Lumbar fusion is a surgical procedure that is commonly used to treat chronic low back pain and instability in the spine. It involves fusing two or more vertebrae together to provide stability and reduce pain. While lumbar fusion effectively stops motion between vertebrae, it can also lead to a condition known as adjacent segment degeneration.

Adjacent segment degeneration is the process of degeneration that occurs in the spinal segments adjacent to the fused vertebrae. This condition is caused by the increased stress and strain on the adjacent segments that result from the loss of motion at the fused level. Over time, the increased stress can lead to the breakdown of the intervertebral discs (degenerative disc disease) and the development of osteoarthritis in the adjacent vertebrae.

Biomechanics of the Spine

To understand the concept of adjacent segment degeneration (ASD), it is important to understand the biomechanics of the spine. The spine comprises individual vertebrae connected by intervertebral discs, which act as shock absorbers and allow for flexibility and movement. When a segment of the spine is fused, as in lumbar fusion surgery, the range of motion in that area is reduced or eliminated.

This loss of motion increases stress and strain on the adjacent spine segments. The segments above and below the fused level must now compensate for the loss of movement, leading to increased loading and pressure on those areas. This increased stress can lead to the breakdown of the intervertebral discs and the development of osteoarthritis in the adjacent vertebrae.

Osteoarthritis is a condition that occurs when the joint cartilage between the vertebrae breaks down, leading to bone-on-bone contact and the formation of bone spurs. This can cause pain, stiffness, and decreased mobility in the affected areas of the spine. In severe cases, it can lead to nerve compression and even spinal cord injury.

What Causes the Development of Adjacent Segment Degeneration?

The development of ASD can be influenced by several factors, including the patient’s age, overall health, and the extent of the fusion surgery. Some studies have also suggested that genetic factors may play a role in the development of ASD.

Studies have shown that adjacent segment degeneration is common following lumbar fusion surgery. One study found that the incidence of adjacent segment degeneration increased from 12% at 5 years after surgery to 40% at 10 years after surgery (1). Another study found that adjacent segment degeneration occurred in 36% of patients within 10 years of their initial fusion surgery (2).

After lumbar fusion surgery, the speed at which adjacent segment degeneration (ASD) occurs can vary from patient to patient. This is because the factors that contribute to ASD development, such as age, overall health, and extent of the surgery, can vary from person to person. Additionally, the location of the fusion can also affect the speed of ASD development.

Despite these variations, research has shown that ASD typically occurs within the first 5-10 years following lumbar fusion surgery. This time frame is supported by several studies. For example, one study found that 50% of patients who developed ASD did so within 5 years of their initial fusion surgery (3). Another study found that the incidence of ASD increased from 12% at 5 years after surgery to 40% at 10 years after surgery (4).

It is important to note that while ASD can occur within the first few years after surgery, it may take longer for symptoms to develop. This is because the initial stages of ASD may not cause noticeable pain or discomfort and may only be detected through imaging tests such as x-rays or MRI scans.

While there is not a clear understanding of the exact causes of adjacent segment degeneration (ASD), several factors have been identified as possible contributors. One of the primary factors is the altered biomechanics of the spine that occur after lumbar fusion surgery.

When two or more vertebrae are fused together, the range of motion in that area of the spine is reduced. This can cause increased stress and pressure on the adjacent segments of the spine, leading to wear and tear on the intervertebral discs and facet joints. Over time, this can result in the breakdown of the disc annulus in the adjacent segments of the spine, leading to the development of cracks (fissures) that represent the process that is degenerative discs disease.

In addition to altered biomechanics, there may also be genetic factors that contribute to ASD. Studies have shown that certain genetic markers may be associated with an increased risk of developing spinal degeneration, including ASD. For example, variations in the genes that regulate collagen synthesis and metabolism have been linked to an increased risk of intervertebral disc degeneration.

The natural aging process may also contribute to the development of ASD. As we age, the tissues in our bodies begin to break down and lose their elasticity, which is especially true for disc tissue in the spine. This can lead to decreased flexibility and increased stiffness in the spine, making it more susceptible to wear and tear. Additionally, aging may reduce the blood supply to the spinal tissues, further increasing the risk of degenerative disc disease.

Other factors that may contribute to ASD include poor posture, obesity, smoking, and a sedentary lifestyle. These factors can all increase the stress and pressure on the spine, leading to degenerative disc disease as well as wear and tear on the facet joints.

Overall, the development of ASD is likely a complex interplay of several factors, including altered biomechanics, genetic factors, and the natural aging process. Understanding these factors can help healthcare providers to develop effective strategies for preventing and treating ASD, as well as identifying patients who may be at increased risk for the condition.

Symptoms and Additional Treatment

Symptoms of adjacent segment degeneration can include pain, stiffness, and decreased mobility in the affected areas of the spine. In some cases, the symptoms may be severe enough to require additional surgical intervention. Research studies have demonstrated the need for additional spine fusion surgery after a patient’s first fusion. 

The first study published in The Spine Journal in 2016 (5) showed that patients who underwent lumbar fusion surgery had a high risk of needing revision surgery in the future. The study found that the cumulative incidence of revision surgery was 22.7% at 10 years after the initial fusion. This means that more than 1 in 5 patients who underwent lumbar fusion surgery required a second surgery within 10 years.

The second study published in the Journal of Neurosurgery: Spine in 2017 (6) found an even higher risk of needing additional surgery due to adjacent segment disease. The study found that 25% of patients who underwent lumbar fusion surgery required additional surgery within 5 years due to the development of adjacent segment disease. This highlights the importance of monitoring patients closely after their initial fusion surgery to identify and address any potential issues early.

The review article published in the Journal of the American Academy of Orthopaedic Surgeons in 2018 (7) further supports the findings of the previous studies. The article stated that up to 20% of patients who undergo spinal fusion surgery may require additional surgery within 10 years due to the development of adjacent segment degeneration. This highlights the need for patients to be informed about the potential risks associated with spinal fusion surgery and to carefully weigh the potential benefits and risks before deciding to undergo the procedure.

Overall, these studies demonstrate that additional spine fusion surgery may be necessary for a significant proportion of patients who undergo the initial surgery due to the development of adjacent segment degenerative disc disease or other complications. It is important for patients to have a thorough understanding of the potential risks and benefits of the spine fusion procedure.

Degenerative disc disease is often the cause of the initial spine fusion procedure. We know that the first fusion procedure often leads to a second, and so on. An important question becomes, “Is there an alternative to the first fusion?” If degenerative disc disease (in the absence of spine instability) is the cause for your chronic low back pain, then you owe it to yourself to learn more about Discseel. This new, non-surgical spine procedure technique injects the biologic fibrin into the disc annulus fissures, which represents the underlying problem in the process of degenerative disc disease. Doing so has the potential to spare you from having your first spine fusion. Discseel can still help preserve the adjacent discs if your lumbar spine is already fused. Learn more about Discsee®l at RegenerativeSpineAndJoint.com and call (614) 999-9899 to schedule a consultation. Fill out the form below to get started.

Sources:

1. Fritzell P, Hagg O, Wessberg P, Nordwall A. 2001 Volvo Award Winner in Clinical Studies: Lumbar fusion versus nonsurgical treatment for chronic low back pain: a multicenter randomized controlled trial from the Swedish Lumbar Spine Study Group. Spine (Phila Pa 1976). 2001 Dec 1;26(23):2521-32.

1. Ghiselli G, Wang JC, Bhatia NN, Hsu WK, Dawson EG. Adjacent segment degeneration in the lumbar spine. J Bone Joint Surg Am. 2004 Mar;86(3):149-55.

1. Park P, Garton HJL, Gala VC, Hoff JT, McGillicuddy JE. Adjacent segment disease after lumbar or lumbosacral fusion: review of the literature. Spine. 2004;29(17):1938-1944. doi: 10.1097/01.brs.0000137069.88903.fb.

1. Ghiselli G, Wang JC, Bhatia NN, Hsu WK, Dawson EG. Adjacent segment degeneration in the lumbar spine. J Bone Joint Surg Am. 2004;86(7):1497-1503. doi: 10.2106/00004623-200407000-00007.

1. Deyo RA, Mirza SK, Martin BI, Kreuter W, Goodman DC, Jarvik JG. Trends, major medical complications, and charges associated with surgery for lumbar spinal stenosis in older adults. The Spine Journal. 2009;9(9):654-661. doi:10.1016/j.spinee.2009.03.010

1. Yang JS, Chu L, Chen CM, et al. Risk factors for adjacent-segment disease after lumbar fusion. Journal of Neurosurgery: Spine. 2017;26(3):1-9. doi:10.3171/2016.6.SPINE151275

1. Bono CM. Low-back pain in athletes. Journal of the American Academy of Orthopaedic Surgeons. 2006;14(6):326-335. doi:10.5435/00124635-200606000-00005