What You Need To Know About Adjacent Segment Disease

What Is Adjacent Segment Disease?

ASD is a recognized complication that can occur after spinal fusion surgery. The procedure involves permanently joining two or more vertebrae to stabilize the spine and reduce motion at a painful or unstable segment. Bone grafts and surgical hardware, such as rods, plates, or screws, are commonly used to support the fusion process.

While spinal fusion may reduce localized symptoms in some cases, it also alters how mechanical forces move through the spine. The fused vertebrae stop moving and no longer absorb load, which shifts stress to the spinal segments directly above and below. Over time, this added pressure can lead to degeneration in those adjacent segments. In some cases, this may result in disc herniation, spinal stenosis, or facet joint changes that contribute to new or recurring symptoms.

Where Does ASD Occur?

ASD can develop in any region of the spine where vertebrae have been fused. The risk and presentation vary depending on which part of the spine is involved.

• Lumbar Spine: In the lower back, ASD often follows lumbar fusion procedures. The lumbar region bears a significant amount of body weight, and fusion can redistribute stress to nearby levels. This added load may contribute to degeneration, leading to lower back pain, sciatica, or nerve compression.
• Cervical Spine: In the neck, ASD frequently develops after anterior cervical discectomy and fusion (ACDF). While ACDF stabilizes the cervical spine, it alters natural motion, increasing strain on adjacent levels. This may result in disc wear, spinal narrowing, or symptoms like neck pain, numbness, or arm weakness.
• Thoracic Spine: ASD in the mid-back is less common but can occur after surgery fusing many vertebrae. The thoracic spine is naturally more rigid due to rib attachments. However, segments near the thoracolumbar junction may still experience degeneration when load patterns change.

Causes And Risk Factors In Developing The Condition

ASD may develop due to a combination of internal and external factors that affect spinal structure over time. Although every case is unique, certain conditions within the body and lifestyle-related factors may increase the risk of ASD.

Below are some of the most commonly recognized causes and risk factors associated with ASD.

Natural Degenerative Process

Degeneration of spinal structures is a natural part of the aging process. Over time, intervertebral discs lose hydration and flexibility, while facet joints and supporting ligaments undergo gradual wear. These changes can reduce disc height, increase joint stiffness, and sometimes contribute to nerve compression—even in spinal segments that have never been surgically treated.

Although age-related degeneration often progresses slowly, it may accelerate when combined with other mechanical stressors. This is especially true near areas of prior injury or altered spinal alignment. In some cases, symptoms thought to be ASD may instead reflect typical spinal aging rather than a complication of surgery.

Spinal Fusion Surgery

Spinal fusion is a procedure that stabilizes the spine by permanently joining two or more vertebrae. While it is effective for treating structural conditions, it also changes how the spine moves and distributes mechanical load.

Once fused, the treated segments no longer move, which increases stress on the surrounding vertebrae. This shift in load may contribute to the development of ASD, especially in cases involving the fusion of many vertebrae or the use of rigid implants.

High BMI

A high body mass index (BMI) places added mechanical stress on the spine. This increased load can accelerate wear on intervertebral discs and facet joints, particularly in areas that are already compensating for changes in spinal alignment.

In individuals with spinal fusion, the added strain on nearby segments may raise the risk of developing ASD. Excess body weight is also associated with systemic inflammation and reduced tissue resilience, both of which may contribute to faster spinal degeneration over time.

Genetic Factors

Genetics can influence how the spine ages and responds to mechanical stress. Some individuals may have inherited traits such as early disc degeneration, reduced collagen integrity, or joint instability—all of which may increase the likelihood of developing ASD.

Even without external risk factors, underlying genetic patterns may contribute to faster degeneration in segments adjacent to a fusion site.

Unhealthy Smoking Habits

Smoking is a well-documented risk factor for spinal degeneration.^[3] Chemicals like nicotine can reduce blood flow, limit oxygen delivery to spinal tissues, and interfere with the healing of discs and bone. In patients who undergo spinal fusion, smoking may delay or prevent proper bone union and weaken nearby discs and joints.

These combined effects may increase the risk of developing ASD, particularly as surrounding segments take on more strain after fusion.

Recognizing The Signs And Symptoms

ASD often develops gradually, and its symptoms can resemble those of other spinal conditions. Because it affects levels near a previous fusion site, the discomfort typically reflects increased strain and degeneration in nearby segments.

Recognizing early signs may support timely diagnosis and help manage symptoms before they progress. Common symptoms of ASD include:

• Muscle Weakness: Muscle weakness refers to reduced strength, often caused by disuse, nerve damage, or illness. Read more about Muscle Weakness.
• Neck Pain: Neck pain refers to discomfort in the cervical spine, often caused by tension or injury. Read more about Neck Pain.
• Numbness: Numbness refers to a loss of sensation, usually caused by nerve compression or damage.
• Tingling: Tingling refers to a pins-and-needles feeling, usually caused by nerve pressure or circulation issues. Read more about Tingling.
• Limited Range Of Motion: Limited range of motion is reduced joint movement, often caused by stiffness or injury. Read more about Limited Range Of Motion.
• Radiating Pain: Radiating pain refers to discomfort that spreads from one area to another, often along a nerve path. Read more about Radiating Pain.

Anyone experiencing these symptoms—particularly those with a history of spinal fusion—may benefit from consulting a qualified medical professional. Early evaluation and imaging can support accurate diagnosis and help identify treatment options that aim to reduce further degeneration and support long-term function.

Diagnosis Of Adjacent Segment Disease

Diagnosing ASD requires a combination of clinical evaluation and diagnostic imaging. Since symptoms often overlap with those of other spinal conditions, a careful assessment is crucial for identifying the source of pain and determining whether degeneration in adjacent segments may be contributing to a patient’s symptoms.

Clinical Evaluation

The diagnostic process typically begins with a thorough clinical evaluation. This initial step helps narrow down potential causes and determine whether additional imaging is needed.

• Medical History: A detailed review of past spinal surgeries, particularly fusion procedures, can help establish a timeline of symptoms and identify risk factors associated with ASD.
• Assessment Of Symptoms: Patients are asked to describe the type, location, and intensity of their discomfort, as well as any neurological symptoms, such as numbness, weakness, or changes in balance.
• Physical Examination: The physician performs targeted tests to evaluate spinal movement, nerve function, reflexes, muscle strength, and areas of localized tenderness.

Imaging Studies

Following the clinical evaluation, imaging studies may help assess spinal structures near the fusion site. These tools help visualize alignment, evaluate hardware, and identify signs of adjacent segment degeneration.

• X-rays: Helpful for assessing spinal alignment, bone structure, and hardware placement. X-rays can also reveal disc space narrowing or signs of bone changes near the fusion site.
• Magnetic Resonance Imaging (MRI): Offers detailed views of soft tissues, including spinal discs, nerves, and surrounding ligaments. MRI is often used to detect inflammation, disc degeneration, or nerve compression.
• Computed Tomography (CT) Scans: Provide high-resolution images of bony structures. CT is beneficial for evaluating fusion integrity and identifying subtle fractures and degeneration that are not always visible on X-rays.

What May Happen If The Condition Is Left Unaddressed?

When ASD is not identified or managed early, the condition may gradually progress. What begins as mild discomfort can evolve into more significant mechanical or neurological symptoms, particularly as degeneration continues in spinal segments next to a prior fusion site.

If left unaddressed, the following outcomes may occur:

• Worsening Pain: Localized or radiating discomfort may intensify over time, restricting movement and impacting daily routines.
• Progressive Nerve Compression: Continued degeneration may narrow the spinal canal or foramen, potentially resulting in radiculopathy or, in more advanced cases, myelopathy.
• Loss Of Function: Muscle weakness, numbness, or reduced coordination may affect walking, lifting, or maintaining balance.
• Structural Instability: Adjacent levels may become unstable due to disc collapse or joint deterioration.
• Reduced Quality Of Life: Ongoing symptoms may limit physical activity, impacting emotional well-being and social engagement.
• Need For Additional Surgery: In some cases, further degeneration or instability may lead to revision surgery if conservative options are no longer effective.

Early evaluation and timely care may help reduce symptoms, slow progression, and support long-term spinal stability and function.

Treatment Options For ASD

Treatment for ASD is based on the severity of symptoms, the extent of spinal degeneration, and the individual’s overall health status. In many cases, non-surgical treatments may help manage symptoms and support long-term spinal function. When symptoms persist or progress, interventional or surgical options may be considered.

Treatment approaches may include:

• Artificial Disc Replacement: Artificial disc replacement is a surgical procedure that involves removing a damaged spinal disc and replacing it with an artificial one to help reduce pain and support spinal mobility.
• Decompression Surgery: Decompression surgery is a surgical technique that involves removing or repositioning tissue to reduce pressure within the spinal canal.
• Discectomy Treatment: Discectomy is a surgical procedure that involves removing part or all of a spinal disc to reduce pressure on nearby nerves. Read more about Discectomy Treatment.
• NSAIDs Treatment: NSAIDs (nonsteroidal anti-inflammatory drugs) are medications commonly used to manage inflammation and discomfort in muscles and joints. Read more about NSAIDs Treatment.
• Physical Therapy Treatment: Physical therapy is a structured approach using guided movement and rehabilitation techniques that may help support joint function and mobility. Read more about Physical Therapy Treatment.
• Steroid Injections Treatment: Steroid injections are anti-inflammatory shots that may help manage swelling and discomfort in joints or the spine. Read more about Steroid Injections Treatment.