(89 days)
This device is indicated for moderate to severe knee instability, significant bone loss and/or ligament deficiencies caused by neoplasms, trauma, rheumatoid arthritis, osteoarthritis, traumatic arthritis, polyarthritis, collagen disorders, avascular necrosis of the femoral condyle, valgus, varus, or flexion deformities and/or for the salvage of previously failed surgical attempts. This device is intended for cemented use only.
The NexGen Rotating Hinge Knee (RHK) is a knee prosthesis that is constrained in the anterior/posterior and medial/lateral directions but allows flexion/extension and rotation between the femoral and tibial components. Constraint in the anterior/posterior and medial/lateral directions is accomplished by means of a femoral hinge post extension inserted through the polyethylene articular surface into the tibial baseplate. This prosthesis is designed to be used with Zimmer NexGen Complete Knee Solution patellar components, femoral and tibial augments, and stem extensions. The articular surface is available in multiple thicknesses to facilitate soft tissue tensioning and joint line restoration. Tibial baseplate components are available in multiple sizes to allow for optimal bone coverage and surgical options.
The provided document is a Summary of Safety and Effectiveness for the Zimmer NexGen® Complete Knee Solution Rotating Hinge Knee, a medical device. This document describes the device itself and its comparison to a predicate device for 510(k) clearance, which is a regulatory pathway for medical devices in the US.
It is important to understand that this document describes a medical device (a knee prosthesis), not an AI/software device. Therefore, the questions related to AI/software performance criteria, test sets, ground truth, experts, and training sets are not applicable to this submission.
The "acceptance criteria" and "study that proves the device meets the acceptance criteria" in this context refer to the engineering and biomechanical testing performed to demonstrate that the new device (NexGen Rotating Hinge Knee) is substantially equivalent to a legally marketed predicate device (Finn Knee System). This is a different type of evaluation than what would be performed for an AI/software product.
Here's an analysis of the provided information based on the context of a medical device submission, explicitly stating why certain questions about AI are not applicable:
Acceptance Criteria and Study for Zimmer NexGen® Complete Knee Solution Rotating Hinge Knee
1. Table of Acceptance Criteria and Reported Device Performance:
| Acceptance Criteria (Implied from Predicate Comparison) | Reported Device Performance (Non-Clinical) |
|---|---|
| Similar Indications for Use | The NexGen RHK has similar indications to the Finn Knee System: moderate to severe knee instability, significant bone loss/ligament deficiencies due to various conditions (neoplasms, trauma, arthritis, etc.), and salvage of failed surgical attempts. Intended for cemented use only. (Substantially equivalent) |
| Similar Design | Both are constrained, rotating hinge knee prostheses. The NexGen RHK is anterior/posterior and medial/lateral constrained, allowing flexion/extension and rotation, with a femoral hinge post extension into a tibial baseplate. |
| Similar Materials | While specific materials aren't detailed as "acceptance criteria," the document states "similar indications, design... materials and mechanical safety" as points of substantial equivalence to the predicate. |
| Mechanical Safety / Performance Equivalence | |
| - Constraint Testing Applicability | Not applicable to this constrained prosthesis (i.e., the prosthesis is inherently constrained, so specific constraint testing for range of motion beyond its design would be unnecessary per the submission). |
| - Contact Area | Contact area was greater for the RHK than the Finn for the range 0 - 120°. At 130°, the Finn had greater contact area. This implies the RHK maintained acceptable contact characteristics. |
| - Distraction (Lift-off) Testing (Interlock Mechanism) | The RHK interlock mechanism passed all distraction (lift-off) testing. |
| - Tibial Baseplate Fatigue Strength | All RHK test samples completed the 10 million cycle Tibial Baseplate Fatigue Strength testing without evidence of fracture or cracking. |
| - Patellofemoral Joint Stability | No additional lateral stability data was needed because the RHK uses similar patella femoral tracking as previously cleared NexGen femoral components. |
| - Shear Strength / Medal-backed Patella Tensile Data | No additional shear strength or metal-backed patella static tensile data was needed because the RHK uses previously cleared patella devices. |
| - Combined Load Fatigue & Pin Loosening | The RHK components passed all combined load fatigue and pin loosening testing. |
| - Wear Testing | Not needed for the RHK device because the minimum polyethylene thickness is greater than 6 mm (indicating it meets a threshold where wear testing is not typically required for predicate comparison). |
| Clinical Performance Equivalence | Clinical data and conclusions were not needed for this device, implying that the non-clinical performance and design similarity were sufficient to establish substantial equivalence to the predicate device, which itself had established clinical safety and effectiveness. |
Regarding the AI/Software specific questions (2-9):
2. Sample size used for the test set and the data provenance:
- Not Applicable. This is a physical medical device (knee prosthesis), not an AI/software product. The "test set" refers to the physical samples of the device and components that underwent mechanical and material testing, as described above. The "data provenance" would refer to the testing lab and methodology.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
- Not Applicable. Ground truth in the context of AI/software refers to expert-validated labels for data. For a physical device, "ground truth" is established by engineering standards, validated testing protocols, and comparison to the predicate device's known performance, often overseen by qualified biomechanical engineers and regulatory specialists.
4. Adjudication method for the test set:
- Not Applicable. Adjudication methods (like 2+1 or 3+1) are used for resolving disagreements among multiple human readers/experts in AI/software validation. For a physical device, testing results are typically objective measurements or observations during standardized mechanical tests.
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. MRMC studies are specific to evaluating the impact of AI on human reader performance, typically in diagnostic imaging or similar scenarios. This device is a physical implant.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:
- Not Applicable. This question relates to AI algorithm performance. The "performance" of this device is its mechanical and functional integrity as a joint replacement.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):
- Not Applicable in the AI sense. For this physical device, the "ground truth" for its performance is derived from:
- Engineering specifications and design requirements: Ensuring the device meets critical dimensions, material properties, and functional goals.
- Validated mechanical and fatigue testing standards: Demonstrating durability, strength, and wear resistance under simulated physiological loads.
- Comparison to the predicate device: Establishing substantial equivalence by showing similar performance characteristics and safety profile to an already approved device.
8. The sample size for the training set:
- Not Applicable. There is no "training set" for a physical device in this context. The manufacturing process is controlled, and product testing ensures consistency.
9. How the ground truth for the training set was established:
- Not Applicable. As there is no training set as understood in AI/ML, this question doesn't apply.
Summary regarding the device:
The Zimmer NexGen® Complete Knee Solution Rotating Hinge Knee achieved regulatory clearance (510(k)) by demonstrating substantial equivalence to a predicate device (Finn Knee System). This equivalence was established through:
- Non-clinical performance data:
- Demonstration of similar indications for use, design, materials, and mechanical safety.
- Specific mechanical tests showing performance (e.g., contact area, interlock mechanism, fatigue strength, combined load fatigue, pin loosening) to be acceptable and comparable or superior to the predicate for critical aspects.
- Rationale for why certain tests (like constraint testing or clinical data) were not needed, often due to the nature of the device (constrained) or existing data on similar pre-cleared components (patellofemoral tracking, existing patella devices, polyethylene thickness).
- Lack of clinical data requirement: The FDA determined that clinical data was not needed based on the strong non-clinical data and comparison to the established predicate.
Essentially, the "study" proving the device met "acceptance criteria" was a series of engineering and biomechanical tests designed to confirm that the new device performs as safely and effectively as the predicate, satisfying the 510(k) pathway requirements.
§ 888.3510 Knee joint femorotibial metal/polymer constrained cemented prosthesis.
(a)
Identification. A knee joint femorotibial metal/polymer constrained cemented prosthesis is a device intended to be implanted to replace part of a knee joint. The device limits translation or rotation in one or more planes and has components that are linked together or affined. This generic type of device includes prostheses composed of a ball-and-socket joint located between a stemmed femoral and a stemmed tibial component and a runner and track joint between each pair of femoral and tibial condyles. The ball-and-socket joint is composed of a ball at the head of a column rising from the stemmed tibial component. The ball, the column, the tibial plateau, and the stem for fixation of the tibial component are made of an alloy, such as cobalt-chromium-molybdenum. The ball of the tibial component is held within the socket of the femoral component by the femoral component's flat outer surface. The flat outer surface of the tibial component abuts both a reciprocal flat surface within the cavity of the femoral component and flanges on the femoral component designed to prevent distal displacement. The stem of the femoral component is made of an alloy, such as cobalt-chromium-molybdenum, but the socket of the component is made of ultra-high molecular weight polyethylene. The femoral component has metallic runners which align with the ultra-high molecular weight polyethylene tracks that press-fit into the metallic tibial component. The generic class also includes devices whose upper and lower components are linked with a solid bolt passing through a journal bearing of greater radius, permitting some rotation in the transverse plane, a minimal arc of abduction/adduction. This generic type of device is limited to those prostheses intended for use with bone cement (§ 888.3027).(b)
Classification. Class II.