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510(k) Data Aggregation
(84 days)
NEXGEN COMPLETE KNEE SOLUTION LEGACY POSTERIOR STABILIZED (LPS); LPS-FLEX FIXED BEARING FEMORAL AND ARTICULAR
This device is intended to reduce or relieve pain and restore function and motion to the knee joint. 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. This device may also be indicated in the salvage of previously failed surgical attempts if the knee can be satisfactorily balanced and stabilized at the time of surgery.
The LPS-Flex Fixed Bearing Knee provides increased flexion capability for patients who have both the flexibility and desire to increase their flexion range. The LPS-Flex femoral, when used with LPS-Flex articular surfaces, is designed for use with both cruciate ligaments excised and when load bearing range of motion (ROM) is expected to be less than or equal to 155 degrees. This device is intended for cemented use only.
The LPS-Flex Fixed Bearing Knee is a semiconstrained, condylar system for use without the cruciate ligaments when additional stability is required to prevent anterior subluxation of the femur relative to the tibia in flexion. The LPS-Flex Fixed Bearing Knee consists of an LPS-Flex femoral and an LPS-Flex articular surface.
This is a 510(k) premarket notification for a medical device (NexGen® Complete Knee Solution Legacy® Posterior Stabilized (LPS); LPS-Flex Fixed Bearing Femoral and Articular Surface Components), not an AI/ML device. Therefore, the requested information about acceptance criteria, study details, and AI/ML-specific performance metrics (e.g., sample sizes for test/training sets, expert ground truth, MRMC studies) is not applicable or available in the provided document.
The document focuses on demonstrating substantial equivalence to a predicate device (NexGen® Complete Knee Solution Legacy® LPS Knee) through non-clinical performance evaluations and comparisons of design, materials, and mechanical performance.
Here's an analysis of the provided information, focusing on what is available:
1. Table of Acceptance Criteria and Reported Device Performance
The document does not present a formal table of quantitative acceptance criteria with corresponding performance values in the way you might expect for an AI/ML device. Instead, it compares the proposed device to a predicate device across several parameters and concludes that they are "Similar" or "Identical."
| Parameter | Acceptance Criteria (Implicit from Predicate Comparison) | Reported Device Performance (LPS-Flex) |
|---|---|---|
| Constraint (ASTM F1223) | Not significantly different from predicate device. | "negligible displacement variances between the LPS-Flex and the predicate device. Constraint was not significantly different." |
| Contact Area | Increased conformity compared to predicate. | "showed an increase in conformity for the device as compared to the predicate." |
| Tibial Baseplate Interlock Mechanism | Same as predicate device, with enhanced fixation for high flexion in some cases. | "the same as the predicate device. A screw is added to some LPS-Flex articular surfaces to enhance fixation during high flexion." |
| Fatigue Strength (Tibial Baseplate) | Same as predicate device. | "No additional fatigue strength data was needed because the device uses the predicate tibial baseplate." "The LPS-Flex knee uses the predicate tibial baseplate and has the same fatigue strength." |
| Design (Sagittal Plane Conformity) | Modified for increased conformity during walking gait angles and extended flexion range compared to predicate. | "The LPS-Flex femoral has a modified sagittal plane as compared to the predicate. This gives the LPS-Flex increased conformity during walking gait angles of flexion and accommodates the extended flexion range." |
| Design (Cam/Spine Geometry) | Modified to improve resistance to subluxation, correct rollback, kinematics, and reduce bending load on the spine compared to predicate. | "the shape of the femoral cam was modified and the clearance posterior to the polyethylene spine was deepened. This improves resistance to subluxation beyond the predicate and provides for the correct rollback and kinematics of the LPS-Flex joint. The cam and spine geometries of the LPS-Flex were also designed to provide a low cam/spine contact which reduces the bending load on the spine during high load flexion activities, such as squatting." |
| Materials | Same as predicate, with an additional Tivanium insert for LPS-Flex. | "Femoral component is Zimaloy® Cobalt-Chromium-Molybdenum Alloy for both the predicate and LPS-Flex. Articular surface is UHMWPE for both the predicate and LPS-Flex. A Tivanium insert is added to the LPS-Flex." |
| Patellofemoral Joint Stability | Same as predicate. | "The patellar groove design and stability of the LPS-Flex femoral component is the same as the predicate." |
| Wear Data (Polyethylene Thickness) | Minimum polyethylene thickness of 6.5 mm; design maintains conformity to minimize wear. | "The LPS-Flex has a minimum polyethylene thickness of 6.5 mm. Even though the LPS-Flex increases the maximum active flexion angle to 155 degrees, the design has maintained the conformity necessary to minimize or eliminate any new movement mechanisms that could affect wear." |
| Sterility | Identical to predicate; terminally sterilized by gamma radiation to SAL of 10^-6 or better. | "Both are terminally sterilized by gamma radiation...validated dosimetric release program designed to provide a sterility assurance level (SAL) of 10^-6 or better." |
| Biocompatibility | Meets or exceeds ASTM standards; materials common to orthopedic products. | "Material specifications for both the predicate and LPS-Flex meet or exceed ASTM standards, are common to orthopaedic products today and do not require additional biocompatibility testing." |
| Pyrogenicity | Not labeled as nonpyrogenic, as per USP XXIII, NF18 (1995 edition) for orthopedic products. | "Neither the predicate or the LPS-Flex are labeled as nonpyrogenic. Per USP XXIII, NF18 (1995 edition), page 1719, "These requirements do not apply to orthopaedic products."" |
2. Sample Size Used for the Test Set and Data Provenance
Not applicable. This is a medical device clearance based on substantial equivalence, primarily using non-clinical (mechanical/material) testing and comparison to an existing predicate device. There is no "test set" in the context of an AI/ML study. The studies mentioned (e.g., ASTM F1223) refer to standard test methods for mechanical properties.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and the Qualifications of Those Experts
Not applicable. There is no clinical "test set" requiring expert ground truth in the context of an AI/ML study. The evaluation relies on engineering principles, material science, and established ASTM standards.
4. Adjudication Method for the Test Set
Not applicable. There is no "test set" in the AI/ML sense, and thus no adjudication method for ground truth.
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 not an AI/ML device, and no MRMC study was conducted or is relevant to its clearance.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done
Not applicable. This is not an AI/ML device.
7. The Type of Ground Truth Used (expert consensus, pathology, outcomes data, etc.)
Not applicable in the AI/ML sense. The "ground truth" for this device's performance is established by:
- Mechanical Testing Results: Adherence to established ASTM standards (e.g., F1223 for constraint).
- Design Specifications: Comparison of design features to the predicate device and engineering rationale.
- Material Specifications: Compliance with ASTM standards for materials.
- Sterility Validation: Adherence to ISO standards (e.g., ANSI/AAMI/ISO 11137-1994) for sterility assurance level (SAL).
8. The Sample Size for the Training Set
Not applicable. This is not an AI/ML device.
9. How the Ground Truth for the Training Set was Established
Not applicable. This is not an AI/ML device.
Summary of the Device's Approval and Basis:
The Zimmer NexGen® Complete Knee Solution Legacy® Posterior Stabilized (LPS); LPS-Flex Fixed Bearing Femoral and Articular Surface Components received 510(k) clearance based on its substantial equivalence to the predicate device, NexGen® Complete Knee Solution Legacy® LPS Knee.
The study that "proves" the device meets acceptance criteria primarily consists of:
- Non-clinical performance evaluations:
- Constraint analysis per ASTM F1223, showing negligible displacement variances compared to the predicate.
- Contact area determination, showing increased conformity compared to the predicate.
- Confirmation that the tibial baseplate interlock mechanism and fatigue strength are equivalent to or improved over the predicate.
- Detailed technological comparison: Demonstrating similarities and differences in design, materials, and other performance aspects, with explanations for modifications (e.g., modified sagittal plane, cam, and spine geometries for increased flexion and stability) and why these changes do not raise new questions of safety or effectiveness.
- Adherence to recognized standards: For sterility (gamma radiation to SAL 10^-6 per ANSI/AAMI/ISO 11137-1994) and biocompatibility (materials meeting ASTM standards).
The conclusion was that "Clinical data and conclusions were not needed for this device" because the non-clinical data sufficiently demonstrated substantial equivalence to a legally marketed predicate device.
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