Sensory Mapping of Lumbar Facet Joint Pain

Low back pain is a major contributor to the chronic pain burden in the community. Although there are numerous pain generators in the spine, lumbar facet joints are one of the most common sources of pain. A variety of measures such as physiotherapy, oral analgesics and minimally invasive injections are used to treat lumbar facet joint pain. Facet joint steroid injections and radiofrequency denervations of the facet joint are the most commonly performed minimally invasive pain procedures for lumbar facet joint pain. Radiofrequency denervation is carried out by thermal lesioning of the medial branches that supply the facet joints. Conventionally two medial branches have been shown to innervate one facet joint and based on this, the norm is to lesion two nerves to denervate one facet joint. However, there is some variation in the nerve supply which may account for failure or false negative results of the diagnostic blocks. The aim of the present study is to explore the feasibility of sensory mapping, thereby referral pattern of the lumbar medial branches using suprathreshold stimulation and to correlate the referral patterns with painful areas in the back and leg. It will also test if the present method of lesioning two nerves to denervate one facet joint is appropriate.