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POSTERIOR APPROACH TO THE OCCIPITOCERVICAL JUNCTION AND CERVICAL SPINE

USES

The posterior approach to the midline cervical spine is used for a wide variety of indications. Simple decompressive procedures such as laminectomy, foraminotomy, and laminoplasty are commonly employed to treat a host of pathologies, including foraminal compression, facet arthropathy, cervical spondylytic disease, cervical myelopathy, cervical stenosis, ossified posterior longitudinal ligaments, intra- and extradural spinal cord tumors, nerve root tumors, and infections. For cases of instability due to tumor, fracture, or infection, a host of arthrodesis and stabilization techniques can be used from a posterior midline approach, including posterior laminar wiring, Brooks or Gallie fusions, lateral mass plating, translaminar wiring or screw placement, transarticular screw placement, Luque rectangle placement, pedicular screw placement, and in-situ bony fusion. For cases of occipitocervical or atlantoaxial instability (e.g., trauma or rheumatoid arthritis), exposure of the foramen magnum and the occipital bony squama also allows for extension of the stabilization construct. Decompression for cases of Chiari malformation or basilar invagination can also be achieved.

ADVANTAGES

As detailed above, the midline posterior cervical approach is highly versatile. It can be performed over a few segments for focal pathology or instability, or it can be extended for extensive instrumentation of the occipitocervical or cervicothoracic junction. If the exposure is kept to the midline of the subaxial cervical spine, few neurovascular structures are at risk. This is in contrast to anterior cervical exposures, which place a far greater number of vital structures in harm’s way. Additionally, posterior cervical approaches allow for many levels to be simultaneously exposed, whereas anterior approaches are more limited. Numerous fixation sites are available for fusion and instrumentation, such as the lateral masses, facets, lamina, and spinous processes.

DISADVANTAGES

Anterior pathology is poorly visualized through a posterior approach and places the cervical spinal cord at untoward risk. Severe anterior canal or cord compression typically requires an anterior surgical corridor for resection. Extensive resection of posterior bony elements to decompress a straightened, kyphotic, or flexible neck carries with it an increased risk of progressive deformity. In cases of severe deformity with loss of anterior column support, a posterior approach does not allow for grafting and restoration of intervertebral height.

STRUCTURES AT RISK

Unlike other spine approaches, the posterior cervical approach places several structures at risk prior to incision. As the cervical spine is highly mobile, it is at risk for subluxation and spinal cord injury during the intubation procedure itself. After the patient is paralyzed, the cervical spine is at further risk during the turn to the prone position. This is especially true for cases of unstable fractures and anterior spinal cord compression. The head must typically be immobilized in a Mayfield head rest, Gardner-Wells tongs, or a HALO device. All these items require the use of head pins and place the cranial venous sinuses and intracerebral contents at risk. Traction should also be placed gradually to avoid additional spinal deformity. Thus, great caution must be used for all phases of the early perioperative preparation. The use of awake neurological testing, fiberoptic intubation, and somatosensory evoked potentials are all helpful in preventing iatrogenic neurological injury. After positioning, radiographic confirmation of the spinal alignment should be sought immediately.

Immediately in the midline, few neurovascular structures are at immediate risk. The C1 ring and lamina are often very thin and can be cracked under excessive pressure. Subperiosteal dissection in the high cervical spine should be performed gently with electrocautery. Far lateral dissection during the exposure places the vertebral arteries, nerve roots, and brachial plexus at risk. A venous plexus typically overlies the artery at the level of the foramen transverserium and can be cauterized with bipolar or gently tamponaded with Gelfoam and a cotton patty.

The course of the vertebral arteries should be completely familiar to the operative surgeon. Anomalous courses and ectatic variants are not uncommon. Preoperative computed tomography (CT), CT-angio, and magnetic resonance imaging/arthography (MRI/MRA) are helpful to exclude such anomalies. For cases of occipitocervical exposure, the foramen magnum dura and vertebral arteries during their transverse turn are also easily injured. There is frequently a notch along the superior aspect of the C1 ring approximately 1.5 cm from the midline posterior tubercle, where the vertebral artery lies superficial and posterior. A lateral triangle of fascia typically surrounds the vertebral artery at this point and should be opened cautiously with scissors.

Related posts:

Volar Approach to the Basal Joint of the Thumb (for Bennett’s Fracture) Paronychium Approach Anterior Approach Anterolateral (Internervous) Approach Midline Approach Anterior Approach to the Cervical Spine

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