The sacroiliac joint (SIJ) is responsible for 15-25% of cases of chronic low back pain. The difficulty in its diagnosis means that sacroiliac pain is frequently underestimated and not adequately treated, giving rise to chronic pain conditions of long duration in its evolution. Many patients with unilateral low back pain, pain radiating to the leg or hip or gluteal region actually suffer from SIJ pain. The complex anatomy of this joint may be responsible for its ignorance and diagnostic difficulties.
Fortunately, more and more pain unit specialists are becoming aware of the existence of this condition and are improving the criteria for its correct diagnosis and treatment.
Location of the pain in the sacroiliac joint
Sacroiliac joint pain is very often associated with pain from the lower lumbar vertebrae. It is typically reflected as low back pain (75%), gluteal pain (94%) or radiating leg pain (28%). The pain may originate in any of the sacroiliac joint structures: articular surfaces, periarticular ligaments and sacroiliac musculature, or a combination of these.
Diagnosis of sacroiliac joint pain
Clinical diagnosis by examination and provocative testing can be very unclear. There is no clinical evidence to link a symptom to a specific disease. The most indicative is if there is unilateral pain below the L5 vertebra or on palpation of the SIJ and absence of other diseases such as neoplasms, tumor or inflammation or neurogenic pain. Likewise, conventional radiology, ultrasound and MRI can result in a high number of false positives and negatives, so the best diagnostic method is considered to be a test block of the sacroiliac joint using local anesthetics. It is a simple block that is performed under radiological or ultrasound control and, if positive, confirms the diagnosis and establishes the basis for definitive treatment.
Treatment of sacroiliac joint pain
Conservative treatments, such as anti-inflammatory and analgesic drugs, rehabilitation and physiotherapy, intra-articular corticoid injections, etc., have been shown to be effective only in some cases, but even so they should be tested beforehand in more aggressive procedures.
In resistant cases, the therapy of choice is radiofrequency of the nerve fibers reaching the sacroiliac structures, i.e. in the posterior branch of L5 and S1, S2 and S3. The nerve reach to the SIJ is mostly dependent on posterior branches, which makes them accessible to the posterior approach with little risk. The variability of the results is explained by the anatomical differences in the distribution of the sacroiliac innervation. In any case, it is a procedure that is performed on an outpatient basis, although within the sterile environment of an operating room. It consists of the interruption by means of electric current of the fibers that carry the painful innervation of the SIJ and is performed percutaneously.
Among the many radiofrequency methods used and widely studied, improvements are reported in 50-70 % of patients for periods as long as 36 months. Fixed intra-articular radiofrequency is the least effective (50%), “cold” radiofrequency causes larger lesions but its efficacy has not been shown to be greater. Among the methods that I prefer for their greater efficacy are the so-called palisade method (consisting of placing the electrodes in a 6 cm path from the sacral foramina to the joint, forming a continuous line of interruption of the nerve transit (image on the left)) or the most technically difficult, the selective blockade of the dorsal roots L5 and S1, S2 and S3 at the exit of the sacral foramina (image on the right) using bipolar radiofrequency.
These techniques, performed with the appropriate precautions, verifying sensory and motor reaction and impedance (relation between the tension and intensity applied and the response produced in the body), hardly report side effects and can be performed with a mild sedation in 20-40 minutes, being of ambulatory regime.