The U2 Total Knee system is indicated in knee arthroplasty for reduction or relief of pain and/or improved knee function in skeletally mature patients with severe knee pain and disability due to rheumatoid arthritis, osteoarthitis, primary and secondary traumatic arthritis, polyarthritis, collagen disorders, avascular necrosis of the femoral condyle or pseudogout, posttraumatic loss of joint configuration, particularly when there is patellofemoral erosion, dysfunction or prior patellectomy, moderate valgus, varus, or flexion deformities. This device may also be indicated in the salvage of previously failed surgical attempts if the knee cannot be satisfactorily balanced and stabilized at the time of surgery. For cemented femoral components, patellar components, tibial baseplate components and tibial inserts components: This device is a single use implant and intended for cemented use only. For porous coated femoral component: This device is a single use implant and intended for cementless use only.
Device Story
The U2 Total Knee System, XPE Tibial Insert, PS PLUS is a prosthetic component for total knee arthroplasty. It functions as a constrained tibial insert that mechanically locks into a metallic tibial baseplate. The device is used in conjunction with a Posterior Stabilized (PS) femoral component. The design features a modified post and anterior lip compared to predicate devices to provide enhanced varus/valgus and internal/external rotation constraint, improving joint stability and resisting paradoxical anterior femoral slide. It is intended for use by orthopedic surgeons in a clinical/surgical setting. The device is available in eight sizes and ten thicknesses. It benefits patients by restoring joint function and reducing pain in cases of severe knee disability.
Clinical Evidence
Bench testing only. Performance evaluation included constraint evaluation, contact area and contact pressure analysis on the femorotibial joint, and tibiofemoral range of motion (ROM) analysis to verify safety and effectiveness of the design modifications.
Indicated for skeletally mature patients requiring knee arthroplasty for pain relief or improved function due to rheumatoid arthritis, osteoarthritis, traumatic arthritis, polyarthritis, collagen disorders, avascular necrosis, pseudogout, or posttraumatic joint loss (including patellofemoral erosion/dysfunction or prior patellectomy) and moderate valgus, varus, or flexion deformities. Also indicated for salvage of failed surgical attempts where knee balancing/stabilization is required.
Regulatory Classification
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).
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April 21, 2021
Image /page/0/Picture/1 description: The image shows the logo of the U.S. Food and Drug Administration (FDA). The logo consists of two parts: the Department of Health and Human Services logo on the left and the FDA logo on the right. The FDA logo is a blue square with the letters "FDA" in white, followed by the words "U.S. FOOD & DRUG ADMINISTRATION" in blue.
United Orthopedic Corporation Lois Ho Regulatory Affairs Manager No 57, Park Ave 2, Science Park Hsinchu, 30075 TAIWAN
## Re: K210961
Trade/Device Name: U2 Total Knee System, XPE Tibial Insert, PS PLUS Regulation Number: 21 CFR 888.3560 Regulation Name: Knee Joint Patellofemorotibial Polymer Semi-Constrained Cemented Prosthesis Regulatory Class: Class II Product Code: JWH Dated: March 31, 2021 Received: March 31, 2021
Dear Lois Ho:
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 to devices 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. Although this letter refers to your product as a device, please be aware that some cleared products may instead be combination products. The 510(k) Premarket Notification Database located at https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm identifies combination product submissions. 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. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.
If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to 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
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requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Part 801); medical device reporting of medical device-related adverse events) (21 CFR 803) for devices or postmarketing safety reporting (21 CFR 4, Subpart B) for combination products (see https://www.fda.gov/combination-products/guidance-regulatory-information/postmarketing-safety-reportingcombination-products); good manufacturing practice requirements as set forth in the quality systems (OS) regulation (21 CFR Part 820) for devices or current good manufacturing practices (21 CFR 4, Subpart A) for combination products; and, if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.
Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR Part 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to https://www.fda.gov/medical-device-safety/medical-device-reportingmdr-how-report-medical-device-problems.
For comprehensive regulatory information about mediation-emitting products, including information about labeling regulations, please see Device Advice (https://www.fda.gov/medicaldevices/device-advice-comprehensive-regulatory-assistance) and CDRH Learn (https://www.fda.gov/training-and-continuing-education/cdrh-learn). Additionally, you may contact the Division of Industry and Consumer Education (DICE) to ask a question about a specific regulatory topic. See the DICE website (https://www.fda.gov/medical-device-advice-comprehensive-regulatoryassistance/contact-us-division-industry-and-consumer-education-dice) for more information or contact DICE by email (DICE@fda.hhs.gov) or phone (1-800-638-2041 or 301-796-7100).
Sincerely,
Ting Song, Ph.D., R.A.C. Assistant Director DHT6A: Division of Joint Arthroplasty Devices OHT6: Office of Orthopedic Devices Office of Product Evaluation and Quality Center for Devices and Radiological Health
Enclosure
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# Indications for Use
510(k) Number (if known)
K210961
Device Name
U2 Total Knee System, XPE Tibial Insert, PS PLUS
### Indications for Use (Describe)
The U2 Total Knee system is indicated in knee arthroplasty for reduction or relief of pain and/or improved knee function in skeletally mature patients with severe knee pain and disability due to rheumatoid arthritis, osteoarthitis, primary and secondary traumatic arthritis, polyarthritis, collagen disorders, avascular necrosis of the femoral condyle or pseudogout, posttraumatic loss of joint configuration, particularly when there is patellofemoral erosion, dysfunction or prior patellectomy, moderate valgus, varus, or flexion deformities. This device may also be indicated in the salvage of previously failed surgical attempts if the knee cannot be satisfactorily balanced and stabilized at the time of surgery.
For cemented femoral components, patellar components, tibial baseplate components and tibial inserts components: This device is a single use implant and intended for cemented use only.
For porous coated femoral component: This device is a single use implant and intended for cementless use only,
Type of Use (Select one or both, as applicable)
| <div> <span> <svg fill="none" height="16" viewbox="0 0 16 16" width="16" xmlns="http://www.w3.org/2000/svg"> <path d="M13.25 3.375L5.75 10.875L2.75 7.875" stroke="#000000" stroke-linecap="round" stroke-linejoin="round" stroke-width="1.5"></path> </svg> Prescription Use (Part 21 CFR 801 Subpart D) </span> </div> |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| <div> <span> <svg fill="none" height="16" viewbox="0 0 16 16" width="16" xmlns="http://www.w3.org/2000/svg"> <rect height="12" stroke="#000000" stroke-width="1.5" width="12" x="2" y="2"></rect> </svg> Over-The-Counter Use (21 CFR 801 Subpart C) </span> </div> |
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Image /page/3/Picture/1 description: The image shows the logo for United Orthopedic. The logo consists of a green letter U with a white circle inside, and the words "UNITED ORTHOPEDIC" in black text to the right of the U. The word "UNITED" is above the word "ORTHOPEDIC".
# 510(K) SUMMARY
# Special 510(k)
[as required by 21 CFR 807.92(c)]
## Submitter information
| Company Name: | United Orthopedic Corporation |
|--------------------|-------------------------------------------------------------|
| Address | No 57, Park Ave 2, Science Park, Hsinchu City 30075, Taiwan |
| Telephone | +886-3-5773351 ext. 2220 |
| Fax | +886-3-577156 |
| Contact Person | Lois Ho, Regulatory Affairs Manager |
| Email address | lois.ho@unitedorthopedic.com |
| Date of submission | March 30, 2021 |
## Trade Name, Common Name, Classification
| Device Common Name: | Tibial Insert |
|----------------------------------------------------------------------------------------------------------------|--------------------------------------------------|
| Trade name: | U2 Total Knee System, XPE Tibial Insert, PS Plus |
| Submitter Establishment Number: | 9681642 |
| Classification Regulation Number: | 21CFR 888.3560 |
| Classification Panel: | Orthopedic |
| Product Code: | JWH |
| Device Class: | Class II |
| Classification name: Knee joint patellofemorotibial polymer/metal/polymer semi-constrained cemented prosthesis | |
## Predicate devices and reference devices
| Primary Predicate | 510(k) Number | Manufacturer |
|-----------------------------------------|---------------------------|-------------------------------|
| U2 Total Knee System, Tibial Insert, PS | K150829 | United Orthopedic Corporation |
| Reference Predicate | | |
| U2 Total Knee System, Tibial Insert, PS | K103733, K131864, K161705 | United Orthopedic Corporation |
| Device description | The U2 Total Knee System include femoral components, patellar<br>components, tibial baseplate components and tibial inserts components<br>which are designed to be used together to achieve total replacement of<br>the knee joint. This system includes Cruciate Retained (CR) type, |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Posterior Stabilized (PS) type and Ultracongruent (UC) type. The subject device, U2 Total Knee System, XPE Tibial Insert, Posterior Stabilized PLUS (PS PLUS), belongs to U2 Total Knee System PS type. | |
| U2 Total Knee System, XPE Tibial Insert, PS PLUS (Subject device) is a constrained design insert mechanically locked with metallic tibial baseplate. It is manufactured from Gamma irradiated UHMWPE which conform to ASTM F2565-13, while the UHMWPE raw material is in accordance with ASTM F648-14 and ISO 5834-1:2005. | |
| The Subject device is used with the Posterior Stabilized (PS) type Femoral Component. In comparison to the marketed predicate devices, the Subject device has slightly modified width and height of the post, the height of the anterior lip. The Subject device provides constraint in varus/valgus and internal/external rotation to enhance joint stability and resist paradoxical anterior femoral slide. | |
| Except for the differences of the post and anterior lip, the size distribution the Subject device is identical to the previously cleared Tibial Inserts of U2 Total Knee System predicates. The Subject device is available in eight proportional sizes (#0~ #7) and ten thicknesses (thicknesses of poly insert + tibial baseplate: 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm and 18mm). The minimum thickness of poly insert of Subject device is 6 mm on the bearing surface, identical to the primary predicate. | |
| Surgical procedures with the use of the Subject device shall be performed with the support of orthopedic instrumentation, to facilitate their proper insertion and removal from the patient. The surgical instruments have been previously cleared as part of the predicate devices. | |
| Indications for use | The U2 Total Knee system is indicated in knee arthroplasty for reduction or relief of pain and/or improved knee function in skeletally mature patients with severe knee pain and disability due to rheumatoid arthritis, osteoarthritis, primary and secondary traumatic arthritis, polyarthritis, collagen disorders, avascular necrosis of the femoral condyle or pseudogout, posttraumatic loss of joint configuration, particularly when there is patellofemoral erosion, dysfunction or prior patellectomy, moderate valgus, varus, or flexion deformities. This device may also be indicated in the salvage of previously failed surgical attempts if the knee cannot be satisfactorily balanced and stabilized at the time of surgery. |
| | For cemented femoral components, patellar components, tibial<br>baseplate components and tibial inserts components: This device is a<br>single use implant and intended for cemented use only.<br>For porous coated femoral component: This device is a single use<br>implant and intended for cementless use only. |
| Technological<br>Characteristics | The Subject device fundamental scientific principles and technological<br>characteristic, including: the intended use, material and general design, are the<br>same as, or similar to, the primary predicate and the chosen additional<br>predicate device.<br>Summary of the technological characteristics:<br>✓ Intended use: identical<br>✓ Indications for Use, Anatomical sites, operating principles and conditions<br>of use are identical<br>✓ No new risks associated to the Subject device compared to those of the<br>predicate devices.<br>✓ Verification activities on Subject devices demonstrated equivalent safety<br>and effectiveness as compared to the predicate devices.<br>✓ Material: are identical to the primary predicate.<br>✓ Geometry and size: Sizes of the Subject device are bracketed in size by<br>the predicates.<br>✓ Sterilization: identical method as predicate.<br>The technological characteristics of the Subject device are substantially<br>equivalent to the predicate device(s). |
| Performance Analysis | Based on the modification items of the design rational of the Subject<br>device, the following tests were conducted to evaluate the safety and<br>effectiveness of the subjected device, and the test results indicated that<br>this device is safe and effective.<br>Constraint evaluation Contact area and contact pressure analysis on femorotibial joint Tibiofemoral range of motion (ROM) analysis |
| Conclusion | Based upon equivalences in: intended use, patient population, site of<br>application, conditions of use, operating principles, and the non-clinical<br>performance data, the changes introduced in the Subject device have been<br>shown to be safe and effective and to perform equivalently as compared to<br>the legally marketed predicate devices.<br>Therefore, the changes to primary predicate for Subject devices are<br>substantially equivalent to the legally marketed predicate devices. |
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Image /page/4/Picture/1 description: The image shows the logo for United Orthopedic. The logo consists of a green circle with a white "U" shape inside, and the words "UNITED ORTHOPEDIC" in black text to the right of the circle. The word "ORTHOPEDIC" is stacked below the word "UNITED".
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Image /page/5/Picture/1 description: The image shows the logo for United Orthopedic. The logo consists of a green circular shape with a white dot inside, resembling the letter 'U'. To the right of the symbol, the words "UNITED" and "ORTHOPEDIC" are written in black, stacked on top of each other.
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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.
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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.
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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.
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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.
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7. Product codes and the regulations tree
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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.