5.1.1 Principal Indications

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  Occipitocervical instability

  
  
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  Degenerative changes

  
  
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  Trauma

  
  
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  Tumors

5.1.2 Positioning and Incision

The patient is placed in the prone position with a cushion under the chest. The head rests on a padded U-shaped brace and is slightly flexed ( Fig. 5.1 ). When necessary (fracture-dislocations, cervicooccipital instability in rheumatoid arthritis), cranial traction may be applied. Extensive shaving of the back of the neck and head is required. The median skin incision is begun two fingerbreadths above the external occipital protuberance and continued as far as the tip of the seventh spinous process (vertebra prominens).

After splitting of the subcutaneous tissue, self-retaining wound retractors are inserted, and hemostasis is performed. Using a diathermy scalpel, a median incision is now made through the nuchal fascia onto the nuchal ligament. At this point, the trapezius, which is coherent with the fascia, can be bilaterally mobilized, and the wound retractor can be moved to the plane that is next deepest ( Fig. 5.2 ).

5.1.3 Exposure of the Spine

The nuchal ligament is transected in the midline and incised as far as the tips of the spinous processes. The muscle layer that has been transected in the midline is retracted with the wound retractor. The deep muscle layer is then detached from the spinous processes using the diathermy scalpel. The dissection is effected near the bone, from cranial to caudal, beginning at the spinous process of the second cervical vertebra. If necessary (occipitocervical fusion), the muscles taking origin from, or attached to, the occiput (trapezius, semispinalis capitis) may be detached by a T-shaped dissection ( Fig. 5.3 ). With the use of a sharp raspatory, the short rotator and multifidus muscles are now detached—moving in a caudal direction from the second spinous process—from the spinous processes and the articular processes, and subperiosteal exposure is performed as far as the lateral boundary of the facet joints. Hemostasis is effected by the application of gauze swabs. Subsequently, that portion of the squamous part of the occipital bone which is caudal to the external occipital protuberance is exposed subperiosteally with a sharp raspatory. This invariably leads to bleeding from the suboccipital venous plexus, which can be stopped by electrocoagulation.

Now the posterior tubercle of the atlas, located deeply in the midline, is palpated with the fingertip. The muscle originating here (rectus capitis posterior minor) is detached on both sides, and, using the raspatory, the arch of the atlas is subperiosteally exposed on both sides for about 1.5 cm ( Fig. 5.4 ). The tip of the raspatory should remain in continuous contact with the bone so that injury to the vertebral artery can be avoided. The vertebral artery, after passing through the transverse foramen of the atlas, runs bilaterally in a medial direction in the groove for the vertebral artery, the ridge of which becomes visible and palpable upon careful exposure ( Fig. 5.5 ). More laterally, the posterior branch of the second cervical nerve, the main branch of which is the greater occipital nerve, emerges between the first and second cervical vertebrae. This nerve should also be spared. The wound retractors are inserted into the deepest muscle layer and opened wider. The vertebral arches, the ligamenta flava, and the atlantooccipital membrane are uncovered with curettes and small raspatories. The interspinal ligaments are removed as a rule if posterior fusion is desired ( Fig. 5.6 ).