xStep (xStep)

The xStep is a transcutaneous electrical spinal cord stimulation device intended to deliver programmed electrical pulses in conjunction with functional task practice to improve hand sensation and strength in patients aged 18-75 with chronic, incomplete cervical spinal cord injury (C2-C8). It is for prescription use in medical centers and works by activating spinal neural circuits below the injury level through external electrodes placed on the skin.

The xStep uses a dual-frequency waveform (burst frequency and high-frequency carrier wave) delivered via rectangular pulses at 10000 Hz intra-burst frequency, 100 µs pulse width, 30 Hz frequency, 1 ms pulse width, and 0-200 mA amplitude through two channels with Axelgaard PALS electrodes. It has a rechargeable battery, manual button control, digital display, ABS plastic enclosure, and 60-minute program duration, compared to the predicate ARC-EX which supports up to 4 channels and 1-180 minute durations.

IEC 60601-1, IEC 60601-1-2, IEC 60601-2-10, ANSI C63.4, IEC 62133-2:2017, UN38.3, EN IEC 55035, and IEC 62304 for software verification and validation. Testing included electrical safety, EMC, electrical stimulation parameter characterization, battery safety, and mechanical/packaging testing.

The xStep is substantially equivalent to the predicate ARC-EX because both devices share the same intended use (improving hand sensation and strength via transcutaneous spinal cord stimulation in incomplete SCI patients), use identical electrode technology (Axelgaard PALS K132422), and employ the same fundamental mechanism (noninvasive electrical stimulation with carrier frequencies). Minor design differences in stimulation parameters and channel count are within clinically used ranges and do not raise new safety or effectiveness questions, as confirmed by non-clinical performance testing.