For decades, the surgical treatment of degenerative lumbar spondylolisthesis has lived in a philosophical tug-of-war.
On one end of the operating table: decompression alone — preserve what stability you can, avoid fusion, and hope the slip behaves.
On the other: decompression plus fusion — take the facets, restore alignment, lock it down, and accept the biomechanical consequences.
Now enter a third contender: motion-preserving posterior arthroplasty. And not just in theory — but tested head-to-head against fusion in a prospective, randomized FDA trial.
Let’s talk about the landmark study of the TOPS System — a posterior facet replacement device evaluated in a multicenter IDE trial against TLIF for grade I degenerative spondylolisthesis.
The Problem: Stenosis + Slip = Surgical Identity Crisis
Spine surgeons know the pathology well. Degenerative spondylolisthesis creates central canal stenosis, lateral recess compression, foraminal narrowing, facet hypertrophy, ligamentum flavum thickening and dynamic instability.
The question has never been whether to decompress symptomatic patients with claudication and radiculopathy; rather, it’s been “What do you do after you remove the facets?”
Decompression alone risks destabilization and, while fusion restores stability, it also sacrifices motion and increases adjacent-level stress.
Posterior facet arthroplasty asks a provocative question: “What if you could resect the pathological facets completely…and replace them with a motion-preserving stabilizer?”
The Device: What Exactly Is TOPS?
The TOPS System (Total Posterior Spine System) is a pedicle screw–based posterior facet replacement implant designed to allow flexion/extension, permit lateral bending, allow axial rotation, control translation and limit abnormal motion.
Design Highlights
The implant consists of two titanium endplates, internal articulating titanium components, polycarbonate urethane buffers, a flexible polyurethane boot and an interlocking woven PEEK ribbon.
The polyurethane boot contains the articulating core and any potential wear debris, protecting neural structures.
It’s not a hinge. It’s not a rod. It’s not a dynamic screw.
It’s a constrained posterior motion device engineered to restore controlled segmental kinematics after complete facetectomy.
It is designed for L2–3, L3–4, and L4–5 — though in this trial, 95% of cases were at L4–5.
TOPS first began development 20 years ago at a small start-up named Impliant. Ron Sacher became Impliant’s CEO in 2001 and guided the company through the design and implementation of the initial TOPS investigational device exemption (IDE) study.
Sacher, however, left Impliant in 2007 to start two other medical device companies, and during this time Impliant was faced with regulatory and financial struggles leading the company to shutdown in 2010. Still believing in the potential of the TOPS System, Sacher in 2011 came back and renamed the company Premia Spine and began working on a redesign of a smaller, easier to implant TOPS System.
The system was approved by the U.S. Federal Drug Administration for commercial sale in the U.S. in 2023. It is indicated for patients between 35 and 80 years of age with symptomatic degenerative spondylolisthesis up to Grade I.
And, notably and uniquely, the TOPS System was statistically superior to spine fusion in its FDA trial.
The Study: A Real Randomized Trial
This wasn’t a registry. This wasn’t a single-center enthusiasm study. It was a prospective, randomized, 37-center FDA Investigational Device Exemption trial (NCT03012776).
Design: 2:1 randomization (TOPS vs TLIF), grade I degenerative spondylolisthesis, moderate lumbar stenosis, failed ≥ 6 months conservative care, Oswestry Disability Index (ODI) ≥ 40, Visual Analog Score (VAS) leg pain ≥ 40 and a minimum 24-month follow-up.
Primary Endpoint: Composite Clinical Success (CCS), defined as: no revision/removal/supplemental fixation, no device breakage, ≥15-point ODI improvement AND no new/worsening neurologic deficit.
Miss one criterion? You fail.
That’s a tough endpoint.
The Cohort: 249 patients, 170 randomized to TOPS, 79 randomized to TLIF.
Demographics? Essentially identical. Mean age: ~63–64, BMI: ~29, Baseline ODI: ~56, VAS back pain:~68 and VAS worst leg pain: ~84
These patients were miserable.
Operative time, blood loss, and length of stay? Similar between groups.
So, this wasn’t a “simpler surgery bias” situation.
The Results: Composite Clinical Success
At 24 months: TOPS: 85%, TLIF: 64%, p = 0.0138
That’s not a subtle signal.
That’s a meaningful separation.
To meet CCS, patients had to improve functionally, avoid reoperation, avoid hardware failure, and avoid neurological decline.
TOPS outperformed TLIF across the board.
Functional Outcomes: ODI. Let’s talk disability.
≥15-Point ODI Improvement: TOPS: 93%, TLIF: 81%
≥30% ODI Improvement: TOPS: 95%, TLIF: 73%, p = 0.004
Mean Improvement: TOPS: 48.4 points, TLIF: 36.2 points
A nearly 50-point ODI improvement is enormous.
For context, prior decompression-alone and fusion trials often report mean improvements in the 17–26 range. These are not incremental gains. These are life-altering shifts in disability.
Back Pain: The Unexpected Twist
You expect leg pain to improve with decompression. But back pain is where things get interesting.
At 24 months: ≥20-Point VAS Back Pain Improvement:
TOPS: 87%, TLIF: 64%, p = 0.015
That’s significant. Why might that be?
Biomechanics Hypothesis
When you remove degenerated facets, eliminate pathological facet loading, restore controlled motion and avoid rigid fixation you may, based on the TOPS study data, reduce abnormal shear forces, decrease muscular guarding, avoid stress concentration at adjacent levels while also preserving physiological load sharing.
Fusion eliminates motion — but it also eliminates normal kinematics. Facet arthroplasty preserves motion — but constrains instability.
That difference may explain the back pain separation.
Leg Pain: Both Work
Leg pain improvement: TOPS: 90%; TLIF: 88%
No meaningful difference.
Both procedures decompress effectively. The difference isn’t neural decompression. It’s what happens biomechanically after decompression.
Reoperation Rates
Surgical reintervention (any lumbar level): TOPS: 5.8% , TLIF: 8.8%
Not statistically significant — but clinically relevant.
More interesting? Adjacent segment disease: TOPS: 0, TLIF: 3 cases.
Range of Motion: The Whole Point
Flexion/Extension ROM: Pre-op TOPS: 3.75° and 24 months post-op: 3.86°
That’s essentially unchanged.
Lateral Bending?: Maintained.
TLIF? Flexion/extension dropped ~3° and lateral bending dropped ~2.5°
As expected, fusion fuses. TOPS maintains motion.
And that’s the central philosophical divide.
How Does This Compare to Decompression Alone Trials?
Consider prior randomized studies: decompression-alone trials often show similar short-term functional gains, reoperation rates tend to be higher and ODI improvements often more modest.
Facet arthroplasty offers something unique: aggressive decompression (like fusion), stability restoration, motion preservation AND low reoperation rate
It attempts to solve the “destabilization vs fusion” dilemma.
The Disease Biomechanics: Why TOPS Works
Degenerative spondylolisthesis involves facet incompetence, disc degeneration, shear instability and dynamic translation.
Fusion treats instability by eliminating motion. By contrast facet arthroplasty treats instability by removing pathological facets, replacing them with a constrained motion device and preserving physiologic rotation and translation limits.
This may, therefore, normalize instantaneous axis of rotation, preserve disc load sharing, prevent hypermobility at adjacent levels and reduce paraspinal muscular compensation.
In other words: It tries to restore normal kinematics instead of abolishing them.
Posterior Arthroplasty vs Lumbar Disc Replacement
There are two FDA-approved lumbar disc replacements: prodisc-L and activ-L. Both are placed anteriorly.
| Disc Replacement | Facet Replacement |
| Anterior approach | Posterior approach |
| Treats axial back pain | Treats stenosis + slip |
| Indirect decompression | Direct decompression |
| Vascular exposure | Familiar posterior corridor |
Posterior arthroplasty fits more naturally into the workflow of stenosis surgery. You’re already there.
You already decompress. Now instead of placing rods and an interbody cage — you implant a motion device.
Safety Profile
Neurologic worsening: TOPS: 3.4%, TLIF: 12.1%
Motor deficits? None in either group.
Device breakage? TOPS: 0, TLIF: 1 case
Adverse events were comparable. No explosion of complications. No unexpected failure pattern.
Narcotics Use: The Quiet Win
At 24 months: TOPS opioid use: 9.9% while TLIF opioid rose to 22.2%.
Not statistically significant — but clinically meaningful. In the era of opioid awareness, fewer chronic pain medications matter.
Surgical Workflow Considerations
From a technical standpoint, facet arthroplasty requires complete facetectomy, uses pedicle screw fixation, avoids interbody work and maintains disc height if preserved.
It may shorten cage-related complications, avoid anterior column violation while also reducing subsidence.
But it demands careful screw placement, precise implant sizing and comfort with motion-device biomechanics.
Limitations
This was an FDA IDE study, so the strict IDE criteria limits generalizability. Follow-up was 24 months — adjacent-level disease needs longer observation. Industry sponsorship always warrants scrutiny and the inclusion criteria was Grade I only — no high-grade slips.
This is not a universal solution for all instability. But for single-level, Grade I degenerative spondylolisthesis with stenosis?
The data are compelling.
The Bigger Question
Spine surgery is at an inflection point.
You have motion preservation in the cervical spine, decades long arthroplasty follow up data, increasing awareness of adjacent segment disease and patients demanding durability and mobility.
The real question isn’t: “Does fusion work?” It does. The question is: “Can we do better than fusion?”
This trial suggests that for the right patient, posterior facet arthroplasty may offer superior composite clinical success, better back pain improvement, maintained motion, comparable safety and LOW reoperation rates.
That’s not incremental.
That’s paradigm-challenging.
Final Takeaway for Spine Surgeons
The TOPS System trial is one of the first high-quality randomized comparisons of posterior motion preservation versus fusion for degenerative spondylolisthesis.
It demonstrates that:
- You can decompress aggressively.
- You can remove pathological facets.
- You can stabilize dynamically.
- You can preserve motion.
- And you may outperform fusion at 2 years.
For decades, we’ve lived in a binary world: Decompress alone…or fuse.
Facet arthroplasty suggests a third option: Resect. Replace. Restore motion.
The next decade will determine whether this is a niche innovation — or the beginning of a new chapter in lumbar spine surgery.
But one thing is certain: The fusion-only era is no longer unchallenged.
Origin Study Title: Prospective, randomized controlled multicenter study of posterior lumbar facet arthroplasty forthe treatment of spondylolisthesis
Authors: Domagoj Coric, M.D.; Ahmad Nassr M.D.; Paul K. Kim M.D.; William C. Welch M.D.; Stephen Robbins M.D.; Steven DeLuca DO; Donald Whiting M.D.; Ali Chahlavi M.D.; Stephen M. Pirris M.D.; Michael W. Groff M.D.; John H. Chi M.D., MPH; Jason H. Huang M.D.; Roland Kent M.D.; Robert G. Whitmore M.D.; Scott A. Meyer M.D.; Paul M. Arnold M.D.; Ashvin I. Patel M.D.; R. Douglas Orr M.D.; Ajit Krishnaney M.D.; Peggy Boltes RN; Yoram Anekstein M.D.; and Michael P. Steinmetz M.D.