When a patient undergoes spinal surgery that has involved spinal instrumentation, special care must be taken with the vertebrae located above and below the fixed segment (arthrodesis). This concern is due to the fact that with the passage of time changes may occur in these areas that, in some cases, generate pain or functional limitation. This set of alterations is known as adjacent level syndrome or adjacent disc syndrome.
It is a recognized process in spinal neurosurgery and is one of the most frequent reasons why patients undergoing spinal fixation surgery, whether at the lumbar or cervical level, seek specialized assessment. Far from becoming a cause for alarm, understanding its origin helps to make informed decisions and to plan a treatment strategy adapted to the needs of each individual.
What do we mean by adjacent level syndrome?
The spine is a dynamic structure made up of vertebrae, intervertebral discs, facet joints, ligaments and musculature. Each segment is designed to move in harmony with the rest.
When two or more vertebrae are fixed, this balance is modified: when the intervened segment is “fixed”, the neighboring vertebrae must compensate for this loss, increasing their mobility. As time goes by, this overload can generate accelerated degenerative changes in the adjacent levels.
This phenomenon is called adjacent segment disease and involves the wear and tear of the disc close to the arthrodesis, generating structural and functional alterations in the tissues surrounding the fixed level. All this can produce lumbar or cervical pain, irradiation towards the extremities, sensation of stiffness or limitation in daily activities.
Sometimes, studies show degenerative signs without a relevant clinical picture. At other times, the patient presents discomfort that affects quality of life. Individual assessment is essential.
What exactly are adjacent vertebrae?
We call adjacent vertebrae those immediately above or below the fixed segment. If a patient has undergone a lumbar spine fusion at the L4-L5 level, the adjacent vertebrae would be:
- L3-L4 (upper segment)
- L5-S1 (lower segment)
It is in these sections that accelerated deterioration after surgery is most frequently observed. It does not occur in all patients, but it is a known pattern in spinal biomechanics.
Causes of adjacent level syndrome
The origin of adjacent disc syndrome is multifactorial. It is usual to explain that there is no single responsible. Several elements are involved:
Biomechanical alteration after vertebral fixation.
Arthrodesis eliminates motion in a particular segment. As a result, forces that were previously evenly distributed must be rearranged.
Adjacent vertebrae increase their range of motion to compensate for the stiffness of the intervened level, and over time, this increased load may result:
- Accelerated disc degeneration
- Facet overload
- Ligamentous thickening
- Osteophyte formation
- Narrowing of the canal or lateral recesses
This mechanical adaptation is one of the main drivers of the syndrome.
2. Degenerative changes prior to surgery.
Many patients come to the operation with several affected discs, even if only one has caused the most relevant symptoms. Arthrodesis is performed at the level responsible for pain or nerve compression, but the rest may follow their natural degenerative course over the years.
When this evolution coincides with the segment adjacent to the fixation, the symptoms may be mistaken for a deterioration exclusively caused by surgery, when in fact it is part of the natural progression of disc pathology.
3. Level set and length of arthrodesis
The greater the number of fused vertebrae, the more the stress on the free segments increases. Extensive fusions (three levels or more) increase the likelihood of degeneration appearing in contiguous sections in later years.
4. Changes in the physiological curvature of the spine.
Restoring lumbar lordosis or cervical lordosis in fixation surgery is essential. A fused segment without proper alignment changes the overall posture and increases the load on neighboring levels.
Even slight losses of lordosis can alter the distribution of forces and accelerate deterioration.
5. Individual factors
Each spine has its own history. In consultation we assess aspects that clearly influence the risk of developing adjacent level syndrome:
- Age
- Bone quality
- Prolonged sedentary lifestyle
- Obesity
- Smoking
- Rheumatologic diseases
- Weakness associated with the paravertebral musculature.
What factors increase the risk of adjacent level syndrome?
Although anyone who has undergone arthrodesis can develop it, there are profiles in which it is more frequent:
Patients with previous multiple degeneration
When nearby discs already showed signs of wear prior to surgery, they are more likely to progress to symptomatic deterioration.
Advanced age
The spine ages along with the rest of the body. After fixation, adjacent levels may lose hydration and disc height more rapidly.
Suboptimal alignment
A fusion with loss of lordosis increases biomechanical stress on neighboring vertebrae.
Long arthrodesis
The more levels set, the greater the likelihood that adjacent levels will suffer.
Lifestyle and metabolic factors
Smoking, overweight and lack of exercise reduce the capacity of tissues to adapt.
High physical demand
Jobs that require repeated loads or impact sports can accelerate the onset of symptoms.
Most common symptoms
- Persistent low back or neck pain
- Irradiation to extremities
- Tingling or numbness
- Stiffness or a feeling that the back “loses mobility”.
- Episodes of lumbosciatica or brachialgia, in the case of the cervical spine.
- Difficulty sitting or standing for a long time
- Loss of strength in the affected limb (in advanced cases)
When these complaints appear years after spinal fixation, it is advisable to perform complementary examinations and a detailed examination.
How is adjacent level syndrome diagnosed?
The evaluation begins with a clinical interview to understand the evolution of the symptoms. Then we perform a neurological examination and imaging tests.
The main diagnostic tools include:
- Magnetic resonance imaging (MRI): shows the state of the adjacent disc, the dimension of the canal, the presence of herniations or inflammatory changes.
- Dynamic radiographs: to assess mobility, global alignment and stability.
- CT: useful to evaluate facet joints or bone changes, as well as the actual situation of the instrumentation system.
Treatment options when adjacent level syndrome occurs
Conservative treatment
In many patients it works effectively:
- Specialized physiotherapy
- Therapeutic exercise
- Pain control with prescribed medication
- Infiltrations in facet joints
- Foraminal or epidural blocks
- Radiofrequency in selected cases
This approach is usually sufficient if symptoms do not severely limit quality of life.
Minimally invasive surgery
In recent years, minimally invasive techniques have made it possible to resolve numerous cases in a precise manner and with a faster recovery process. Depending on the specific origin of the problem, the following can be considered:
- Microdiscectomy in adjacent disc herniations
- Minimal decompression in localized stenosis, such as foraminal stenosis of the adjacent level.
- Removal of the previously implanted material (if applicable)
The objective is to relieve the compression of the nerve roots and restore the functionality of the affected segment with the least possible impact on the tissues.
When is it appropriate to request a specialized evaluation?
There are three situations in which I recommend a medical assessment without delay:
- New symptoms appear in an area close to the previous surgery.
- Pain progresses and limits daily activities despite conservative treatment.
- There is loss of strength, gait disturbance or persistent numbness.
An early consultation makes it possible to detect whether it is a reversible process or a condition requiring specific intervention.
In summary, adjacent level syndrome is a possible consequence after spinal fixation, but it is not inevitable and should not be viewed as a serious complication. In most cases it progresses slowly and allows stepwise management, starting with conservative treatment and resorting to minimally invasive techniques when necessary.
In-depth knowledge of the biomechanics of the spine and rigorous planning of each surgery are key to minimizing risk. When the problem appears, a specialized assessment makes it possible to determine the exact origin and choose the best therapeutic strategy to recover quality of life.
If you think you may be suffering from this problem, do not hesitate to contact us. Ask for an appointment in one of our offices. We are in Seville, Malaga and Cadiz.
Dr. AndrĂ©s Muñoz – Specialist in Neurosurgery.
đź“ž 609 688 469
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