Background and Aims:
Currently marketed spinal cord stimulation (SCS) systems operate in a fixed-output stimulation configuration without sensing or adjusting to the nerves’ response (open-loop). A new SCS system uses evoked compound action potential (ECAP) to automatically adjust the stimulation current to maintain consistent SC activation (closed-loop). A prospective, multi-center, single-arm study was designed to demonstrate the safety and performance of closed-loop SCS system.

Methods:
Seventy subjects with chronic pain were enrolled. Fifty subjects were implanted with a closed-loop SCS system (ACTRN12615000713594). Post-implantation subjects were followed over 12 months to assess therapy effectiveness and safety.

Results:
At 12 months, back pain was reduced from 81.3 mm (± 1.4) to 22.7 mm (± 4.1) and overall pain was reduced to 21.0 mm (± 3.4) from 81.3 mm (± 1.6). Leg pain responded similarly well to the therapy (Table). At 12 months, 83.7% of subjects reported significant, favorable change as described via PGIC and 88.4% of subjects were “satisfied” or “very satisfied” with their treatment (Table). At baseline, 18.0% of subjects were minimally or moderately disabled on the ODI; at 12 months, this proportion increased to 74.4% (Table).

Conclusions:
The study to date has demonstrated sustained high rates of VAS pain reduction through 12 months. We postulate that the stable level of SC activation is the main factor contributing to achieving this profound level of pain relief. This study continues to monitor the outcomes for subjects through a 2-year follow-up period.

LONG-TERM RESULTS FROM FEEDBACK-CONTROLLED SCS USING EVOKED COMPOUND ACTION POTENTIALS (AVALON STUDY)