ActiGait implanted drop-foot stimulator (common peroneal nerve multi-contact cuff)

One-line verdict: A hybrid implanted-plus-external FES system that uses a multi-contact cuff on the common peroneal nerve to selectively restore ankle dorsiflexion during gait.

Quick tags: Stimulation · Channels: multi-contact cuff (often described as 4-channel control) · Species: Human

Overview

What it is: ActiGait is a partly implantable peroneal nerve stimulation system: an implanted stimulator body connected to a nerve cuff electrode wrapped around the common peroneal nerve, plus external components used to trigger stimulation patterns across gait phases.

Why it matters: It is a concrete, real-world example where cuff contact geometry + multi-channel programming yields functional selectivity (recruitment shaping) in a packaged clinical neuroprosthesis.

Most comparable devices: surface FES drop-foot systems (non-implant); other implantable peroneal nerve stimulators.

Spec Card Grid

Identity

• Device name: ActiGait implanted drop-foot stimulator
• Canonical ID: BTSD-PNI-0002
• Org / manufacturer: ActiGait is a commercial system (manufacturer/branding varies by era and region in publications and clinical materials)
• First demonstrated (year): clinical studies published in the 2000s–2010s
• First implanted (year): mid-2000s era (reported)
• Species: human
• Regulatory / trial status: used clinically in Europe in multiple cohorts; evidence includes prospective studies
• Primary use: stimulation (FES)
• Primary target: common peroneal (fibular) nerve, proximal to bifurcation

Geometry & Architecture

• Interface type: peripheral nerve cuff (multi-contact, multi-channel stimulation)
• Penetrating?: no
• Form factor: implanted stimulator body + cable + cuff electrode; plus external trigger/controller
• Array layout: multi-contact cuff enabling multiple stimulation “channels” around the nerve (exact grouping is implementation-specific)
• Footprint (mm): not consistently reported in open clinical outcomes papers
• Insertion method: surgical placement of cuff around common peroneal nerve proximal to bifurcation; implant body placement in thigh
• Anchoring method: cuff placement + cable routing/strain relief
• Packaging location: hybrid (implanted stimulator + cuff; external controller/trigger)

Electrode & Channel Physics

• Channel count: reported as multi-channel; often described as 4-channel functional control (implementation-dependent)
• Active sites used (vs total): multi-contact cuff (some reports describe ~12 contacts; confirm per specific publication)
• Electrode material: not pinned here
• Recording modality: N/A
• Stimulation capability: yes

Tissue Interface & Bioresponse

• Target tissue: extraneural cuff on peroneal nerve trunk
• Vascular disruption risk: low–moderate (surgical dissection; compression risk if misfit)
• Micromotion sensitivity: low–moderate (strain relief important)
• Encapsulation: expected; long-term cohorts exist
• Typical failure mode: hardware issues, infection, threshold drift/selectivity changes, revision

System Architecture

• Onboard electronics: stimulation in implanted body; none in cuff
• Control path: external trigger/controller coordinates stimulation timing (gait-phase)
• Power: hybrid architecture (model-dependent)
• MRI compatibility: model-specific

Performance Envelope

• Typical yield (acute): selective dorsiflexion recruitment via programming
• Typical yield (chronic): long-term gait improvements reported across cohorts
• Revision / explant: occurs in real-world cohorts (rates vary)

Clinical / Preclinical Evidence

• Evidence base: prospective cohort data in central drop foot (e.g., post-stroke)
• Primary outcomes: gait speed/endurance, functional dorsiflexion, usability
• Key limitations of evidence: mixed etiologies and heterogeneous rehab protocols

Engineering Verdict

Strengths:

• multi-contact cuff enables functional selectivity for gait
• reduces daily placement burden vs surface FES

Limitations / failure modes:

• requires surgery and implanted hardware maintenance
• selectivity depends on nerve anatomy + cuff placement

References

• Martin KD, et al. Restoration of ankle movements with the ActiGait implantable drop foot stimulator: a safe and reliable treatment option for permanent central leg palsy. J Neurosurg. 2016;124(1):70–76. doi: 10.3171/2014.12.JNS142110. PubMed: https://pubmed.ncbi.nlm.nih.gov/26207599/