Fusion & Disc Replacement Surgery Success Rates: Clinical Data

Fusion & Disc Replacement Surgery Success Rates: Clinical Data

As a practicing spine surgeon for 35 years, I’ve seen a lot of change in the industry over the last few decades. From the early days of fusion to disc replacement to today’s total joint replacement, every technological advancement was dependent on the one that came before it—and each of these advancements had something to teach us about how the spine works and how best to heal it. At each stage along the way, tracking clinical data and surgical success rates has been critical to helping the medical community find a better way forward.

Knowing how and why surgical treatments for the spine have progressed over time will help you better understand whether the back surgery you're considering will produce the results you expect. To help you begin to extrapolate that information, take a look below at how and why surgical treatments for the spine have progressed over time. Armed with that knowledge, you can improve the odds of making your own back surgery a success.

Laying The Groundwork—Spinal Fusion

Spinal Fusion Without Hardware

For decades, when people had a problem with their spine that required some form of stabilization, the only option available was spinal fusion. In the 1960s and 1970s, fusion—the surgical process of joining two vertebrae of the spine together to stabilize them—was typically done without any kind of surgical fusion hardware. Instead, surgeons simply removed the diseased disc and used a bone graft (bone harvested from the patient’s own body) to fill the hollow space. It was expected that in the months after the procedure (during which time the patient would be immobile in a full-body cast), the natural bone surrounding the graft would absorb it and take its place.

What we learned: This method had only moderate success. Many people who underwent this type of fusion were never able to completely heal because solid fusion of the vertebrae was never achieved, causing a condition known as pseudoarthrosis. As a result, many fusions without hardware were considered failed procedures.

Clinical Data: A clinical study published in the medical journal Spine in 1991 studied 68 patients to compare single-level lumbar fusion with and without hardware. Of the 68 patients, 39 were fused with hardware and 29 who were fused without. Of the patients who were fused without hardware, 58.6% demonstrated pseudoarthrosis—movement of the bone at the location of the fracture—compared to no pseudoarthrosis in patients with hardware. The conclusion: The fusion rate for patients exhibiting single-level disc disease improves with spinal fixation.

Spinal Fusion With Hardware

The results of these early spinal fusions without hardware showed that some type of fixation device was needed to provide immediate stabilization and set the stage for proper fusion of the bones. The early 1980s marked the beginning of fusion with internal hardware—including plates, rods, wires, screws, and hooks. Hardware increased the rate of successful fusions from what was previously around 50% to over around 90% for many indications.

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But it wasn’t long before the concept of a “successful” fusion was called into question once again by a new fact: People with hardware fusion were being re-operated on more frequently than ever before.

What we learned: A greater number of people were developing problems in the areas of the spine adjacent to the fusion due to the extreme rigidity in the fused area. In fusions without hardware, the fused area was often very thin and usually had some plasticity to it. Hardware, on the other hand, introduced complete rigidity into the fused part of the spine, while the surrounding areas remained mobile. Therefore, the stress caused by daily movement was being transferred to the sections of spine above and below the fused location, creating a heavy burden on those adjacent levels. For many patients, those adjacent levels rapidly degenerated as a result, with many studies now reporting 30-40% failure rates within 10 years. Today, for these reasons, fusion has fallen out of favor with many doctors, patients, and insurance companies.

Clinical Data: A study published in Spine in 2016 studied lumbar spine fusion patients in comparison with a group of patients treating back pain with “structured conservative treatment” (non-operative methods). For both groups, substantial disability remained years after the surgery (with a mean follow-up time of 12.8 years after surgery).

Forward Progress: Disc Replacement Surgery Success Rates

Lumbar Disc Replacement Surgery

Meanwhile, medical advancements for hip and knee replacements were taking place, which would eventually have a major impact on the spine. Previously, fusion had been common for arthritic knees and hips. When hip and knee joint replacements came along, those joints were allowed to move naturally after surgery. Movement seemed to be the key, with those surgeries having a 95%+ success rate even 15 years after surgery. Using this information, spine surgeons looked for a way to maintain motion in the spine while still providing stabilization, which was the beginning of artificial disc replacement surgery. In this procedure, surgeons replace a degenerated disc with a new, artificial one, leaving the facet joints intact for movement.

What we learned: Artificial disc replacement surgery only solved part of the mobility problem. The procedure allowed patients to keep moving after surgery, but many people were left with unaddressed pain points. For example, because the procedure was done through the front of the body (an angle from which surgeons didn’t have access to the compressed nerve), there was no way to treat pinched nerves. That often meant additional surgery to decompress the nerve and alleviate pain. Additionally, some patients were left with borderline-arthritic facet joints that would continue to degenerate and cause pain, and would also need to be addressed with additional surgery. As a result, although artificial disc replacement surgery worked very well in the “perfect” patient, challenges with pinched nerves and degenerated facets - which most people have - caused the overall adoption rates to be minimal. Today, anterior disc replacement patients are still considered to be at high risk of needing additional surgery; and most insurance companies are hesitant to pay for this procedure.

Clinical Data Samping: Studies have shown that only a small proportion of fusion and anterior disc replacement patients have experienced a substantial decrease in back pain as a result of surgery (this summary was compiled based on multiple studies). Another study compared fusion patients with anterior disc replacement patients and found that anterior lumbar disc replacement was associated with fewer early reoperations, though beyond one year, rates of reoperation were similar.

Cervical Disc Replacement Surgery Success Rates

At the same time anterior lumbar disc replacement surgery was falling out of favor, more research was being done on cervical disc replacement surgery (in the neck) as an alternative to cervical fusion.

The mechanical loads in the neck are dramatically lower than that of the low back (the 12- to 14-pound weight of the head vs. two-thirds of a person’s entire body weight spread across the hips), which is part of the reason why disc replacement in the neck proved to be successful early on. Cervical disc replacement surgery success rates were also promising: Clinical scores for pain reduction were as good as or better than fusion, and the reoperation rate was four or five times less than fusion. Whereas cervical fusion patients had a 30% chance of needing a second operation within 10 years, we are now seeing a dramatic drop with cervical disc replacements.

Clinical Data Sampling: A study published in PLoS One in 2016 investigated the mid- to long-term outcomes of cervical disc replacement versus cervical fusion. It showed that cervical disc replacement was superior over fusion in terms of overall success, neurological success, serious implant/surgery-related adverse events, secondary procedure, functional outcomes, patient satisfaction and recommendation, and adjacent segment degeneration.

An Important Breakthrough: Total Lumbar Arthroplasty (Joint Replacement)

If disc replacement surgery was a small step forward in restoring spinal health, BalancedBack Total Joint Replacement is a giant leap. All the previous advancements have taught us the importance of motion in addition to stabilization of the spine. BalancedBack Total Joint Replacement is the only technology available that addresses the whole issue (stenosis, facet, and disc degeneration causing leg and back pain).

Rather than eliminating the joint (like fusion) or replacing only the disc (like a disc replacement), the BalancedBack device replaces an entire functional unit of the spine—both the disc and the facet joints. It adds stability after the surgical procedure, just like fusion, but also lets you retain your spine’s natural range of movement.

BalancedBack is the only motion solution that can address leg pain as well as back pain. Because the procedure is performed using a posterior approach (from the back), your surgeons can directly address the conditions causing both leg and back pain, including pinched nerves from spinal stenosis.

BalancedBack patients have experienced a dramatic decrease in back and leg pain after surgery. Patients typically resume their normal, daily activities three months after surgery, with no limitations in movement. As we continue to gather more clinical data related to BalancedBack Total Joint Replacement, we are optimistic that it will change the current landscape of spinal surgery—and change many more patients’ lives for the better.

You can find more about patient outcomes and Patient Stories on our website.

Lumbar Total Joint Replacement

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