• At each level in the spine there are a pair of small joints called facet joints, which control movements between adjacent vertebrae. The orientation of these joints changes in different parts of the spine, and therefore determines the types of local movement available.
  • Lumbar spine facet joints are orientated perpendicular to your PC screen, allowing the lumbar spine to bend forwards and backwards (flex and extend), as well as bending to either side (side bending).
    • Back View
    • Side View
    • Facet Joint Movement
  • In the upright position, rotation is prevented by one half of a joint contacting the other half (bony locking). Rotation can occur when the lumbar spine is fully flexed forwards, the position of greatest vulnerability to lifting sprains. The lumbar facets change their orientation from the L1 to L5. At L1 they lie perpendicular to the screen, while at L5 they are angled outwards by about 20 degrees. This outward angulation helps prevent the L5 vertebra from slipping forwards in relation to the sacrum.
  • Thoracic spine facet joints are orientated in the horizontal plane of your PC screen, allowing the thoracic spine to bend forwards and backwards (flex and extend), as well as to rotate left and right along its long axis.
    • Back View
    • Side View
  • Side bending is limited in most of the thoracic spine because of the attachment of the ribcage to the thoracic vertebrae. Ribs 1 to 10 are attached to the thoracic vertebrae behind, and to the sternum and lower costal cartilages in front. Ribs 11 and 12 are floating (not attached to the rest of the rib cage), allowing more side bending movement at these levels.
  • Cervical spine  facet joints are also orientated in the horizontal plane of your PC screen, allowing the cervical spine to bend forwards and backwards (flex and extend), rotate left and right along its long axis, and to side bend to either side.
    • Back View
    • Side View
  • The cervical spine therefore has the greatest degree of flexibility of any part of the spine.
• Nerve Supply - as each main spinal nerve passes through the exit foramen of the spine, it gives off a branch (posterior primary ramus) which supplies the structures at the back of the spine, while the main spinal nerve (anterior primary ramus) continues onwards to supply peripheral structures. The posterior primary ramus then divides into 3 branches - medial, intermediate and lateral. The medial branch supplies one half of a facet joint, the central spinal muscles (multifidus), the spinal ligaments and a small area of skin in the midline of the back.The intermediate and lateral branches supply back muscles further away from the midline. As each facet joint is supplied by two medial branch nerves, denervation techniques (see below) require radio frequency lesions to be made at two levels to render one joint painless.
• Facet Joint Arthrosis / occurs most commonly at L4/5 and L5/S1 in the lumbar spine, and at C5/6 and C6/7 in the cervical spine. It is less common in the thoracic spine, in part due to the overall reduced movements of the thoracic joints. Other levels in the spine may be affected as shown on x/rays and MRI scans.

• Indications - Diagnostic intra-articular injections are usually performed to assess whether the source of spinal pain is coming from inflamed osteoarthritic joints. Diagnostic means the treatment is an academic exercise to find the cause of the pain, not to treat it. Intra-articular means the injection is put into the joint space. Afterwards a decision will be made about the need for more permanent treatment. See Warning below. Facet joint injections are performed commonly at the lumbar and cervical levels, but less commonly in the thoracic spine.

• Technique - Injections are performed using x-ray guidance. Local anaesthetic is used to numb the skin before starting. A small diameter 3.5 inch spinal needle is guided into the joint, and then a small volume (less than 1 ml) of local anaesthetic mixed with steroid is injected. Single joints or groups of joints are usually injected at the same sitting. Intravenous sedation with midazolam is sometimes used.

  • Lumbar Facet Injections - Back View

  • Cervical Facet Injections - Back View

  • Cervical Facet Injections - Side View

  • Thoracic Facet Injections - Oblique View

• Problems - The joints can be difficult to inject in people over 65 years due the presence of bony overgrowths at the lip of the joint, which prevent the needle entering. Medial branch blocks are sometimes performed instead under these circumstances. 

• Aftercare - Initial soreness can occur because the needle can bruise some of the local back muscles on the way in. This usually settles with simple pain killers. The injection lasts for about 2-3 weeks, and during this time patients are often asked to keep a diary about the back pain afterwards so that a decision can be made about the result of the treatment and whether further treatment is indicated. 

Medial Branch Blocks

• Indications - some doctors prefer to perform medial branch nerve blocks instead of facet joint injections. They are also used when the joints cannot be entered for anatomical reasons. See Warning below.

• Technique - as for intra-articular injections. In the Lumbar Spine the nerves are blocked as they pass over the upper corner of the transverse process of the vertebra. In the Cervical Spine they are blocked as they pass over the mid point of the waist of each vertebra. In these diagrams the medial branches are labelled as mb. Usually 1.5  ml of local anaesthetic is injected next to the nerve at each level. As each joint has a twin nerve supply from two spinal levels, so that two nerves have to be blocked to cover a single joint.

• Problems - the local anaesthetic lasts only a few hours, so patients have only a short time to find out whether the blocks have been successful before the local anaesthetic wears off. A decision is then made about further treatment.

• Aftercare - local soreness can occur as for intra-articular injections.

• Indications - if there is a favourable response to intra-articular injections OR medical branch blocks, then more permanent techniques may be considered. Facet denervation (rhizolysis) is most commonly performed in the lumbar and cervical regions of the spine. It is rarely performed in the thoracic region. A Radio-frequency Lesion Generator produces an irreversible destructive lesion of the medial branch nerve, blocking the passage of painful messages from the affected facet joint to the rest of the central nervous system. The procedure has risks of being made permanently worse, so careful consideration must be given to the risks and benefits before proceeding. Please discuss these issues with your doctor. See Warning below.

• Technique - The procedure is carried out under intravenous sedation , local anaesthetic and x-ray guidance.  A needle is inserted onto the transverse process of the vertebra where the medial branch nerve is found (mb on the left side of the diagram). When the correct position is found a series of electrical tests are performed to confirm that the needle is as close to the medial branch nerve as possible. An electrical grounding plate is used on the thigh to complete the circuit through the needle and radio-frequency lesion generator. Another electrical test is then carried out to ensure that the needle is far enough away from the main nerve to the legs. Once the correct position has been achieved a radio-frequency electro-cautery lesion is made around the nerve. The medial branch nerve is gently cooked to 80 degrees centigrade for 60 - 90 seconds. For double sided spinal pain, up to six lesions may be needed (three each side). For single sided back pain up to three lesions are made on the side affected. After the lesion has been made, a small amount of local anaesthetic and steroid is placed around the nerve to help reduce inflammation and pain afterwards.

• Problems - the technique is more difficult in the elderly due to osteoporosis causing poor x-ray visualisation. Moderate pain may occur during lesioning and can be helped by entonox and intravenous sedation with midazolam. A general anaesthetic cannot be used because verbal contact has to made at all times during the procedure to help prevent incorrect needle placement during electrical testing. If a lesion is made in a main spinal nerve instead of the medial branch, then the result will be permanent numbness, weakness, and pain in the leg or arm depending on the spinal level treated. This can be avoided by proper electrical testing prior to lesioning, and by the use of x-ray guidance.

• Aftercare - I prefer to keep patients overnight on Meriden Wing to ensure good pain relief. Some doctors allow their patients to go home after a short while. Increased pain in the first 1 - 2 weeks is common in the spine and leg/arm, as the medial branch nerve often complains afterwards. This period usually requires an increase in analgesic consumption. Discuss this with your doctor if you have concerns about this aspect.

• As with any medical treatment, there is a small chance that the pain could be worse afterwards. This means worse spinal pain and worse pain in the arm / leg. In most cases the cause is reactive muscle spasm caused by the needle bruising local muscles (see Analgesic Flow Chart).

• In the case of radio-frequency lesioning the pain can be worse due to inflammation around the lesioned nerves and can last up to 6 weeks afterwards.

• In a small proportion of people permanent nerve pain can result possibly from RF damage to the spinal nerve to the legs. There is no technique to undo this damage, but the pain may be helped by drugs for nerve pain (see nerve pain, anti/convulsants, anti/depressants, anti/arrhythmics).