (IL-34) is a molecule whose expression is increased in conditions such as autoimmune disorders, inflammation, and infections. Our study aims to determine the role of IL-34 in the diagnosis, follow-up, and prognosis of Coronavirus Disease-19 (COVID-19).Method A total of 80 cases were included in the study as 40 COVID-19 positive patient groups and 40 COVID-19 negative control groups. The COVID-19-positive group consisted of 20 intensive-care unit (ICU) patients and 20 outpatients. Serum IL-34, c-reactive protein (CRP), ferritin, D-dimer, troponin I, hemogram, and biochemical parameters of the cases were studied and compared between groups.Results IL-34 levels were significantly higher in the COVID-19-positive group than in the negative group. IL-34 levels increased in correlation with CRP in predicting the diagnosis of COVID-19. IL-34 levels higher than 31.75 pg/m predicted a diagnosis of COVID-19. IL-34 levels did not differ between the outpatient and ICU groups in COVID-19-positive patients. IL-34 levels were also not different between those with and without lung involvement.Conclusion While IL-34 levels increased in COVID-19-positive patients and were successful in predicting the diagnosis of COVID-19, it was not found to be significant in determining lung involvement, risk of intensive care hospitalization, and prognosis. The role of IL-34 in COVID-19 deserves further evaluation.Öğe Carbonic Anhydrase IX as a Marker of Disease Severity in Obstructive Sleep Apnea(Mdpi, 2022) Geckil, Aysegul Altintop; Kiran, Tugba Raika; Berber, Nurcan Kirici; Otlu, Onder; Erdem, Mehmet; In, ErdalBackground and Objectives: Carbonic anhydrase (CA) enzymes are a family of metalloenzymes that contain a zinc ion in their active sites. CA enzymes have been implied in important situations such as CO2 transport, pH regulation, and oncogenesis. CA-IX is a transmembrane glycoprotein and stimulates the expression of hypoxia-inducible factor-1 (HIF-1) CA-IX. This study aimed to determine serum CA-IX levels in OSA patients in whom intermittent hypoxia is important and to investigate the relationship between serum CA-IX levels and disease severity. Materials and Methods: The study included 88 people who applied to Malatya Turgut Ozal University Training and Research Hospital Sleep Disorders Center without a history of respiratory disease, malignancy, and smoking. Patients were divided into three groups: control (AHI < 5, n = 31), mild-moderate OSA (AHI = 5-30, n = 27) and severe OSA (AHI > 30, n = 30). The analysis of the data included in the research was carried out with the SPSS (IBM Statistics 25, NY, USA). The Shapiro-Wilk Test was used to check whether the data included in the study had a normal distribution. Comparisons were made with ANOVA in multivariate groups and the t-test in bivariate groups. ANCOVA was applied to determine the effect of the CA-IX parameter for OSA by controlling the effect of independent variables. The differentiation in CA-IX and OSA groups was analyzed regardless of BMI, age, gender, and laboratory variables. ROC analysis was applied to determine the parameter cut-off point. Sensitivity, specificity, and cut-off were calculated, and the area under the curve (AUC) value was calculated. Results: Serum CA-IX levels were 126.3 +/- 24.5 pg/mL in the control group, 184.6 +/- 59.1 pg/mL in the mild-moderate OSA group, and 332.0 +/- 39.7 pg/mL in the severe OSA group. Serum CA-IX levels were found to be higher in the severe OSA group compared to the mild-moderate OSA group and control group and higher in the mild-moderate OSA group compared to the control group (p < 0.001, p < 0.001, p < 0.001, respectively). In addition, a negative correlation between CA-IX and minimum SaO(2) and mean SaOI(2) (r = -0.371, p = 0.004; r = -0.319, p = 0.017, respectively). A positive correlation between CA-IX and desaturation index (CT90) was found (r = 0.369, p = 0.005). A positive correlation was found between CA-IX and CRP (r = 0.340, p = 0.010). When evaluated by ROC curve analysis, the area under the curve (AUC) value was determined as 0.940 (95% CI 0.322-0.557; p < 0.001). When the cut-off value for CA-IX was taken as 254.5 pg/mL, it was found to have 96.7% sensitivity and 94.8% specificity in demonstrating severe OSA. Conclusions: Our study found that serum CA-IX value was higher in OSA patients than in control patients, and this elevation was associated with hypoxemia and inflammation. CA-IX value can be a fast, precise, and useful biomarker to predict OSA.Öğe Comparison of popliteal anesthesia and spinal anesthesia in patients with the diabetic foot: Our clinical series(2021) Akdemir, Ovunc; Tatar, Burak Ergun; Erdem, Mehmet; Kostekci, HaticeAim: Surgery is of great importance in the treatment of diabetic foot. We aimed to compare unilateral spinal anesthesia and ultrasound-guided popliteal block procedures in patients diagnosed with a diabetic foot ulcer. Materials and Methods: In this study, we included 54 patients diagnosed with diabetic foot ulcers in our hospital between September 2010 and December 2012. The patients were randomly divided into two groups of 27 patients each: Group I (Spinal group) and Group II (Popliteal group). Spinal anesthesia was performed in Group I, whereas ultrasound-guided popliteal block was performed in Group II. During and after the anesthesia, the total isotonic fluid given, average patient and surgeon satisfaction score, and length of hospital stay were evaluated. Results: In Group I, the average length of hospital stay was 6.07 ± 1.2 days, the total isotonic fluid given was 1832.2 ± 280.7 ml, and the average patient and surgeon satisfaction score was 2.44 ± 0.5. In Group II, the average length of hospital stay was 6.5 ± 1.04 days, the total isotonic fluid given was 731.11 ± 130.2 ml, and the average patient and surgeon satisfaction score were 3. In addition, in Group I, 9 patients had bradycardia and 12 patients had hypotension and nausea. The findings of the study indicate a statistically significant difference in terms of the total isotonic fluid given and average patient and surgeon satisfaction scores (p < 0.05). However, no statistically significant difference was observed in terms of hospital stay (p > 0.05). Conclusion: In conclusion, we believe that ultrasound-guided popliteal block provides more reliable and efficient analgesia than spinal anesthesia in patients with diabetic foot ulcersÖğe The effects of disease severity and comorbidity on oxidative stress biomarkers in obstructive sleep apnea(Springer Heidelberg, 2024) Kiran, Tugba Raika; Otlu, Onder; Erdem, Mehmet; Geckil, Aysegul Altintop; Berber, Nurcan Kirici; In, ErdalPurposeIschemia-modified albumin (IMA), total oxidant status (TOS), and total antioxidant status (TAS) are biomarkers used to evaluate oxidative stress status in various diseases including obstructive sleep apnea (OSA). In this study, we investigated the effects of disease severity and comorbidity on IMA, TOS and TAS levels in OSA.MethodsPatients with severe OSA (no-comorbidity, one comorbidity, and multiple comorbidities) and mild-moderate OSA (no-comorbidity, one and multiple comorbidities), and healthy controls were included in the study. Polysomnography was applied to all cases and blood samples were taken from each participant at the same time of day. ELISA was used to measure IMA levels in serum samples and colorimetric commercial kits were used to perform TOS and TAS analyses. In addition, routine biochemical analyses were performed on all serum samples.ResultsA total of 74 patients and 14 healthy controls were enrolled. There was no statistically significant difference between the disease groups according to gender, smoking status, age, body mass index (BMI), HDL, T3, T4, TSH, and B12 (p > 0.05). As the severity of OSA and comorbidities increased, IMA, TOS, apnea-hypopnea index (AHI), desaturation index (T90), cholesterol, LDL, triglyceride, AST, and CRP values increased significantly (p < 0.05). On the other hand, TAS, minimum desaturation, and mean desaturation values decreased significantly (p < 0.05).ConclusionsWe concluded that IMA, TOS, and TAS levels may indicate OSA-related oxidative stress, but as the severity of OSA increases and with the presence of comorbidity, IMA and TOS levels may increase and TAS levels decrease. These findings suggest that disease severity and presence/absence of comorbidity should be considered in studies on OSA.Öğe Efficacy of serum apelin and galectin-3 as potential predictors of mortality in severe COVID-19 patients(Wiley, 2023) Berber, Nurcan Kirici; Geckil, Aysegul Altintop; Altan, Nazife Ozge; Kiran, Tugba Raika; Otlu, Onder; Erdem, Mehmet; In, ErdalApelin is a cardioprotective biomarker while galectin-3 is a pro-inflammatory and profibrotic biomarker. Endothelial dysfunction, hyperinflammation, and pulmonary fibrosis are key mechanisms that contribute to the development of adverse outcomes in Coronavirus disease 2019 (COVID-19) infection. This study aims to analyze the prognostic value of serum apelin and galectin-3 levels to early predict patients at high risk of mortality in patients hospitalized for severe COVID-19 pneumonia. The study included 78 severe COVID-19 patients and 40 healthy controls. The COVID-19 patients were divided into two groups, survivors and nonsurvivors, according to their in-hospital mortality status. Basic demographic and clinical data of all patients were collected, and blood samples were taken before treatment. In our study, serum apelin levels were determined to be significantly lower in both nonsurvivor and survivor COVID-19 patients compared to the control subjects (for both groups, p < 0.001). However, serum apelin levels were similar in survivor and nonsurvivor COVID-19 patients (p > 0.05). Serum galectin-3 levels were determined to be higher in a statistically significant way in nonsurvivors compared to survivors and controls (for both groups; p < 0.001). Additionally, serum galectin-3 levels were significantly higher in the survivor patients compared to the control subjects (p < 0.001). Positive correlations were observed between galectin-3 and age, ferritin, CK-MB and NT-proBNP variables (r = 0.32, p = 0.004; r = 0.24, p = 0.04; r = 0.24, p = 0.03; and r = 0.33, p = 0.003, respectively) while a negative correlation was observed between galectin-3 and albumin (r = -0.31, p = 0.006). Multiple logistic regression analysis revealed that galectin-3 was an independent predictor of mortality in COVID-19 patients (odds ratio [OR] = 2.272, 95% confidence interval [CI] = 1.106-4.667; p = 0.025). When the threshold value for galectin-3 was regarded as 2.8 ng/ml, it was discovered to predict mortality with 80% sensitivity and 57% specificity (area under the curve = 0.738, 95% CI = 0.611-0.866, p = 0.002). Galectin-3 might be a simple, useful, and prognostic biomarker that can be utilized to predict patients who are at high risk of mortality in severe COVID-19 patients.Öğe Evaluation of pre-cycle hysteroscopy findings and its pathological results of 458 patients undergoing IVF: A retrospective cohort study(2022) Demirdag, Erhan; Kutlucan, Hazal; Safarova, Sahila; Guler, Ismail; Cevher Akdulum, Munire Funda; Bozkurt, Nuray; Erdem, Mehmet; Erdem, AhmetAim: To evaluate the hysteroscopy results performed before IVF treatment and its pathological findings that may affect pregnancy outcomes in patients undergoing the first IVF cycle. Materials and Methods: This descriptive study was carried out retrospectively at Gazi University Hospital and a private IVF Clinic between January 2016 and December 2021. A total of 458 patients who had hysteroscopy procedures prior to the planned IVF cycle were analyzed. Appropriate surgery was performed simultaneously during hysteroscopy in patients with uterine cavity abnormalities. Outcome measures were the frequency of uterine abnormalities detected during the hysteroscopy and confirmation of these abnormalities with their pathological findings. Results: Unexplained infertility was the most frequent infertility etiology among patients (50.9%). The most finding abnormality was endometrial polyp detected in 45.2% of patients during hysteroscopy. The second frequent abnormal finding was intrauterine adhesion, with a ratio of 15.9% of patients. The uterine cavity was seen as normal in 9.6% of patients during the hysteroscopy procedure. Endometrial sampling was performed in 75.5% of patients. The most common pathological result was endometrial polyp that was consistent with hysteroscopy findings (44.3%). Only 20.8% of patients had normal findings after pathological examination on the endometrial tissue samples. Conclusion: Evaluating the uterine cavity before the IVF cycle is necessary to reach successful outcomes. Undetected intrauterine lesions are frequently observed during hysteroscopy in asymptomatic patients previously examined by conventional methods. Hysteroscopy may be a reasonable approach to assess and restore the uterine cavity in patients undergoing the first IVF cycle.Öğe Experimental investigation of kerf of Ti6Al4V exposed to different heat treatment processes in WEDM and optimization of parameters using genetic algorithm(Springer London Ltd, 2015) Altug, Mehmet; Erdem, Mehmet; Ozay, CetinIn this study, microstructure, mechanical, and conductivity characteristics of alloy Ti6Al4V were changed with different heat treatments and the effect of such characteristics on its machinability with wire electrical discharge machining (WEDM). Optical microscope, scanning electron microscope (SEM), and X-ray diffraction (XRD) examinations were performed to determine various characteristics, and additionally microhardness and conductivity measurements were conducted hereof. L18 Taguchi test design was conducted with three levels and six different parameters to determine the effect of such alterations on its machinability with WEDM, and post-processing kerf (cutting width) values were determined. Microchanges were ensured successfully by using applied heat treatments. Results obtained with the optimization technique of genetic algorithm gave minimum kerf. Values obtained by using response surface method along with this equation completely match with those achieved in the experiments. The best kerf value was obtained from sample E which was quenched from dual phase area. The microstructure of this sample was composed of primary alpha and alpha' phases.Öğe Investigation of mechanical, microstructural, and machining properties of AISI 420 martensitic stainless steel welded by laser welding(Springer London Ltd, 2016) Erdem, Mehmet; Altug, Mehmet; Karabulut, MustafaIn this study, AISI 420 stainless steel sheets of 1.8 mm in thickness were joined by laser welding. To determine the mechanical and microstructural properties of these sheets, microhardness, tensile, optical microscope, and SEM and XRD examinations were made. The following results were obtained: the carbides dissolved in austenite near the weld metal of heat affected zone. The increase in laser pulse frequency was more effective in determining the penetration and width of the weld metal than current and focal diameter. The highest yield and tensile strength values were 269 and 857.34 MPa, respectively, at the welded sheet joined with no.7 parameter. The grain size and microstrain values of untempered welded sample were 229.322 nm and 0.00347, respectively, at the welded sheet joined with no.6 parameter. The narrowest kerf and the lowest microhardness were 161 mu and 293 HV, successively, and these were obtained in the weld metal of sample number 5.Öğe Investigation of structure and mechanical properties of copper-brass plates joined by friction stir welding(Springer London Ltd, 2015) Erdem, MehmetIn this study, copper and brass plates of 3-mm thickness were joined by friction stir welding at three different rotation rates and traverse speeds. The goal of this study is to determine weldability and mechanical properties of welded copper and brass plates. In order to determine the mechanical and microstructure properties of these plates, microhardness, tensile, bending, optical microscope, scanning electron microscope, and X-ray diffraction examinations were made. The following results were obtained; due to dynamic recrystallization effect, the grains in the stirred zone became fine. Microhardness values of the stirred zone were observed between 87 and 255 HV. According to the X-ray diffraction results, no phase transformation was observed in the stirred zone. In the stirred zone, a small tunnel-shaped joint defect was observed. It was determined that when heat input decreased, the mechanical properties and microstrain increased.Öğe INVESTIGATION OF THE BALLISTIC AND MECHANICAL PROPERTIES OF THE PRE AND POST-WELDED 7039 ALUMINUM ALLOY(Gazi Univ, Fac Engineering Architecture, 2011) Erdem, Mehmet; Turker, MehmetIn this study, the special weld grooves was created on 7039 Al-Zn armor plate with different thickness of 12.7 and 38 mm and they were welded with MIG welding technique via multiple pass. After that, the ballistic and mechanical properties of these plates were examined. V-50 ballistic limit values of the base metal, the heat affected zone and the weld metal of the welded plate of 38 mm thickness were determined by shooting with laboratory bullets of 12.7 mm. 12.7 mm thickness welded plates were used for determining the mechanical properties. It is observed that the ballistic and mechanical properties of the welded samples decrease. Moreover the highest V-50 ballistic limit value was obtained from the base metal whereas the lowest V-50 ballistic limit value was obtained from the welded metal.Öğe Investigation of the Microstructure and Mechanical Properties of Etial 1050 Al Alloy Joints Produced by Friction Stir Welding(Gazi Univ, 2016) Erdem, Mehmet; Karabulut, MustafaIn this study, ETIAL 1050 H14 Al alloy plates of 3 mm thickness were joined by friction stir welding using a vertical milling machine at three different rotational speeds (720-910-1120 rpm) and at three different welding speeds (20-50-80 mm/minute). Grinding, polishing and etching were applied to the surface of the welded samples in order to ascertain the microstructure and micro hardness characteristics of the samples. Generally the hardness values of all the welded joints decreased from base the plate towards the stirred zone. Base metal exhibited elongated grains in rolling direction and its micro hardness was determined to be 45 HV. The heat affected zone displayed a coarse-grain structure and its micro hardness was 27-38 HV. The experiments have shown that the grains on the thermomechanically affected zone oriented towards the direction of the rotation of the stirring pin. The hardness of this zone was higher than that in the heat affected zone. It was also determined that fine equiaxed grains were formed in the stirred zone due to dynamic recrystallization.Öğe Mechanical and ballistic properties of powder metal 7039 aluminium alloy joined by friction stir welding(Elsevier, 2016) Erdem, Mehmet; Cinici, Hanifi; Gokmen, Ugur; Karakoc, Halil; Turker, Mehmet7039 Al alloy plates which were used as armor materials were produced by powder metallurgy method. The prepared mixed powders were pressed and plated by extrusion process. These plates, after being subjected to T6 heat treatment, were joined double-sided by friction stir welding method. Microstructure and microhardness of the welded plate were investigated. It was determined that the finest grain structure and the lowest hardness value occurred in the stir zone as 2-6 mu m and HV 80.9, respectively. In order to determine the ballistic properties of welded plates, 7.62 mm armor piercing projectiles were shot to the base metal (BM), heat affected zone (HAZ), and thermomechanically affected zone+stir zone (TMAZ+SZ). Ballistic limits (v(50)) of these zones were determined. The ballistic limits of the BM, TMAZ+SZ, and HAZ of the plate were approximately 14.7%, 15.3%, and 17.9% lower than that of the standard plate at the same thickness, respectively. It was determined that the armor piercing projectiles created petaling and ductile hole enlargement failure types at the armor plate. Ballistic and mechanical results can be enhanced by hot-cold rolling mills after extrusion and particle reinforcement.Öğe Pedikül vida revizyonlarında polimetilmetakrilat ile güçlendirilmiş ve ucu genişleyebilen pedikül vidalarının biyomekanik karşılaştırılması(2009) Bostan, Bora; Esenkaya, İrfan; Güneş, Taner; Erdem, Mehmet; Aşçı, Murat; Keleştemur, Halidun; Şen, CengizÖz: Amaç: Pedikül vidalarının revizyonlarında çeşitli yöntemler ve seçenekler kullanılmaktadır. Bunlardan ikisi vidaların çimentoyla güçlendirilmesi ve ucu genişleyebilen pedikül vidalarının (UGPV) kullanılmasıdır. Bu biyomekanik çalışmada, pedikül vida revizyonlarında kullanılan iki farklı tekniğin sıyırma güçleri karşılaştırıldı. Çalışma planı: Ortalama 15 aylık dört adet dananın lomber omurgalarından, her biri yedi adet omur içeren iki grup oluşturuldu. Omurların sağ pediküllerine 6 mm çaplı monoaksiyel pedikül vidaları uygulandı ve 10 mm/dk hızında aksiyel sıyırma testi yapıldı, yetmezlik değerleri kaydedildi. Grup 1’deki pediküllerin revizyonu 6 mm’lik pedikül vidası ve po- limetilmetakrilat güçlendirmesi ile yapıldı. Grup 2’deki pediküllerin revizyonu ise 7 mm’lik, uç kısımları genişleyebilen pedikül vidaları ile yapıldı. Revizyon sonrasında örneklere aynı hızda sıyırma testi uygulandı ve değerler kaydedildi. Sonuçlar: Revizyon öncesi ve sonrası sıyırma güçleri her iki grupta da anlamlı farklılık gösterdi (grup 1’de sırasıyla 2162.9±718.5 N ve 2794.3±979.2 N, p=0.041; grup 2’de 2605.0±487.6 N ve 3327.1±640.8 N, p=0.012). İki grup arasında hem başlangıç sıyırma güçleri hem de revizyon sonrası sıyırma güçleri ortalamaları arasında anlamlı fark bulunmadı (p>0.05). Çıkarımlar: Pedikül vida revizyonlarında, 1 mm daha geniş UGPV’nin sıyırma gücünün, polimetilmetakrilatla güçlendirilmiş ve revizyon öncesiyle aynı çaptaki pedikül vidalarıyla benzer olduğu görüldü. Uç kısmı genişleyebilen pedikül vidaları, pedikül kırığı ve çimento sızma gibi riskleri taşımaması ve daha kolay uygulanabilmeleri nedeniyle revizyon cerrahisinde tercih edilebilir.Öğe Surface roughness of Ti6Al4V after heat treatment evaluated by artificial neural networks(Carl Hanser Verlag, 2016) Altug, Mehmet; Erdem, Mehmet; Ozay, Cetin; Bozkir, OguzThe study examines how, using wire electrical discharge machining (WEDM), the microstructural, mechanical and conductivity characteristics of the titanium alloy Ti6Al4V are changed as a result of heat treatment and the effect they have on machinability. Scanning electron microscope (SEM), optical microscope and X-ray diffraction (XRD) examinations were performed to determine various characteristics and additionally related microhardness and conductivity measurements were conducted. L-18 Taquchi test design was performed with three levels and six different parameters to determine the effect of such alterations on its machinability using WEDM and post-processing surface roughness (Ra) values were determined. Micro-changes were ensured successfully by using heat treatments. Results obtained with the optimization technique of artificial neural network (ANN) presented minimum surface roughness. Values obtained by using response surface method along with this equation were completely comparable with those achieved in the experiments. The best surface roughness value was obtained from sample D which had a tempered martensite structure.
