Facet tropism is defined as the angular asymmetry between left and right facet joint orientation. Several studies attempted to clarify the correlation between facet tropism and degenerative spondylolisthesis and disc herniation. Although there is no defined consensus, these studies suggest facet tropism is related to increased risk of degeneration and disc herniation. In our study, we attempt to explicate the correlation between facet tropism and discogenic pain.
30 patients with low back pain and/or lower extremity radiating pain who visited our spine clinic from 2015 to 2018 were included. Each patient received provocative discography in one or more lumbar levels. The targeted discs were as followings: L2/3 in one patient, L3/4 in six patients, L4/5 in 18 patients and L5/S1 in 12 patients. Discogenic pain was considered positive if the patient felt the same pain he suffered when the relevant intervertebral disc was irritated. Facet joint angles were measured using axial magnetic resonance images that were taken before provocative discography.
In patients with positive results in provocative discography, correlation between age and tropism was noted: the younger the patient, the greater the tropism. We divided the patients into six groups according to their age. Facet angle differences increased from 0.29 in patients over 70 to 5.34 in patients under 30. However, in patients with negative results in provocative discography or with axial low back pain, no positive association was found. Facet angle differences were similar in all age groups, from 4.64 to 8.53. Nonparametric regression analysis was used for statistical measures.
According to our study, correlation between facet tropism and discogenic pain is noted, especially in younger patients. Thus, chronic discogenic pain diagnosed by provocative discography has more diagnostic value in younger patients as they are more influenced by mechanical factors.
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