(255 days)
As a powered muscle stimulator (NMES) the Stim2Go is indicated for the following conditions:
- Relaxation of muscle spasm
- Prevention or retardation of disuse atrophy
- Increasing local blood circulation
- Muscle re-education
- Immediate post-surgical stimulation of calf muscles to prevent venous thrombosis
- Maintaining or increasing range of motion
As a transcutaneous electrical nerve stimulator (TENS) for pain relief the Stim2Go is indicated for the following conditions:
- Symptomatic relief and management of chronic (long-term), intractable pain
- Adjunctive treatment in the management of post-surgical pain and post traumatic acute pain
As a biofeedback device the Stim2Go is indicated for the following condition:
- Muscle re-education purposes
As a functional neuromuscular stimulator, the Stim2Go is indicated for the following conditions:
- Helps to relearn voluntary motor functions of the extremities
The movement-based biofeedback can only be used for patients with an active range of motion (ROM) which is defined as the ability of volitional movement resulting in a change of the concerned limb inclination angle of at least 10 degrees.
The Stim2Go is a portable, hand-held / body-worn electrical stimulation device mainly for the treatment of neurological patients with motor and/or sensory impairments. Stim2Go offers transcutaneous electrical stimulation of peripheral nerves (motor and/or sensory).
Typically, Stim2Go is used to elicit muscle contractions (known as Neuro Muscular Electrical Stimulation (NMES)), to treat pain (known as Transcutaneous Electrical Nerve Stimulation (TENS)) or to be applied as Functional Electrical Stimulation (FES).
Stim2Go uses a built-in sensor to analyze the patient's movement data in real time. Based on the analysis result, pre-configured stimulation patterns can be triggered to achieve a specific, predetermined effect based on the patient's movements.
Stim2Go is intended for use in a clinical setting or when used by end users in home care, then necessarily with assistance. It is intended for use as an on-demand service - not permanently.
Stim2Go is controlled wirelessly by a smart device – the App is freely available in the Appstore. The App allows users to execute a variety of therapy programs and even to control parameters on a very detailed level. Stim2Go is tested and certified according to the international standards for medical electrical devices and systems.
The provided text describes the acceptance criteria and the study proving the device's compliance, focusing on its substantial equivalence to a predicate device.
Here's an analysis of the requested information:
1. Table of Acceptance Criteria and Reported Device Performance
The document presents the acceptance criteria and device performance through side-by-side comparison tables between the new device (Stim2Go) and the predicate device (STIWELL med4) for various modes: Powered Muscle Stimulator (NMES), Functional Electrical Stimulation (FES), Biofeedback, and Transcutaneous Electrical Nerve Stimulator (TENS). The "Comment" column in these tables explicitly states whether the new device is "Substantially equivalent" to the predicate device for each characteristic or specification.
Since no specific numerical acceptance thresholds were stated in terms of diagnostic performance metrics (e.g., AUC, sensitivity, specificity, accuracy), the "Acceptance Criteria" for this submission appears to be demonstrating substantial equivalence to the predicate device across various technical and functional specifications. The "Reported Device Performance" is the new device's specifications as measured and compared to the predicate device.
Given the extensive nature of these tables (pages 6-29), summarizing them entirely in a single table here would be too long. Instead, I will provide a representative excerpt and describe the general approach to demonstrating compliance.
General Acceptance Criteria & Performance Approach:
The overall acceptance criterion for this device appears to be the demonstration of substantial equivalence to the legally marketed predicate device (STIWELL med4, K080950) across all specified functionalities (NMES, TENS, FES, Biofeedback) and safety standards. This is proven by showing that the new device's characteristics and performance are either identical or that any differences do not raise new questions of safety or effectiveness.
Representative Excerpt from Compliance Tables (e.g., for Powered Muscle Stimulator):
| Characteristics / Specifications | New Device Stim2Go (K230701) | Predicate Device STIWELL med4 (K080950) | Comment |
|---|---|---|---|
| Basic Unit Characteristics | |||
| Power Source(s) | Battery Li-Ion 3.7 V (IEC 62133-2 certified) | Battery Pack Li-Ion 11 V | Substantially equivalent |
| Number of Output Channels | 5 | 4 | (PMS1) Substantially equivalent |
| Regulated Current or Regulated Voltage? | Regulated current | Regulated current | Substantially equivalent |
| Automatic Shut Off? | Yes (15 min) | Yes (10 min) | Substantially equivalent |
| Compliance with Voluntary Standards? | IEC 60601, IEC 60601-1-2, IEC 60601-1-6, IEC 60601-1-11, IEC 60601-2-10, IEC 62304 | IEC 60601-1, IEC 60601-1-2, IEC 60601-2-10 | Substantially equivalent |
| Output Specifications | |||
| Waveform | Biphasic symmetrical | Biphasic symmetrical | Substantially equivalent |
| Maximum Phase Charge, (µC) @500 Ω | 75 µC (for 750 µs) | 40µC (for 400 µs) | (PMS5) Substantially equivalent |
| Pulse Width (specify units) | 30-400µs (default) (30-750 µs in steps of 10 µs, adjustable only by therapists) | 50-400 µs | (PMS4) Substantially equivalent |
| Frequency (Hz) | 1,2,3,4,5,10,16,20,25,33,50,100 Hz | 1 - 140 Hz | (PMS4) Substantially equivalent |
Notes on Comments (as explained in the document):
- (PMS1): Different number of channels, but both comply with IEC 60601-2-10 and difference doesn't impact essential performance, basic safety or substantial equivalence.
- (PMS4): The new device has a lower max frequency (100 Hz) and higher max pulse width (750 µs) than predicate, but still complies with IEC 60601-2-10 requirements and differences do not impact essential performance, effectiveness, safety or substantial equivalence. Parameters only adjustable by therapists.
- (PMS5): Higher max phase charge (75 µC) for new device vs. (40 µC) for predicate, but still considered safe per 21CFR890.5850 and complies with IEC 60601-1 and IEC 60601-2-10. Differences don't impact effectiveness, safety, or substantial equivalence.
2. Sample Size Used for the Test Set and Data Provenance
This submission is a 510(k) premarket notification for a Class II medical device (Powered Muscle Stimulator, Product Code IPF). For devices like this, the primary method of demonstrating safety and effectiveness is often through comparative testing against a predicate device and compliance with recognized performance standards, rather than extensive clinical trial data or large observational test sets with human subjects.
The document states that performance testing / standard testing was carried out. This includes:
- Electrical Safety tests according to IEC 60601-1 and IEC 60601-2-10.
- Battery Safety tests according to IEC 62133-2.
- Mechanical and temperature/climate Safety tests according to IEC 60601-1.
- Electromagnetic Compatibility tests according to IEC 60601-1-2.
- FCC Radio Frequency Testing according to 47 CFR 15.247.
- Software Verification in accordance with FDA guidance and IEC 62304.
- Usability/Human Factors Testing.
For these types of tests, the "sample size" refers to the number of devices or components tested, and it is usually a small, representative sample (e.g., a few units) to ensure manufacturing consistency and functionality, not a large patient cohort. The document does not specify the exact number of devices tested for each performance/standard test, but it implies that standard engineering and quality control practices were followed.
Data Provenance:
- The tests were carried out at "certified test house" for electrical safety, battery safety, mechanical/temperature safety, electromagnetic compatibility, and FCC RF testing.
- Software verification testing was carried out "internally", but an "external test house approved the compliance against IEC 62304."
- Usability/Human Factors testing was carried out with both "formative and summative usability evaluation," and an "external test house approved the compliance against IEC 60601-1-6."
The data is prospective in the sense that these tests were specifically conducted for the purpose of demonstrating compliance for this 510(k) submission. There is no information regarding country of origin of the data beyond the certified/external test houses.
3. Number of Experts Used to Establish Ground Truth and Qualifications
This submission does not involve clinical data that would require expert-established ground truth in the context of diagnostic accuracy (e.g., reading medical images). The "ground truth" here is defined by:
- Industry Standards: Compliance with recognized international and national standards (IEC 60601 series, IEC 62133-2, IEC 62304, FCC regulations, etc.).
- Predicate Device Specifications: The established performance and safety profile of the legally marketed predicate device (STIWELL med4).
The "experts" involved are the personnel at the certified/external test houses who perform the standard-defined tests and the company's internal engineers and quality assurance personnel. Their qualifications would be expertise in electrical engineering, biomedical engineering, regulatory affairs, quality assurance, etc., with demonstrated experience in device testing and standard compliance. The document does not specify the exact number or detailed qualifications of these individuals, as it's implied by their role in certified testing facilities.
4. Adjudication Method for the Test Set
As there is no clinical test set involving human interpretation of data for diagnostic or prognostic purposes, an adjudication method (like 2+1, 3+1) is not applicable. The "adjudication" in this context is the process of comparing the new device's measured performance against the specified tolerances within the relevant standards and against the predicate device's specifications, which is done through rigorous engineering and regulatory review.
5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done
No, an MRMC comparative effectiveness study was not done. This type of study is typically performed for AI/CADe (Computer-Assisted Detection) or CADx (Computer-Assisted Diagnosis) devices where human readers' diagnostic performance with and without AI assistance is being evaluated. The Stim2Go is a powered muscle stimulator, not a diagnostic imaging AI device. Its performance is evaluated through technical specifications and hardware/software compliance, not human reader improvement.
6. If a standalone (i.e., algorithm only without human-in-the-loop performance) was done
The concept of "standalone performance" primarily applies to algorithms that interpret data and provide outputs (e.g., classifications, measurements) without immediate human intervention for diagnosis. While the Stim2Go device does have software and embedded algorithms for controlling stimulation and interpreting sensor data (e.g., inclination calculations for biofeedback and triggered FES), its "performance" is evaluated by its ability to meet the output specifications and safety standards as a functional medical device, not as a standalone diagnostic algorithm. The compliance tests (electrical safety, EMC, etc.) can be considered "standalone" in that they verify the device's technical performance independent of patient use at a fundamental level.
7. The Type of Ground Truth Used
The ground truth used for this submission is:
- Technical Specifications and Performance Metrics: Parameters defined in engineering specifications for electrical stimulation, sensor accuracy (e.g., 1 degree for inclination angle), and mechanical operation.
- Compliance with Recognized Standards: The "ground truth" for safety and basic effectiveness is established by the requirements of international medical device standards (e.g., IEC 60601 series, IEC 62133-2, IEC 62304) and FDA regulations (21 CFR 898, etc.). The device's ability to pass these standard tests forms the core evidence.
- Predicate Device Performance: The established safety and effectiveness profile of the STIWELL med4 (K080950) serves as a benchmark for substantial equivalence comparisons.
There is no mention of "expert consensus," "pathology," or "outcomes data" in the typical sense of clinical studies used for diagnostic accuracy.
8. The Sample Size for the Training Set
This document describes a 510(k) submission for a physical medical device, not an AI/ML-driven diagnostic algorithm that relies on a "training set" of data in the machine learning sense. Therefore, the concept of a "training set" and its sample size is not applicable here. The device's internal algorithms (e.g., for inclination calculation, as mentioned under FES5/BF1 discussion) are likely based on established physics and signal processing principles, not learned from a large dataset.
9. How the Ground Truth for the Training Set Was Established
Since there is no "training set" in the context of machine learning, this question is not applicable. The underlying principles for the device's functions (like electrical stimulation parameters, sensor data processing for inclination) are based on fundamental scientific and engineering principles, and their accuracy/performance is verified through the various compliance and performance tests described.
§ 890.5850 Powered muscle stimulator.
(a)
Identification. A powered muscle stimulator is an electrically powered device intended for medical purposes that repeatedly contracts muscles by passing electrical currents through electrodes contacting the affected body area.(b)
Classification. Class II (performance standards).