Yazar "Atmaca, Halil" seçeneğine göre listele
Listeleniyor 1 - 7 / 7
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Changes in the loading of tibial articular cartilage following medial meniscectomy: a finite element analysis study(Springer, 2013) Atmaca, Halil; Kesemenli, Cevdet Cumhur; Memişoğlu, Kaya; Özkan, Arif; Çelik, YusufDepending on the location and extent of the meniscectomy, loading on the tibial articular cartilage alters. The main purpose of the present study was to analyze the loading on the tibial articular cartilage following medial meniscectomy performed in various location and extent, as well as in the healthy knee, via finite element analyses on the solid models. Totally, 11 finite element solid models, including the reference model, were created to investigate the effect of location (anterior, posterior, longitudinal) and extent of meniscectomy (25, 50, 75, and 100 %) on loading of tibial articular cartilage. Maximum equivalent stress of the tibial cartilage was measured 0.86 Megapascal in the reference model and increased approximately by 78 % in 25 % meniscectomy group, 177.9 % in 50 %, 473.8 % in 75 % meniscectomy group, and 752.6 % in total meniscectomy. When only the amount of meniscal tissue removed was considered ignoring the location of meniscectomy, no significant difference was found in the amount of tissue excised between 25 % meniscectomy and 50 % meniscectomy, as well as between 75 % meniscectomy and total meniscectomy. In all meniscectomy models, the loadings on tibial articular cartilage increased. Except total meniscectomy, the highest impact was observed in longitudinal 75 % meniscectomy. During the surgical treatment, the contributions of menisci on load absorption by increasing the tibiofemoral contact area must be considered. In fact, the increase in the rate of loading on tibial articular cartilage depends on according to type and amount of meniscectomy.Öğe Changes in the loadings on the shoulder girdle in the case of scapulothoracic fusion(Wiley-Blackwell, 2016) Atmaca, Halil; Uğur, Levent; Özkan, Arif; Mantelli, Alberto Grassi; Erzincanlı, FehmiBackground Scapulothoracic fusion (STF) may be an alternative and salvage procedure in the treatment of scapular winging. The biomechanical effects of this procedure on the shoulder girdle have not been previously considered. The purpose of this study is to demonstrate the relationship between STF and the stress distribution pattern of the shoulder girdle. Methods Three-dimensional solid modeling of the shoulder girdle was carried out using virtual finite element modeling. STF was applied to the reference model obtained in a computer environment. Dynamic and nonlinear analysis was performed. Results Stress distributions in joints and ligaments were calculated. With respect to loading on the joints, maximum equivalent stresses increased on acromioclavicular (AC) and GH joints in the case of STF during abduction and flexion respectively. Conclusion Results revealed that STF is a non-physiological, static procedure leading to load increase on GH and AC joint cartilages, which may be a cause of potential joint osteoarthritis. Copyright (C) 2015 John Wiley & Sons, Ltd.Öğe Diz osteoartriti olan hastalarda gebelik ve vücut kitle indeksinin etkisi(2013) Atmaca, Halil; Özkan, ArifAmaç: Kadınlarda diz osteoartriti ( gonartroz) ile vücut kitle indeksi (VKİ), doğum sayısı ve yaş gibi değişkenlerin ilişkisini araştırmak. Yöntem: Kliniğimize başvuran ve gonartroz tanısı alan ortalama yaşları 60,4 (40 -88) yıl olan 88 hasta değerlendirmeye alınmıştır. Hastaların yaşları, kilo ve boy değerleri, doğum sayıları, kaydedilmiştir. Şikayeti olan diz için AP -Yan grafil erinden radyolojik evreleme, WOMAC OA indeksi ( The We stern Ontario and Mcmaster Universities Osteoarthritis İndeks) ve Lequesne Diz Osteoartrit Şiddet İndeksi kullanılarak skorlama yapılmıştır. Bulgular : Çalışmada değerlendirilen 88 kadın hastanın ortalama VKİ leri 28,3 (19,8 - 42,7) idi. Ortalama doğum sayısı ise 7 (0 -13). Kellgren -Lawrance evreleme sistemine göre 2 hasta evre 1, 37 evre 2, 36 evre 3, 13 hasta ise evre 4 idi. Hastal arın ortalama toplam WOMAC OA skorları 66,7 (22 -91) iken WOMAC Ağrı skoru ortalama 13,2 (4 -20), Tutukluluk orta lama 4,8(2 -8 ), fonksiyon ortalama 48,6 (16 -65). Lequesne ağrı skoru ortalama 5,2 (2 -8), yürüme mesafesi ortalama 4 (1 -7), günlük aktivite ortalama 4,6 (1 -8) iken toplam Lequesne skoru ise ortalama 13,9 (5 - 23) idi. Hastanın yaşı ile WOMAC toplam, ağrı ve fonksiyon, Lequesne toplam ve yürüme mesafesi skorları arasında istatistiki olarak anlamlı ve pozitif korelasyon bulunurken, WOMAC tutukluluk, Lequesne ağrı, günlük aktivite skorları arasında anlamlı korelasyon bulu nmamıştır. VKİ ile WOMAC toplam skor hari cindeki tüm parametrelerde istatistiki olarak anlamlı pozitif ilişki bulunmuştur. Doğum sayıları incelendiğinde Doğum sayısı arttıkça yine WOMAC toplam skor haricindeki tüm parametrelerde istatistiki olarak anlamlı dercede artış olmaktadır Sonuç : VKİ, yaş ve doğum oranı arttıkça diz ekleminde dejenerasyon artmakta ve yaşam kalitesi azalmaktadır.Öğe The effect of proximal tibial corrective osteotomy on menisci, tibia and tarsal bones: a finite element model study of tibia vara(Wiley-Blackwell, 2014) Atmaca, Halil; Özkan, Arif; Mutlu, İbrahim; Çelik, Talip; Uğur, Levent; Kişioğlu, YasinBackgroundProximal tibial open wedge osteotomy (PTO) is a corrective operation used in the surgery of lower extremities and is applied to patients with varus deformities for sufficient correction. The aim of the study was to evaluate whether the PTO can achieve decreased stress-bearing on the tibia and tarsal bones in addition to correcting the mechanical axis of the lower limb in patients with tibia vara. MethodsThree-dimensional (3D) solid modelling of the lower extremity was carried out using computed tomography (CT) and magnetic resonance (MR)-containing images of all of the bony elements and non-bony structures. PTO was applied to the obtained deformed model in the computer environment and the correction was carried out. ResultsStress distributions in menisci, tibia and tarsal bones were calculated. With respect to loading on the tarsal bones, the maximum equivalent stresses on all bones decreased except for the navicula in the PTO-simulated model in the current study. ConclusionThese results clearly indicate that PTO can achieve decreased stresses on the tarsal bones in patients with tibia vara. Copyright (c) 2013 John Wiley & Sons, Ltd.Öğe The relationship between medial meniscal subluxation and stress distribution pattern of the knee joint: Finite element analysis(Elsevier, 2016) Gökkuş, Kemal; Atmaca, Halil; Uğur, Levent; Özkan, Arif; Aydın, Ahmet TuranBackground: Degenerative changes of the knee joint and clinical follow-up after meniscal subluxation are well documented. In the current study three-dimensional (3D) finite element analysis (FEA) of human lower limb was used to investigate the effect medial meniscal subluxation on the loadings of the knee structures. Methods: Apart from the reference model, a total of ten 3D models were created, according to amount of medial meniscal subluxation. ANSYS (R) 14 was used to analyze the stress/load distribution, that is to say the maximum equivalent stress (MES) (von Mises stress) on bones, cartilages, ligaments and menisci. MES was expressed as Newton/mm(2) = Megapascal (MPa). Results: In a static and standing upright position the MES on all knee structures were evaluated in the reference model. Although MES increased in all structures with the increase of medial meniscal subluxation degree, tibia cartilage was found to be the most affected structure with an increase of 22.73-fold in the 10 mm subluxation model when compared with references values. Conclusion: This study showed that medial meniscus subluxation is associated with increased loadings on all knee structures especially the tibia cartilage. Also the degree of the medial meniscal subluxation correlates with distribution and the amount of loadings on tibia cartilage which may be a prominent feature of knee osteoarthritis. (C) 2015 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.Öğe Stress distribution comparisons of foot bones in patient with tibia vara: a finite element study(Wroclaw Univ Technology, 2013) Özkan, Arif; Atmaca, Halil; Mutlu, İbrahim; Çelik, Talip; Uğur, Levent; Kişioğlu, YasinBlount's disease, or tibia vara, is the most common cause of pathologic genu varum in children and adolescents. Changes in the loading of knee structures such as tibial articular cartilage, menisci and subcondral bone are well documented in case of genu varum. But the mechanical effects of this condition on foot bones are still questionable. In this study, the authors hypothesized that stress distributions on foot bones might increase in patients with tibia vara when compared with patients who had normal lower extremity mechanical axis. Three-dimensional (3D) finite element analyses of human lower limb were used to investigate and compare the loading on foot bones in normal population and patient with tibia vara. The segmentation software, MIMICS was used to generate the 3D images of the bony structures of normal and varus malalignment lower extremity. Except the spaces between the adjacent surface of the phalanges fused, metatarsals, cuneiforms, cuboid, navicular, talus and calcaneus bones were independently developed to form foot and ankle complex. Also femur, tibia and fibula were modeled utilizing mechanical axis. ANSYS version 14 was used for mechanical tests and maximum equivalent stresses (MES) were examined. As a result of the loading conditions, in varus model MES on talus, calcaneus and cuboid were found higher than in normal model. And stress distributions changed through laterally on middle and fore foot in varus deformity model.Öğe Using a Combination of Intralaminar and Pedicular Screw Constructs for Enhancement of Spinal Stability and Maintenance of Correction in Patients With Sagittal Imbalance: Clinical Applications and Finite Element Analysis(Lippincott Williams & Wilkins, 2016) İnanmaz, Mustafa Erkan; Köse, Kamil Çağrı; Atmaca, Halil; Özkan, Arif; Işık, Cengiz; Başar, HakanStudy Design:Case series and finite element analysis.Objective:To report the clinical results of using intralaminar screw-rod (ILS) constructs as supplements to regular pedicle screw (PS) constructs in high risk for implant failure patients and to report the results of a finite element analysis (FEA) of this new instrumentation technique.Summary of Background Data:Despite advances in surgery and implantation techniques, osteoporosis, obesity, revision surgeries, and neuromuscular conditions (such as the Parkinson disease) are challenges against achieving solid arthrodesis and maintaining correction. Additional fixation strategies must be considered in these patients. There is only one study in the literature suggesting that ILS can be used as alternative anchor points and/or to increase fixation strength in conjunction with the PSs.Materials and Methods:Five patients (3 male and 2 female) with mechanical comorbidities underwent PS+ILS to treat sagittal imbalance. In radiologic analysis, thoracic kyphosis, lumbar lordosis, and sagittal vertical axis were analyzed. FEA of ILS augmentation technique were carried out.Four different models were created: (1) the full-construct model with ILS+PS 2 levels above and below the osteotomy of T10; (2) only PS 2 levels above and below T10; (3) ILS+PS 1 level above and below the osteotomy; and (4) short-segment PS with only PSs 1 level above and below the osteotomy. The stress/load distributions on the implants in vertebrae were analyzed.Results:The mean age of the patients included in this study was 41 years and the mean follow-up was 28.2 months. A total of 87 PSs and 39 ILSs were used. Both sagittal vertical axis and kyphosis angles showed significant improvements maintained at the latest follow-up. No pseudarthrosis or instrumentation failures were observed. FEA indicated that addition of ILS construct to a PS construct enabled decreased load bearing and increased implant life.Conclusions:Addition of an ILS construct to PS construct decreases osteotomy line deformation and reduces stress on pedicle fixation points, and the combination improves fixation stability over the conventional PS-rod technique.
