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When used as a pedicle screw fixation system in skeletally mature patients, the N Fix II System is intended to provide immobilization and stabilization of spinal segments as an adjunct to fusion in the treatment of the following acute and chronic instabilities or deformities of the thoracic, lumbar, and sacral spine: degenerative spondylolisthesis with objective evidence of neurological impairment, kyphosis, and failed previous fusion (pseudoarthrosis).

In addition, when used as a pedicle screw fixation system, the N Fix II System is indicated in patients:

• . who are receiving fusions with autogenous graft only:
• . who are having the device fixed or attached to the lumbar or sacral spine;
• who are having the device removed after the development of a solid . fusion mass.

The subject N Fix II device is a posterior instrumentation system consisting of both pedicle screws and connecting rods. Screws are of polyaxial top-loading design, are composed of titanium 6Al-4V ELI alloy, and are available in 5.5mm, 6.5mm, and 7.5mm diameters, in lengths ranging from 35mm to 60mm. Rods are composed of titanium 6Al-4V ELI alloy and synthetic polycarbonate urethane (PCU) polymer, are 6.0mm in diameter, and are available in lengths from 40mm to 200 mm.

Here's an analysis of the provided text regarding the N Fix II Pedicle Screw System, focusing on the requested information:

Analysis of Acceptance Criteria and Study for N Fix II Pedicle Screw System (K061774)

Based on the provided K061774 510(k) summary, the N Fix II Pedicle Screw System is a mechanical device, and its approval process relies on demonstrating substantial equivalence to predicate devices through non-clinical performance testing, rather than studies involving diagnostic accuracy or human reader performance.

Therefore, many of the requested points related to AI/algorithm performance, ground truth establishment for AI, human expert involvement, and MRMC studies are not applicable to this type of device submission.

1. Table of Acceptance Criteria and Reported Device Performance

Note: The acceptance criteria for this type of device are primarily implicit in demonstrating "substantial equivalence" to existing, legally marketed predicate devices. The study supporting these criteria consists of the non-clinical tests described below.

2. Sample Size Used for the Test Set and the Data Provenance

• Test Set Sample Size: Not explicitly stated in terms of number of screws or rods. The "test set" would consist of the various configurations of the N Fix II Pedicle Screw System (different screw diameters, lengths, rod lengths, and material combinations) subjected to bench testing.
• Data Provenance: The tests are non-clinical, likely performed in a laboratory setting. There is no mention of country of origin for data as it's not patient-derived. The tests would be prospective in nature, as they are specifically conducted to support this submission.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts

Not applicable. For a mechanical device like a pedicle screw system, "ground truth" is established by recognized engineering standards and validated testing methodologies, not by human expert consensus or clinical assessment of images. Performance metrics (e.g., fatigue life, pull-out strength) are objectively measured.

4. Adjudication Method for the Test Set

Not applicable. As the tests are non-clinical and objective (e.g., mechanical load testing), there is no need for an adjudication method by human experts. The results are quantitative measurements against predetermined specifications or in comparison to predicate device performance.

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 device is a surgical implant, not an AI diagnostic or assistive tool.

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

Not applicable. This device is a surgical implant, not an AI algorithm.

7. The Type of Ground Truth Used

The "ground truth" for this type of device is based on:

• Engineering Standards and Specifications: Adherence to recognized national and international standards for spinal implants (e.g., ASTM, ISO standards for fatigue, static mechanical properties, material biocompatibility).
• Performance of Predicate Devices: The measured performance parameters of the N Fix II system must be comparable to, or better than, the performance data available for the cited predicate devices.
• Material Specifications: Verification that the materials used meet industry specifications and are appropriate for human implantation.

8. The Sample Size for the Training Set

Not applicable. This device is a surgical implant; there is no "training set" in the context of machine learning or algorithms.

9. How the Ground Truth for the Training Set was Established

Not applicable. There is no training set for this type of device.

Summary of the Study that Proves the Device Meets Acceptance Criteria:

The study proving the N Fix II Pedicle Screw System meets acceptance criteria is a series of non-clinical performance tests. These tests are conducted in accordance with recognized standards, designed to demonstrate the substantial equivalence of the subject device to its predicate devices in terms of:

• Design: Verifying that the physical dimensions and structural configuration are appropriate and comparable.
• Materials: Confirming the use of biocompatible and mechanically suitable materials, identical to or comparable with those in predicate devices.
• Performance: Measuring mechanical properties such as fatigue strength, static strength, and other relevant biomechanical parameters to ensure they are at least equivalent to, if not superior to, the predicate devices. This involves subjecting device components (screws, rods, and assemblies) to simulated physiological loads.

The document explicitly states: "Nonclinical tests, including those conducted in accordance with recognized standards, have demonstrated the substantial equivalence of the subject device to commercially-available predicates in terms of performance." and "The results of all testing demonstrated the substantial equivalence of the subject devices to the predicate devices."

The conclusion is that the N Fix II Pedicle Screw System is substantially equivalent to legally marketed predicate devices, confirming it meets the necessary safety and effectiveness criteria for its intended use through rigorous bench testing.

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