The human sacrum and safe approaches for screw placement.

The human sacrum is the target of lumbosacral instrumentation and decompression procedures. Such surgical interventions require detailed knowledge of the anatomy of the human sacrum. The aim of this study was to measure surgically relevant parameters. Several factors, including the one-piece composition of the sacrum, the angles of the sacral pedicles and the anteroposterior diameter of the sacral vertebral bodies distinguish the sacrum from other parts of spine. Thirty-two measurements of shape, angles and distances between parts were taken of the sacra of 100 adult West Anatolian people using a Vernier caliper accurate to 0.1 mm and goniometer. According to this morphometric study, when measured from the sagittal, the S1 facet angle was measured as 35.71 degrees +/-9.59 and 34.70 degrees +/-9.66, the sacral pedicle anteromedial screw trajectory angle was 35.65 degrees +/-4.73 and 31.95 degrees +/-3.95 and the anterolaterally oriented sacral wing screw trajectory angle was 32.65 degrees +/-3.51 and 29.10 degrees +/-3.14, on the right and left sides, respectively. The distance of the midline oriented S1 pedicle screw was 51.12 mm and 51.26 mm on the right and left side, respectively. The distance for sacral wing oriented screw placement was 50.13 mm and 50.46 mm on the right and left side, respectively. The anteroposterior and transverse diameter of the sacral spinal canal were 21.81 mm and 31.31 mm, respectively. Thus, this study describes anatomical specifications of the sacrum. These defined morphometric details should be taken into consideration during surgical procedures. This study also describes anatomical landmarks which will allow injury of the sacrum during surgery to be avoided.

The thickness and the lengths of the anterior wall of adult maxilla of the West Anatolian Turkish people.

The maxilla is the key structure on facial formation and stability. The knowledge about maxillary thickness and dimensions is crucial during facial reconstruction including this bone. In this study, anthropometric measurements of anterior wall of the maxilla on the dry human skulls were aimed. Sixty maxillae of 30 adult dry skulls of West Anatolian people were evaluated. Four vertical lines were drawn between the piriform aperture and lateral border of the bone and six horizontal lines between the infra-orbital margin and the inferior border of the piriform aperture. After establishing the lines, maxillary thicknesses on the intersection points of the vertical and horizontal lines and the lengths of the vertical lines from the infra-orbital margin to alveolar arch were measured by using a fine caliper. It was found that the thickest point of the anterior wall of the maxillae is on the lateral of the infra-orbital margin (5.17 +/- 2.27 mm), and thinnest one is on the inferior of the infra-orbital foramen (0.92 +/- 1.06 mm). The length of the vertical line tangent to piriform aperture (47.66 +/- 3.61 mm) is the longest. The corresponding data of the left and right maxillae were compared by Student's t test. There was no significant difference between both sides. After collecting the data, a thickness map of anterior wall of the maxilla was drawn. This data may be helpful in clinic during osteotomies, bone reconstructions, screw, or other reconstruction apparatus applications on the maxilla.

Surgical anatomy of the internal branch of the superior laryngeal nerve.

The internal branch of the superior laryngeal nerve (ibSLN) may be injured during anterior approaches to the cervical spine, resulting in loss of laryngeal cough reflex, and, in turn, the risk of aspiration pneumonia. Such a risk dictates the knowledge regarding anatomical details of this nerve. In this study, 24 ibSLN of 12 formaldehyde fixed adult male cadavers were used. Linear and angular parameters were measured using a Vernier caliper, with a sensitivity of 0.1 mm, and a 1 degrees goniometer. The diameter and the length of the ibSLN were measured as 2.1+/-0.2 mm and 57.2+/-7.7 mm, respectively. The ibSLN originates from the vagus nerve at the C1 level in 5 cases (20.83%), at the C2 level in 14 cases (58.34%), and at the C2-3 intervertebral disc level in 5 cases (20.83%) of the specimens. The distance between the origin of ibSLN and the bifurcation of carotid artery was 35.2+/-12.9 mm. The distance between the ibSLN and midline was 24.2+/-3.3 mm, 20.2+/-3.6 mm, and 15.9+/-4.3 mm at the level of C2-3, C3-4, and at the C4-5 intervertebral disc level, respectively. The angles of ibSLN were mean 19.6+/-2.6 degrees medially with sagittal plane, and 23.6+/-2.6 degrees anteriorly with coronal plane. At the area between the thyroid cartilage and the hyoid bone the ibSLN is the only nerve which traverses lateral to medial. It is accompanied by the superior laryngeal artery, a branch of the superior thyroid artery. The ibSLN is under the risk of injury as a result of cutting or compression of the blades of the retractor at this level. The morphometric data regarding the ibSLN, information regarding the distances between the nerve, and the other consistent structures may help us identify this nerve, and to avoid the nerve injury.

Morphometric analysis of human occipital condyle.

OBJECTIVE: The human occipital condyle is the unique bony structure connecting the cranium and the vertebral column. The progress in neuroimaging techniques has increased interest for aggressive craniovertebral surgery. Such surgery requires the knowledge regarding anatomical aspects of the craniovertebral junction. The aim of the present study is to analyze the occipital condyle morphometrically. MATERIAL AND METHODS: 404 occipital condyles of 202 dry skulls were used for this study. Twenty-seven parameters were measured, including length, width and height of occipital condyle, the distances between the occipital condyle and hypoglossal canal, as well as some important condyle-related angles. RESULTS: The length, width and the height of the occipital condyle were found to be 23.4, 10.6, and 9.2 mm, respectively. The anterior and posterior intercondylar distances are 21.0 and 41.6 mm, respectively. Sagittal intercondylar angle was 59.3 degrees. The intracranial orifice of the hypoglossal canal was found in the junction of the second and third quarter on the condyle in more than 55% of specimens. The shape of occipital condyles was classified into eight types as follows--type 1: oval-like condyle; type 2: kidney-like condyle; type 3: S-like condyle; type 4: eight-like condyle; type 5: triangle condyle; type 6: ring-like condyle; type 7: two-portioned condyle and type 8: deformed condyle. The most common type was type 1 (50%), whereas the most unusual type was type 7 (0.8%). CONCLUSION: It is concluded that the occipital condyle may present various shapes, length, width, and orientation, requiring a careful radiological analysis before craniovertebral junction surgery.

An anatomical study of the C-2 pedicle.

OBJECT: The C-2 pedicle plays an important role regarding screw purchase for spinal fixation. The aim of this study was to measure the C-2 pedicle-related linear and angular parameters. METHODS: Seven parameters in 160 C-2 pedicles (80 dry vertebrae) were measured using a Vernier caliper (accurate to 0.1 mm) and goniometer. The Student t-test was used to determine statistical significance. The authors found that the C-2 isthmus (pars interarticularis) and the C-2 pedicle are distinct structures. The C-2 isthmus covers the pedicle. The isthmus is present between the superior and inferior articular processes, and the pedicle is the structure beneath the C-2 isthmus. It connects the lateral mass-inferior articular process to the body of the axis. The heights of the right and the left C-2 pediculoisthmic components (PICs) were 10.3 +/- 1.6 and 9.9 +/- 1.5 mm, respectively. The posterior part of the superior aspect of the PIC was wider than the anterior portion. The widths of the posterosuperior aspect of the PIC were 11.1 +/- 2 and 11 +/- 1.7 mm on the right and left sides, whereas the widths of the anterosuperior aspect of the PIC were 7.9 +/- 1.7 and 8.5 +/- 1.6 mm, respectively. The inferior widths of this component were 6.0 +/- 1.5 and 5.5 +/- 1.3 mm on the right and left side, respectively. The lengths of the component were 28.8 +/- 2.9 mm on the right and 28.8 +/- 3.4 mm on the left side. The PIC exhibits a lateral-to-medial and an inferior-to-superior angle. Its axial angles were 28.4 +/- 2.5 and 28.6 +/- 2.2 degrees on the right and left sides, respectively; its sagittal angles were 18.8 +/- 2.1 and 18.8 +/- 1.7 degrees, respectively. CONCLUSIONS: The C-2 pedicle can be seen in the inferior aspect of the vertebra, and it connects posterior vertebral elements (that is, the lateral mass and inferior articular process) to the axial body. The isthmus drapes the pedicle. The authors suggest that this be termed "the pediculoisthmic component."