Arthritis is a common condition that affects many people, especially as they get older. It causes swelling, pain and stiffness in the joints. When arthritis affects the back, it is called spondylosis or spinal arthritis. This can lead to back pain, stiffness and difficulty moving. MRI scans are often used to get a closer look at the back and investigate the cause of symptoms. But can an MRI detect arthritis in the back? Let’s take a closer look.
What is arthritis?
Arthritis is inflammation and damage to the joints. It causes cartilage, the slippery tissue that covers the ends of bones, to become damaged and worn down over time. This allows the bones to rub together, leading to pain, swelling and stiffness.
There are many different types of arthritis. The most common are:
– Osteoarthritis – this is wear-and-tear arthritis, which usually occurs with aging. It develops gradually over time as the smooth cartilage covering the bones wears away.
– Rheumatoid arthritis – this is an autoimmune disease where the immune system attacks the joints, causing inflammation and joint damage.
– Ankylosing spondylitis – this type of arthritis causes inflammation in the spine joints, leading to chronic pain and stiffness.
What is spondylosis?
Spondylosis is the medical term for spinal arthritis, also known as degenerative arthritis of the spine. It occurs due to age-related wear and tear of the spinal joints and disks in the neck and lower back.
As we age, the disks lose hydration and elasticity. They become thinner, which allows more pressure on the vertebrae. The vertebrae start to rub together, causing the protective cartilage between them to wear away. Bony spurs called osteophytes can also develop and put pressure on spinal nerves.
This degenerative process results in stiffness, pain, numbness/tingling and weakness in the arms or legs. Spondylosis can occur in the cervical (neck) region or lumbar (lower back) region. Lumbar spondylosis mainly affects the lower back.
MRI scans
MRI or magnetic resonance imaging uses strong magnetic fields and radio waves to produce detailed images of the organs and tissues in the body. MRIs can visualize soft tissues like muscles, ligaments, tendons and spinal disks very effectively.
MRI does not use ionizing radiation like X-rays or CT scans. The magnetic fields temporarily realign water molecules in the body. When the fields are turned off, the molecules emit energy that is detected by the scanner. This creates images based on the different water concentrations in various tissues.
Advantages of MRI
Some key advantages of MRI scans are:
– Excellent visualization of soft tissues – MRI can detect subtle changes in structures like spinal disks, vertebrae, nerve roots and tissues around the spine. X-rays cannot capture these details well.
– Multiplanar imaging – MRI scans can acquire images in various planes. This allows evaluation of the spine from many angles.
– No radiation exposure – Unlike CT scans or X-rays, MRI does not use ionizing radiation so there are no risks related to radiation exposure.
– Non-invasive procedure – MRI does not require injections, incisions or implantation of devices. This makes it a relatively safe diagnostic tool.
Limitations of MRI
MRI also has some disadvantages such as:
– Motion artifacts – Any patient movement can affect image quality. Images may need to be reacquired.
– Cannot be used in some medical devices – The magnetic fields used in MRI can disrupt pacemakers, cochlear implants, infusion pumps and other such devices.
– Time-consuming – MRI exams take more time to perform than CT scans or X-rays. Patients have to lie still in the scanner for up to 90 minutes.
– Expensive – MRI scanners are very costly to purchase and maintain. MRI exams are more expensive than other scans.
Can MRI detect arthritis?
Yes, MRI is very effective at detecting spondylosis or degenerative arthritis in the spine. It can spot the signs of arthritis years earlier than X-rays in some cases.
Some of the key things an MRI can show to diagnose spinal arthritis include:
Loss of disk height
MRI can accurately measure the height of intervertebral disks. Disk narrowing and loss of disk height is a hallmark of degeneration. Thinning disks indicate reduced water content and early degeneration.
Disk dehydration
Dehydrated disks appear darker on MRI as they lose signal intensity. Gray or black disks indicate advanced arthritis.
Bone marrow changes
Reactive bone marrow changes occur due to spondylosis. MRI shows edema or fluid in the vertebral body marrow space in areas of compression.
Bone spurs
Osteophytes or bone spurs that form along joint margins and compress the spinal canal are well visualized on MRI.
Spinal cord compression
Severe spondylosis can lead to narrowing of the spinal canal (spinal stenosis). MRI can detect nerve compression and pinched nerves.
Herniated disks
Disk degeneration can cause bulging or herniated disks to compress nerve roots. MRI excellently images the site and severity of disk herniations and nerve involvement.
Inflammation
MRI can detect inflammatory changes in spinal tissues indicating active arthritis. Contrast dye can enhance inflammation visualization.
Comparison of MRI and X-ray findings
X-rays are the first line of imaging for arthritis. But MRI can reveal much more detailed information as illustrated below:
Early arthritis changes
In early osteoarthritis, X-rays may appear normal while MRI already shows subtle cartilage loss, bone marrow lesions and mild inflammation. MRI can thus diagnose arthritis years before it shows up on X-ray.
Soft tissue assessment
X-rays only visualize bones well. MRI also depicts spinal muscles, disks, ligaments and the spinal cord with high resolution.
Bone marrow evaluation
MRI can detect bone marrow edema and inflammation which are not seen on X-rays.
Multiplanar capability
MRI scans in sagittal, axial and coronal planes allow complete assessment of joint structures from all directions. X-rays only provide a 2-dimensional profile view of the spine.
Herniated disks
While X-rays may show indirect signs of nerve compression, MRI can pinpoint the exact location of disk herniations and identify impingement of nerves or the spinal cord.
Spinal stenosis
MRI accurately measures the degree of spinal canal narrowing while X-rays cannot reliably quantify stenosis or its effects on the spinal cord.
Conclusion
In summary:
– MRI provides detailed evaluation of all spine structures – vertebrae, disks, nerves, ligaments, and soft tissues around the joints.
– It can diagnose spinal arthritis in its early stages, much before X-rays show any significant changes.
– MRI is sensitive for detecting even mild disk degeneration, bone marrow lesions, osteophytes and inflammation that confirms arthritis.
– It excellently depicts spinal nerve impingement and cord compression caused by severe spondylosis.
– MRI outperforms X-rays for assessment of soft tissues, bone marrow, multiplanar visualization and quantitative assessment.
So an MRI scan is very effective for diagnosing arthritis or spondylosis of the cervical, thoracic and lumbar spine. It should be considered for anyone with chronic unexplained back pain, especially in the elderly. MRI provides an accurate arthritis diagnosis and helps guide appropriate treatment.