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The KneeAlign® 2 System is a computer controlled system intended to assist the surgeon in determining reference alignment axes in relation to anatomical structures during stereotactic orthopedic surgical procedures. The KneeAlign® 2 System facilitates the accurate positioning of implants and instrumentation, relative to these alignment axes. Example orthopedic surgical procedures include but are not limited to: Total Knee Arthroplasty

The KneeAlign® 2 System is an innovative non-invasive computer assisted surgical navigation system for use in knee arthroplasty procedures. The KneeAlign® System is configured to detect, measure, and display angular measurement changes in a triaxial format. The KneeAlign® 2 System utilizes a palm-sized computer module and reference sensor to generate positional information in orthopedic procedures providing a sequence of steps for registration of anatomical landmarks, calculation of mechanical axes, and positioning of instruments relative to the mechanical axes. In knee arthroplasty procedures, the device assists the surgeon in: Establishing the mechanical axis of the femur, determining the varus/valgus angle and the flexion/extension angle of the cutting block relative to femur. Establishing the mechanical axis of the tibia, determining the varus/valgus angle and the posterior slope angle of the cutting block relative to tibia. The KneeAlign® 2 System comprises a single use computer module and reusable instrumentation.

Here's an analysis of the acceptance criteria and study information based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The provided text does not explicitly state specific numerical acceptance criteria for the KneeAlign® 2 System's performance in terms of accuracy (e.g., within X degrees or Y mm). It instead uses broader statements about the device's ability to be used according to its intended purpose and its substantial equivalence to predicate devices.

However, based on the description of its function, the implicit acceptance criteria would revolve around:

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

• Sample Size for Test Set: The document does not specify a numerical sample size for any of the performance tests. It mentions "bench, and cadaver testing" and "simulated use testing."
• Data Provenance: The document does not explicitly state the country of origin for the data. Given the applicant's location (Aliso Viejo, CA) and the FDA submission, it's highly probable the testing was conducted in the USA. The data is retrospective in the sense that it describes tests performed as part of the device development and validation process before submission.

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

The document does not provide information regarding the number of experts, their qualifications, or how ground truth was established specifically for the test sets (bench, cadaver, or simulated use).

4. Adjudication Method for the Test Set

The document does not describe any adjudication method (e.g., 2+1, 3+1) for the test set.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, and Effect Size

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not explicitly mentioned or described. The study focuses on the device's accuracy and functionality, not its comparative effectiveness with or without human-in-the-loop performance or its impact on human reader performance.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done

The testing described (system accuracy, bench, cadaver, simulated use) would inherently involve standalone performance, as it's evaluating the device's ability to measure and display angles. While the device assists a surgeon, the tests would assess the device's output independently of the surgeon's influence on the measurement capabilities themselves. The system "utilizes algorithms to convert sensor outputs into spatial coordinates, providing graphical representation." This implies the core functionality is algorithmic and tested directly.

7. The Type of Ground Truth Used

The document does not explicitly state the specific type of ground truth. However, for "system accuracy testing" and "bench, and cadaver testing" in the context of orthopedic navigation, ground truth would typically be established by:

• Highly accurate measurement systems/reference standards: For bench testing, this would involve precise mechanical fixtures and measurement tools.
• Anatomical landmarks/pathology: For cadaver testing, ground truth for anatomical axes would be derived from direct anatomical measurements or established radiographic landmarks, potentially verified by experienced surgeons or anatomists.

8. The Sample Size for the Training Set

The document does not provide any information about a specific "training set" or its sample size. This device appears to be a direct measurement and navigation system, rather than a machine learning model that requires a distinct training phase. Its algorithms convert sensor outputs, implying a rule-based or model-based approach rather than a learned one from a large dataset.

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

Since no training set is mentioned (see point 8), there is no information on how ground truth for a training set was established.

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The Navitrack® System – OS Knee Universal is indicated for use as a stereotaxic instrument to assist in the positioning of Total Knee Replacement components intraoperatively. It is a computer controlled image-guidance system equipped with a three-dimensional tracking sub-system. It is intended to assist the surgeon in determining reference alignment axes in relation to anatomical landmarks, and in precisely positioning the alignment instruments relative to these axes by displaying their locations.

Identically as in the predicates, the Navitrack System - OS Knee Universal device consists of software, a computer workstation, an optical tracking system, surgical instruments, and tracking accessories, designed to assist the surgeon in the placement of Total Knee Replacement (TKR) components. Tracking devices are incorporated with given surgical instruments, as well as on to fixation bases that attach to each of the femur and tibia, such to allow the ability to track and display to the user their respective positions intra-operatively. The femur and tibia are displayed to the user in the form of their main alignment axes. The alignment axes are determined and recorded intraoperatively by identifying the key anatomical references that are used clinically to align and position the TKR components. The instruments are schematically represented. The main modifications to the predicates are to incorporate a new set of instruments with universal implant instrument interface features along with corresponding software changes such that the application can be compatible to track a variety of TKR implant lines.

The provided text describes the Navitrack® System - OS Knee Universal and its substantial equivalence to predicate devices, but it does not contain explicit acceptance criteria or a detailed study proving the device meets specific performance criteria.

The document states: "Non-clinical tests were performed to assess that no new safety and efficacy issues were raised in the device. These included tests and analyses to verify that the accuracy and performance of the system was adequate for its intended use and not reduced in comparison to the predicates." However, it does not provide the results of these tests, the specific metrics used, or the thresholds for "adequate" performance.

Therefore, many of the requested sections cannot be filled from the provided text.

Here's a breakdown of what can be extracted and what cannot:

1. A table of acceptance criteria and the reported device performance

2. Sample sized used for the test set and the data provenance (e.g., country of origin of the data, retrospective or prospective)

• Sample size for test set: Not specified.
• Data provenance: Not specified.

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 as the document does not describe a clinical study with expert ground truth establishment. The "non-clinical tests" likely refer to bench testing or simulation.

4. Adjudication method (e.g., 2+1, 3+1, none) for the test set

• Not applicable.

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

• No MRMC study was described. The device is a navigation system, not an AI diagnostic tool for human readers.

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

• The document mentions "non-clinical tests" to verify accuracy and performance "adequate for its intended use and not reduced in comparison to the predicates." This implies standalone testing of the system's accuracy, but no details of the test or results are provided.

7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.)

• Not specified. For non-clinical tests of a navigation system, ground truth would likely involve highly precise measurement instruments (e.g., coordinate measuring machines, optical tracking systems with known accuracy) to establish the true position/orientation of anatomical landmarks or instruments.

8. The sample size for the training set

• The document does not describe a machine learning model that would require a "training set" in the typical sense. This device is a computer-assisted surgical navigation system based on established principles of optical tracking and anatomical landmark registration, not a deep learning model requiring vast training data.

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

• Not applicable.

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