(90 days)
The Natural-Knee™ II Constrained Knee System is intended use in the following diagnostic indications:
- Patient conditions, including but not limited to, inflammatory degenerative joint disease (e.g., rheumatoid arthritis) and noninflammatory degenerative joint disease (e.g., osteoarthritis, avascular necrosis).
- Correctable valgus-varus deformity and moderate flexion contracture.
- Those patients with failed previous surgery where pain, deformity, or dysfunction persist.
- Revision of previously failed knee arthroplasty.
The Natural-Knee™ II Constrained Knee System is intended only for use with bone cement. Uncemented use of the Natural-Knee™ II Constrained Knee System is considered to be investigational in the United States.
The Natural-Knee™ II Constrained Knee System is a non-porous total knee replacement intended for primary and revision knee surgeries. The components are intended for resurfacing of the knee joint where the posterior cruciate ligament is absent, deficient, or has been removed at the time of surgery. The system is a semiconstrained design and both medial and lateral collateral ligaments must be intact.
The Natural-Knee II Constrained Knee femoral component is manufactured from cobalt chromium/molybdenum (CoCr) alloy and is anatomic and asymmetrical in design. The Natural-Knee II Revision Stems may be used with the Natural-Knee II Constrained Knee System femoral component. Femoral spacers manufactured from CoCr alloy are also available for use with the Natural-Knee II Constrained Knee femoral component. A revision adapter spacer, also manufactured from CoCr, converts the internal box geometry of the Natural-Knee II Constrained Knee femoral component to match that of the Natural-Knee II Revision femoral component. The Natural-Knee II Revision Femoral Spacers may be added to the revision adapter spacer if additional augmentation is necessary.
The Natural-Knee II Constrained Knee tibial components include a baseplate and polyethylene insert. The tibial components are also anatomic and asymmetrical in design. The tibial baseplate is manufactured from Titanium alloy (Ti-4A1-6V). The baseplate is designed to be used with the Natural-Knee II Revision Tibial Spacers. The Natural-Knee II Constrained Knee tibial baseplate may be used with the Natural-Knee II Revision Tibial The tibial inserts are manufactured from Ultra High Molecular Weight Stems. Polyethylene (UHMWPe). A CoCr pin passing vertically from the posterior stabilizing eminence of the tibial insert to the tibial baseplate provides additional stability.
The Natural-Knee II Constrained Knee System is to be used with the Natural-Knee II metalbacked and all-poly patellar components.
The provided text is a 510(k) summary for the Natural-Knee™ II Constrained Knee System, a medical device. It focuses on establishing substantial equivalence to previously cleared devices rather than presenting a study demonstrating the device meets specific performance acceptance criteria. Therefore, most of the requested information regarding acceptance criteria, study design, expert involvement, and ground truth establishment is not available in the provided document.
However, I can extract information related to the device's indications for use and the FDA's decision, which serves as a form of "acceptance" for marketing.
1. Table of Acceptance Criteria and Reported Device Performance
| Acceptance Criteria (Stated by FDA or Implied) | Reported Device Performance / Compliance |
|---|---|
| Intended Use: For primary and revision knee surgeries in cases of absent, deficient, or removed posterior cruciate ligament, with intact medial and lateral collateral ligaments. | The device is intended for use in these conditions. The FDA cleared the device for marketing based on these indications. |
| Specific Diagnostic Indications: | The device is intended for use in: |
- Inflammatory degenerative joint disease (e.g., rheumatoid arthritis) and noninflammatory degenerative joint disease (e.g., osteoarthritis, avascular necrosis).
- Correctable valgus-varus deformity and moderate flexion contracture.
- Patients with failed previous surgery where pain, deformity, or dysfunction persist.
- Revision of previously failed knee arthroplasty. |
| Fixation Method: Intended only for use with bone cement in the United States. | The FDA explicitly states that the device is approved for cemented use only. Labeling must prominently state this. |
| Minimum Tibial Insert Thickness: The thinnest tibial insert available (nominal "9mm") must have a minimum polyethylene thickness under the condyles of 6.00mm. | The FDA notes this as a limitation and condition of clearance, implying the device design must meet this specification. |
| Substantial Equivalence: Must be substantially equivalent to predicate devices. | The device was found substantially equivalent to: Natural-Knee II System, Maxim Constrained Knee, and Coordinate Revision Knee. |
2. Sample size used for the test set and the data provenance
- Not applicable. This document is a 510(k) summary for substantial equivalence, not a report of a clinical trial or performance study with a test set. There is no mention of a test set, sample size, or data provenance in this context.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts
- Not applicable. No test set or ground truth establishment by experts is described in this regulatory submission. The FDA's decision is based on a review of the design, materials, and comparison to predicate devices, not on a clinical ground truth study.
4. Adjudication method for the test set
- Not applicable. No test set is described, therefore no adjudication method is mentioned.
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
- Not applicable. This device is a knee prosthesis, not an AI-assisted diagnostic tool. Therefore, an MRMC study related to AI assistance for human readers is irrelevant and not mentioned.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done
- Not applicable. This device is a knee prosthesis, not an algorithm.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.)
- Not applicable. As there is no performance study with a test set described, there is no ground truth concept applied in this document beyond the inherent design specifications and clinical indications that the device is intended to address. The "ground truth" for regulatory clearance is the comparison to already legally marketed predicate devices, and the FDA's evaluation of the submitted documentation.
8. The sample size for the training set
- Not applicable. This is a physical medical device, not an AI algorithm requiring a training set.
9. How the ground truth for the training set was established
- Not applicable. As above, this is not an AI algorithm.
§ 888.3560 Knee joint patellofemorotibial polymer/metal/polymer semi-constrained cemented prosthesis.
(a)
Identification. A knee joint patellofemorotibial polymer/metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace a knee joint. The device limits translation and rotation in one or more planes via the geometry of its articulating surfaces. It has no linkage across-the-joint. This generic type of device includes prostheses that have a femoral component made of alloys, such as cobalt-chromium-molybdenum, and a tibial component or components and a retropatellar resurfacing component made of ultra-high molecular weight polyethylene. This generic type of device is limited to those prostheses intended for use with bone cement (§ 888.3027).(b)
Classification. Class II.