K033810 · Centerpulse Orthopedics, Inc. · HRY · Mar 5, 2004 · Orthopedic
Device Facts
Record ID
K033810
Device Name
NATURAL-KNEE II UNICOMPARTMENTAL KNEE SYSTEM
Applicant
Centerpulse Orthopedics, Inc.
Product Code
HRY · Orthopedic
Decision Date
Mar 5, 2004
Decision
SESE
Submission Type
Traditional
Regulation
21 CFR 888.3530
Device Class
Class 2
Attributes
Therapeutic
Indications for Use
The Natural-Knee II Unicompartmental Knee is intended for use in: - Unicompartmental noninflammatory degenerative joint disease (NIDJD), e.g., 1. avascular necrosis, osteoarthritis and arthritis secondary to a variety of diseases and anomalies: - Passively correctable valgus-varus deformity and moderate flexion contracture; 2. - Those patients with failed previous surgery where pain, deformity or dysfunction persists. The proposed N-K II Unicompartmental All-Poly Tibia is intended to be used only with bone cement. The N-K II Unicompartmental Modular Tibia and Femur are intended for use with or without bone cement.
Device Story
Natural-Knee II Unicompartmental Knee System is a prosthetic implant for resurfacing one compartment of the knee joint. Components include a modular metal-backed tibia (wrought titanium alloy), an all-polyethylene tibia, and a femoral component. The metal-backed tibia features a symmetric baseplate with three smooth pegs for rotational stability and an optional central screw hole. The all-poly tibia utilizes a single keel with cement grooves and dovetail channels for fixation. The system is used by orthopedic surgeons in a clinical/surgical setting to treat degenerative joint disease. The device provides a conservative alternative to total knee replacement, aiming to restore joint function and reduce pain. The femoral component allows for cementless use. The system is implanted via surgical procedure, with the all-poly tibia requiring bone cement and the modular components allowing for cemented or cementless application.
Clinical Evidence
No clinical data provided; substantial equivalence is based on design, material, and intended use comparisons to legally marketed predicate devices.
Technological Characteristics
Materials: Wrought titanium alloy (tibial baseplate), polyethylene (all-poly tibia/inserts). Design: Modular metal-backed tibia (symmetric, 3 pegs, optional screw fixation) and all-poly tibia (single keel, cement grooves/dovetail channels). Fixation: Cemented (all-poly) or cemented/cementless (modular metal-backed). Sizes: 6 sizes (1-6) for tibias; modular inserts in 3 thicknesses (9, 11, 13 mm); all-poly inserts in 4 thicknesses (7, 9, 11, 13 mm).
Indications for Use
Indicated for patients with unicompartmental noninflammatory degenerative joint disease (e.g., avascular necrosis, osteoarthritis, arthritis secondary to anomalies), passively correctable valgus-varus deformity, moderate flexion contracture, or failed previous surgery with persistent pain, deformity, or dysfunction.
Regulatory Classification
Identification
A knee joint femorotibial metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace part of 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 consist of a femoral component made of alloys, such as cobalt-chromium-molybdenum, and a tibial component made of ultra-high molecular weight polyethylene and is limited to those prostheses intended for use with bone cement (§ 888.3027).
Predicate Devices
Natural-Knee II Unicompartmental Knee System (K955778)
Natural-Knee Unicompartmental Knee System (K883969)
Natural-Knee II Total Knee System with CSTi (P940002)
Wright Medical ADVANCE® Unicompartmental Knee (K012591)
Plus Orthopedics UC Plus™ Unicompartmental Knee (K982859)
Submission Summary (Full Text)
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## 510(k) SUMMARY
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Centerpulse Orthopedics, Inc., a division of Zimmer SPONSOR NAME: 9900 Spectrum Drive Austin, TX 78717
Audrey Swearingen CONTACT: Phone: (512) 432-9255 Audrey Swearingen@Zimmer.com E-Mail:
Natural-Knee® II Unicompartmental Knee System TRADE NAME:
Unicompartmental Knee COMMON NAME:
Unicompartmental Knees are Class II, reviewed by the CLASSIFICATION: Orthopedic Devices panel, per 21 CFR §888.3530 and 888.3535.
#### PREDICATE DEVICES.
The predicate devices chosen to demonstrate substantial equivalence are:
- Natural-Knee II Unicompartmental Knee System (K955778) .
- Natural-Knee Unicompartmental Knee System (K883969) .
- Natural-Knee II Total Knee System with CSTi (P940002) .
- Wright Medical ADVANCE® Unicompartmental Knee (K012591) .
- DePuy Preservation™ Unicompartmental Knee (K010810) .
- Plus Orthopedics UC Plus™ Unicompartmental Knee (K982859) .
#### DEVICE DESCRIPTION:
The Natural-Knee II Unicompartmental Knee System is a conservative, cost-effective alternative to total knee replacement for patients with osteoarthritis primarily confined to one compartment. The N-K II Unicompartmental Knee System is intended for resurfacing of one side of the knee joint.
The N-K II Unicompartmental Modular Metal-backed Tibia is similar to the previously cleared N-K II Unicompartmental Tibia (K955778). The wrought titanium alloy tibial baseplate is a symmetrically designed component, eliminating the need for left/right orientations. The baseplate features three smooth pegs on the underside which aid in positioning and rotational stability. A smooth surface finish is provided on the inner surface of the tibial tray to minimize the potential for polyethylene wear. A screw hole is placed in the center of the baseplate for optional screw fixation. The baseplate is available in either a porous or non-porous version.
The all-poly tibia is designed with a single keel to position the component on the tibia and increase stability. Cement grooves on both the medial and lateral side of the keel increase the anchoring effect of the keel, while a dovetail cement channel around the perimeter of the distal surface, along with a T-pattern dovetail cement channel, act to resist movement in all directions. It is to be used only with bone cement for application directly onto the patient's resected proximal tibia.
The metal-backed and the all-poly tibias are both available in 6 sizes (1-6). The modular
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033810
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000135
metal-backed tibia will be offered in 3 thicknesses (9, 11, and 13 mm). The insert thickness reflects the total amount of bone to be resected. The all-poly insert will be available in 4 thicknesses (7, 9, 11, and 13mm), in which the thickness is measured at the thinnest point from the distal to the proximal surface of the component.
The design of the femoral component of the proposed N-K II Unicompartmental Knee System will not change. This premarket notification only seeks to obtain clearance for the addition of cementless use of the previously cleared porous-coated femur (K955778).
### INTENDED USE:
The Natural-Knee II Unicompartmental Knee is intended for use in:
- Unicompartmental noninflammatory degenerative joint disease (NIDJD), e.g., 1. avascular necrosis, osteoarthritis and arthritis secondary to a variety of diseases and anomalies:
- Passively correctable valgus-varus deformity and moderate flexion contracture; 2.
- Those patients with failed previous surgery where pain, deformity or dysfunction ന persists.
These indications for use are identical to the indications for the previously cleared Natural-Knee II Unicompartmental System (K955778) and Natural Knee Unicompartmental System (K883969).
The proposed N-K II Unicompartmental All-Poly Tibia is intended to be used only with bone cement. The N-K II Unicompartmental Modular Tibia and Femur are intended for use with or without bone cement.
# BASIS OF SUBSTANTIAL EQUIVALENCE:
Comparisons of device design features, indications for use, materials and labeling of the Natural-Knee II Unicompartmental Knee System demonstrate that it is substantially equivalent to the predicate devices listed above.
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DEPARTMENT OF HEALTH & HUMAN SERVICES
Image /page/2/Picture/1 description: The image shows the seal of the Department of Health & Human Services (HHS) of the United States. The seal features a circular border with the text "DEPARTMENT OF HEALTH & HUMAN SERVICES - USA" arranged around the perimeter. Inside the circle is a stylized eagle emblem, with three horizontal bars forming the body and wings, and a head facing left. The eagle's tail feathers are depicted as wavy lines.
Food and Drug Administration 9200 Corporate Boulevard Rockville MD 20850
MAR - 5 2004
Audrey Swearingen Manager, Regulatory Affairs Centerpulse Orthopedics, Inc. 9900 Spectrum Drive Austin, Texas 78717
Re: K033810
Trade/Device Name: Natural-Knee® II Unicompartmental Knee System Regulation Numbers: 21 CFR 888.3530 and 21 CFR 888.3535 Regulation Names: Knee joint, femorotibial, metal/polymer semi-constrained cemented Prosthesis, Knee joint, femorotibial (unicompartmental) metal/polymer porous-coated uncemented prosthesis
Regulatory Class: II Product Codes: HRY, NJD Dated: December 5, 2003 Received: December 8, 2003
Dear Ms. Swearingen:
We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or 10 dcvices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration.
If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to such additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.
Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Part 801); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820); and if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.
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Page 2 – Ms. Audrey Swearingen
This letter will allow you to begin marketing your device as described in your Section 510(k) premarket notification. The FDA finding of substantial equivalence of your device to a legally marketed predicate device results in a classification for your device and thus, permits your device to proceed to the market.
If you desire specific advice for your device on our labeling regulation (21 CFR Part 801), please contact the Office of Compliance at (301) 594-4659. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21CFR Part 807.97). You may obtain other general information on your responsibilities under the Act from the Division of Small Manufacturers, International and Consumer Assistance at its toll-free number (800) 638-2041 or (301) 443-6597 or at its Internet address http://www.fda.gov/cdrh/dsma/dsmamain.html
Sincerely yours,
William W. Weber, Ph.D., M.D.
Celia M. Witten, Ph.D., M.D. Director Division of General, Restorative and Neurological Devices Office of Device Evaluation Center for Devices and Radiological Health
Enclosure
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# Indications for Use
510(k) Number (if known): K033810
Device Name: Natural-Knee® II Unicompartmental Knee System
Indications For Use: The Natural-Knee II Unicompartmental Knee is intended for use in:
- Unicompartmental noninflammatory degenerative joint disease 1. (NIDJD), e.g., avascular necrosis, osteoarthritis and arthritis secondary to a variety of diseases and anomalies;
- 2. Passively correctable valqus-varus deformity and moderate flexion contracture;
- 3. Those patients with failed previous surgery where pain, deformity or dysfunction persists.
The N-K II Unicompartmental All-Poly Tibia is intended to be used only with bone cement. The modular metal/polymer N-K II Unicompartmental Tibia and Femur are intended for use with or without bone cement.
Prescription Use X (Part 21 CFR 801 Subpart D) AND/OR
Over-The-Counter Use (21 CFR 807 Subpart C)
(PLEASE DO NOT WRITE BELOW THIS LINE-CONTINUE ON ANOTHER PAGE IF NEEDED)
Concurrence of CDRH, Offically Office Evaluation (ODE)
Wby with
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(Division Sign-Of Division of General. Restorative. and Neurological Devices
Page 1 of
**510(k) Number** K033810
Two short videos show you everything — or skip straight to the written tutorial if you'd rather read. You can reopen this any time from the Tutorial button in the top bar.
Part 1 — Search, results, and everyday workflows 16 min
Part 2 — Embeddings: the galaxy map 3 min
1. Search: exact and fuzzy
Type a phrase like "coronary artery calcification" into the search box. You get two kinds of results. Exact results match the literal phrase — prefix searches work ("coronary artery calcificati") but suffix searches do not. Fuzzy results match on the meaning and intent of your phrase rather than the exact words, and are sorted by relevance score. Hover over the Exact or Fuzzy badge on any row to see exactly why it matched.
Use the checkboxes above the results to narrow: SaMD keeps only software-only devices, AI / ML keeps only devices with AI.
Exact vs. fuzzy search: what's the difference?
Exact matches on the literal phrase (prefix search works, suffix does not). Fuzzy matches on the meaning and intent of the phrase rather than the exact words. Hover over the badge on any row to see why it matched.
You search "coronary artery calcification" and want only software devices with AI. What two filters do you apply?
Narrow by SaMD (software-only devices), then narrow by AI/ML (devices with AI).
2. The results table
Scroll right in the results table. The intended use is extracted for you — no need to open the PDF. The device story gives a high-level snapshot of what the device does and how it's used. The AI Performance sub-table shows each output name, acceptance criteria, observed values, and development/test dataset descriptions — the same format Innolitics uses for regulatory strategy outputs, and the fastest high-level fingerprint of an AI device. It is AI-generated but has been very reliable in practice.
Where do you find a device's intended use without opening the PDF?
Scroll right in the search results table. The intended use column is extracted for you; no need to dig into the 510(k) summary PDF.
What does the AI Performance sub-table show, and why is it useful?
Output name, acceptance criteria, observed values, development dataset description, and test dataset description. It's the same format we use for regulatory strategy output and Fast 510(k) input, and the fastest high-level fingerprint of an AI device. AI-generated but reliable in practice.
3. Judging fuzzy relevance
Fuzzy results trail off in relevance as you scroll. Use three signals to decide how far down to go: the fuzzy badge explanations, the intended use column, and whether your target output (e.g., Cobb angle) still appears in the AI Performance sub-table. Once it stops appearing, you're past the relevant zone. A top hit with a low score (~0.4) and a stretched explanation is a hint the closest predicates are far away — the project may be headed for De Novo. Note the fuzzy search is a pattern match: it doesn't handle negation ("not") well, and hardware devices can appear — filter by SaMD/AI ML to cut them.
How do you judge how far down fuzzy search results to go?
Use the relevancy signals: the fuzzy badge explanations, the intended use column, and whether the target output (e.g., Cobb angle) still appears in the AI Performance sub-table. Once it stops appearing, results are trailing off in relevancy.
4. Device detail page: chat and citations
Click a device name to open its detail page: device facts on the left, a chat window on the right. Ask something like "Describe the training data". The answer carries little citation bubbles — click one to jump to the highlighted passage in the source PDF, so you can verify every AI answer against the document. There's also a Download PDF button for sharing.
How do you verify an AI chat answer on the device detail page?
Click the citation bubbles to jump to the relevant highlight in the source document.
Reading rule for every project: how many summaries do you read in full?
At least the three most relevant 510(k) or De Novo summaries, in full. After that, use targeted chat questions to confirm your memory quickly. The tool supports this professional habit — it doesn't replace it.
5. Side-by-side comparison
Select multiple rows in the results table (aim for under ~10), then open the PDF Viewer tab. Ask one question — it goes to all selected devices in parallel, each with citations. This is the fastest way to compare and contrast devices: training data, PCCP scope, how they handled adding new scanners, and so on.
What does the side-by-side PDF viewer mode do?
Select multiple devices, open the PDF viewer tab, and ask one question (e.g., "Describe the training data"). It queries all selected devices simultaneously with citations, so you can compare and contrast quickly.
6. Collections
With rows selected, go to the Collections tab and create a labeled collection (e.g., "Cobb Angle Project"). Reload that selection any time — before a client call, pull up the collection and ask questions across all of its devices at once.
How do you save a set of selected devices for later use?
Select the rows, go to the Collections tab, and create a labeled collection (e.g., "Cobb Angle Project"). You can reload the selection anytime and carry it into the PDF viewer and other tabs that support selections.
7. Product codes and the regulations tree
Click a product code in the results to jump to it in the regulations tree — identification text, sibling product codes, and devices you can open in a PDF viewer on the right. Click a regulation number to see its identification, special controls, and related product codes. You can also search by product code or regulation number at the top of the tree. Always read the special controls if any exist for your device — it broadens your search and sharpens pre-kickoff research.
What can you do from the regulations tree view?
Browse product codes and regulation numbers, read the identification text and special controls, browse sibling product codes, open device PDFs on the right, and search by product code or regulation number at the top of the tree.
8. Chart view
Click Show Chart and segment by regulation number (or product code) to see which regulations dominate your result set. Clicking a regulation takes you into the regulations tree. Great for spotting that most matches are, say, hardware laparoscopic devices — a cue to go back and filter.
How do you see which regulations dominate a search result set?
Click "Show Chart" and segment by Regulation Number. Clicking a regulation takes you to the regulations tree.
9. The predicate graph
Open the Predicates tab for a family-tree view of predicate relationships. Click a node to trace its parents and children; selections from search carry over pre-selected. Commonly predicated devices are worth reading — a lot of people predicated them for a reason. The visual lineage is also handy on client calls, e.g. to show how a predicate family evolved and justify why your predicate still holds.
In the predicate graph, why are commonly predicated devices worth reading?
A lot of people predicated them for a reason. Clicking a node traces parents and children, and selections from search carry over pre-selected.
10. Embeddings: the galaxy map
The Embeddings tab plots every matching document in a 2-D "galaxy map" where semantically similar devices cluster together. Hover or click clusters to explore, and let AI label the clusters for you. Embeddings beat product codes for grouping: two devices can carry different product codes (LLZ vs. QIH) yet do the same thing — the embedding captures the meaning of the intended use and device story. This is also exactly how retrieval-augmented generation (RAG) works under the hood, and it makes a great visual on client calls.
Try it yourself
Head to the search page and work through a few of these AI/ML fuzzy searches to build intuition: perivascular fat on CT · aortic valve calcification opportunistic screening on noncontrast CT · breast cancer prediction on digital pathology slides · autism detection · gestational age prediction · a hearing aid that can also detect a pulse · foundation model based analysis of ECG · large language models · penetration test. Watch how the relevance scores, intended use, and AI Performance tables tell you when results stop being meaningful.
