It is a medical sub-specialty that focuses on treating pain in a minimally invasive manner. In recent years, interventional pain management has experienced exponential growth due to:
- Increased awareness of pain.
- Technological improvement and greater availability of imaging techniques.
- The fact that many of the systemic drugs used for the treatment of pain have limited efficacy and a large number of side effects.
Interventional techniques are capable of relieving pain for long periods of time, reducing the consumption of analgesic drugs and improving quality of life. They should be considered in the multidisciplinary management of patients with chronic pain. They can also be a very valuable tool in diseases with a complicated diagnosis, or to decide or plan a specific surgery.
Although they are very safe, in poorly trained personnel they are techniques that can present serious complications, so it is essential that they are performed by sufficiently trained personnel and under appropriate conditions.
We must remember that the treatment of chronic pain should be multimodal and often multidisciplinary, and these treatments are just one more link in an approach that should include physiotherapy, rehabilitation and often psychotherapeutic support.
In this regard, the most common interventional techniques are:
- Nerve blocks: this consists of administering anesthetics and other substances to the periphery of the nerves involved in the painful process to block nerve conduction and prevent pain transmission. They can be performed for diagnostic and/or therapeutic purposes and are important because many times the physical examination and complementary tests are not sufficient to determine the origin of the pain.
- Epidural (epidural) infiltration: epidural infiltrations are used to relieve cervical, dorsal or lumbar pain in the extremities that occurs as a consequence of pathologies that affect these structures. They are indicated for pain secondary to irritation or inflammation of a nerve root (radicular pain or radiculalgia), but have also been used successfully in other pain syndromes, such as discogenic pain (pain produced by lesion of the intervertebral disc), persistent pain after lumbar surgery (formerly known as failed back surgery), canal stenosis (narrow vertebral canal), etc.
- Infiltration of trigger points: used to treat pain due to muscle contracture (myofascial pain), they are based on administering local anesthetic at the point whose palpation triggers the pain (trigger points). It blocks the painful stimulus and relaxes the musculature. In cases of myofascial pain that does not subside after conservative treatment, botulinum toxin can also be used.
- Intra-articular infiltrations: these are used to administer therapeutic substances such as corticosteroids, hyaluronic acid, platelet-rich plasma or even stem cells into the affected joints. Their function is to reduce inflammation, relieve pain, assist physiotherapy and improve mobility. It is advisable to perform them under direct vision (ultrasound, fluoroscopy, computed tomography, magnetic resonance imaging), to confirm the presence of the needle in the intra-articular space. The most commonly treated joints are the shoulder, hip, knee and sacroiliac joints.
- Treatment of posterior vertebral joint pain or facet pain: the facet or interapophyseal joints are behind the spine and are responsible for performing the flexion and extension movements of our spine and are often responsible for back pain. The purpose of infiltration is to diagnose and/or relieve pain that has not responded to other conservative treatments (physiotherapy, rehabilitation, medication, etc.). The techniques are based on locating under direct vision (fluoroscopy or ultrasound) these joints or their anatomical relationships and administer medication, either inside the joint (intrarticular block), or in the periphery of the nerve that provides the painful sensitivity of the joint (blockade of the medial branch of the posterior branch) the latter is performed primarily as a diagnostic method to subsequently perform more lasting procedures such as neurolysis or radiofrequency.
- Sympathetic nervous system blocks: The sympathetic nervous system is part of the autonomic nervous system and involuntarily regulates various functions of our body. Among other things, it participates in the reaction to stress, controls the reflexes of internal organs, and participates in the origin and maintenance of different chronic pains, including visceral pain (internal organs) and neuropathic pain (pain due to nerve injury or malfunction). Selective blocks of the sympathetic nervous system are an option to manage pain mediated by this system. They are always performed under direct visualization with the aid of radiology or ultrasound and use local anesthetics and other substances such as clonidine or corticosteroids. The most common sympathetic blocks are those of the stellate ganglion, the thoracic, celiac, hypogastric and lumbar sympathetic plexuses, the splanchnic nerves and the ganglion impar. In selected cases, for prolonged pain control, ablation (destruction) of the sympathetic plexus responsible for the pain can be performed. Some pain syndromes associated with increased sympathetic nervous system activity include: complex regional syndrome, neuropathic pain, phantom limb, postherpetic neuralgia, etc. They are also used in diseases related to decreased blood flow such as Raynaud’s disease, and peripheral vascular ischemic pain or in uncontrollable visceral pain related to cancer (e.g. pancreatic cancer) or other pathologies such as chronic pelvic pain.
- Neuroablation or neurolysis: The objective of these procedures is to interrupt pain transmission in a prolonged or permanent manner by lesioning the nerve structures responsible for the pain. The lesion can be performed with temperature (heat: thermal radiofrequency, or cold: cryoablation), with chemical substances (alcohol or phenol) or surgically. Prior to these procedures, it is recommended to perform a diagnostic block to predict their effectiveness.
- Thermal or conventional radiofrequency: It consists in injuring with heat the small nerve endings that transmit pain. A special needle is used which is connected to a radio wave generator (radiofrequency) generating heat at the tip of the needle. The lesion of the nerve endings causes the interruption of the transmission of the pain message that reaches the brain and comes from the injured joint. The most frequent indications for thermal radiofrequency are vertebral facet pain (cervical, dorsal or lumbar), trigeminal neuralgia, sacroiliac pain, etc.
- Other types of thermal radiofrequency:
- Bipolar radiofrequency: where the passage of current is between two needles used as electrodes thus increasing the size of the lesion.
- Cooled radiofrequency: special cannulas and a device that uses liquid to cool the tip of the needle are used to achieve greater tissue injury.
- Neuromodulation: Consists of using devices that deliver electrical or chemical agents to reversibly modify the activity of neurons with the intention of treating pain and other diseases. In our routine practice the most commonly used neuromodulation techniques are transcutaneous electrical therapy, pulsed radiofrequency, peripheral nerve stimulation, spinal cord stimulation, dorsal root ganglion stimulation and administration of neuroaxial drugs.