Facet joint injections for back pain
The facet joints are paired joints at each level of the vertebral column except between the upper two vertebrae of the cervical spine. The joints interlock like roof tiles to maintain the alignment of the vertebral bodies while allowing limited twisting or bending movements. Like joints elsewhere in the body, facet joints can undergo osteoarthritic changes, especially in the older age group or where subject to excessive forces. This causes pain and loss of function but the location of these joints can cause unique problems. The joints are supplied with sensory nerves arising from the adjacent nerve roots and each joint is supplied from two levels. Pain arising from the joints is interpreted as arising from the nerve root distribution (referred pain) and may therefore be felt in the arm for cervical facets or the leg for lumbar facets where it is one possible cause of sciatica. In addition, bony and ligament swelling at these arthritic joints may compress the nerve roots which run adjacent to them and cause symptoms identical to nerve root compression caused by disc prolapse. The joints most frequently affected are the joints which undergo most movement: that is the joints in the lower cervical and lower lumbar spine particularly at the L3/L4, L4/L5 and L5/S1 levels. Surgical treatment for facet joint arthritis is rarely undertaken unless the bony overgrowth around the joints is causing spinal stenosis (cord compression or corda equina syndrome). However it is possible to inject these joints with steroids just as other synovial joints are often injected. While this is not a permanent cure and will not reverse the bony overgrowth (osteophytes) that occurs, it does reduce pain and inflammation and result in some shrinkage of the inflamed joint capsule. Lumbar facet joint injection is a safe procedure which can be repeated if effective. The joints lie at a variable depth from the skin but it is not unusual for the lumbar facets to be 10 cm or more deep in an obese person. The joints can only be adequately injected using x-ray screening. Blind injection is most unlikely to result in adequate needle position. Possible risks from lumbar facet joint injections, like any other joint injection, include infection. There has only been the occasional case reported world wide and never inHereford of many thousands of injected joints over 12 years. A more frequent risk is temporary numbness in the leg due to local anaesthetic around the nerve root but this wears off in an hour or two. Cervical facet joints are close to the vertebral arteries, which supply the brain. Cervical facet joint injection is potentially more hazardous. Safe injection of these joints requires very accurate needle placement preferably using CT scanning.Scientific evidence for the effectiveness of facet joint injections is not strong and is difficult to obtain. It is difficult to separate the placebo effect from the pharmacological effect of such injections but approximately two thirds of patients report worthwhile relief of symptoms and many report relief of symptoms for many months. This is better that the short term effect typically found with the placebo effect. Successful facet joint injection can also be diagnostic and help identify the cause of back pain. Facet injections are generally carried out after disc prolapse and other causes of back pain have been excluded, generally by MRI scan. Lumbar facet injections are almost always done with local anaesthethic and without sedation. Patients can usually go home immediately but should not drive for four hours. Facet joint injections are not widely available in NHS hospitals in the UK. Private medical insurers such as BUPA will cover the cost of these injections but usually require a referral from a specialist. The consultant radiologists at Hereford Radiology Group (www.uk-radiology.co.uk) offer self paying patients lumbar facet injections for a fixed fee of £300 for up to four joints. They do not undertake cervical facet joint injection. MRI scanning is also available for £200. Income from private patients supports the local NHS radiology department.