Researcher: Özer, Ali Fahir
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Özer, Ali Fahir
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Publication Metadata only Clinical results of anterior odontoid screw fixation for type II odontoid fractures(Turkish Neurosurgical Society, 2014) Keskin, Fatih; Gomleksiz, Cengiz; Sasani, Mehdi; Oktenoglu, Tunc; Suzer, Tuncer; Özer, Ali Fahir; Faculty Member; School of Medicine; 1022AIM: In this study, 31 patients with a diagnosis of Type II odontoid fractures were reported. All patients were treated with anterior transodontoid screw fixation and clinical outcomes were reported. MATERIAL and METHODS: In this study, the retrospective clinical analysis of 31 patients with traumatic type II odontoid fractures who were treated through anterior transodontoid fixation in Neurosurgery Department at VKV American Hospital between 1998 and 2012 was performed. The age, sex, cause of injury, diagnosis time, neurological examination before and after surgery, follow-up period were evaluated. The neurological status of patients was classified according to the Frankel scale. RESULTS: In 4 patients, 2 transodontoid screws were inserted. The mean hospital stay was 3.35 days. Posterior occipito-cervical fusion was done in 1 patient due to the lack of fusion in the first operation. No vascular injury, screw malposition, infection, neurologic deterioration, or complications were observed during the peroperative and postoperative stage. The mean postoperative follow-up period was 36 months after surgery. Radiological imaging of patients were performed at the early and late postoperative stage. CONCLUSION: We found satisfying fusion rates and better patient comfort during the postoperative period. We think that stabilization and fusion through a transodontoid screw is a minimal invasive method.AMAÇ: Çalışmada, Tip II odontoid fraktürü tanısı alan 31 olgu bildirilmiştir. Olguların hepsi anterior transodontoid vida fiksasyonu ile tedavi edilmiş ve klinik sonuçları bildirilmiştir. YÖNTEM ve GEREÇLER: Çalışma, VKV Amerikan Hastanesi Nöroşirürji Bölümü’nde 1998-2012 yılları arasında travmatik tip II odontoid kırığı nedeniyle anterior transodontoid fiksasyon ile cerrahi tedavi uygulanan 31 hastanın retrospektif klinik analizleri yapılmıştır. Tüm olguların yaş, cinsiyet, travma nedeni, teşhis zamanı, cerrahi girişim öncesi ve sonrasında nörolojik muayeneleri, takip süresi değerlendirilmiştir. Olguların nörolojik durumları Frankel skalasına göre sınıflandırılmıştır. BULGULAR: Dört hastaya 2 adet transodontoid vidası yerleştirildi. Hastanede kalış süresi ortalama 3,35 gün idi. 1 hastada postop takibinde füzyon oluşmaması nedeniyle ikinci bir operasyon ile posteriordan oksipitoservikal füzyon yapıldı. İşlem sırasında ve sonrasında damar yaralanması, vida malpozisyonu, enfeksiyon, nörolojik bozulma gibi komplikasyonlar izlenmedi. Hastalar ameliyat sonrasında ortalama 36 ay takip edildi. Hastaların erken ve geç dönemde radyolojik görüntülemeleri yapıldı. SONUÇ: Postoperatif dönemde hastaların takiplerinde tatmin edici füzyon oranı ve hasta konforunun daha iyi olduğunu saptadık. Tip II odontoid kırıklarının cerrahi tedavisinde minimal invaziv yöntem olan transodontoid vida ile fiksasyonun yüksek avantajlarından dolayı ilk seçenek olabileceğini düşünüyoruz.Publication Metadata only Dynamic stabilization of the lumbar spine using the Dynesys® system(Turkish Neurosurgical Soc, 2020) Cevik, Orhun Mete; Akyoldaş, Göktuğ; Süzer, Süleyman Tuncer; Sasani, Mehdi; Öktenoğlu, Bekir Tunç; Özer, Ali Fahir; Faculty Member; Faculty Member; Faculty Member; Faculty Member; Faculty Member; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; 203677; 221691; 219451; 220898; 1022AIM: To present the clinical results in patients with minor instability with "Dynesys (R)"a soft spinal stabilization system. Material and Methods: A total of 83 patients were operated upon and the Dynesys (R) system was applied. Indications for surgery included painful degenerative disc disease, degenerative spondylolisthesis and lumbar canal stenosis. Results: The results for the Dynesys (R) system were satisfactory, and we have calculated the overall complication rate to be 20.4% (n=17), which is in agreement with the literature. Conclusion: The Dynesys (R) dynamic stabilization system effectively protects lumbar motion and achieves lumbar stability in patients with lumbar spinal problems. Our clinical result support literature that Dynesys (R) system is a strong alternative to fusion and instrumentation system in patient with chronic instabilities.Publication Metadata only A computational biomechanical investigation of posterior dynamic instrumentation: combination of dynamic rod and hinged (dynamic) screw(Asme, 2014) Kiapour, Ali; Goel, Vijay K.; N/A; N/A; Erbulut, Deniz Ufuk; Öktenoğlu, Bekir Tunç; Özer, Ali Fahir; Researcher; Faculty Member; School of Medicine, College of Engineering; School of Medicine; 37661; 220898; 1022Currently, rigid fixation systems are the gold standard for degenerative disk disease treatment. Dynamic fixation systems have been proposed as alternatives for the treatment of a variety of spinal disorders. These systems address the main drawbacks of traditional rigid fixation systems, such as adjacent segment degeneration and instrumentation failure. Pedicle-screw-based dynamic stabilization (PDS) is one type of these alternative systems. The aim of this study was to simulate the biomechanical effect of a novel posterior dynamic stabilization system, which is comprised of dynamic (hinged) screws interconnected with a coiled, spring-based dynamic rod (DSDR), and compare it to semirigid (DSRR and RSRR) and rigid stabilization (RSRR) systems. A validated finite element (FE) model of L1-S1 was used to quantify the biomechanical parameters of the spine, such as range of motion, intradiskal pressure, stresses and facet loads after single-level instrumentation with different posterior stabilization systems. The results obtained from in vitro experimental intact and instrumented spines were used to validate the FE model, and the validated model was then used to compare the biomechanical effects of different fixation and stabilization constructs with intact under a hybrid loading protocol. The segmental motion at L4-L5 increased by 9.5% and 16.3% in flexion and left rotation, respectively, in DSDR with respect to the intact spine, whereas it was reduced by 6.4% and 10.9% in extension and left-bending loads, respectively. After instrumentation-induced intradiskal pressure at adjacent segments, L3-L4 and L5-S1 became less than the intact in dynamic rod constructs (DSDR and RSDR) except in the RSDR model in extension where the motion was higher than intact by 9.7% at L3-L4 and 11.3% at L5-S1. The facet loads were insignificant, not exceeding 12N in any of the instrumented cases in flexion. In extension, the facet load in DSDR case was similar to that in intact spine. The dynamic rod constructions (DSDR and RSDR) led to a lesser peak stress at screws compared with rigid rod constructions (DSRR and RSRR) in all loading cases. A dynamic construct consisting of a dynamic rod and a dynamic screw did protect the adjacent level from excessive motion.Publication Metadata only Lumbar dynamic stabilization with 2-stage surgery: early results(Elsevier, 2022) HekimoǧLu, Mehdi Akgül, Turgut Özbek, Muhammet Arif; Özer, Ali Fahir; Ateş, Özkan; Sasani, Mehdi; Öktenoğlu, Bekir Tunç; Günerbüyük, Caner; Aydın, Ahmet Levent; Başak, Ahmet Tulgar; Faculty Member; Faculty Member; Faculty Member; Faculty Member; Teaching Faculty; Doctor; Doctor; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; Koç University Hospital; School of Medicine; 1022; 118533; 219451; 220898; 380939; N/A; N/ABackground: Screw loosening, which is a major problem in dynamic systems, can be easily overcome with 2-stage surgery. In this article, the clinical and radiological results of patients undergoing dynamic stabilization with a Dynesys device in 2 stages are discussed. Methods: A total of 10 male and 13 female adult patients were included in this single-center retrospective study conducted between 2018 and 2021. The mean age of the patients was 65.6 years. All of the patients had pain complaints that affected their daily lives. Bone density T scores were determined with the dual-energy x-ray absorptiometry method before patients were admitted for surgery. In the first surgery, Dynesys system pedicle screws were inserted. After 6 months of osteointegration, Dynesys system spacers and elastic bandages were placed. Preoperative, early postoperative, and late postoperative visual analog pain scale (VAS) scores and Oswestry Disability Index (ODI) scores were determined and statistically compared. Results: Patients were followed for an average of 30 months. Complications and recurrence were not observed. Neurological deficits were not observed after patients recovered from anesthesia. Significant improvement was observed in the ODI and VAS parameters in the preoperative (ODI: 66.2%, VAS: 7.8), early postoperative (ODI: 20.3%, VAS: 2.4), and late postoperative (ODI: 6.8% and VAS: 1.1) periods. Symptomatic improvement was seen in all patients. No screw breakage or loosening was detected by radiological evaluation in any of the patients during the 2-year follow-up period. Conclusions: In our experience, the insufficiency of the proximal and distal end screws is eliminated when 2 stages of dynamic system stabilizations are completed after osteointegration of the screws.Publication Metadata only Endoscopic endonasal removal of an intrasphenoidal paranasal sinus meningioma mimicking a squamous cell carcinoma(Edizioni Minerva Medica, 2011) Sasani, Mehdi; Ramazanov, M.; Öktenoǧlu, Tunç B.; Peker, Kamil R.; N/A; Özer, Ali Fahir; Faculty Member; School of Medicine; 1022Extracranial meningiomas comprise 1% to 2% of all meningiomas. Primary extracranial paranasal meningiomas are even less common. A pure intrasphenoidal localization is exceptional, and it may cause misdiagnosis. A 60 year old male patient was suffering from a headache. Anosmia was the only neurological finding determined, but he was not aware of it. The magnetic resonance imaging demonstrated an intrasphenoidal mass resembling a squamous cell carcinoma; the patient underwent an endoscopic endonasal procedure. The histopathological studies revealed a meningotheliomatous meningioma. Postoperative course was uneventful. Different behaviors of a tumor in an unusual location may cause misdiagnosis. The possibility of an intrasphenoidal paranasal meningioma has to be considered in the differential diagnosis of sphenoidal region masses. Also, the use of an endoscopy can help to avoid significant nasal injury. A verification of their etiology, adequate diagnosis, and management principles will allow for a satisfactory procedure.Publication Metadata only Effect of posterior dynamic instrumentation on high-intensity zone in lumbar degenerative disc disease(Turkish Neurosurgery Society, 2015) Canbay, Suat; Ataker, Yaprak; Kabaoğlu, Zeynep Ünal; Öktenoğlu, Bekir Tunç; Sasan, Mehdi; Canbulat, Nazan; Özer, Ali Fahir; Faculty Member; Faculty Member; School of Medicine; School of Medicine; 58534; 1022Aim: To investigate high-intensity zone (HIZ) changes after lumbar posterior dynamic instrumentation. MaterIal and Methods: Our study included 53 patients: 27 patients in group 1, 26 patients in group 2. All patients had one or two levels of degenerative disc disease with an HIZ confirmed by magnetic resonance imaging (MRI). Group 1 underwent one- or two-level dynamic lumbar posterior instrumentation. Group 2 was treated conservatively with an exercise program. Patients were evaluated using MRI, a numerical visual analog pain scale (VAS), and the Oswestry Disability Index (ODI) at baseline, at 1 year after surgery, and at final follow-up evaluation. Results: The mean duration of follow-up was 49.3 months in group 1 and 47.19 months in group 2. The baseline VAS and ODI scores were similar for both groups. The mean VAS score of group 1 was significantly improved at 1 year after surgery and at final follow-up. The mean ODI value was lower in group 1 than in group 2 at 1 year and at final follow-up. Pfirrmann grades in group 1 significantly differed at 1 year and at final follow-up but did not change in group 2. The number of HIZs significantly decreased in from baseline to 1 year and from baseline to final follow-up in group 1 but did not differ in group 2. ConclusIon: Dynamic lumbar stabilization systems are promising. Observations such as Pfirrmann grade improvements and disappearance of HIZs are concordant with improvements in VAS and ODI scores demonstrate that dynamic stabilization systems may provide an environment for regeneration. / AMAÇ: Lomber posterior dinamik enstrümantasyonun yüksek intensite bölgesi (YİB)’ne etkisini incelemek. YÖNTEM ve GEREÇLER: Çalışmaya 53 hasta dahil edildi; grup 1: 27 hasta, grup 2: 26 hasta. Bütün hastalarda Manyetik Rezonans Görüntüleme (MRG) ile tespit edilen bir veya iki seviyede YİB içeren dejeneratif disk hastalığı vardı. Birinci gruptaki hastalara bir veya iki seviyeli posterior dinamik enstrümantasyon yapıldı. İkinci grup egzersiz tedavisi ile takip edildi. Hastalar MRG, sayısal görsel ağrı skalası (GAS), Oswestry Özürlülük İndeksi (OÖİ) ile tedavi öncesi, cerrahi sonrası 1. yıl ve geç dönemde değerlendirildi. BULGULAR: Birinci grup ortalama 49,3 ay, ikinci grup ise 47,19 ay takip edildi. Başlangıç GAS ve OÖİ ölçümleri her iki grupta benzerdi. Birinci grubun ortalama GAS skoru cerrahi sonrası 1. yıl ve geç dönemde belirgin olarak azaldı. Birinci grubun ortalama OÖİ skoru 1. yıl ve geç takipte 2. Gruba göre daha düşük bulundu. Birinci grubun Pfirrmann evreleri 1. yıl ve geç takipte belirgin olarak değişirken, ikinci grupta değişiklik görülmedi. Birinci gruptaki YİB sayısı ilk değerlendirmeye göre 1. yıl ve geç takipte azalırken, ikinci grupta değişiklik gözlenmedi. SONUÇ: Dinamik lomber stabilizasyon sistemleri ümit vericidir. Pfirrmann evrelerinde görülen gelişim, YİB’nin kaybolması ve bunların GAS ve OÖİ skorlarındaki gelişmeler ile uyumlu olması dinamik stabilizasyon sistemlerinin rejenerasyon için uygun ortam sağlayabileceğini göstermektedir.Publication Metadata only Development of a finite element model of the human cervical spine(Turkish Neurosurgery Society, 2014) N/A; N/A; Department of Mechanical Engineering; N/A; Zafarparandeh, Iman; Erbulut, Deniz Ufuk; Lazoğlu, İsmail; Özer, Ali Fahir; PhD Student; Researcher; Faculty Member; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; School of Medicine; College of Engineering; School of Medicine; N/A; 37661; 179391; 1022The finite element model has been used as an effective tool in human spine biomechanics. Biomechanical finite element models have provided basic insights into the workings of the cervical spine system. Advancements in numerical methods during the last decade have enabled researchers to propose more accurate models of the cervical spine. The new finite element model of the cervical spine considers the accurate representation of each tissue regarding the geometry and material. The aim of this paper is to address the new advancements in the finite element model of the human cervical spine. The procedures for creating a finite element model are introduced, including geometric construction, material-property assignment, boundary conditions and validation. The most recent and published finite element models of the cervical spine are reviewed. / Sonlu eleman yöntemi efektif bir araç olarak omurga biyomekaniğinde yaygın kullanılmaktadır. Servikal omurga içerisinde meydana gelebilecek biyomekanik değişimlerin incelenmesine fırsat verebilmektedir. Geçtiğimiz on yıl içerisinde, geliştirilmiş olan nümerik metodlar sayesinde, daha gerçekçi omurga modellerinin çıkarılması sağlanmıştır. Günümüzde, servikal omurga modellerinde kullanılan geometri ve malzeme özellikleri olabildiğince gerçeğe yakın oluşturulabilmektedir. Bu makalenin amacı, sonlu eleman yöntemi kullanılarak insan servikal modellinin oluşturulmasını örneklerle açıklamaktır. Servikal omurga modelinin sonlu eleman yöntemi ile oluşturulmasının her bir adımı detaylı ele alınmıştır. Literatürde en son yayınlanan servikal omurga sonlu eleman modelleri incelenmiş ve karşılaştırılmıştır.Publication Metadata only Effect of asymmetry on finite element model of cervical spine(The American Society of Mechanical Engineers (ASME), 2013) N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; N/A; Zafarparandeh, Iman; Erbulut, Deniz Ufuk; Lazoğlu, İsmail; Özer, Ali Fahir; PhD Student; Researcher; Faculty Member; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; School of Medicine; N/A; 37661; 179391; 1022The cervical region of spinal column has been known as a frequent site of injuries. The major causes of injuries are vehicle accidents and sports. Clinical instability is known as one of the important topics in cervical spine research. It clarifies the relation between the mechanical dysfunction of the spine and the neurologic dysfunction and pain. From the clinical point of view, if the spinal segment exhibits abnormal large increase in rotational or translational displacements under physiological load, it is considered as unstable. There are different biomechanical models available to understand the underlying mechanisms of injury and dysfunction. Finite element (FE) models have been used as a strong tool to provide the basic insights into the workings of the cervical spine system. Furthermore, they have been clinically useful in the development of the definition of clinical instability and of diagnostic guidelines.Publication Metadata only Complications of 2-level dynamic stabilization: a correlative clinical and radiological analysis at two-year follow-up on 103 patients(2018) Yılmaz, Atilla; Erbulut, Deniz Ufuk; N/A; Çıplak, Necati Mert; Süzer, Süleyman Tuncer; Şentürk, Salim; Yaman, Onur; Sasani, Mehdi; Öktenoğlu, Bekir Tunç; Özer, Ali Fahir; Doctor; Doctor; Doctor; Doctor; Faculty Member; Faculty Member; Faculty Member; N/A; N/A; N/A; N/A; School of Medicine; School of Medicine; School of Medicine; Koc University Hospital; N/A; 221691; N/A; 219524; 219451; 220898; 1022AIM: To investigate the postoperative complications, such as screw loosening, screw breakage and adjacent segment disease (ASD), in patients who underwent surgery with 2-level dynamic stabilization systems. MATERIAL and METHODS: Postoperative complications, clinical improvements and radiological parameters in patients who underwent surgery using a dynamic system for 2-level lumbar stabilization were retrospectively reviewed. A total of 103 patients with lumbar degenerative spinal instability underwent 2-level dynamic stabilization. Clinical findings were reviewed at 2-year follow-up. Screw breakage and loosening were evaluated during this duration together with clinical findings. ESULTS: Visual analog scale (VAS) and Oswestry Disability Index (ODI) scores were significantly decreased at the four-month evaluation, and they were also decreased at the 1-year follow up and at the 24th postoperative month. ASD was diagnosed in twelve (8 females, 4 males) of the 103 patients in the follow-up radiological and clinical controls. There were 9 screw breakages and 4 screw loosening cases. The complication rate of 2-level dynamic stabilization was high in this study. CONCLUSION: Our results showed that complications (screw loosening or breakage and adjacent segment disease) are not rare after 2-level dynamic stabilization, unlike the acceptable results with the single-level dynamic system. The most probable explanation is that the instrument system behaves more rigidly with every additional segment.Publication Metadata only Posterior dynamic stabilization for the treatment of patients with lumbar degenerative disc disease: long-term clinical and radiological results(Turkish Neurosurgical Soc, 2013) Canbay, Suat; Aydin, Ahmet Levent; Aktas, Elif; Erten, Serhat Fuat; Basmaci, Mehmet; Sasani, Mehdi; Özer, Ali Fahir; Faculty Member; School of Medicine; 1022AIM: Comparison of long-term preoperative and postoperative clinical and radiological results for patients diagnosed with degenerative disc disease that underwent posterior dynamic stabilization. Lumbar disc degeneration is caused by a variety of factors. Disruptions in the vertebral endplate result in defects in disc nutrition and, thus, disc degeneration. The aims of dynamic stabilization are to unload the disc/facet joints, preserve motion under mechanical load, and restrict abnormal motion in the spinal segment. MATERIAL and METHODS:Twenty-five patients diagnosed with lumbar degenerative disc disease were enrolled.Totally, 25 vertebral segments were subjected to posterior dynamic stabilization. Patients were clinically evaluated in the preoperative and postoperative periods using the Oswestry Disability Index (ODI) and Visual Analog Scale (VAS). Segmental movement was evaluated radiologically in the late postoperative period by measuring the segmental angles during flexion and extension. RESULTS: Significant postoperative improvements were observed in the ODI and VAS measurements (P<0.01). During the long postoperative period (averaging 5 years and 2 months), lumbar lordosis angles, intervertebral space ratio and segmental ratio were measured and compared statistically. Adjacent segment disease developed in two patients. Both patients received L5-S1 discectomy. CONCLUSION: Good clinical outcomes were observed in the treatment of lumbar degenerative disc disease with a posterior dynamic system. / AMAÇ: Dejeneratif disk hastalığı tanısı almış ve posterior dinamik stabilizasyon sistemi uygulanmış hastaların uzun dönem preoperatif ve postoperatif klinik ve radyolojik sonuçlarının karşılaştırılması. Lomber dejeneratif disk hastalığına birçok etken sebep olur. Bu etkenler sonuç olarak omurga son plaklarında dejenerasyona ve disk dokusunun beslenmesinin bozulmasına yol açar. Dinamik stabilizasyon sistemleri, omurlar arasındaki hareketi korurken, disk ve faset eklemleri üzerindeki aşırı yüklenmeyi azaltır, aynı zamanda da omurga segmentindeki anormal hareketlenmeyi önler. YÖNTEM ve GEREÇLER: Bu çalışmada, dejeneratif disk hastalığı tanısı konmuş 25 hasta ele alınmıştır. Toplamda 25 omurga segmentine posterior dinamik stabilizasyon uygulanmıştır. Hastalar, preoperatif ve postoperatif dönemde Oswestry Disability Index (ODI) and Vizüel Analog Skala (VAS) ile klinik olarak değerlendirilmiştir. Segmental hareketi değerlendirmek için geç postoperatif dönemde radyolojik olarak fleksiyon ve ekstansiyon grafileri kullanılmıştır. BULGULAR: Postoperatif dönemde ODI ve VAS ölçümlerinde anlamlı düzelmeler kaydedilmiştir (P<0,01). Ameliyatlardan sonraki uzun dönem takiplerinde (ortalama 5 yıl 2 ay), lomber lordoz açısı, intervertebral aralık oranı ve segmental oran ölçülmüş ve istatiksel olarak değerlendirilmiştir. İki hastada postoperatif dönemde komşu segment hastalığı tespit edilmiş ve bu hastalarda L5-S1 diskektomi uygulanmıştır. SONUÇ: Lomber dejeneratif disk hastalığının cerrahi tedavisinde posterior dinamik stabilizasyon sistemi başarılı sonuçlar vermektedir.