Posterior Approach to the C1-2 Vertebral Space

Orthopedic Approachs 2022, Nov, 19 | 12:00 am

Posterior Approach to the C1-2 Vertebral Space

posterior Approach to the C1-2 Vertebral Space ‌

The posterior approach to the specialized cervical vertebrae C1 and C2, the atlas and the axis, is similar to that for the rest of the cervical spine. Because the two vertebrae differ slightly in their anatomy and function, however, they are discussed separately. The uses for this approach are the following:

Spinal fusion 20
Decompression laminectomy
Treatment of tumors
Stabilization of fractures of C1 or C2

Position of the Patient

Place the patient prone, with the head and neck flexed to separate the occiput and the ring of the atlas (C1; see Fig. 6-50).

Landmarks and Incision

Landmarks

Palpate the external occipital protuberance high in the midline of the skull at the midpoint of the superior nuchal line. Although the spinous process of C2 is the largest spinous process in the proximal part of the cervical spine, it is hard to palpate except as a resistance. C1 has no spinous process at all and is not palpable.

Incision

Make an incision in the midline from the external occipital protuberance inferiorly for 6 to 8 cm (Fig. 6-65).

Internervous Plane

The midline plane lies between paracervical muscles supplied by branches of the left and right posterior primary rami of the proximal cervical nerve roots. The plane is internervous and extensile.

Figure 6-65 Make an incision in the midline from the external occipital protuberance inferiorly for 6 to 10 cm.

Superficial Surgical Dissection

Deepen the wound in line with the skin incision by incising the fascia and nuchal ligament in the midline of the neck, cutting down onto the large spinous process of C2 (Figs. 6-60, 6-66, and 6-67). Extend this fascial incision distally onto the spinous process of C3 and then proximally onto the tubercle of C1. Continue proximally, cutting down onto the external occipital protuberance.

Carefully remove the paracervical muscles from the posterior elements of C1 and C2 (Fig. 6-68). Use a wide dissecting instrument (such as a Cobb elevator) to avoid inadvertently breaching the spinal canal. Note that the facet joints between C1 and C2 are about an inch further anterior than are those between C2 and C3. Carry the dissection up to the base of the occiput, if necessary, to expose the superior margin of the ring of C1 (see

Fig. 6-68).

Deep Surgical Dissection

If necessary, the ligamentum flavum (posterior atlantoaxial ligament) can be removed from between C2 and C1, and the posterior atlantooccipital membrane can be removed from between C1 and the occiput (Fig. 6-69). This rarely is necessary. Usually, separating these membranes from bone is all that is needed to pass a wire underneath the arch of C1 so that the area can retain bone graft. Once these posterior ligaments have been removed, the dura of the cervical portion of the spinal cord is uncovered.

Dang

Nerves

In nontumorous conditions, a considerable gap exists between the dura and the bony ring at the level of C1-2, and the cord rarely has to be retracted. Retracting the cord is extremely hazardous, because overzealous retraction can cause death from respiratory paralysis; in principle, it simply should not be retracted.

Figure 6-66 Deepen the wound in line with the skin incision by incising the fascia and nuchal ligament in the midline of the neck.

Two large cutaneous nerves, the greater occipital nerve (C2) and the third occipital nerve (C3), cross the operative field (see Figs. 6-59 and 6-62 ). These nerves, which are branches from the posterior rami, supply a large area of skin at the back of the scalp. They run upward from a lateral position, and midline dissection does not damage them. Take care when dissecting laterally to stay on bone and avoid damaging these nerves .

Vessels

The vertebral artery crosses the operative field. It passes from the transverse foramen of the atlas, immediately behind the atlantooccipital joint, and pierces the lateral angle of the posterior atlantooccipital membrane. It is vulnerable at that point during the approach (see Fig. 6-

62).

How to Enlarge the Approach

Local Measures

Extend the skin incision proximally and dissect the paracervical muscles from their attachments to the skull. Extend the incision distally and strip the muscles off the posterior bony elements of C3.

Extensile Measures

Extend the incision distally. Then continue the midline approach to the spinous processes of the remaining cervical vertebrae. Theoretically, the approach can be extended down to the coccyx.

Figure 6-67 Incise the nuchal ligament down onto the large spinous processes of C2. Lateral view (inset). Note that the ring of C1 is further anterior than the spinous process of C2.