A neurosurgical view of anatomical evaluation of anterior C1-C2 for safer transoral odontoidectomy.

An anatomical study for evaluation of anterior C1-C2. To provide essential anatomic data for safer transoral odontoidectomy. The surface dimensions of the atlas vertebra and the transoral approach for odontoidectomy have been described in detail. Anterior arcus of C1 must be drilled out to reach odontoid process for transoral odontoidectomy. The thickness of anterior ring of C1 has not been studied before. Sixty, dried adult atlas and 60 axis vertebrae and ten cadaveric craniocervical specimens were measured for the following: (1) bony drilling depth (BDD), the distance from the anterior wall of anterior ring of C1 to anterior wall of odontoid; (2) minimum drilling diameter (MDD), distance of minimum C1 anterior ring removal for odontoid resection on horizontal plane; (3) maximum bony drilling diameter (MBDD), distance of maximum C1 anterior ring removal for odontoid resection on horizontal plane. Lateral border of this diameter is limited by medial borders of the lateral mass; (4) the widest odontoid diameters (WOD) on coronal sections were measured. On 60 atlas and axis vertebrae, the BDD was 7.0 +/- 1.2 mm on dry bones, the distance between the medial borders of the lateral mass (MBDD) was 16.1 +/- 1.5 mm, and the WOD on coronal sections (WOD) was 9.8 +/- 0.8 mm. On cadavers, the distance between the two edges of C1 anterior ring removal for odontoid resection (MDD) was 10.8 +/- 1.1 mm and the WOD on coronal sections (WOD) was 10.1 +/- 1.4 mm. An odontoid surgery through transoral approach is safe and feasible. A quantitative understanding of the anterior anatomy of C-1 and C-2 is necessary when considering transoral odontoid resection. In this study the authors define safe zones for anterior atlas and axis.

The possibility of nervus ilioinguinalis and nervus iliohypogastricus injury in lower abdominal incisions and effects on hernia formation.

AIM: The aim of this study was to determine the distances of nervus ilioinguinalis and nervus iliohypogastricus to McBurney's and paramedian incisions. MATERIALS AND METHODS: This study was performed on 12 adult cadavers. Right and left inguinal regions of the cadavers were dissected by inguinal incision. The points where the nerves perforated the internal obliquus muscles were determined, and the distances of these points to the spina iliaca anterior superior (SIAS) and to the umbilicus were measured. These distances were marked over a diagram, and distances of the nerves to McBurney's and paramedian incisions were measured by illustrating these incisions on the same diagram. FINDINGS: While the distance of the iliohypogastric nerve from the SIAS was 1.5-8 cm on the right and 2.3-3.6 cm on the left, the distance of the ilioinguinal nerve from the SIAS was 3-6.4 cm on the right and 2-5 cm on the left. The distance of the ilioinguinal nerve from McBurney's incision was 0.2-6.1 cm on the right and 1.8-7.5 cm on the left, and that of the iliohypogastric nerve was 2.2-6.9 cm on the right and 2.9-6.2 cm on the left. The distances of the nerves from paramedian incision were found to be 4.6-10 cm on the right and 6.4-11.2 cm on the left for the ilioinguinal nerve and 5-11.2 cm on the right and 7.4-11.6 cm on the left for the iliohypogastric nerve. CONCLUSION: Both nerves perforate the musculus obliquus internus, scattered in a wide area. Considering the distances, the paramedian incision seems to be more reliable with respect to the risk of nerve injury. Incisions performed in the lower abdomen carry the risk of injury to the ilioinguinal and iliohypogastric nerves.