Kayihan Sahinoglu

Morphometric evaluation of subaxial cervical vertebrae for surgical application of transpedicular screw fixation.

Study Design. A morphometric evaluation of pedicle projections in 29 cervical spinal columns (C3–C7) for three-dimensional surgical anatomy for safe surgery was proposed. Objective. In this study, pedicles and intimate structures of the subaxial vertebrae from C3 to C7 were evaluated to provide some morphometric data for cervical transpedicular screw fixation. Summary of Background Data. Detailed knowledge of surgical anatomy and variation of the subaxial vertebrae is a must for safe and effective surgery of the region. Although there are several clinical studies of transpedicular fixation, few studies have been performed on cervical pedicle measurements and their projection. Methods. In 29 dried bone cervical spinal columns (C3–C7), pedicle dimensions (pedicle height, width, length), measurements of lateral mass and pedicle length distance and pedicle axis length, investigation of distances of superior facet-midpedicle axis and inferior facet-midpedicle axis, and transverse and sagittal angles of the pedicles were performed in linear and angular measurements. Results. The obtained data from the series revealed that the mean values were approximately ranging from 6.7 to 7.2 mm for pedicle height, 4.4 to 4.9 mm for pedicle width, 5.3 to 6.2 mm for pedicle length, 15.3 to 16.0 mm for lateral mass and pedicle length, 22.2 to 27.7 mm for pedicle axis length, 3.8 to 5.3 mm for superior facet-midpedicle axis distance, 9.9 to 12.0 mm for inferior facet-midpedicle axis distance, 42.3° to 51.5° for transverse angle, and 5.2° to 14.1° for sagittal angle. Conclusions. Linear measurements of pedicle dimensions and also axial angles from horizontal and vertical planes may provide some anatomic limitations for subaxial cervical transpedicular screw fixation, and also contribute to the safety of the surgical procedure. One should also rely on tomographic data and computer-assisted guidance systems.

Surface anatomy of the posterolateral cranium regarding the localization of the initial burr-hole for a retrosigmoid approach

Knowing the location of the venous sinuses is essential for the localization of the initial burr–hole for a retrosigmoid approach, in order to avoid inadvertent entry into the venous sinuses and limitation of the size of the bony opening. In this anatomic study, external landmarks of the posterolateral cranium have been studied, in order to reveal the relationship with the venous sinuses. Eighty-four dried adult human skulls were studied and study of both sides yielded 168 sides. Morphometric measurements of the posterolateral cranium have been performed and relations of the external landmarks with the venous sinuses have been studied. The anatomic position of the asterion was variable. The superior nuchal line was roughly parallel and below the lower margin of the sulcus of transverse sinus in all specimens. The sigmoid sinus, between the superior and inferior bends, seemed to descend along an axis defined by the junction of the squamosal–parietomastoid suture and the mastoid tip, in a slightly oblique fashion. In conclusion, a burr–hole placed just below the superior nuchal line and posterior to the axis defined by the mastoid tip and the squamosal-parietomastoid suture junction is appropriate for both avoiding inadvertent entry into the sinus and limiting the size of the craniotomy.

Evaluation of the bony landmarks in transcondylar approach

Background. The aim of this study is to define the anatomic landmarks which are necessary for transcondylar approach and to determine the importance of these structures during surgical resection. Methods. 56 dry skulls were included in this study. Landmarks were detected. Some distances and angles, which were determined before, were measured and the anatomical structures were observed. 21 parameters were examined and analysed in totally 56 dry skulls using 56 foramen magnum, 112 hypoglossal canal and 112 occipital condyles. The landmarks which were used were the anterior and posterior borders of the occipital condyle, the medial and lateral margin of the occipital condyle, basion, opisthion, hypoglossal canal and posterior condylar canal. The measurements were made separately for the right and left sides. Results. The mean length of the occipital condyle was found as 23.1 mm. The distance betweeen the intracranial edge of the hypoglossal canal and anterior margin of the occipital condyle was measured as 11.2 mm in both sides. The distance betweeen the intracranial edge of the hypoglossal canal and posterior margin of the occipital condyle was measured as 12.5 mm at the right side and 12.6 mm at the left one. The mean length of the hypoglossal canal was measured as 10.5 mm at the right side and 10.6 mm at the left one. 14 hypoglossal canals were divided into two compartments by a septum. Conclusions. In transcondylar approach, the anatomical landmarks should be well known in order to make a safe occipital condyle resection. The distance betweeen the intracranial edge of the hypoglossal canal and posterior margin of the occipital condyle is important for a safe occipital condyle resection, and it was found to be 12.55 ±0.05 mm in our study. Approximately 12 mm occipital condyle resection can be made without giving damage to the neural tissue. This value is appropriate to the ½ of the occipital condyle.

The mendosal suture

Purpose. The knowledge regarding the mendosal suture is still on debate in the literature. Though reports of the closure of this childhood suture are variable, a few reports show the presence of the suture in the adults. This study was conducted to determine the occurrence and a better topographic location of the mendosal suture. Methods. We used 129 dry skulls for this study. In the specimens, which were determined to have a mendosal suture, the morphometric traits of the mendosal suture and the angle between the mendosal suture line and lambdoidal suture line (α angle) were measured. Results. We found mendosal suture on 18 specimens, 11 of them were bilateral and 7 were unilateral. The length of these sutures ranged from 10.4 to 23.8 mm on the right side and 10.8 to 31.6 mm on the left side, respectively. The angle between two suture lines ranged from 36 to 68° on the right side and 32 to 75° on the left side. Conclusions. We believe that, these data will be of use to clinicians in order to avoid any misinterpretation of the mendosal suture with cranial fractures.

A multipurpose landmark for skull-base surgery: Henle’s spine

OBJECTIVE To determine whether Henles spine could be used as a reliable and multipurpose landmark for the other important structures of the skull base. MATERIALS AND METHODS Ninety-two specimens from 46 cadaveric adult dry skulls were studied. Two imaginary lines and a triangle were defined: a spinopterygoidal line extending from Henles spine to the root of the medial pterygoid plate, a bispinal line extending from one Henles spine to the contralateral one, and a parapetrosal triangle lying between the spinopterygoidal line, the bispinal line and the sagittal midline. The parapetrosal triangle encompasses nearly all the main structures of the skull base, including the petrosal internal carotid artery. RESULTS Along the spinopterygoidal line the distance from Henles spine to the spine of the sphenoid was found to be about 3 cm, to the foramen spinosum 3.5 cm, to the posterior and anterior margins of the foramen ovale 4 and 4.5 cm, to the root of the lateral pterygoid plate 5 cm, to the root of the medial pterygoid plate 5.5 cm, and to the vomer 6.5-7 cm. Along the bispinal line, the distance from Henles spine to the stylomastoid foramen was found to be about 1.5 cm, to the lateral and medial margins of the jugular foramen 2.5 and 3.5 cm, to the external orifice of the hypoglossal canal 4 cm, and to the foramen magnum 5 cm. CONCLUSION Henles spine with its superficial and central position can be used to localize important anatomical structures during skull-base surgery.