Optimal Performance of RFA of the Nerves Supplying the Posterior Sacroiliac Joint Complex.

The procedure is supposed to ablate the sacral lateral branches that form the medial cluneal nerves (MCN). The anatomy of the sacral lateral branches is such that, in addition to innervating the SIJ, distal branches of these nerves also innervate the skin over the buttock through MCN (12,13). SLB blocks (usually with 0.5 ml of 1% Lidocaine or 0.5% Bupivacaine) are performed proximal to the origin of both the nerves to the SIJ and the cutaneous branches. Therefore, a technically accurate block should anesthetize not only the SIJ but also the skin of the buttock regardless of the patient symptoms. Hypoesthesia of the buttock would, therefore, be a quality-assurance sign that the block has been performed in a technically correct fashion. Similarly, if the target nerves have been accurately ablated by RFA hypoesthesia of the buttock should ensue, as an expected effect of the procedure.