Procedural Steps

1. Choosing the entry point for the instruments. The entry point for the instruments is usually chosen by measuring the distance from the mid-line on a CT scan that shows the whole abdomen through the disc space of interest. The path is calculated to the center of the disc passing just anterior to the facet joint. Using a CT scan in this manner excludes the possibility that the bowel will be in the path of the instruments and also eliminates the possibility of choosing an entry point too far medial or lateral.

2. Patient positioning. The patient is placed in the lateral decubitus position with a towel roll under the hip. Sterile preparation and draping are carried out. Since discitis is the only major complication to be worried about with APLD, we take special care with the skin prep. We carry out a 10-minute scrub with Betadine soap and then use three layers of Betadine followed by two layers of alcohol. We also give prophylactic antibiotics intravenously with coverage for Streptococcus epidermidis as well.

3. Intradiscal steroid and local anesthetic injection. Prior to placement of the disc aspiration probe, we make a disc injection of approximately 3 mL of a 50:50 mixture of 0.5% bupivacaine and betamethasone. This injection rehydrates the disc and improves the aspiration, and also helps decrease inflammation associated with the HNP. We have found that this can markedly hasten the recovery time after the procedure.

4. Placement of the aspiration probe. A lateral fluoroscopic view is used to place the 18-gauge trocar. When properly placed, the trocar should be at the posterior vertebral body line when the annulus is felt. At this point the AP view is obtained, and the tip of the trocar should be lateral to the medial border of the pedicles. This confirms that the trocar is not going through the thecal sac on the way to the center of the disc (Figure 8.5). Once confirmed to be outside the medial border of the pedicles, the trocar is advanced into the center of the disc and is confirmed on both views to be in the disc center. The cannula and dilator are placed over the trocar; then a trephine is used to in-

Thecal Sac Anatomy

Lateral View Frontal View

Lateral Aspect Body

Figure 8.5. Correct placement of needle against the annulus. The top view shows the correct trajectory of the instrumentation to the center of the nucleus. When the tip of the trocar is against the an-nulus and in the proper trajectory, it should lie at a line that connects the posterior vertebral bodies (PVBL, posterior vertebral body line), and in the frontal view should be lateral to a line that connects the medial border of the pedicles. Only after these views have confirmed that the trocar is not passing through the thecal sac can the instrumentation be passed into the center of the disc.

Figure 8.5. Correct placement of needle against the annulus. The top view shows the correct trajectory of the instrumentation to the center of the nucleus. When the tip of the trocar is against the an-nulus and in the proper trajectory, it should lie at a line that connects the posterior vertebral bodies (PVBL, posterior vertebral body line), and in the frontal view should be lateral to a line that connects the medial border of the pedicles. Only after these views have confirmed that the trocar is not passing through the thecal sac can the instrumentation be passed into the center of the disc.

cise the disc. The nucleotome is then placed into the disc, and final confirmation of its position is obtained in two views.

5. Aspiration of the disc. The disc is aspirated until no more material can be obtained. This usually takes about 20 minutes. The instrument can be moved back and forth and angled to obtain more disc material. We take advantage of the patient's being awake and in the lateral decubitus position by having the patient flex and extend during the procedure to facilitate disc removal.

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