Residency · Residency · Chronic Pain Management

Spinal Cord Stimulation: Surgical Technique and Complications

Introduction

Successful spinal cord stimulation outcomes depend not only on appropriate patient selection and programming but also on meticulous surgical technique. The implantation process is divided into two phases: a trial period that confirms therapeutic benefit and a permanent implant if the trial succeeds. Both phases require precision in lead placement, anchoring, and IPG positioning, and an understanding of the complications that can occur at each stage is essential for managing them effectively.

The SCS Trial

Purpose and Duration

The trial serves as a test drive of the therapy before committing to permanent implantation. It typically lasts 5-10 days, giving the patient enough time to assess pain relief across different activities, body positions, and pain scenarios. The standard success criterion is 50% or greater pain reduction on the numeric rating scale (NRS) combined with improved function and patient satisfaction. Many centers also require demonstration of functional improvement -- increased walking distance, better sleep quality, or decreased medication use -- before moving forward.

Trial Technique

The trial is performed in a fluoroscopy suite or operating room under sterile conditions. Local anesthesia with sedation is preferred over general anesthesia because the patient needs to be awake to provide real-time feedback during intraoperative paresthesia mapping (when tonic stimulation is used). The patient is positioned prone on a radiolucent table, and epidural access is obtained with a 14- or 15-gauge Tuohy needle, typically at the L1-L2 or T12-L1 interlaminar space for thoracic lead placement. Entry into the epidural space is confirmed using the loss of resistance technique with saline or air. Percutaneous leads are then advanced under continuous fluoroscopic guidance to the target vertebral level -- T8-T10 for low back and leg pain, C2-C4 for cervical conditions.

Intraoperative Testing

With tonic stimulation, the leads are activated and the patient is asked to confirm that paresthesia coverage overlaps with the painful area. With subperception waveforms (HF10, burst), the procedure relies on anatomic lead placement without paresthesia mapping, and the lead position at the target vertebral level is confirmed on fluoroscopy. The lead position is adjusted until optimal coverage or anatomic positioning is achieved. The leads are then externalized through a separate skin puncture site and connected to an external pulse generator for the duration of the trial.

<image>Intraoperative fluoroscopic illustration showing percutaneous SCS trial lead placement, depicting a posterior AP view of the thoracolumbar spine with a Tuohy needle inserted at the L1-L2 interlaminar space and two octapolar percutaneous leads advanced cephalad through the epidural space with tips positioned at the T8 and T9 vertebral levels flanking the midline, alongside a lateral view confirming the leads are in the posterior epidural space dorsal to the spinal cord, with labeled vertebral levels, needle entry point, and lead electrode contacts</image>

Percutaneous Lead Placement (Permanent Implant)

Technique

Permanent percutaneous lead placement is performed in the operating room with full sterile technique. The approach to epidural access and lead positioning is the same as during the trial. Once the final lead position is confirmed fluoroscopically and with intraoperative testing, the lead is secured with an anchor device.

Anchoring Techniques

Anchoring is performed with mechanical devices -- silicone or titanium anchors that grip the lead body and are sutured to the supraspinous ligament or deep fascia with non-absorbable sutures. The anchor is positioned at the needle entry site. Between the anchor and the IPG, a strain relief loop is created in the subcutaneous tissue to accommodate spinal flexion and extension without transmitting mechanical tension to the lead tip. Proper anchoring deserves particular attention because lead migration is the most common complication of SCS, and its incidence is directly related to anchoring quality.

Advantages of Percutaneous Leads

Percutaneous leads are minimally invasive (no laminotomy required), reversible (leads can be removed percutaneously), and carry lower perioperative morbidity than paddle leads. Their cylindrical electrode configuration delivers current in 360 degrees, which provides flexibility during programming.

Paddle (Surgical) Lead Placement

Indications

Paddle leads are considered when percutaneous leads have migrated and need a more stable platform, when broader or more specific electrode coverage is needed, when dorsal column access at challenging levels (such as the upper cervical spine) is required, or when the inherent stability of a paddle within the epidural space is desired to prevent recurrent migration.

Surgical Technique

Paddle lead placement requires a small laminotomy or flavotomy at one or two vertebral levels. The patient is placed under general anesthesia, and neurophysiologic monitoring is used in place of awake paresthesia mapping. A midline incision is made over the target vertebral level, subperiosteal dissection exposes the lamina, and a limited laminotomy or interlaminar flavotomy is performed. The paddle lead is inserted into the dorsal epidural space under fluoroscopic guidance. Somatosensory evoked potentials (SSEPs) and/or electromyography (EMG) are monitored during placement. Paddle leads have a flat, directional electrode array that concentrates current delivery toward the dorsal columns and away from the dorsal roots.

Advantages of Paddle Leads

Paddle leads have significantly lower migration rates compared to percutaneous leads (1-2% versus 5-15%). They are more energy-efficient because their unidirectional current delivery requires lower amplitudes, extending battery life. Modern paddle designs can accommodate up to 32 contacts, offering broader electrode spacing options.

<image>Comparative surgical illustration showing percutaneous versus paddle lead placement for spinal cord stimulation — left panel depicting percutaneous technique with a Tuohy needle passing through the interlaminar space and a cylindrical eight-contact lead threading through the needle into the posterior epidural space, and right panel depicting paddle lead placement through a limited laminotomy with retractors exposing the epidural space and a flat sixteen-contact paddle lead being advanced under the lamina into the dorsal epidural space, both with cross-sectional insets showing the lead position relative to the dura, CSF, and spinal cord</image>

IPG Placement

Location

The implantable pulse generator (IPG) is typically placed in the posterior flank, superior gluteal region, or lower abdominal wall. The site should allow comfortable recharging (for rechargeable devices) and should avoid areas subject to frequent bending or pressure. A subcutaneous pocket is created deep to the dermis, large enough to accommodate the IPG without tension, with the device sitting approximately 2-3 cm below the skin surface.

Tunneling

A tunneling tool creates a subcutaneous tract from the lead anchor site to the IPG pocket. Extension cables connect the leads to the IPG through this tunnel. All connections are secured with set screws, and the connection site (boot) is positioned away from the incision line to minimize the risk of wound complications.

Battery Types

Primary cell (non-rechargeable) IPGs require surgical replacement every 2-5 years depending on programming parameters and are simpler for patients who cannot manage a recharging routine. Rechargeable IPGs last 9-15 or more years and require regular recharging (every 1-7 days depending on stimulation parameters). Rechargeable batteries are generally preferred for high-frequency waveforms, which consume more energy.

Complications

Lead Migration

Lead migration is the most common complication of SCS, occurring in 5-15% of percutaneous leads. It presents as loss of therapeutic paresthesia coverage or a change in the stimulation pattern. Diagnosis is made by comparing the current lead position on fluoroscopy with the post-implant reference images. Risk factors include poor anchoring technique, excessive physical activity in the early postoperative period, and obesity. Management typically requires revision surgery to reposition the lead; for recurrent migration, conversion to a paddle lead should be considered.

Infection

Infection occurs in 3-8% of SCS implants, most commonly caused by Staphylococcus aureus and Staphylococcus epidermidis. Infections can range from superficial wound infections to deep infections and epidural abscesses. Superficial infections may respond to antibiotics alone, though hardware removal is often necessary. Deep infection or epidural abscess requires urgent hardware explantation and intravenous antibiotics. Prevention measures include perioperative antibiotics (cefazolin), strict aseptic technique, chlorhexidine skin preparation, and limitation of operating room traffic.

Hardware Failure

Lead fracture occurs in 5-9% of cases and presents as sudden loss of stimulation or impedance changes. It is diagnosed by impedance testing showing open circuits. IPG malfunction is rare but can manifest as premature battery depletion or connector failure. Extension cable issues -- disconnection, fracture, or fluid intrusion at connection sites -- also occur.

Epidural Hematoma

Epidural hematoma is rare but potentially catastrophic. Risk factors include anticoagulant or antiplatelet therapy, coagulopathy, and difficult epidural access. It presents with acute neurological deterioration -- leg weakness, bowel or bladder dysfunction, and severe back pain -- within hours to days of the procedure. Emergency MRI and neurosurgical consultation for decompressive laminectomy are indicated when the neurological deficit is progressive. Prevention depends on strict adherence to ASRA anticoagulation guidelines for neuraxial procedures.

Spinal Cord Injury

Direct spinal cord injury is extremely rare, with a risk estimated at less than 0.01%. It may occur from direct trauma during lead insertion or as a consequence of epidural hematoma. The risk is highest during paddle lead placement requiring laminotomy. Intraoperative neurophysiologic monitoring (SSEPs and EMG) provides an additional safety layer.

Other Complications

Seroma or hematoma at the IPG pocket is usually self-limiting and may require aspiration if large. Pain at the IPG site is common (5-10% of patients) and may require pocket revision or relocation. Rare complications include allergic reactions to lead or IPG materials, CSF leak or post-dural puncture headache from inadvertent dural puncture during Tuohy needle placement, and uncomfortable stimulation or positional variability (which can often be addressed through programming adjustments).

<image>Compilation of four radiographic and clinical images showing common SCS complications — panel A showing a lateral spine fluoroscopic view with lead migration of 3 vertebral levels from original position marked by comparison, panel B showing an AP view with lead fracture visible as a discontinuity in the conductor wire with corresponding impedance values shown, panel C showing an axial MRI of the thoracic spine with an epidural hematoma compressing the spinal cord adjacent to an SCS lead, and panel D showing a clinical photograph of erythema and wound dehiscence at an IPG pocket site indicating surgical site infection</image>

Postoperative Management

Immediate Postoperative Care

A neurological examination is performed immediately after the procedure and before discharge. AP and lateral fluoroscopic or radiographic images are obtained to document the final lead position, which serves as a reference for future comparison if migration is suspected. Patients receive wound care instructions to keep incision sites clean and dry for 10-14 days. BLT restrictions -- no bending, lifting, or twisting -- are enforced for 6-8 weeks to allow scar tissue to form around the leads and anchor them in place.

Follow-Up Schedule

Follow-up visits are scheduled at 2 weeks (wound check and initial programming optimization), 6 weeks (programming adjustment and gradual return to activity), 3 months (comprehensive assessment of pain, function, and medication use), and then every 6-12 months for ongoing programming optimization, battery assessment, and impedance checks.

Clinical Pearls

Lead migration is the most common reason for SCS revision surgery, and the best defense is meticulous anchoring with non-absorbable sutures and adequate strain relief loops at the time of initial implant. During the SCS trial, the same waveform and lead configuration planned for the permanent implant should be used; a trial with tonic stimulation followed by permanent implant with HF10 may produce discordant results. Baseline imaging (AP and lateral) should always be obtained after permanent implant to serve as a reference for evaluating suspected migration later. ASRA anticoagulation guidelines must be followed strictly, because while the epidural hematoma risk is low, the consequences are devastating. Patients should understand that BLT restrictions for 6-8 weeks post-implant are not optional -- premature activity is the leading modifiable risk factor for lead migration.

References

1. Deer TR, Lamer TJ, Pope JE, et al. The Neurostimulation Appropriateness Consensus Committee (NACC) recommendations for infection prevention and management. Neuromodulation. 2017;20(1):31-50.
2. Hayek SM, Veizi E, Hanes M. Treatment-limiting complications of percutaneous spinal cord stimulator implants: A review of eight years of experience from an academic center database. Neuromodulation. 2015;18(7):603-609.
3. Narouze S, Benzon HT, Provenzano D, et al. Interventional spine and pain procedures in patients on antiplatelet and anticoagulant medications: Guidelines from the American Society of Regional Anesthesia and Pain Medicine. Reg Anesth Pain Med. 2018;43(3):225-262.
4. North RB, Kidd DH, Petrucci L, Dorsi MJ. Spinal cord stimulation electrode design: A prospective, randomized, controlled trial comparing percutaneous with laminectomy electrodes — Part II: Clinical outcomes. Neurosurgery. 2005;57(5):990-996.

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