Preparation and Procedures

Preparation of the patient includes: Pain physician visit – evaluation/patient selection process, psychological evaluation and diagnostic imaging – Ideally, MRI imaging of the epidural space. Procedures include trial stimulation and permanent implantation.

The implantation of the SCS device divides into two steps, the trial and the permanent SCS implantation. The trial allows the patient to evaluate the effect of the SCS device on their particular pain pattern. If they have more than 50% pain relief, increased activity level, and/or decreased medication use during this time, the trial is considered successful, and they can be scheduled for a permanent SCS procedure.

Both the trial and the permanent SCS placement are sterile procedures performed in the operating room under sedoanalgesia. Anteroposterior fluoroscopic images are obtained, making sure the spinous processes are placed midline to the pedicles. The needle entry site is just lateral to the spinous process. The epidural space is identified by the loss-of-resistance technique. It is recommended that the lateral fluoroscopic views be checked during needle insertion, in order to assess needle depth (Figure 51.1a,b).

Epidural needle placement is at an angle of fewer than 45° to facilitate threading of the lead (Figure 51.2). A perpendicular angle needs to be avoided at all times since this would require bending the lead as it is introduced into the epidural space. The curved lead tip can facilitate the desired lead positioning and threading. The lead is advanced through the posterior paramedian epidural space until the appropriate location providing coverage of the patient’s pain region, which may require one or more leads. Most commonly, this location ranges between T9 and T11. Once adequate lead position is obtained, trial stimulation is performed. It is important that stimulation paresthesias should provide overlap with the patient’s pain location [5].

There are two types of SCS trial, percutaneous lead trial (most common) and permanent lead trial.

1. SCS percutaneous trial

In this approach, after placement of the lead or leads in the appropriate location on the spine, the epidural needle is removed. The lead is then adhered to the skin using a suture, surgical adhesive or skin glue. The remaining portion of the lead connects to an external pulse generator, which is also secured to the skin using a suture or skin glue, a chlorhexidine patch and a sterile dressing. The device is programmed perioperatively and once again in the recovery room before discharging the patient home.

Even although this procedure requires the patient to return to the OR for a permanent lead placement if the trial is successful, it is the preferred method used by most providers. It avoids a second incision and post-operative pain during the trial.

2. Permanent SCS trial

In the permanent trial method, once the leads are in the appropriate location, a local anesthetic is injected around the epidural needle. A midline incision is made through the skin down to the supraspinous fascia. The leads are anchored in this space using a non-absorbable suture and an anchoring device. This device is placed as close as possible to the fascia with the tip protruding into the fascia, which minimizes bending the leads. The anchoring device is secured using a non-absorbable suture (Figure 51.3). The permanent lead is tunneled from the midline incision into the lateral pocket. At this point, an extension wire is connected to the permanent wire to tunnel the lead away from the lateral pocket. This method ensures that the leads remain in the same location if the SCS is permanently implanted.

For low back pain and lower extremity pain, the T9–11 levels are recommended; for neck pain and upper extremity pain, the C2–C7 levels are usually desired; however, there is high intersubject variations in these guidelines. A stimulation trial is warranted before proceeding with permanent spinal cord stimulation implantation. The criteria for a successful trial include at least a 50% pain intensity reduction, a decrease in analgesic intake and a significant functional improvement [6]. Minimal trial time should be at least 1 week, although many centers perform 1- to 4-week trials.

Hardware-related Complications

Lead Migration

Lead migration is the most common complication associated with the device. Its incidence was reported at rates ranging from 1.37–13.6% in the relevant literature [2]. As a result of lead migration, loss of stimulation/paresthesia or abnormal stimulation occurs in the area of chronic pain.

The diagnosis of lead migration is clinically established and radiologically confirmed. In cases of suspected lead migration, the first approach is to compare with X-ray imaging of the actual location of the leads with images recorded immediately after implantation (Figure 51.4).

In case of lead migration, reprogramming should be done first. If reprogramming cannot cover the patient’s chronic pain area, then reoperation/revision is required. It was reported that in SCS systems using a dual-electrode multichannel system, the likelihood of success was higher via reprogramming subsequent to lead migration, and the need for reoperation was lower [7].

Although positioning the IPG generator in the gluteal region rather than in the abdomen provides advantages such as lower infection rate, lower localized pain in the IPG region and shorter surgical time, there is the disadvantage of a higher lead migration rate in gluteal placement [8].

Anchors made from different materials such as hard plastic and silicone are manufactured for secure and durable attachment of the leads. Although some authors suggest that recent developments in anchor systems have reduced lead migration, there is no anchor type with proven superiority over others. In the first 4 weeks following permanent implantation, the patient should be advised to refrain from movements such as excessive bending, leaning, and heavy lifting (Figure 51.5).