“Bamboo spine” is a potential complication of ankylosing spondylitis (AS), a chronic inflammatory condition. People with bamboo spine have backbones that have fused, forming one long bone.

The adult spine has 24 small bones, or vertebrae, from the neck to the lower back. These stack on top of each other, forming the spinal column. Usually, these bones can move independently and are flexible. However, in those with bamboo spine, the bones join up and become rigid, causing movement difficulties.

Bamboo spine only occurs in advanced cases of AS, but not everyone with the condition develops it.

This article looks at how bamboo spine develops, the causes of AS and bamboo spine, how doctors diagnose it, and what treatment options are available.

Bamboo spine is a complication of AS, a chronic type of arthritis that causes the spine and other areas of the body to become inflamed. Sometimes, this inflammation leads to the bones of the spine fusing, resulting in one long bone.

This is known as bamboo spine because of how the spine resembles a long, grooved stick of bamboo. The condition causes symptoms that can worsen over time, such as:

  • reduced flexibility in the spine
  • difficulty with movement
  • back pain

Bamboo spine develops due to calcification. During AS flare-ups, the tissues that connect ligaments and tendons to bones become inflamed. They heal, but repeated inflammation and repair can lead to scarring and the formation of extra bone instead of healthy new tissue.

If this happens often enough, the extra bone grows big enough to fuse with other bones, joining them. The vertebrae then stop being able to move independently. When this affects a large portion of the spine, a person has bamboo spine.

Is bamboo spine genetic?

It is not clear exactly what causes AS, but many people with the condition have a particular gene that researchers believe increases the risk of developing AS. This gene produces a genetic marker called HLA-B27. Some scientists think that up to 9 in 10 people with AS have the HLA-B27 marker.

However, the Spondylitis Association of America (SSA) points out that many individuals carry the HLA-B27 marker and never develop AS. In fact, researchers have identified more than 60 other genes that also have links to AS and diseases related to the condition. These include the following genes:

  • ERAP 1
  • IL-12
  • IL-17
  • IL-23

Bamboo spine differs from a healthy spine in that it is much less flexible and features a distinctly different shape.

Usually, the spine has a slight “S” shape when in profile. This shape helps it withstand pressure and distribute body weight evenly. However, when bamboo spine develops, it forces the vertebrae to straighten.

This also makes the spine more rigid and vulnerable to stress, and it cannot absorb shocks as effectively when it becomes fused. It means people with bamboo spine are more prone to spinal fractures, even from small injuries or trauma.

To diagnose bamboo spine, a doctor will perform a physical examination to check the shape and flexibility of the spine.

Bamboo spine can also affect how the chest expands, so a doctor may ask a person to take deep breaths and compare their chest expansion to what they consider typical.

Additionally, a healthcare professional will ask someone about their symptoms. If a person does not already have an AS diagnosis, they may ask questions that help them identify the condition.

If there is evidence they may have bamboo spine or AS, they may recommend an X-ray of the spine to look at how the bones appear. They will look for bones that are square in appearance and close together. They may also recommend an MRI scan to get a more detailed image.

There is no cure for AS or bamboo spine. However, treatment for the condition can help relieve symptoms.

The earlier a doctor can provide treatment, the more they can delay or even prevent the process of the spine fusing.

According to the SSA, treatment for AS involves:

In some cases, a doctor may recommend surgery if the pain is severe or if someone with AS cannot hold their head up, eat, or drink due to the spine’s shape. A doctor may also recommend surgery if the person has sustained an unstable spinal fracture.

Surgery may involve one of the following procedures:

  • Spine osteotomy: Involves opening and straightening the vertebrae in the spine. A surgeon may also insert rods or screws to fuse the remaining bones into a better position, a procedure known as spinal fusion.
  • Laminectomy: Involves removing a part of the spine known as the lamina to create more space for the spine to straighten.
  • Hip replacement: Involves removing the entire hip joint and replacing it with a prosthetic hip. People who have had ankylosing spondylitis for a long time, usually since childhood, are more likely to need a hip replacement.

Osteoporosis is a common complication of AS, so treatment may also involve maintaining bone strength to reduce the risk of fractures. Treatment for osteoporosis may include:

  • bisphosphonates, which help maintain bone density and slow bone loss
  • selective estrogen receptor modulators, which help maintain bone density and reduce the risk of fractures
  • parathyroid hormone, which stimulates the production of new bone cells

People who are consulting a doctor or rheumatologist about AS or bamboo spine may wish to ask the following questions:

  • What is my risk of having bamboo spine?
  • How can we prevent it from developing?
  • I have concerns that I have bamboo spine — how can you test for it?
  • What treatments are available?
  • Is there anything I can do at home to improve the symptoms?
  • Am I a candidate for surgery?
  • Is there a way to lower the risk of complications?

Bamboo spine is a complication of AS that involves the spine’s bones fusing. This changes the spine’s shape and flexibility. A doctor can see if someone has bamboo spine by performing a physical examination and taking medical images, such as an X-ray.

Bamboo spine can reduce movement, make the spine more fragile, and cause pain and stiffness. Early treatment for AS may help prevent the condition. Treatment for bamboo spine may include physical therapy, medication to prevent fractures in the spine, and in some cases, surgery.