The spine is divided into motion segments that include the vertebral bones and the discs. A spinal segment is comprised of the two vertebral body bones and the intervening disc. The discs are the pads between the bones and allow the bones to move on each other. Another important portion of the boney anatomy is the facet joint. These small joints are on the back portion of the bones that provide the stability for the bones to be able to move and rotate, without becoming separated from the discs. As the facet joints move, the cartilage in these joints will wear or degenerate. This arthritis in the facet joint can be caused by the natural wear of the joint or by an injury that has damaged the joint.
All of our joints that have a cartilage surface and also have a lubricating fluid called synovial fluid. The fluid acts to decrease the friction on the cartilage and allow the joints to move more smoothly. In the presence of arthritis, our joints will increase the production of synovial fluid. This excess fluid can help smooth the roughness in the joint a bit more, but may also decrease the motion in the joint. The joint itself can only hold a certain amount of fluid, so as the fluid increases in the joint, the soft-tissues around the joint will become tight like balloon being filled with water. There are times when the fluid leaks out of the joint due to the pressure. If the tissue on the outside of the joint cannot hold the fluid, small holes may develop and allow the fluid to collect in small pockets just outside of the joint. This collection of fluid is called a cyst. These are benign collections of fluid, although some patients feel concern when a cyst is mentioned.
Because the facet joints are next to the nerves in the spine, cysts that form around an arthritic facet joint may press on the nerves. The nerve pressure can cause pain along the course of the nerve. This will cause pain in the arm or leg even though the nerve that is being pinched is in the neck or lower back. These cysts may also form towards the central portion of the spinal canal. If the cyst becomes large enough, it can fill enough of the spinal canal to cause compression on all of the spinal nerves and cause pain in both of the arms or legs. This spinal canal compression is called spinal stenosis. Continued pressure on the nerves can be painful as well as limit the function of the nerve and lead to weakness in the arms or legs. The spinal stenosis may also cause difficulty walking or in handwriting.
The nerve compression, pain and loss of function is usually what brings patients to see an orthopaedic spine specialist. After conducting a complete history and physical, the MRI scan is the way to diagnose the problem in the spine and visualize the size and extent of the nerve compression. Unlike other nerve compression from a disc herniation or bone spur, the cyst can get bigger or smaller in relation to the amount of fluid in the cyst. This can lead to the nerve symptoms to be worse or better within a period of time.
The treatment options are somewhat limited for facet cysts. Some attempts have been made at draining the cysts and injecting cortisone. This has a small chance of relieving the nerve compression for a short period of time. As this method does not change the underlying arthritis that has caused the cyst, the cyst will re-fill with fluid as the joint continues to make synovial fluid to ease the joint roughness. Unfortunately, the only way to effectively treat the cyst is to surgically remove the tissue that creates the envelope for the fluid and then fix the underlying arthritis is by stopping the motion at the facet joint. In order to remove the pressure from the nerve and the cyst material has to be extracted from the spinal canal. This is done through a laminectomy. A fusion of the joint is done so that it no longer moves. When the joint stops moving, it will not need to make the synovial fluid which caused the cyst, which then pressed on the nerve(s). Because it is the mechanical pressure that causes the nerve pain, this procedure works very well to relieve the pain and accompanying loss of function and strength.
If you are found to have a facet joint cyst, it is best to discuss your options with a fellowship-trained spine surgeon to get all the needed information to make an informed decision.
Dr. Jeffrey R. Carlson is a Fellowship-trained, Board-certified, Orthopaedic Spine Specialist who practices at Orthopaedic & Spine Center in Newport News, VA. For more information about Dr. Carlson and his practice, go to www.osc-ortho.com . Check out the Patient Testimonials posted by Dr. Carlson’s patients. For an appointment, please call 757-596-1900.