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The Wenzel Spine VariLift® Interbody Fusion System (VariLift®-A) is indicated for intervertebral body fusion of the lumbar spine, from L2 to S1, in skeletally mature patients who have had six months of non-operative treatment. The device is intended for use at either one level or two contiguous levels for the treatment of degenerative disc disease (DDD) with up to Grade I spondylolisthesis. DDD is defined as back pain of discogenic origin with degeneration of the disc confirmed by history and radiographic studies.

VariLift®-L is designed to be implanted bi-laterally via a posterior (PLIF) approach or as a single device via a transverse (TLIF) approach. VariLift®-A is designed to be implanted bi-laterally via an anterior (ALIF) approach. VariLift®-L and VariLift®-A may be implanted with or without supplemental fixation and is intended for use with autograft to facilitate fusion.

The VariLift®-L Interbody Fusion Device may be implanted bi-laterally via a posterior lumbar (PLIF) approach or as a single device via a transverse (TLIF) approach. The VariLift®-L is a selftapping, expandable device with an interior sliding wedge and a posterior end cap. The devices are cylindrical-ovoid in shape, which is adapted to the general shape of the vertebral endplates. The VariLift®-L devices are made of titanium alloy (Ti6AI4V ELI per ASTM F136) and are provided sterile.

A design change was made on all sizes of the VariLift®-L devices to increase the surface in contact at the superior and inferior vertebrae. Additionally dimensional modification were made to the instrumentation to ensure all instruments work with all sizes of the modified devices.

This document describes the regulatory submission for the VariLift®-L Interbody Fusion Device (K151900). It focuses on demonstrating substantial equivalence to a predicate device, primarily through non-clinical performance testing.

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

1. Table of Acceptance Criteria and Reported Device Performance:

The document doesn't explicitly state numerical acceptance criteria in a table format. Instead, the acceptance criterion for the non-clinical tests is implicitly that the VariLift®-L Interbody Fusion Devices are "substantially equivalent" to the predicate devices in terms of mechanical performance.

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

• Sample Size: The document mentions that testing was conducted on "the smallest and longest of the new proposed sizes (10x28mm)" for additional device sizes and "the smallest and longest of the proposed new sizes (10x28mm)" for design modifications to existing sizes. It does not specify the exact number of devices tested for each type of test (e.g., how many 10x28mm devices were subjected to static compression).
• Data Provenance: The studies are non-clinical performance tests, usually conducted in a laboratory setting. There is no mention of country of origin of data or whether it's retrospective or prospective, as these terms typically apply to clinical studies with human subjects.

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

Not applicable. The tests are non-clinical mechanical performance studies, not clinical studies requiring expert interpretation of patient data or images to establish ground truth. The "ground truth" here is the physical measurement of mechanical properties according to established ASTM standards.

4. Adjudication Method for the Test Set:

Not applicable. This refers to the process of resolving discrepancies in expert opinions on ground truth in clinical or image-based studies. Mechanical testing relies on objective measurements.

5. If a Multi Reader Multi Case (MRMC) Comparative Effectiveness Study Was Done:

No. An MRMC study is a clinical study involving multiple human readers interpreting medical cases. The provided document describes non-clinical mechanical testing for device equivalence, not a clinical effectiveness study. Therefore, there's no information on how much human readers improve with AI vs. without AI assistance.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done:

Not applicable. This device is not an AI algorithm. It's an interbody fusion device, and the evaluation is mechanical performance.

7. The Type of Ground Truth Used:

The "ground truth" for the non-clinical tests is established by adhering to widely accepted mechanical testing standards from ASTM (e.g., ASTM 2077, ASTM F2267, ASTM Draft Standard F-04.25.02.02). These standards define how to objectively measure properties like static compression, shear, dynamic axial testing, subsidence, and expulsion forces.

8. The Sample Size for the Training Set:

Not applicable. This device does not involve a "training set" in the context of machine learning or AI models.

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

Not applicable, as there is no training set mentioned or implied for this device.

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The Wenzel Spine VariLift Interbody Fusion System (VariLift-L and VariLift-A) is indicated for intervertebral body fusion of the lumbar spine, from L2 to S1, in skeletally mature patients who have had six months of non-operative treatment. The device is intended for use at either one level or two contiguous levels for the treatment of decenerative disc disease (DDD) with up to Grade I spondylolisthesis. DDD is defined as back pain of discogenic origin with degeneration of the disc confirmed by history and radiographic studies.

VariLift-L is designed to be implanted bi-laterally via a posterior (PLIF) approach or as a single device via a transverse (TLIF) approach. VariLift-A is designed to be implanted bl-laterally via an anterior (ALIF) approach. VariLift-L and VariLift-A may be implanted with or without supplemental fixation and are intended for use with autograft to facilitate fusion.

The Wenzel Spine VariLift Interbody Fusion System is offered in two (2) configurations of various sizes that are designed based on surgical approach, and consist of:

• 1. VariLift-L®, which may be implanted bi-laterally via a posterior lumbar (PLIF) approach or as a single device via a transverse (TLIF) approach.
• 2. VariLift-A®, which may be implanted bi-laterally via an anterior (ALIF) approach.

A design change was made on all sizes of the VariLift-L® devices to eliminate the risk of orientation error when loading the implant on the insertion instruments. Additionally, dimensional and threadform modifications were made to the instrumentation to ensure all instruments work with the modified devices.

The VariLift-L® and VariLift-A® are self-tapping, expandable devices with an interior sliding wedge and a posterior end cap. They are grooved and fluted devices with large fenestrations (graft windows) positioned between each of the four quadrants that provide bony contact with the endplates. The devices are made of titanium alloy (per ASTM F136).

The provided text discusses the substantial equivalence of the Wenzel Spine VariLift-L Interbody Fusion Device to a predicate device based on non-clinical performance testing. It does not describe acceptance criteria, a study proving device meets acceptance criteria, or any information related to AI/algorithm performance.

Therefore, I cannot provide the requested information. The text focuses on the mechanical performance of the VariLift-L device and modifications, concluding that it is substantially equivalent to a previously cleared device. There is no mention of an algorithm, AI, human readers, ground truth, or any of the other specific study parameters you asked about.

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