What the Clinical Evidence Says About TOPS vs. Spinal Fusion

What exactly did the FDA approve?

TOPS is a motion-preserving implant placed in the back of the lumbar spine after a decompression. Decompression is surgery that makes more room for pinched nerves. TOPS attaches with pedicle screws. It is meant to stabilize the treated level without locking that level into a rigid fusion.^[1]

The approved use is narrower than many clinic websites suggest. The FDA indication covers patients who are 35 to 80 years old and have all of the following at one level from L3 to L5:^[1]

• symptomatic degenerative spondylolisthesis up to Grade I (a mild forward slip of one vertebra on another)
• moderate to severe lumbar spinal stenosis (narrowing around the nerves)
• thickening of the ligamentum flavum and/or scarring of the facet joint capsule

Approval means FDA concluded that the device has a reasonable assurance of safety and effectiveness for that labeled use.^[2]It does not mean TOPS is appropriate for every person with spinal stenosis, back pain, or a recommendation for fusion. People outside that age range, people with more than Grade I slip, people who need treatment at more than one level, or people whose problem sits outside L3-L5 are outside this indication.^[3]

Spine Motion Guide is independent of Premia Spine. How that is described, and how sources are handled, is on theAbout andeditorial policy pages.

How was the U.S. clinical trial designed?

The pivotal study was run under FDA investigational device exemption G160168. Patients were treated between 2017 and 2022 at 37 U.S. sites. Researchers randomized 321 people. Of those, 306 had surgery. Assignment was 2 to 1: more people were assigned to TOPS than to lumbar fusion.^[2]

FDA did not wait for every enrolled patient to reach two years. The approval decision used the group that had theoretically reached the 24-month visit when the data were locked in July 2022. That group included 115 TOPS patients and 53 fusion patients. Observed 24-month composite outcome data were available for 108 TOPS patients and 46 fusion patients.^[2]

That is why the same FDA document lists several sample sizes. Three hundred twenty-one people were randomized. Three hundred six had an operation. One hundred sixty-eight had reached the two-year mark on the calendar. One hundred fifty-four of those had a known composite success result. None of these numbers is a typo. They describe different slices of the same study.^[2]

The public ClinicalTrials.gov record linked from the PMA isNCT01933607. The detailed U.S. methods, counts, and 24-month results used for approval are in the SSED.^[4][2]

What did “clinical success” mean?

The trial’s main score was a composite clinical success endpoint at 24 months. Composite means a patient had to clear every required item, not just feel better on one questionnaire. Fail any one item, and that person was not counted as a composite success.^[2]

The required pieces included:

• at least a 15-point improvement on the Oswestry Disability Index, a 100-point scale of how back and leg problems interfere with daily life
• no new neurologic problem, and no worsening problem that stayed worse
• no specified lumbar injections, nerve blocks, or spinal cord stimulator treatment for back or leg pain
• the expected motion or fusion result for the assigned treatment: TOPS was not supposed to fuse; fusion was supposed to fuse
• no implant revision or removal
• no extra hardware at the treated level or the levels next to it
• no major device-related adverse event, such as breakage, loosening, or a one-grade increase in slip

This bar is stricter than “Did pain go down?” A person could have less leg pain and still miss composite success because of an injection, a second operation, or a missed fusion in the control group. That design is why the fusion success rate on this endpoint looks much lower than many patients expect from fusion in everyday practice.^[2]

The main 24-month result

Among patients with observed 24-month composite results, 75.9% of TOPS patients (82 of 108) met every required item. In the fusion group, 23.9% (11 of 46) did. The observed difference was 52 percentage points.^[2]

Observed difference: 52 percentage points.^[2]

The FDA concluded that TOPS was superior to the fusion control for the prespecified composite clinical success endpoint at 24 months in the evaluated patient population.^[2]

Additional findings from the same study

The table below uses outcomes that appear in the FDA SSED. Each row includes how FDA described the comparison. Numbers that look favorable still need that context.

A peer-reviewed paper by Pinter and colleagues reported one-year results from the TOPS investigational arm of the same IDE program. That paper is useful background. It is not a substitute for the 24-month randomized comparison in the FDA SSED.^[5]

Safety and risks

Both TOPS and fusion in this trial were major lumbar spine operations. People can have surgical complications, nerve injury, infection, implant problems, ongoing pain, or another operation. The patient brochure and labeling list these categories in more detail.^[3]

In the FDA safety population used for the approval comparison (115 TOPS patients and 53 fusion patients who had reached the 24-month window), overall adverse-event rates were considered comparable. Any adverse event occurred in 71.3% of TOPS patients and 73.6% of fusion patients.^[2]

Serious adverse events occurred in 34.8% of TOPS patients (40 of 115) and 28.3% of fusion patients (15 of 53). That difference was not statistically significant. The 95% confidence interval included zero. Device-related serious adverse events were reported in 6.1% of TOPS patients (7 of 115) and 9.4% of fusion patients (5 of 53).^[2]

Read the official labeling and patient information for contraindications, warnings, and the fuller risk list. Those documents are linked from the FDA PMA record and the FDA device overview page.^[1][3]

Important limitations

• The approval analysis used an interim 24-month cohort. Not every randomized patient had reached 24 months when FDA reviewed the file.^[2]
• The labeled indication is a selected group: ages 35 to 80, Grade I degenerative spondylolisthesis, moderate to severe stenosis, and one level from L3 to L5.^[1]
• Several additional outcomes showed differences that were not statistically significant, including the time-to-reoperation comparison and the opioid-and-injection comparison.^[2]
• Longer follow-up still matters for durability, implant performance, and changes at the levels next to surgery. FDA required continued follow-up to 60 months in the pivotal cohort.^[2]
• The pivotal study was conducted for a PMA submitted by the device manufacturer, Premia Spine, Ltd. Industry sponsorship does not make the trial unusable. It is a fact readers should know when they weigh the evidence.^[2][4]
• FDA approval is not a personalized treatment recommendation. A qualified spine surgeon has to match imaging, symptoms, and surgical options to one person.

Questions to ask a spine surgeon

These questions are for a clinic visit, not a website quiz. You can also gather history on the candidacy questionnaireand compare procedure ideas on thefusion versus TOPS page.

1. Does my diagnosis match the FDA-approved indication for TOPS?
2. Which spinal level is affected, and is it between L3 and L5?
3. Do my imaging findings show degenerative spondylolisthesis up to Grade I and moderate to severe stenosis?
4. Why are you recommending fusion, decompression alone, or a motion-preserving implant in my case?
5. Which outcomes matter most for me: walking distance, leg pain, back pain, or avoiding another operation?
6. What risks are specific to my health, bone quality, and anatomy?
7. How much experience do you have with each procedure you are discussing?
8. What alternatives should I consider before I decide, including non-surgical care if it is still reasonable?

Sources

1. U.S. Food and Drug Administration.Premarket Approval (PMA) database: TOPS System, P220002. Decision date June 15, 2023.https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpma/pma.cfm?id=P220002
2. U.S. Food and Drug Administration.Summary of Safety and Effectiveness Data: TOPS System, PMA P220002. 2023.https://www.accessdata.fda.gov/cdrh_docs/pdf22/P220002B.pdf
3. U.S. Food and Drug Administration.TOPS System - P220002. Recently approved devices overview, with links to labeling. Approval date June 15, 2023. Patient information (labeling PDF):https://www.fda.gov/medical-devices/recently-approved-devices/tops-system-p220002andhttps://www.accessdata.fda.gov/cdrh_docs/pdf22/P220002C.pdf. Approval order:https://www.accessdata.fda.gov/cdrh_docs/pdf22/P220002A.pdf.
4. U.S. National Library of Medicine.ClinicalTrials.gov. A Study to Evaluate the Safety and Effectiveness of the TOPS System (NCT01933607). Record linked from PMA P220002.https://clinicaltrials.gov/study/NCT01933607
5. Pinter ZW, et al.A Prospective Study of Lumbar Facet Arthroplasty in the Treatment of Degenerative Spondylolisthesis and Stenosis: Results from the Total Posterior Spine System (TOPS) IDE Study. Clinical Spine Surgery. 2023;36(2):E59-E69.https://pubmed.ncbi.nlm.nih.gov/36191093/