The role of thoracic facet joints in chronic back pain has received very little attention, as compared to lumbar and cervical facet joints. Thoracic spinal pain can be as chronic and disabling as neck and low back pain, even though it is less common. Linton et al estimated the prevalence of all spinal pain in the general population as 66%, with 15% reporting thoracic pain, 44% reporting neck pain and 56% reporting low back pain.
It is well known that thoracic facet joints can be a source of thoracic pain. Interventional treatments should be considered in patients who fail to respond to conservative management. The diagnosis can be confirmed after the pain is temporarily relieved with diagnostic thoracic medial branch blocks. If the pain relief is at least 50%, radio frequency treatment should be considered for sustained response. Cooled RF is a revolution in radiofrequency technology – giving physicians the power of targeted treatment for symptomatic patients, even in difficult to treat spine anatomy.
Thoracic facet joint syndrome was not described until 1987. In 1994, Dreyfuss et al and Fukui et al in 1997 described thoracic zygapophysial joint pain patterns. Manchikanti et al evaluated thoracic facet joints as potential sources of chronic pain.
Thoracic intra-articular injections have been used to describe the facet joint referral pain patterns, whereas medial branch blocks have been used to determine the prevalence of thoracic facet joint pain as well as for therapeutic purposes. Radiofrequency neurotomy also has been used to manage thoracic facet joint pain.
The thoracic facet joints are paired synovial joints formed by the articulation of the superior and inferior articular facets of adjacent vertebrae. They are true joints in that they are lined with synovium and possess a true joint capsule that is richly innervated and so can become a pain generator. The poor localization of facet joint pain is explained in part by the pattern of overlapping of the sensory innervation of these joints and their close proximity to one another. The posterior rami of a nerve root diverge from the spine at the intervertebral foramen and pass dorsally and caudally through the intertransverse ligament where they divide into medial, lateral, and intermediate branches. The medial branch crosses over the top of the transverse process at a variable point lateral to the point at which the transverse process meets the vertebra. The nerve then travels medially and inferiorly across the surface of the transverse process to innervate the facet joint. The medial branch supplies the lower pole of the facet joint at its own level and the upper pole of the facet joint below. Therefore each facet joint receives its innervation from a medial branch nerve of two posterior primary rami. One branch arises from the nerve at the same level as the joint, and the other from the segmental level above. This explains why the dorsal nerve from the vertebra above the affected level must often also be blocked to provide complete pain relief.
Thoracic medial branch blocks are useful in the diagnosis of pain mediated by thoracic medial braches, usually arising from facet joints. A prognostic medial branch block is useful for predicting whether radiofrequency lesioning of the affected joint(s) may provide long-lasting relief of pain originating from the facet joints. Pain relief from radiofrequency treatment can last between 6 months to 2 years, though this may not always be the case.
The procedure is usually done on an outpatient basis. The procedure is performed under fluoroscopic guidance to ensure accuracy of needle placement. This involves injection of local anaesthetic around the medial branches innervating the relevant facet joints. Patients who experience good pain relief following diagnostic injections are offered radiofrequency denervation treatment.
Thoracic medial branch blocks are diagnostic injections designed to determine if patients back pain is emanating from the thoracic facet joints.
A positive response is considered as one with at least 50% pain relief of at least 2 hours duration when lidocaine is used, and at least 3 hours or longer when bupivacaine was used. Thoracic medial branch blocks are not intended to provide therapeutic benefit. Patients with positive response to thoracic medial branch blocks are offered radiofrequency denervation treatment for a sustained response.
Injections are generally avoided in patients with systemic infection or skin infection over puncture site, bleeding disorders or coagulopathy, allergy to local anaesthetics or any of the medications to be administered.
Complications are rare, particularly if injections are performed using a precise needle-positioning technique. Severe allergic reactions to local anaesthetics are uncommon. Post-procedural pain flare-up is uncommon as steroids are not used for these diagnostic injections. However flare-up is likely following radio frequency treatment, though temporary, lasting between 2-6 weeks. Neurological complications including paraesthesias, numbness and paralysis have been described but are rare. Infections can occur but the incidence is very low as the procedure is performed under strict aseptic conditions. Pneumothorax is a known complication due to proximity of the lung and may need to be treated with insertion of a chest drain.
Radiofrequency neurotomy is recognised as an effective minimally invasive treatment for chronic pain originating in the facet joints. But in order to deliver relief for patients suffering from debilitating pain, successful RF lesioning requires reaching the pain source. Until now, a major challenge in effectively treating chronic thoracic facet pain has been the variable course of the medial branch nerve, particularly at levels T5 to T8.
Variable medial branch paths in the thoracic region make the clinical outcomes of conventional RF ablation inconsistent. COOLIEF thoracic cooled RF uses revolutionary cooling technology for thoracic medial branch neurotomy. Unlike conventional RF, COOLIEF Cooled RF enables placement of a large volume, spherical, repeatable lesion that is optimised in size and position to compensate for the variable nerve course, which increases the probability of capturing the target medial branch nerve.
Cooled RFA uses a cooling probe technology that allows for adjacent tissue to be cooled during the procedure rather than charring of tissues. Cooling is regulated by an attached computer. Internally cooled electrodes can create lesions 8 to 10 millimeters (mm) in diameter, with the depth extending distal to the electrode tip. During the cooled RF procedure, power may be applied for longer periods of up to 150 seconds at 60 degrees Celsius.
Clinical studies of COOLIEF Cooled RF addressing other sources of pain have demonstrated up to 24 months pain relief with improved physical function and a reduction in paid medication usage.