(123 days)
The Innovative Neurotronics WalkAide External Neuromuscular Stimulator (WalkAide System) is intended to address the lack of ankle dorsiflexion in patients who have sustained damage to upper motor neurons or pathways to the spinal cord. During the swing phase of gait, the WalkAide System electrically stimulates the appropriate muscles that cause ankle dorsiflexion and may thus improve the gait in patients with chronic stroke. Medical benefits of Functional Electrical Stimulation (FES) may include prevention of disuse atrophy, increased local blood flow, muscle reeducation, and maintained or increased joint range of motion.
The WalkAide is an external functional electrical stimulator. It is a small device that attaches to the leg just below the knee, near the head of the fibula. During a gait cycle, the WalkAide stimulates the common peroneal nerve, which innervates the tibialis anterior and other muscles that cause dorsiflexion of the ankle. The WalkAide System consists of the WalkAide Patient Kit and the WalkAide Clinician Kit. The WalkAide Patient Kit comprises of all the components and accessories that the patient will take home and use. The Clinician System comprises the accessories that a clinician (i.e., orthotic specialist, physiotherapist, occupational therapist, etc.) will use to set up a patient's WalkAide.
Here's an analysis of the acceptance criteria and study information based on the provided document:
Acceptance Criteria and Device Performance
The document describes the WalkAide System and primarily focuses on extending its "Indications for Use" to specifically include chronic stroke patients for improved gait. Given that the device itself (hardware and software) is stated to be "identical to the predicate K123972" except for this indication, the acceptance criteria here are implicitly tied to demonstrating the device's effectiveness and safety for this expanded indication compared to a standard treatment.
The document doesn't present a specific table of quantitative acceptance criteria from the FDA for a new device, but rather a Comparison Conclusion Table (on pages 16-17) that highlights the identity of the current device to its predicate (K123972) in terms of technical specifications. The key acceptance is based on the clinical study supporting the new indication.
Implicit Acceptance Criteria (for the new indication) and Reported Device Performance:
| Acceptance Criteria Category (Implicit) | Reported Device Performance (from the study) |
|---|---|
| Effectiveness for Gait Improvement in Chronic Stroke: The device should demonstrate improvement in gait velocity and overall quality of gait in chronic stroke patients. | "The results of this study show the WA to be equivalent to the AFO for improvements in gait velocity..." |
| "The WA produces physiological dorsiflexion, with all the motor and sensory benefits inherent in active muscle contraction, including improved gait speed and improved overall quality of gait for individuals poststroke." | |
| Equivalence to Standard of Care (AFO): The device should perform at least as well as the Ankle-Foot Orthosis (AFO) in relevant clinical outcomes for this population. | "...the WA to be equivalent to the AFO for improvements in gait velocity, SIS composite score and safety." |
| Safety in Chronic Stroke Population: The introduction of the device for this population should not introduce new safety concerns compared to the AFO. | "...equivalent to the AFO for improvements in gait velocity, SIS composite score and safety." |
| Functional Improvements: The device should lead to clinically relevant functional ambulation improvements. | "Results from this study support the fact that use of the WA produces clinically relevant in functional ambulation..." |
| Applicability to Chronic Phase: Improvements should be observable even in the chronic phase of stroke. | "...these results were reported in a population of individuals averaging 6.9 years from onset of stroke, this study demonstrates that functional improvements can be obtained in the chronic phase of stroke..." |
Study Information:
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Sample size used for the test set and the data provenance (e.g. country of origin of the data, retrospective or prospective)
- Sample Size: The exact sample size is not explicitly stated in the provided document. It only mentions "a randomized trial utilized an unblinded, parallel group design."
- Data Provenance: The document does not specify the country of origin. The study was a "randomized trial," which suggests it was prospective. Data analysis used "an intention to treat analysis with missing data points calculated using multiple imputations."
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Number of experts used to establish the ground truth for the test set and the qualifications of those experts (e.g. radiologist with 10 years of experience)
- This information is not provided in the document. The study compared the device (WA) to an Ankle-Foot Orthosis (AFO) and measured "gait velocity, SIS composite score and safety." These seem to be objective and standardized outcome measures, rather than requiring subjective expert ground truth establishment for the test set.
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Adjudication method (e.g. 2+1, 3+1, none) for the test set
- This information is not provided in the document. Given the outcome measures (gait velocity, SIS score, safety), it's unlikely that an adjudication method for image interpretation or diagnosis was required.
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If a multi reader multi case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance
- No, this was not an MRMC comparative effectiveness study involving human readers and AI assistance. This was a clinical trial comparing a medical device (WalkAide) against a conventional treatment (AFO) in patients. The document does not mention human readers or AI assistance in the context of interpretation.
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If a standalone (i.e. algorithm only without human-in-the-loop performance) was done
- No. The WalkAide System is a functional electrical stimulator used by patients with setup and monitoring by a clinician. It is a human-in-the-loop device. The study itself was a clinical trial assessing patient outcomes with the device.
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The type of ground truth used (expert consensus, pathology, outcomes data, etc)
- The "ground truth" for evaluating the device's effectiveness was based on clinical outcomes data, specifically:
- Gait velocity
- SIS composite score (Stroke Impact Scale or similar, implying a functional assessment)
- Safety data
- The "ground truth" for evaluating the device's effectiveness was based on clinical outcomes data, specifically:
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The sample size for the training set
- This information is not applicable and therefore not provided. The WalkAide system is a hardware device (functional electrical stimulator) with accompanying software for configuration and analysis. It is not an AI/ML algorithm that is trained on a dataset in the typical sense. The study was a clinical trial to demonstrate effectiveness for an indication, not to train or validate an algorithm.
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How the ground truth for the training set was established
- This information is not applicable for the reasons stated above. The device doesn't have a "training set" in the context of artificial intelligence. Its functionality is based on established principles of electrical stimulation and biomechanics. Its performance is validated through clinical trials.
§ 882.5810 External functional neuromuscular stimulator.
(a)
Identification. An external functional neuromuscular stimulator is an electrical stimulator that uses external electrodes for stimulating muscles in the leg and ankle of partially paralyzed patients (e.g., after stroke) to provide flexion of the foot and thus improve the patient's gait.(b)
Classification. Class II (performance standards).