The Sixth Lumbar Vertebrae: The Anatomy Behind the Rare Extra Bone

Zawn Villines | November 02, 2015

Sixth Lumbar Vertebrae - Extra Bone in Spine


If you're like most spinal cord injury survivors, your injury has necessitated a crash course in spinal anatomy. Maybe you've even become something of an expert. If so, you know that there are five vertebrae in the lumbar region of the spinal cord, the portion of the spine that curves in your lower back. But like many biological “facts,” there are exceptions to every rule.

Sixth lumbar vertebrae in your spine are uncommon, but far from extraordinary. About 10% of the population has an extra bone in this region, and while additional vertebrae don't typically affect your health, they can complicate treatment for spinal cord injuries.

A Sixth Vertebrae?

The sixth vertebra is typically located just below L5, making it the lowest vertebra and positioning it next to your tailbone. The extra bone is essentially just a harmless anomaly; sometimes it's because one vertebra failed to fuse with another, but in other cases it's unclear why the bone appeared. L6 vertebrae don't grow overnight. If you have the condition, you've always had it. In the overwhelming majority of people, this condition causes no symptoms.

Learn the full anatomy of the spine by downloading the:
Simplified Guide to Understanding a Spinal Cord Injury.


How an Extra Bone Affects Spine Health

An L6 vertebra is not, in and of itself, cause for concern, and most people go through their entire lives without even knowing they have the condition. However, this additional bone can complicate spinal health in some situations.

Doctors sometimes vary the direction they count when identifying spinal structures, and the presence of an additional bone can cause them to give the wrong number; a doctor who doesn't know your condition might label your bottommost lumbar vertebra L5 when it is in fact L6.

Rarely, the L6 vertebra becomes fused to another vertebra, causing back pain. This portion of the spine is also vulnerable to bulging or herniated discs. And because there is an additional bone fitted into the space of five vertebrae, the presence of an L6 can decrease the flexibility of the spine. Lastly, if your spinal cord injury is very low, it might affect your L6 vertebrae.

Will an Extra Vertebrae Affect Spinal Cord Injury Treatment?

A sixth lumbar vertebra should not affect treatment for your spinal cord injury though you should ensure that every physician who treats you knows about the condition. This ensures no one inaccurately counts to the wrong portion of your spine.

An additional vertebra does not increase the odds of suffering a spinal cord injury since the additional vertebra is in essentially the same spot as L5. Moreover, injuries to this vertebrae are unlikely to cause complete immobility since the injury is so low. Pain from this area, due to fusion to another vertebra, may worsen symptoms of a spinal cord injury. If you experience new or worsening symptoms, be sure to notify your doctor.

Learn More About Lumbar Spinal Cord Injuries


Topics: Spinal Cord Injury

Zawn Villines

Written by Zawn Villines

Zawn Villines is a writer specializing in health and legal journalism. Raised by a lawyer and lobbyist who advocated for spinal cord injury survivors, she is a lifelong advocate for spinal injury victims and their loved ones. You can connect with Zawn on Google+ below.

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