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The Wenzel Spine VariLift® Cervical Interbody Fusion System is indicated for use in skeletally mature patients with degenerative disc disease (DDD) of the cervical spine with accompanying radicular symptoms at one disc level. DDD is defined as discogenic pain with degeneration of the disc confirmed by patient history and radiographic studies. These DDD patients may have up to Grade 1 spondylolisthesis or retrolisthesis at the involved level.

The Wenzel Spine VariLift Cervical Interbody Fusion System is used to facilitate intervertebral body fusion in the cervical spine and is placed in a unilateral fashion via an anterior approach at the C3 to C7 disc levels using autograft and/or allograft comprised of cancellous and/or corticocancellous bone graft. The Wenzel Spine VariLift Cervical Interbody Fusion System may be used with or without supplemental fixation. Patients should have at least six (6) weeks of non-operative treatment prior to treatment with an intervertebral fusion device.

The Wenzel Spine VariLift® Interbody Fusion System (VariLift®-L/LX 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 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/LX is designed to be implanted bi-laterally via a posterior (PLF) approach or as a single device via a transverse (TLIF) approach. VariLift®-L/LX may be implanted with or without supplemental fixation and is intended for use with autograft and/or allograft comprised of cancellous and/or corticocancellous bone graft to facilitate fusion. VariLift®-A is designed to be implanted bi-laterally via an anterior (ALIF) approach. VariLift®-A may be implanted with or without supplemental fixation and is intended for use with autograft and/or allograft comprised of cancellous and/or corticocancellous bone graft to facilitate fusion.

VariLift-LX Interbody Fusion Device: The VariLift-LX is a self-tapping, 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-LX devices are made of titanium alloy (Ti6AI4V ELI per ASTM F136) and are provided sterile. The VariLift-LX Interbody Fusion Device may be implanted bi-laterally via a posterior lumbar (PLIF) approach or as a single device via a transverse (TLIF) approach.

VariLift-C Interbody Fusion Device: The Wenzel Spine VariLift Cervical Interbody Fusion System is a self-tapping, expandable device with an interior sliding wedge. The devices are cylindrical-ovoid in shape, which is adapted to the general shape of the vertebral end plates. All components are composed of Titanium-6A1-4V ELI alloy that conforms to ASTM F136. The VariLift Cervical device is grooved and fluted with large fenestrations (graft windows) positioned between each of its four quadrants that provide bony contact with the endplates. The device is supplied sterile.

This document is a 510(k) summary for the VariLift®-LX Interbody Fusion System and the VariLift®-C Interbody Fusion System. It primarily establishes substantial equivalence to predicate devices and does not describe acceptance criteria or a specific study proving the device meets those criteria in the way a diagnostic AI device would.

However, I can extract the information provided about performance testing to infer how the device's mechanical performance was assessed.

Here's a breakdown of the available information regarding acceptance criteria and performance, as best as can be inferred from a device clearance document focused on substantial equivalence:

1. Table of Acceptance Criteria and Reported Device Performance

Strict acceptance criteria per se (e.g., sensitivity, specificity, or specific numerical thresholds for clinical outcomes) are not explicitly stated in this 510(k) summary, as it's for a physical implant device designed for mechanical stability and fusion, not a diagnostic AI system.

However, the "performance" described pertains to mechanical testing compared to predicate devices for substantial equivalence. The implicit "acceptance criteria" appear to be that the subject devices perform similarly or equivalently to the predicate devices in biomechanical tests.

• Static compression
• Compression shear
• Torsion testing
• Dynamic compression testing (per ASTM 2077-14)
• Subsidence testing (per ASTM F2267-04)
• Expulsion testing |

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

This document describes mechanical testing of physical device samples, not testing with a "test set" of data in the context of an AI/diagnostic device.

• Sample Size for Test Set: Not applicable in the context of a data-driven test set. For the VariLift-C, testing was conducted on "the smallest new size," implying a limited number of physical samples of that specific device configuration. The exact number of physical devices tested is not specified, but it would typically be a small, statistically justified sample for mechanical tests.
• Data Provenance: Not applicable in the context of data. The "provenance" here is the result of laboratory mechanical testing of physical implants.

3. Number of Experts Used to Establish Ground Truth and Qualifications

Not applicable. This device is a physical implant, not a diagnostic AI device requiring expert ground truth for image or data interpretation.

4. Adjudication Method

Not applicable. This is not a study involving human interpretation or annotation that would require an adjudication method.

5. Multi Reader Multi Case (MRMC) Comparative Effectiveness Study

Not applicable. This is a medical device clearance for an implant, not an AI diagnostic tool that undergoes MRMC studies to assess improvement in human reader performance.

6. Standalone Performance (i.e., algorithm only without human-in-the-loop performance)

Not applicable. This is a physical interbody fusion device, not an algorithm.

7. Type of Ground Truth Used

• For the VariLift-C, the "ground truth" for mechanical performance was established by comparing its performance to established ASTM standards (ASTM 2077-14 and ASTM F2267-04) and to the mechanical performance of the legally marketed predicate device (VariLift-C Interbody Fusion Device, K120603). The implication is that if it performs comparably or better than the predicate device and meets relevant standard recommendations, it's considered safe and effective.

8. Sample Size for the Training Set

Not applicable. This is a physical medical device, not an AI algorithm requiring a training set of data.

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

Not applicable.

In summary: This document is a 510(k) summary for interbody fusion systems, emphasizing substantial equivalence to predicate devices through similar design, materials, and biomechanical performance. It does not contain the types of information typically found in a submission for an AI-powered diagnostic device, such as specific clinical outcome acceptance criteria, sample sizes for data sets, or ground truth established by experts. The "study" described is a series of non-clinical, mechanical tests designed to demonstrate that the new devices perform acceptably and comparably to existing, cleared devices.

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