ENDOSCOPIC ANTERIOR CERVICAL MICROFORAMINOTOMY
DR. JHO'S TECHNIQUE WITH DESTANDAU'S ENDOSPINE
Cervical radiculopathy caused by degenerative cervical spine disorders is a common medical problem. Compressive radiculopathy is a result of several factors, posterolateral disc herniation, uncodiscarthrosis, or facet hypertrophy. Until now two major surgical techniques have been favored, the anterior and posterior approaches. The anterior technique is a standard technique, but the lateral osteophytes are difficult to resect. Fusion is usually necessary. Posterior approach is less invasive, effective, and not associated with need for fusion. Posterior approach has disadvantage of requiring the manipulation of the cervical nerve root to access anteriorly located offending processes.
PRINCIPLES OF THE ANTEROLATERAL APPROACH
The concept is based on the fact that anterolateral compression of the cervical nerve root, caused by a posterolateral disc herniation or uncodiscarthrosis causing foraminal stenosis, needs to be treated by an anterolateral approach because it gives direct access to the offending pathology. This approach was first described by Verbiest 40 years ago.
ADVANTAGES OF THE ANTEROLATERAL APPROACH
- Disc excision is limited to its lateral part, facet jt. is not damaged.
- Nerve root decompression is achieved without much manipulation under vision.
- Vertebral artery is under vision.
DISADVANTAGES OF THE ANTEROLATERAL APPROACH
- Bilateral radiculopathies require bilateral approach.
- Technique requires steep learning curve.
The pt. is placed in supine position. Skin incision is marked on the symptomatic side after localization and two third incision is medial to border of sternocleidomastoid and one third is lateral to it. After dissection the trachea and oesophagus retracted medially and carotid sheath laterally. The outer tube of Endospine helps in retracting the important structures with less trauma. Then the pathological disc space confirmed with fluroscopy again. Medial portion of the longus colli muscle excised to expose the medial parts of the transverse processes of the upper and lower vertebrae.
In between the two transverse processes the uncovertebral joint can be seen.
MICRODISECTOMY AND MICROFORAMINOTOMY
The uncovertebral jt. is removed with a high speed microsurgical drill 3mm tip to achieve anterior microforaminotomy. With drill the end plates and cortical bones of the uncovertebral junction of lower vertebra and lower corner of upper vertebra are removed. As drilling advances posteriorly, the direction of the drill is gently inclined medially. When the posterior longitudinal ligament is exposed, a piece of thin cortical bone is left behind attached laterally to the periosteal and ligamentous tissue covering the VA (Vertebral Artery). This lateral remnant of the uncinate process is dissected from ligamentous tissue and fractured at the base of uncinate process. It is further disscected from the surrounding soft tissue and then removed, which exposes the VA in between the two transverse processes and can be appreciated by its pulsations. The size of the hole made by the drilling at the uncovertebral joint is usually approximately 5-6mm wide transversely and 7-8 mm vertically. If there is no ruptured disc fragment behind the posterior longitudinal ligament, this will be the end of the nerve root decompression.
If the nerve root is compressed by a subligamentous or an extruded posterolateral disc herniation, the blunt nerve hook is used to remove the disc fragment. The posterior ligament is incised and removed with 1 mm. Kerrison punch. Now we can see the anterior duramater and nerve root emerging from the dura. Any extruded disc herniation is mobilized and pulled out, releasing the nerve root compression. After the completion of the procedure, the cervical root is fully exposed from its dural origin to its posterior crossing with the VA.
This anterior endoscopc microforaminotomy preserves the motion unit anatomically as well as functionally.