Spinal Disc Replacement

Thoracic SpineIn human anatomy, twelve thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. They are intermediate in size between those of the cervical and lumbar regions; they increase in size as one proceeds down the spine, the upper vertebrae being much smaller than those in the lower part of the region. They are distinguished by the presence of facets on the sides of the bodies for articulation with the heads of the ribs, and facets on the transverse processes of all, except the eleventh and twelfth, for articulation with the tubercles of the ribs.

A Discectomy (also called open discectomy) is the surgical removal of herniated disc material that presses on a nerve root or the spinal cord. The procedure involves removing the central portion of an intervertebral disc, the nucleus pulposus, which causes pain by stressing the spinal cord or radiating nerves. Advances in options have produced effective alternatives to traditional discectomy procedures.

With traditional disc surgery, surgeons make an incision in the center of the back at the same level as the herniated disc and then strip the muscles of the back away from the bones of the spinal column in order to see the area where the disc has herniated. Once the herniated disc has been removed, the muscles are put back in place and the incision is closed. A new minimally-invasive technique called a microdiscectomy uses a special type of muscle-spreading instrument that reduces muscle damage. This allows herniated fragments to be removed safely while protecting the nerve roots and spinal cord. This procedure causes much less pain after the surgery, and allows the patient to recover and return to rehabilitation and normal activity much sooner.

Thoracic microdiscectomy is a surgical technique, utilizing a specially constructed tubing (thorascope) that contains a camera with lighting and allows insertion of surgical instruments, that is most commonly performed to treat pain that radiates around the torso due to pressure on the thoracic nerve root, or to decompress the spinal cord itself.

Utilizing a thorascope (ie: thorascopy) is an alternative to opening the patient up as with traditional surgical procedures. It involves internal examination, biopsy, and/or resection of disease or masses within the pleural cavity and thoracic cavity. Thoracoscopy may be performed either under general anaesthesia or under sedation with local anaesthetic.

Indications for Thoracoscopic Spinal Surgery (VATS)

Patient with kyphosis Patient with Kyphosis

Indications for performing a thoracoscopy can be extrapolated from the five basic indications for surgery of the spine patient.

Deformity: These include an anterior release for scoliosis or Scheuermann's kyphosis.

Instability: In cases of spinal fractures for instance, in addition to decompression, anterior column reconstruction using bone grafts and/or internal fixation devices can also be applied through a thoracoscopic approach.

Neural compression: This is probably the most common indication for a thoracoscopic spinal surgery. Nerve roots and the spinal cord can be decompressed through the resection of thoracic herniated nucleus pulposus.

Pathologic lesions: A thoracoscopic approach may be used for the treatment of infection or tumor through biopsy, debridement, drainage of an abscess, resection of a tumor, or corpectomy.
Pain: Thoracoscopy may be used for the treatment of symptomatic spondylosis and/or degenerative disc disease by fusion of the painful motion segment (bone dowels or cages).

Herniated Nucleus Pulpous Herniated Nucleus Pulpous

Thoracoscopy is a technique used in managing herniated thoracic discs. The advantages of thoracoscopy over the conventional transthoracic open procedures are:

  • enhanced visualization while using standard instruments through minimal incisions
  • more extensive visualization of thoracic anatomy
  • decreased incisional pain
  • decreased need for chest tube drainage
  • decreased respiratory complications
  • decreased blood loss
  • decreased potential for infection
  • decreased postoperative pain which results in shorter hospital duration, shorter rehabilitation, and decreased medical costs
O.R. setup for VATS O.R. setup for VATS

Approach and Technique for Thoracoscopic Spinal Surgery (VATS) Prior to attempting endoscopic techniques, the physician should be comfortable performing open thoracic procedures because they involve essentially the same surgical techniques and procedures. There are some basic technical concepts that are important to understand prior to initiating the thoracoscopic procedure.

Trocar site placement is critical. If the trocars are placed too close together, the instruments will not have adequate working space and Afence@ with each other. Additionally, the trocars should be place far enough away from the surgical lesion as to permit adequate visualization of the surgical lesion. Rigid trocars should be avoided to prevent intercostal neuralgia. Instrumentation should be inserted and positioned at a 180° arc and face the same direction as the camera to avoid mirror imaging.

Lateral Decubitus Position Lateral Decubitus Position

Do not manipulate instrumentation without visualizing through the scope to avoid soft tissue injuries. Avoid random movements of the camera to avert confusion. Zoom in and out to gain adequate visualization and perspective. Once the patient is laterally positioned, anesthesia is induced, and the surgical site is prepped. The first incision is made in the 6th or 7th intercostal space on the midaxillary line for the insertion of the first trocar. The camera is inserted so that all other trocar insertions may be visualized.

The insertion technique for trocars is similar to that of a chest tube insertion. An incision 15-20 mm long is made over the intercostal space and extended through the parietal pleura. The first trocar is usually inserted at the 6th or 7th intercostal space. Caution is exercised when inserting a trocar below the T7 level to avoid penetrating the diaphragm. Once the first trocar is placed one lung ventilation should be confirmed and hemostasis verified. The remaining trocars may then be placed. Usually four or more trocars are required.

Trocar Placement Trocar Placement

Visual inspection of the contents of the thoracic cavity should be performed initially. If the surgical lesion is in the mid–thorax, the azygos vein, aorta, intercostal vessels, and rib heads should be identified. If the surgical lesion is in the upper thorax, the subclavian artery and veins, ribs one and two, longus colli muscle and superior intercostal vein should be identified. Ribs should be counted and x–rays performed to confirm the location of a surgical lesion such as a herniated nucleus pulposus.

Once the general exposure is complete, which may require a thoracic surgeon, the spinal exposure may be initiated by the orthopaedic surgeon or neurosurgeon.

Anatomy of Chest Cavity Anatomy of Chest Cavity

The surgical approach to the midthoracic spine (T6–T10), lower thoracic spine (T10–L1), and upper thoracic spine (T2–T6) differ slightly with respect to the placement of trocars. Once, the approach is made and the anatomy identified, the spine surgeon may then begin the specific thoracic procedure, most commonly a thoracic microdiscectomy.

The operation may take from one to two hours, depending on the difficulty of the case.
A follow-up procedure may take 1.5 to 3 hours, depending on the amount of scar tissue present from the prior surgery.