(166 days)
Total knee replacement is indicated for 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. These devices may also be indicated in the salvage of previously failed surgical attempts or for a knee in which satisfactory stability in flexion cannot be obtained at the time of surgery. Intended for cemented use only.
The NexGen Convex Inset Patella is made of ultra-high molecular-weight polyethylene (UHMWPE). This patellar component is axisymmetrical. The fixation side geometry is convex in shape. It tapers toward a single post that is coincident with the symmetry axis.
The provided document is a 510(k) Pre-Market Notification for the NexGen® Complete Knee Solution, Convex Inset Patella. It describes the device, its intended use, and indicates that its substantial equivalence to predicate devices is based on performance data and clinical data found in the literature. However, it does not contain a study explicitly detailing "acceptance criteria" and how the device individually "meets" those criteria in the way a structured performance study for an AI/ML device would.
Instead, the submission relies on:
- Performance Data: Shear Testing and Pull-Out Testing. These are standard mechanical tests for orthopedic implants to assess their structural integrity and fixation strength.
- Clinical Data: Reference to existing literature demonstrating satisfactory results with cemented patellar components. This suggests that the fundamental design principles and materials are similar to established, safe, and effective devices.
Given the nature of this submission (a 510(k) for a medical device that is not an AI/ML diagnostic or prognostic tool), many of the requested details, such as sample size for test sets, ground truth establishment by experts, adjudication methods, or MRMC studies, are not applicable or present in this type of regulatory document.
Here's a breakdown of the information that can be extracted or inferred, and where the requested information is not applicable:
1. A table of acceptance criteria and the reported device performance
| Acceptance Criteria (Inferred from Predicate Equivalence) | Reported Device Performance |
|---|---|
| Mechanical Performance: | |
| Sufficient shear strength and pull-out resistance to ensure stable fixation in bone cement. | Shear Testing: Conducted |
| Pull-Out Testing: Conducted | |
| (Specific numerical results or acceptance thresholds are not provided in this summary, but would have been part of the full 510(k) submission). | |
| Clinical Performance: | |
| Satisfactory results comparable to legally marketed cemented patellar components for total knee replacement. | Clinical Data: "Studies in the literature demonstrate that satisfactory results are obtained through the use of cemented patellar components." (Specific studies are referenced in the full 510(k) but not detailed in this summary). |
| Material Biocompatibility & Durability: | |
| Made of Ultra-High Molecular Weight Polyethylene (UHMWPE), a commonly used and accepted material in orthopedic implants. | Device Material: UHMWPE |
| Geometric & Functional Design: | |
| Axisymmetrical, with a convex fixation side and a single post, similar to predicate devices. | Device Description: Matches the described geometry. |
2. Sample size used for the test set and the data provenance (e.g. country of origin of the data, retrospective or prospective)
- Not Applicable in the traditional sense for this type of device. The "test set" here refers to mechanical tests of the physical device components and a review of existing clinical literature.
- For mechanical tests (Shear and Pull-Out), the sample size of tested components would have been determined by engineering standards, but is not specified in this summary.
- For clinical data, the "data provenance" refers to the body of scientific literature, which would be global and retrospective.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts (e.g. radiologist with 10 years of experience)
- Not Applicable. "Ground truth" in the context of this device's regulatory review is established through:
- Engineering analysis and testing by Zimmer's R&D engineers for mechanical properties.
- Clinical consensus and established practice as reflected in cited medical literature, interpreted by regulatory review staff.
- The FDA's own review processes, which involve expert medical and scientific reviewers, but not in the "establishing ground truth for a test set" manner of an AI study.
4. Adjudication method (e.g. 2+1, 3+1, none) for the test set
- Not Applicable. Adjudication methods are typically associated with human interpretation of data where consensus is needed, such as in clinical trials or diagnostic accuracy studies. For mechanical testing, results are quantitative. For literature review, it's a matter of scientific interpretation and regulatory assessment.
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 is a physical orthopedic implant, not an AI/ML diagnostic tool. Therefore, MRMC studies and "improvement with AI" are irrelevant.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done
- Not Applicable. This is not an algorithm; it's a physical device.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.)
- Mechanical Performance: Ground truth is defined by engineering specifications and physical measurements (e.g., force, displacement during pull-out tests).
- Clinical Performance: Ground truth is established by long-term clinical outcomes data and expert consensus reflected in the medical literature for similar predicate devices. The "satisfactory results" mentioned in the document would stem from observed positive patient outcomes (pain relief, improved function, implant survivorship) over time for cemented patellar components.
8. The sample size for the training set
- Not Applicable. This device does not use an AI/ML model that requires a training set. The "training" for such a device comes from decades of biomedical engineering research, material science, and clinical experience with similar implants.
9. How the ground truth for the training set was established
- Not Applicable. As explained above, there's no "training set" in the AI/ML sense. The "ground truth" for the design and manufacturing of such a device is rooted in validated engineering principles, material properties, biomechanical studies, and clinical follow-up of predicate devices.
§ 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.