An Orientational Harvesting Occipital Artery Technique via far Lateral Approach: A Cadaveric Study.

OBJECTIVE: To provide further information on the identification of the occipital artery (OA) and suggest an improved approach to its anterograde dissection technique for harvesting. METHODS: Six cadaveric specimens were prepared for surgical simulation, and the anterograde approach was used to harvest the OA; a hockey stick incision was made from the C2 spinous process through the nuchal ligament to the mastoid tip. By retracting the scalp flap from the posterior arch of C2 to the transverse process, the suboccipital triangle was reflected by a single myocutaneous flap from the inferior nuchal line. In addition, 70 head computed tomography angiography scans were assessed bilaterally (n = 140) to study the running pattern of the OA. RESULTS: The mean total length of the mobilized OA was 11.8 ± 0.7 cm, with a diameter of 1.5 ± 0.1-2.1 ± 0.2 mm at the suboccipital segment and 1.3 ± 0.1 mm at the upper edge of the surgical incision. The average distance of OA at the inferior nuchal line to the midline was 2.9 ± 0.3 cm, the average distance of OA at the superior nuchal line to midline was 4.1 ± 0.2 cm, the average distance of OA at incision edge to midline was 5.2 ± 0.3 cm. CONCLUSION: Orientational anterograde technique for OA harvesting is a fast and easy approach. This approach avoids critical neurovascular structures. The most important step is to identify the OA near the lateral edge of the superior oblique muscle. Subsequently, in conjunction with preoperative computed tomography angiography, an imaginary line that crosses the inferior and superior nuchal lines may be established to assist in the separation of the OA.

Densitometric comparison of 3 occipital regions for suitability of fixation.

OBJECTIVE: Atlantooccipital fixation is an important technique in the treatment of upper cervical spine instability. Important considerations for implant devices are obtrusiveness and propagation of torque through the device caused by cervical rotation. The authors evaluated the feasibility of 3 regions of the occiput as sites for occipitocervical fixation by examining bone mineral density at these locations. METHODS: Unembalmed occiputs of 9 male and 4 female cadavers were used (mean age at time of death was 61.6 years, range 36-68 years). Studies were undertaken using caliper measurements and dual-energy x-ray absorptiometry of the superior nuchal line (SNL), the external occipital protuberance (EOP), and the inferior nuchal line (INL). RESULTS: Data indicate that the bone at the INL has a similar volumetric bone density as the bone at the SNL, despite having half the thickness. Also, the volumetric bone density increases laterally along the nuchal lines. CONCLUSIONS: Most hardware fixation is centered on stabilization at the EOP and the SNL. On the basis of these radiological results, the INL shows promise as a potential alternative site for screw placement in occipitocervical fixation.