Esin Korman

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.

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.

Morphologic and radiologic anatomy of the occipital bone

Several diseases may cause craniovertebral instability warranting occiput-cervical fusion. As occipital screw and rod constructs are becoming more popular, requiring that screws be placed either medially or laterally in the occipital bone, the need for clearer anatomical and computed tomography (CT)-confirmed data regarding the relative thickness of the occiput in its various localities has become more critical. In 18 cadaveric specimens, the occipital bone was divided into 35 measurable segments. Transversely, the occipital bone was divided into five lines starting at the level of the inion; horizontal lines then proceeded inferiorly in 1-cm segments, 1, 2, 3, and 4 cm below the level of inion. In a comparable fashion, the occipital bone was divided vertically, starting at the midline, and proceeding laterally also in 1-, 2-, and 3-cm segments. Anatomical measurements of thickness were directly performed using a Vernier caliper. Results were directly correlated with axial CT measurements of bony thickness. Anatomical and CT measurements closely correlated within the same specimen, but there was significant interspecimen variability. The marked differences in the occipital bone anatomy noted between specimens indicates that patients undergoing occipital screw placement for cranial-cervical instability would benefit from preoperative occipital CT evaluations.