(374 days)
The ARGO ReWalk™ orthotically fits to the lower limbs and part of the upper body and is intended to enable individuals with spinal cord injury at levels T7 to L5 to perform ambulatory functions with supervision of a specially trained companion in accordance with the user assessment and training certification program. The device is also intended to enable individuals with spinal cord injury at levels T4 to T6 to perform ambulatory functions in rehabilitation institutions in accordance with the user assessment and training certification program. The ReWalk™ is not intended for sports or stair climbing.
The device is a wearable exoskeleton device (refer to Figure 2 below) that allows the user to enable ambulation over the course of the day (refer to Figure 1 below). The control of the device is achieved through a wrist-worn user-operated wireless communicator, tilt sensor and specific body movements. The movement of the swing leg is controlled by a set of gears and DC motors at the knee and hip joints.
Here's a breakdown of the acceptance criteria and the studies that prove REWALKTM meets them, based on the provided text:
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria for the ReWalk™ device are not explicitly stated as quantitative performance metrics in a single table, but rather as a combination of safety, functionality, and performance demonstrations across various studies. The reported device performance is extracted from the clinical study results.
| Acceptance Criteria Category | Specific Criteria (Inferred from Special Controls/Risks) | Reported Device Performance and Study Findings (from Clinical Studies) |
|---|---|---|
| Safety | Prevention of Instability & Falls: Device must maintain stability and minimize falls. | Study 1: No falls reported. |
| Study 2: No falls reported. | ||
| Study 3: No falls reported. | ||
| Minimization of Skin/Soft Tissue Injury: Device design and fit should prevent bruising, skin abrasions, pressure sores, and soft tissue injury. | Study 1: 2 subjects sustained one hematoma each; 3 subjects sustained a total of 13 skin lesions. | |
| Study 2: 6 incidents of skin tears in 5 subjects, 3 incidents of bruising in 2 subjects, 1 blister, 1 lower extremity edema. | ||
| Study 3: 3 subjects sustained mild skin abrasions, 2 subjects sustained moderate skin abrasions. | ||
| Physiological Stability (BP, HR): Device use should not cause significant adverse changes in blood pressure or heart rate. | Study 1 & 2: Pulse and blood pressure measured at beginning and end of each session, but no specific adverse trends or limits are reported as being exceeded. | |
| Biocompatibility: Materials in contact with the patient must be biocompatible. | Components in direct skin contact were identified and assessed for biocompatibility as adequate, given common usage in prosthetic applications. (Bench Study E) | |
| Battery Safety/Reliability: Adequate detection of low battery, prevention of premature failure. | Low battery detection ensured with ~15 mins life remaining and alarm. (Bench Study 3) | |
| Electrical Safety/Thermal Safety: Conformance to IEC 60601-1, thermal limits below specified thresholds. | Device conformed to IEC 60601-1:2005. Thermal limits below specified IEC 60601-1:2005. (Bench Study 1 & C) | |
| EMC/EMI: Compatibility with other electrical equipment, conformance to IEC 60601-1-2. | Conformed to IEC 60601-1-2:2007, and tested at higher levels for non-institutional use. (Bench Study 2) | |
| Device Malfunction (Unanticipated Op./Stoppage): Software/hardware safeguards to prevent unintended movement, graceful collapse in case of power loss. | Self-check at startup; default to manual control on main computer failure; software limits on joint angles; graceful sitting/collapse in case of balance loss or power loss. (Fault Safety section). | |
| Durability/Structural | Working Life (5 years): Device must withstand repeated loads of daily use (sit-to-stand, gait). | Sit-to-stand: 2 devices completed 73,000 cycles (5 years with safety factor) without structural failure. (Bench Study PT-10-06) |
| Hip Joint (Gait): 2 devices completed over 1,000,000 cycles without mechanical failure (corresponding to 6M gait cycles with safety factor). (Bench Study PT-10-07) | ||
| Structural Integrity: Frame must not fracture, deform, or fail under repeated loads. | Finite Element Analysis confirmed frame would not fracture, deform, or fail after repeated loads, for largest size configurations. (Structural Analysis section) | |
| Functionality/Performance | Enabling Ambulation: The device should allow individuals with SCI to perform ambulatory functions. | Study 1 (6MWT): 10-79 meters; (10MWT): 40-163 seconds. |
| Study 2 (6MWT): 0-100+ meters; (10MWT): 10-100+ seconds. | ||
| Study 3 (6MWT): 50.5-166 meters; (10MWT): 20-62 seconds. | ||
| Training Program Effectiveness: Training program must enable clinicians, users, and companions to safely use the device and identify safe environments. | Training program with detailed skill evaluations for basic, advanced, and companion skills (Tables 7-13). |
2. Sample Sizes and Data Provenance
- Study 1 (Pilot Study):
- Test Set Sample Size: 7 subjects enrolled. 6 subjects completed the 6MWT and 10MWT.
- Data Provenance: Not explicitly stated, but implies a prospective clinical trial in a single center given the "pilot study" designation.
- Study 2 (Multi-Center Study):
- Test Set Sample Size: 24 subjects enrolled. Results provided for 20 subjects for 6MWT, 22 subjects for 10MWT, and 13 subjects for Ashworth scale.
- Data Provenance: Prospective, multi-center study conducted at two sites: Moss Rehab and Centro Villa Beretta.
- Study 3 (Exoskeletal-Assisted Walking for Persons with Motor-Complete Paraplegia):
- Test Set Sample Size: A convenience sample of 12 potential participants screened, 7 included in the results (5 were excluded).
- Data Provenance: Pilot study (single group, pre/post intervention), likely prospective, but not explicitly stated. A footnote indicates the source as "Force Sustainment: Rehabilitation, Regeneraton and Prosthetics for Reintegration to duty. Meeting Proceedings STO-MP-HFM-228, Paper 6." It also mentions "Additional retrospective data from this study was provided in a separate master file."
3. Number of Experts and Qualifications for Ground Truth
The concept of "ground truth" as typically used in AI/medical device contexts (e.g., expert consensus on image interpretation) is not directly applicable here. This device's performance is measured directly by patient physical performance metrics and observed adverse events. There were no "experts" establishing ground truth in the sense of reviewing or labeling a dataset for algorithmic training or testing. The outcomes (e.g., distance walked, time taken, presence of skin lesions) are direct measurements from the subjects using the device.
4. Adjudication Method for the Test Set
Not applicable. The clinical studies measured direct physical performance (e.g., 6MWT, 10MWT) and observed adverse events. There was no need for expert adjudication of case interpretations.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No. An MRMC comparative effectiveness study was not conducted for the ReWalk™ device. This type of study is typically used for diagnostic devices where human readers interpret medical images or data, and the AI's impact on their performance is being evaluated. The ReWalk™ is a therapeutic/assistive device, and its effectiveness is measured more directly by functional outcomes. There is no mention of "human readers" or "AI assistance" in this context.
6. Standalone (Algorithm Only) Performance Study
No, a standalone (algorithm only) performance study was not explicitly mentioned in the sense of the device operating without a human user. The device inherently requires a human user-in-the-loop for its operation (e.g., wearing the device, using crutches, operating the wrist communicator, providing body movements for walking). The "device performance" relies on the human-device interaction.
However, extensive non-clinical/bench studies were performed that tested the device in a standalone manner for its mechanical integrity, electrical safety, durability, and software functionality (e.g., cyclic testing of joints, battery testing, EMC/EMI testing, software verification/validation). These tests ensure the components and underlying algorithms perform as intended and safely, independent of a human user, but the overall "performance of ambulation" requires a human.
7. Type of Ground Truth Used
The ground truth used for these studies was primarily:
- Objective Physiological Measurements: Distances walked (6MWT, 10MWT), time taken for 10MWT.
- Clinical Assessments: Ashworth scale for spasticity, Visual Analog Scale (VAS) for pain and fatigue (results not extensively detailed in the provided text).
- Observable Adverse Events: Falls, hematomas, skin lesions, bruising, blisters, edema.
- Direct Observation of Functional Skills: Standing, walking, sit-to-stand, stand-to-sit, and maneuvering on various surfaces.
8. Sample Size for the Training Set
There is no mention of a separate "training set" in the context of an AI/machine learning model whose performance on a "test set" is being evaluated. The subjects in the clinical studies (1, 2, and 3) were participants who received training on how to use the device. Their performance after training was then measured. The term "training set" in this document refers to the population of subjects who underwent the manufacturer's training program to learn how to operate the ReWalk™ device, not a data set for machine learning.
- Study 1: 7 subjects
- Study 2: 24 subjects
- Study 3: 7 subjects
9. How Ground Truth for the Training Set Was Established
Given that "training set" here refers to human subjects undergoing training rather than an algorithm's dataset, the concept of "ground truth for the training set" doesn't apply in the typical sense of labeled data. Instead, the training program itself defines what constitutes correct and proficient use. The "ground truth" for successful training was established through:
- Manufacturer-Developed Training Program: The sponsor proposed a tiered training system (Table 7) with defined basic and advanced skills (Tables 8 & 9) and companion skills (Tables 12 & 13).
- Scoring Metrics: Proficiency was assessed using scoring metrics, including a FIM (Functional Independence Measure) based scoring system (Tables 10 & 11) for individual skills, where a "Pass" score (5 or greater) indicated successful completion with supervision or independently. For companion skills, a score of 2 indicated full understanding.
These scoring criteria and the structured program set the "ground truth" for what constitutes successful human user training and proficiency with the device.
§ 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).