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.

Device Description

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.

AI/ML Overview

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:1. Inflammatory degenerative joint disease (e.g., rheumatoid arthritis) and noninflammatory degenerative joint disease (e.g., osteoarthritis, avascular necrosis).2. Correctable valgus-varus deformity and moderate flexion contracture.3. Patients with failed previous surgery where pain, deformity, or dysfunction persist.4. 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.

Summary

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K97 3412

DEC - 8 1997

510(k) SUMMARY

In accordance with the Food and Drug Administration Rule to implement provisions of the Safe Medical Devices Act of 1990 and in conformance with 21 CFR 807, this is to serve as a Summary of Safety and Effectiveness for the Natural-Knee™ II Constrained Knee System.

Submitter:	Sulzer Orthopedics Inc.9900 Spectrum DriveAustin, Texas 78717(512) 432-9900
Date:	July 18, 1997
Contact Person:	Jacquelyn HughesManager, Regulatory Affairs
Classification Name:	Prosthesis, knee, patellofemorotibial, semi-constrained,cemented, polymer/ metal/polymer 21 CFR 888.3560
Common/Usual Name:	Knee Prosthesis, Partially Constrained
Trade/Proprietary Name:	The Natural-Knee™ II Constrained Knee System

PRODUCT DESCRIPTION

The Natural-Knee II Constrained Knee System is to be used with the Natural-Knee II metalbacked and all-poly patellar components.

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This device is intended for use with the following previously cleared devices:

Natural-Knee II All-Poly Patella I
Natural-Knee II Metal-Backed Patella
Natural-Knee II Revision Stems
Natural-Knee II Tibial Spacers I
Natural-Knee II Revision Tibial Stems

The Natural-Knee II Constrained Knee Tibial Baseplate may also be used with existing Natural-Knee II tibial inserts. The existing Natural-Knee II tibial inserts are not compatible with the Natural-Knee II Constrained Knee Femoral Component.

SPECIFIC DIAGNOSTIC INDICATIONS

The Natural-Knee II Constrained Knee System is intended use in the following diagnostic indications :

1. 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).
1. Correctable valgus-varus deformity and moderate flexion contracture.
1. Those patients with failed previous surgery where pain, deformity, or dysfunction persist.
1. Revision of previously failed knee arthroplasty.

The Natural-Knee II Constrained Knee System is intended only for use with bone cement in the United States. Uncemented use of the Natural-Knee II Constrained Knee System is considered to be investigational in the United States. This device is intended for single use only.

SUBSTANTIAL EQUIVALENCE

The Natural-Knee II Constrained Knee System is substantially equivalent to the Natural-Knee II System (Sulzer Orthopedics), the Maxim Constrained Knee (Biomet), and the Coordinate Revision Knee (DePuy).

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Image /page/2/Picture/2 description: The image shows the logo for the U.S. Department of Health & Human Services. The logo consists of a circular seal with the words "DEPARTMENT OF HEALTH & HUMAN SERVICES - USA" arranged around the perimeter. Inside the circle is a stylized image of an eagle with three human profiles incorporated into its body.

Food and Drug Administration 9200 Corporate Boulevard Rockville MD 20850

DEC - 8 1997

Ms. Jacquelyn Hughes Manager, Regulatory Affairs Sulzer Orthopedics, Inc. 9900 Spectrum Drive Austin, Texas 78717

Re : K973412 The Natural-Knee II Constrained Knee System Requlatory Class: II Product Code: JWH Dated: September 8, 1997 September 9, 1997 Received:

Dear Ms. Hughes:

We have reviewed your Section 510(k) notification of intent to market the device referenced above and we have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act). This decision is based on this device being equivalent only to similar devices labeled and intended to be fixed within bone with acrylic "bone cement." You may, therefore, market your device subject to the general controls provisions of the Act and the following limitations:

The thinnest tibial insert available is the nominal "9mm" 1. sized insert, which has a minimum polyethylene thickness under the condyles of 6.00mm.
This device may not be labeled or promoted for non-2. cemented use.
3 . All labeling for this device, including package label and labeling included within the package, must prominently state that the device is intended for cemented use only.

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Page 2 - Ms. Jacquelyn Hughes

Any non-cemented fixation of this device is considered 4. investigational and may only be investigated as a significant risk device in accordance with the investigational device exemption (IDE) regulation under 21 CFR, Part 812. All users of the device for noncemented fixation must receive approval from their respective institutional review boards (IRBs) and the Food and Druq Administration (FDA) to conduct the investigation.
The general controls provisions of the Act include requirements for annual reqistration, listing of devices, good manufacturing practices, labeling, and prohibitions against misbranding and adulteration.

If vour device is classified (see above) into either class II (Special Controls) or class III (Premarket Approval), it may be subject to such additional controls. Existing major regulations affecting your device can be found in the Code of Federal Requlations, Title 21, Parts 800 to 895. A substantially equivalent determination assumes compliance with the current Good Manufacturing Practice requirement, as set forth in the Quality System Regulation (QS) for Medical Devices: General regulation (21 CFR Part 820) and that, through periodic (QS) inspections, the Food and Drug Administration (FDA) will verify such assumptions. Failure to comply with the GMP requlation may result in regulatory action. In addition, FDA may publish further announcements concerning your device in the Federal Reqister. Please note: this response to your premarket notification submission does not affect any obligation you might have under sections 531 through 542 of the Act for devices under the Electronic Product Radiation Control provisions, or other Federal Laws or Requlations.

This letter will allow you to begin marketing your device as described in your 510(k) premarket notification immediately. An FDA finding of substantial equivalence of your device to a legally marketed predicate device results in a classification for your device and permits your device to proceed to the market.

If you desire specific advice for your device on our labeling regulation (21 CFR Part 801 and additionally 809.10 for in vitro diagnostic devices), please contact the Office of Compliance at (301) 594-4659. Additionally, for questions on the promotion and advertising of your device, please contact the Office of Compliance at (301) 594-4639. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR 807.97). Other general information on your responsibilities under the Act may be

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Page 3 - Ms. Jacquelyn Hughes

obtained from the Division of Small Manufacturers Assistance obtained from the Division of Small Mark (300) 443-6597 or at
at its toll-free number (800) 638-2041 or addon'demain html" at its toll-free number (600) 650 2041 Of (600) 600 - 1000
its Internet address "http://www.fda.gov/cdrh/dsmamain.html".

Sincerely yours,

Celia M. Witten, Ph.D., M.D.
Director
Division of General and

Restorative Devices Office of Device Evaluation Center for Devices and Radiological Health

Enclosure

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510(k) Number (if known):_____________________________________________________________________________________________________________________________________________________

Device Name: Natural-Knee™ II Constrained Knee System

Indications For Use:

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 1. disease (e.g., rheumatoid arthritis) and noninflammatory degenerative joint disease (e.g., osteoarthritis, avascular necrosis).
1. Correctable valgus-varus deformity and moderate flexion contracture.
Those patients with failed previous surgery where pain, deformity, or 3. dysfunction persist.
1. Revision of previously failed knee arthroplasty.

(PLEASE DO NOT WRITE BELOW THIS LINE - CONTINUE ON ANOTHER PAGE IF NEEDED)

Concurrence of CDRH, Office of Device Evaluation (ODE)

(Division Sign-Off) Division of General Restorative Devices

510(k) Number.

Prescription Use

Over-The-Counter Use

(Optional Format 1-2-96)

Regulation Number and Section

§ 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.