(154 days)
The Phoenix orthotically fits to the lower limbs and trunk. The device is intended to enable individuals with spinal cord injury at levels T4 to L5 to perform ambulatory functions in rehabilitation institutions in accordance with the user assessment and training certification program. This device is not intended for sports or stair climbing.
The Phoenix™ is a wearable, powered exoskeleton that assists a trained user to sit, stand, walk, and turn. The Phoenix consists of a pair of motorized leg braces coupled to a torso module, a lithium-ion battery pack, a main controller unit, and a wireless user interface attached to the handle of an assistive device (such as a crutch, walker, or parallel bars), control software, and mobile Android tablet hosting a mobile app. The Phoenix dimensions, such as spine length, torso hip width, femur length, femur bracket, tibia length, tibia bracket, and foot plate length can be adjusted individually. The Phoenix is coupled to the user via soft-good components (i.e. shoulder straps, waist pads, thigh straps, and shin pads), which can be adjusted to accommodate various users' dimensions.
The provided document describes the Phoenix™ powered exoskeleton and its regulatory submission (K183152). It outlines performance data to demonstrate its safety and effectiveness and its substantial equivalence to a predicate device.
Here's a breakdown of the requested information based on the document:
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria are not explicitly stated in a quantitative manner as pass/fail thresholds for specific metrics before the study. Instead, the study objectives and the results achieved are presented as evidence that the device meets its intended purpose. The table below synthesizes the implicit acceptance criteria from the study objectives and the reported performance.
| Acceptance Criterion (Implied from Study Objective) | Reported Device Performance (Result) |
|---|---|
| Safe and effective for intended use (SCI T4-L5 non-ambulatory to poorly ambulatory to stand up and walk under various conditions) | Safety: "Adverse Events (AE) reported during the study included minor instances of bruising. The causes attributed to these reported incidents were related to improper fitting or improper padding... There were no Unanticipated Adverse Events (UAE)." "The clinical study concluded that the Phoenix device is safe and effective for its intended use..." |
| Effectiveness: All detailed performance metrics below support effectiveness. | |
| Participants with SCI T4-L5 can safely complete transitional movements (stand up, turn, sit down) and walk using Phoenix with minimal contact assistance or Functional Independence Measure (FIM) | Transitional Movements (TUG Test): 39 out of 40 subjects completed with minimal contact assistance (FIM score of 4 or higher); 1 subject completed with moderate contact assistance (FIM score of 3). |
| Level of Assistance (WISC-II): Averaged mean scores of 8.60 (±2.19) for the final assessment. | |
| Level of Assistance (FIM): "FIM scores as noted previously support that subjects were capable of managing all scenarios presented..." | |
| Participants with SCI T4-L5 are able to achieve walking during the 10 Meter Walk Test (10MWT) and 6 Minute Walk Test (6MWT). | 10MWT: All participants (40/40) were able to complete the 10MWT. Mean FIM was 4.6 (±0.50). Average completion time was 61.9 seconds (±34.64), with a mean speed of 0.12 m/s (±0.06). |
| 6MWT: Mean FIM was 4.37 (±0.49), "indicating an acceptable level of functional independence." | |
| User exertion for basic level-ground walking (Modified Borg Rating of Perceived Exertion) | Averaged results of 3.3 for indoor level-ground walking at the end of sessions, corresponding to an exertion level just above "moderate." |
2. Sample size used for the test set and the data provenance
- Sample Size: 40 subjects.
- Data Provenance: The document does not specify the country of origin of the data. It states, "The study was performed in compliance with Good Clinical Practices (GCP) with subjects enrolled in an IRB approved study that were consented for participation according to the intended use of the device, defined inclusion criteria, and defined exclusion criteria..." This implies a prospective clinical study.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts
The document does not mention the use of experts to establish a "ground truth" for the test set in the traditional sense of diagnostic accuracy studies (e.g., radiologists interpreting images). Instead, the study evaluates the functional performance and safety of the exoskeleton in human subjects. The outcome measures (FIM, WISC-II, 10MWT, 6MWT, TUG Test, Modified Borg) are objective measures or standardized assessments commonly used in rehabilitation, performed by trained clinicians/investigators within the study protocol. The "ground truth" here is the direct, observed performance of the subjects using the device.
4. Adjudication method (e.g., 2+1, 3+1, none) for the test set
The concept of an adjudication method (like 2+1 for conflicting interpretations) is not applicable here as this is a functional performance and safety study, not a diagnostic study requiring interpretation of outcomes by multiple experts. The clinical outcomes were directly measured or observed by the study staff.
5. 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, a multi-reader, multi-case (MRMC) comparative effectiveness study was not done. This study is a clinical trial assessing the performance of a medical device (exoskeleton), not an AI-powered diagnostic tool. Therefore, the concept of human readers improving with or without AI assistance is irrelevant to this document.
6. If a standalone (i.e., algorithm only without human-in-the-loop performance) was done
No, a standalone algorithm-only performance study was not done. The Phoenix™ is a physical medical device (exoskeleton) intended for use by individuals with spinal cord injury in rehabilitation settings. Its entire purpose involves human-in-the-loop performance (the user wearing and operating the device under clinician supervision).
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.)
For this functional performance study, the "ground truth" consists of observed clinical outcomes data and standardized functional assessment scores collected directly from the subjects using the Phoenix™ device in a controlled clinical setting. These include:
- Functional Independence Measure (FIM) scores
- WISC-II scores (likely a typo for WISCI II - Walking Index for Spinal Cord Injury)
- 10 Meter Walk Test (10MWT) results (time, speed)
- 6 Minute Walk Test (6MWT) results (implied distance/FIM score)
- Timed Up-and-Go (TUG) Test results
- Modified Borg Rating of Perceived Exertion scores
- Adverse Event (AE) reporting.
8. The sample size for the training set
The document mentions "training with the device" for the 40 subjects enrolled in the clinical study as part of their 20 sessions. This training is for the actual users (patients) and clinicians to learn how to operate the device, not an algorithm's training data.
The document does not refer to a "training set" in the context of machine learning or AI algorithms. The Phoenix™ is a powered exoskeleton, not an AI diagnostic tool that requires a separate training data set for model development.
9. How the ground truth for the training set was established
As there is no mention of a "training set" for an algorithm in this context, this question is not applicable to the provided document. The device itself is "trained" in terms of its parameters and control mechanisms during its engineering and development phase, but this is distinct from "ground truth for a training set" in AI/ML performance studies.
§ 890.3480 Powered lower extremity exoskeleton.
(a)
Identification. A powered lower extremity exoskeleton is a prescription device that is composed of an external, powered, motorized orthosis that is placed over a person's paralyzed or weakened limbs for medical purposes.(b)
Classification. Class II (special controls). The special controls for this device are:(1) Elements of the device materials that may contact the patient must be demonstrated to be biocompatible.
(2) Appropriate analysis/testing must validate electromagnetic compatibility/interference (EMC/EMI), electrical safety, thermal safety, mechanical safety, battery performance and safety, and wireless performance, if applicable.
(3) Appropriate software verification, validation, and hazard analysis must be performed.
(4) Design characteristics must ensure geometry and materials composition are consistent with intended use.
(5) Non-clinical performance testing must demonstrate that the device performs as intended under anticipated conditions of use. Performance testing must include:
(i) Mechanical bench testing (including durability testing) to demonstrate that the device will withstand forces, conditions, and environments encountered during use;
(ii) Simulated use testing (
i.e., cyclic loading testing) to demonstrate performance of device commands and safeguard under worst case conditions and after durability testing;(iii) Verification and validation of manual override controls are necessary, if present;
(iv) The accuracy of device features and safeguards; and
(v) Device functionality in terms of flame retardant materials, liquid/particle ingress prevention, sensor and actuator performance, and motor performance.
(6) Clinical testing must demonstrate a reasonable assurance of safe and effective use and capture any adverse events observed during clinical use when used under the proposed conditions of use, which must include considerations for:
(i) Level of supervision necessary, and
(ii) Environment of use (
e.g., indoors and/or outdoors) including obstacles and terrain representative of the intended use environment.(7) A training program must be included with sufficient educational elements so that upon completion of training program, the clinician, user, and companion can:
(i) Identify the safe environments for device use,
(ii) Use all safety features of device, and
(iii) Operate the device in simulated or actual use environments representative of indicated environments and use.
(8) Labeling for the Physician and User must include the following:
(i) Appropriate instructions, warning, cautions, limitations, and information related to the necessary safeguards of the device, including warning against activities and environments that may put the user at greater risk.
(ii) Specific instructions and the clinical training needed for the safe use of the device, which includes:
(A) Instructions on assembling the device in all available configurations;
(B) Instructions on fitting the patient;
(C) Instructions and explanations of all available programs and how to program the device;
(D) Instructions and explanation of all controls, input, and outputs;
(E) Instructions on all available modes or states of the device;
(F) Instructions on all safety features of the device; and
(G) Instructions for properly maintaining the device.
(iii) Information on the patient population for which the device has been demonstrated to have a reasonable assurance of safety and effectiveness.
(iv) Pertinent non-clinical testing information (
e.g., EMC, battery longevity).(v) A detailed summary of the clinical testing including:
(A) Adverse events encountered under use conditions,
(B) Summary of study outcomes and endpoints, and
(C) Information pertinent to use of the device including the conditions under which the device was studied (
e.g., level of supervision or assistance, and environment of use (e.g., indoors and/or outdoors) including obstacles and terrain).