To determine the remaining battery capacity of rechargeable neurostimulators after 10 years of implant.

The first rechargeable implantable neurostimulators were approved for treatment of chronic pain in 2004, and since then rechargeable implants have seen widespread adoption. But how well do rechargeable neurostimulator batteries hold up over time? With the earliest devices now more than 15 years old, is there enough remaining battery capacity to be usable after 10 years of use?

Forty-four (N=44)  neurostimulators (Boston Scientific) were randomly selected from an inventory of returned field devices. The average implant age (from date of implant to present) was 13.05 years while the average battery age (from date of manufacture to present) was 14.03 years. The average implant duration was 9.95 years. To measure the remaining capacity, the batteries were extracted from the implants and connected to an Arbin battery tester.

The average remaining cell capacities were 191.5 mAh (95.8% of initial nominal capacity) on the first cycle, 192.4 mAh (96.2% of initial nominal capacity) on the second cycle, and 192.5 mAh (96.3% of initial nominal capacity) on the third cycle when cells were discharged at a C/5 rate (40 mA). 37 out of 44 cells (84.1%) had remaining capacities of greater than 180 mAh, or greater than 90% of the initial nominal capacity. An additional fourth cycle discharged the cell at a C/100 rate (2 mA) to simulate a high patient use condition. The average remaining cell capacity was 191.0 mAh, or 95.5% of the initial nominal capacity. 40 out of 44 cells (90.9%) had remaining capacities of greater than 180 mAh, or greater than 90% of the initial nominal capacity.

Rechargeable neuromodulation batteries can retain on average greater than 95% of the initial nominal capacity even after 10 years of implanted use.