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    Anatomical and surgical aspects of the lobes of the thyroid glands
    (Springer, 2011) Ozgur, Zuhal; Celik, Servet; Govsa, Figen; Ozgur, Tomris
    Variation in the descent of the thyroid gland and during fetal life and regression of the thyroglossal duct is associated with many variations in form of the mature gland. The shape and morphometric details of gland, its extension as the pyramidal lobe (PYR-L) and attachments of the levator glandulae thyroidea were studied in 40 cadavers. We categorized the shape of the thyroid into 12 types. The most frequent type was PYR-L with 22.5% which started from the left lobe and moved across by intercrossing the larynx. Horseshoe-shaped gland and the gland with separate lobes were the most frequently observed glandular shapes, with 17.5 and 20%, respectively. The incidences of the PYR-L and the levator glandulae thyroideae were 60 and 17.5%, respectively. The pyramidal lobe branched off more frequently from the left part of the isthmus (14 specimens) than from the right (5 specimens) or the midline (2 cases). Knowledge about the glandular landmarks and anatomic measurements around the thyroid will be helpful for the surgeon to constitute a simplification of the topographic anatomy, plan and decide on a safe approach to the thyroid gland, and to avoid postoperative complications.
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    Computer-assisted analysis of anatomical relationships of the ethmoidal foramina and optic canal along the medial orbital wall
    (Springer, 2015) Celik, Servet; Ozer, Mehmet Asim; Kazak, Zuhal; Govsa, Figen
    Typically, the medial orbital wall contains an anterior ethmoidal foramen (EF) and a posterior EF, but may also have multiple EFs transmitting the arteries and nerves between the orbit and the anterior cranial fossa. The aim of this study is to determine a patient-friendly landmark of the medial orbital wall and to specify a precise location of the ethmoidal foramens (EF) in order to standardize certain anatomical marks as safe ethmoidal arteries. Orientation points on the anterior ethmoidal foramen (AEF), posterior ethmoidal foramen (PEF) and middle ethmoidal foramen (MEF) were investigated in 262 orbits. Using a software program, distances between each foramen and the midpoint of the anterior lacrimal crest (ALC), the optic canal (OC), and some important angles were measured. The EFs were identified as single in 0.8 %, double in 73.7 %, triple 24,4 % and quadruple in 1.1 % specimens. The mean distances between ALC and AEF, ALC and PEF and ALC and MEF were 27.7, 10.6, and 12.95 mm, respectively. The distances from ALC-AEF, AEF-PEF, and PEF-OC were 27.7 +/- A 2.8, 10.6 +/- A 3.3, 5.4 +/- A 1 mm. The angles from the plane of the EF to the medial border of the OC were calculated as 13.2A degrees and 153A degrees, respectively. The angle from the AEF to the medial border of the OC was based on the plane between the ALC and AEF was 132A degrees. The occurrence of multiple EF with an incidence of 25 % narrows the borders of the safe region in the medial orbital wall. Safe distance of the ALC-EF was measured as 22.1 mm on medial wall. The line of the location of the EF was calculated 16.2 mm. In this study, it was possible to investigate the variability of the orbital orifice of the EF and the feasibility of the EA, to observe various angles of the orbital wall bones and to calculate the lengths of some parameters with the help of certain software.
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    The first step of patient-specific design calvarial implant: A quantitative analysis of fresh parietal bones
    (Springer, 2018) Govsa, Figen; Celik, Servet; Turhan, Tuncer; Sahin, Volkan; Celik, Meral; Sahin, Korhan; Kazak, Zuhal
    BackgroundAccurate knowledge of the fracture of cranial bone can provide insight into the prevention of skull fracture injuries and help aid the design of energy-absorbing head protection systems and safety helmets. When cranial bone needs to be removed or is lost, subsequent reconstruction of the defect is necessary to protect the underlying brain, or correct esthetic deformities, or both. Ideal reconstruction of defected bone is possible utilizing a biocompatible implant with a bone-like design individualized for the specific patient. The purpose of this study is to investigate the anatomical and mechanical characteristics of fresh frozen human parietal bones and determine compliance of polylactic acid-based personalized three-dimensional implants in terms of mechanical properties in order to replace such defective bones.MethodsParietal bone specimens were extracted from 19 fresh frozen cadavers. Morphological parameters of individual bone specimens were measured using Image J software. Three-point bend tests were performed to extract Young's modulus and tensile strength of the specimens from the measured force and displacement data by modeling the bone specimens as curved linear elastic beams. Also, three-point bend tests were performed to polylactic acid-based three-dimensional replicas mimicking geometry of the bone specimens in order to determine whether the material's Young's modulus and tensile strength properties comply with parietal bones.ResultsEntire fresh parietal specimens were observed to be comprised of a three-layered structure: external layers consisting of compact, high-density cortical bone and the central layer consisting of low-density, irregularly porous bone structure. Mean thickness of three-layered structure was 6.251.46mm. Mean Young's modulus and tensile strength of the specimens were 1.401.34GPa and 44.56 +/- 21.94MPa, respectively where no statistically significant differences among genders were detected (p>0.05). Mean Young's modulus and tensile strength of the polylactic acid-based three-dimensional implants mimicking geometry of the bone specimens were 1.8 +/- 0.7GPa and 72.8 +/- 2.5MPa, respectively.ConclusionsPolylactic acid-based three-dimensional implants can be considered as acceptable candidates for temporary replacement of parietal defects in terms of mechanical properties.Level of Evidence: Not ratable.
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    Navigational area of the cranio-orbital foramen and its significance in orbital surgery
    (Springer France, 2014) Celik, Servet; Kazak, Zuhal; Ozer, Mehmet Asim; Govsa, Figen
    The cranio-orbital foramen (COF) is located on the lateral wall of the orbit. It is a potential source of hemorrhage during deep lateral orbital dissection, since it functions as an anastomosis between the lacrimal artery and the middle meningeal artery. The aim of this study was to guide and facilitate the surgical procedures in the orbit, so as to determine a navigational area and the precise location of the COF and to standardize certain anatomical marks. The navigational area of the COF and topographical features were studied in 75 craniums with presented COF. 33 bilateral main COFs, 41 (18 on the right, 23 on the left) unilateral main COFs at the main cranium and 19 accessory COFs were studied for their navigational features on the orbit. The distances between the COF and the fronto-zygomatic suture, supraorbital notch, lateral angle of the superior orbital fissure (SOF) and Whitnall's tubercle were measured. The mean distance of the COF from the fronto-zygomatic suture, supraorbital notch, lateral angle of the SOF and Whitnall's tubercle was 26.3, 37.3, 92 and 27.1 mm, respectively. For the navigational area signs of the COF, areas of the orbit that form the transversal and vertical lines are generated on the reference points. Whilst the upper outer area of the orbit contains a potential bleeding risk, the bottom section of the outer column is identified as safe for the surgical operations of the lateral orbital wall. The fronto-zygomatic suture and Whitnall's tubercle are recommended as the most reliable navigational landmarks for identifying the COF. Hence, the transversal and vertical orientation of the COF should be mastered by the surgeons reconstructing the anterior base of the skull and the orbit.
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    Redesign and treatment planning orbital floor reconstruction using computer analysis anatomical landmarks
    (Springer, 2016) Ozer, Mehmet Asim; Govsa, Figen; Kazak, Zuhal; Erdogmus, Senem; Celik, Servet
    Orbital floor fractures are one of the most commonly encountered maxillofacial fractures due to their weak anatomical structure. Restoration of the orbital floor following a traumatic injury or a tumor surgery is often difficult due to inadequate visibility and lack of knowledge on its anatomical details. The aim of this study is to investigate the locations of the inferior orbital fissure (IOF), infraorbital groove (G), and infraorbital foramen (Fo) and their relationship with the orbital floor using a software. Measurements from the inferior orbital rim (IOR) using the Fo, the IOF, G, and the optic canal (OC) were calculated in 268 orbits as reference points. The surgical landmarks from the G and the OC, the G and the IOF, the G and the intersection point were measured as 31.6 +/- A 6, 12.9 +/- A 4, and 12 +/- A 5 mm, respectively. The mean distances between the G and the IOR, the Fo and the IOF, and the Fo and the OC were found as 8.3 +/- A 2.1, 28.7 +/- A 3.5, and 53.6 +/- A 5.9 mm, respectively. The mean angles were calculated as OC-IOF-G 68.1A degrees A A +/- A 16.4A degrees; intersection-G-IOF as 61.4A degrees A A +/- A 15.8A degrees; IOF-OC-G as 19A degrees A A +/- A 5.5A degrees; OC-G-intersection as 31.5A degrees A A +/- A 11.9A degrees, G-intersection-OC as 129.5A degrees, IOF-intersection-G as 50.5A degrees. Furthermore, variable bony changes on the orbital floor which may lead to the differences at intersection point of the G and Fo were determined. In 28 specimens (20.9 %), unilateral accessory Fo (AcFo) was present. In 27 specimens, AcFo was situated supermaedially (96.4 %) on the main aperture. In one specimen, two intraorbital canals and Fo emerged from different points and coursed into different apertures. The measured mean distances of the AcFo-IOR and the AcFo-Fo were as 7 +/- A 2 and 7.3 +/- A 3.2 mm, respectively. The primary principle in the oculoplastic treatment of orbital floor reconstructions must be repositioning the herniated orbital aperture by maintaining the infraorbital artery and the nerve in the orbital floor. The IOF and the G were recommended as the more reliable oculoplastic surgical landmarks for identifying the orbital floor. To avoid pinching of the orbital floor structures, the triangle (IS-G-IOF) should be equilateral with an exigence of a 70A degrees angle within it. Among each distance of the intersection-IOF, IOF-G, G-intersection should be equal. With the help of certain software, this study made possible to investigate the variability of the orbital floor structures, observe the variety in measurements and calculate the parameters which are crucial in implementing personalized reconstruction and implanting support.
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    Three-dimensional evaluation of the danger zone of ethmoidal foramens on the frontoethmoidal suture line on the medial orbital wall
    (Springer France, 2015) Kazak, Zuhal; Celik, Servet; Ozer, Mehmet Asim; Govsa, Figen
    It is clear that the importance of the ethmoidal foramen (EF) is based on its vascular contents. The frontoethmoidal suture (FS) line is recommended as more reliable navigational landmark for identifying the EF. The vertical orientation between the EF and the FS line was studied in 188 orbits using a computer software program. 146 anterior EFs (77.7 %) and 42 anterior EFs (22.3 %) were situated in the FS line as intrasutural and extrasutural, respectively. 146 posterior EFs (77.25 %) and 8 posterior EFs (4.25 %) were presented as intrasutural and extrasutural, respectively. Although accessory EFs were detected in 25.5 % specimen exhibited an extrasutural location. Majority of the EFs (1-4 EFs) were situated on the FS line. The mean distances from the FS and the anterior EF, the posterior EF and the accessory EF were measured as 2.1 +/- A 0.5, 2.0 +/- A 1.5 and 2.3 +/- A 1.2 mm, respectively. The range of the distances from the FS to the anterior EF, posterior EF and accessory EF were -1.2 to 3.32 , -1.02 to 5.76 and -1.1 to 3.65 mm, respectively. The ranges of EF changed within 1-6 mm. As the FS is not a single point, it is more suitable to make the incision 7 mm above the suture line. The data from this study to help the orbital surgeons explain and avoid unexpected hemorrhage during the orbital procedures such as posttraumatic orbital reconstruction, orbital tumor resections, anterior skull base reconstruction, and orbital decompression surgery.