A spinal cord stimulator (SCS) is an implanted medical device designed to manage chronic pain that has not responded adequately to other treatments. The system delivers low-level electrical impulses directly to the spinal cord nerves, effectively interrupting or masking pain signals before they reach the brain. The SCS is composed of two main parts: thin wires called leads, placed near the spinal cord, and a small, battery-powered implantable pulse generator (IPG), typically placed under the skin in the buttocks or abdomen. Understanding the expected operational life of the SCS is important for long-term pain management planning, as the power source eventually requires surgical replacement.
Understanding Spinal Cord Stimulator Types
The lifespan of a spinal cord stimulator is fundamentally determined by the design of its power source, which falls into two main categories.
Primary Cell (Non-Rechargeable) Systems
Primary Cell systems contain a battery that is depleted over time and cannot be externally replenished. These generators are designed to operate continuously until the internal battery is exhausted, functioning similarly to a traditional pacemaker. This system is advantageous because it requires no patient interaction for power maintenance once implanted.
Rechargeable Systems
Rechargeable systems feature a lithium-ion battery that patients must periodically recharge using an external charging unit. The external charger is held over the skin above the implanted generator, transmitting energy wirelessly. Rechargeable generators are engineered to support the higher energy demands of newer stimulation modalities, such as high-frequency programs. While this design requires a regular charging schedule, it allows the generator to maintain its therapeutic function for a significantly longer period.
Expected Lifespan of the Power Source
The operational life of the SCS leads is generally considered permanent, assuming they remain functional and securely anchored. However, the implantable pulse generator (IPG) houses the battery and dictates the overall device lifespan.
For Primary Cell (non-rechargeable) systems, the typical longevity range is approximately two to five years before the power source is depleted. Clinical data suggests the mean battery life for these devices is often closer to three or four years, depending on the specific model and usage.
Rechargeable systems offer a much longer operational life for the implanted generator, with many manufacturers projecting a lifespan of nine to ten years or more. Some studies have reported a mean rechargeable battery life of around seven to eight years, and in some cases, the generator is designed to last up to 15 years before replacement is necessary. The extended duration of rechargeable devices minimizes the number of replacement surgeries a patient will need over the course of their therapy. In both device types, the end of the device’s useful life is determined by the battery’s depletion.
Factors Influencing Device Longevity
The actual lifespan is highly dependent on the energy demands placed on the system. The specific settings programmed into the SCS are the primary determinants of how quickly the battery drains.
Parameters like stimulation amplitude (intensity of the electrical pulse) and frequency (number of pulses per second) directly correlate with power consumption. Higher amplitudes and frequencies draw more current from the generator, leading to faster battery depletion.
Daily usage time is another significant variable; a patient who uses their stimulator continuously will deplete the battery faster than one who uses it intermittently. For rechargeable systems, consistent adherence to the recommended charging schedule is important for maintaining battery health. Failing to charge the device regularly or allowing the battery to fully discharge repeatedly can compromise the generator’s projected lifespan.
The Generator Replacement Procedure
When the implanted pulse generator approaches the end of its battery life, a minor surgical procedure is performed to exchange the depleted unit. This process, known as a generator replacement, is typically an elective, outpatient procedure that is substantially less involved than the initial implantation surgery.
The surgeon accesses the generator by reopening the original incision site, which is usually located in the lower back or buttocks. The depleted generator is disconnected from the leads, which are left in place and remain functional. A new, fully powered generator is attached to the existing leads and securely repositioned beneath the skin.
Because the leads do not need to be placed or anchored again, the replacement procedure is usually shorter and recovery is minimal. Patients are typically able to return home on the same day, with a brief period of restricted activity to allow the incision to heal.