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This device 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 contraction. This device is intended for use in patients who require augmentation and/or stem extensions due to inadequate bone stock and/or require constrained stabilization for tibiofemoral joint due to soft tissue imbalance.

"UNITED" U2 Total Knee System – PSA Type, Offset Stem Adapter is a modification of cleared Offset Stem Adapter (K082424). This device is manufactured from Ti-6AI-4V alloy (ASTM F136) and identical to the previously cleared offset stem adapter. The Offset Stem Adapter is intended for use in patients with inadequate bone stock. It allows the stem extension to be positioned away from the center of femoral or tibial component, and to center the stem extension within the bone medullar canal. There are three available offset sizes for the subjected device including 2, 4 and 6mm. It is able to be assembled with the femoral component, tibial baseplate and stem component utilizing Morse taper locking mechanism, and the Morse taper design is identical to our cleared Offset Stem Adapter (K082424). The modification does not affect the intended use of the device or alter the fundamental scientific technology of the device.

The provided text describes a 510(k) premarket notification for a medical device, specifically the "U2 Total Knee System - PSA Type, Offset Stem Adapter." The documentation focuses on demonstrating substantial equivalence to predicate devices and includes a section on performance data.

Here's an analysis of the acceptance criteria and the study as described in the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

2. Sample size used for the test set and the data provenance

The document does not specify the sample size used for the fatigue strength test. It also does not explicitly state the data provenance (e.g., country of origin, retrospective or prospective) for this test.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts

Not applicable. This device is a mechanical implant, and its performance is evaluated through engineering tests (fatigue strength), not clinical studies requiring expert ground truth for interpretation of medical data.

4. Adjudication method for the test set

Not applicable, as the evaluation is based on a fatigue strength test rather than subjective interpretation requiring adjudication among experts.

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 document pertains to a mechanical knee implant, not an AI-powered diagnostic device.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done

Not applicable. This document pertains to a mechanical knee implant, not an algorithm.

7. The type of ground truth used

For the fatigue strength test, the "ground truth" would be the engineering standards and specifications against which the device's performance is measured. The document implies that the device met these standards, leading to the conclusion that it is "safe and effective."

8. The sample size for the training set

Not applicable. This document pertains to a mechanical knee implant, not a machine learning model that requires a training set.

9. How the ground truth for the training set was established

Not applicable. As above, this is a mechanical device, not an AI system with a training set.

Summary of the Study:

The primary study mentioned to prove the device meets acceptance criteria is a fatigue strength test. This test was conducted to evaluate the structural integrity and durability of the Offset Stem Adapter. The report concludes that "the test result demonstrated that this device is safe and effective."

The basis for substantial equivalence is primarily focused on the device's similarity in intended use, raw material, design rationale, and sterilization method to previously cleared predicate devices (K082424, K093293, and K102437). This suggests that the fatigue strength test was likely performed to confirm that the modifications (specifically, the different offset sizes) did not negatively impact the mechanical performance compared to the predicate device.

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