The Role of the Features of Facet Joint Angle in the Development of Isthmic Spondylolisthesis in Young Male Patients with L5-S1 Isthmic Spondylolisthesis.

Objective To investigate facet tropism and its role in development of lumbar isthmic spondylolisthesis (IS) in young men. Methods From March 2013 to May 2016, bilateral facet joint angles were measured axially at L3-4, L4-5, and L5-S1 on lumbar computed tomography (CT) in 97 participants (46 patients with IS and 51 control subjects) 20–29 years old. A difference between the 2 corresponding facet angles of 12°, severe tropism. Results We measured 276 facet angles from 46 patients with IS and 306 facet angles from 51 control subjects. For patients with IS, there was no tropism in 43.5% ( n  = 20), moderate tropism in 50% ( n  = 23), and severe tropism in 6.5% ( n  = 3) at L3-4. For L4-5, there was no tropism in 28.3% ( n  = 13), moderate tropism in 60.9% ( n  = 28), and severe tropism in 10.9% ( n  = 5). For L5-S1, there was no tropism in 32.6% ( n  = 15), moderate tropism in 39.1% ( n  = 18), and severe tropism in 28.3% ( n  = 13). For the control group, there was no tropism in 86.3% ( n  = 44), moderate tropism in 13.7% ( n  = 7), and no severe tropism at L3-4. For L4-5, there was no tropism in 80.4% ( n  = 41), moderate tropism in 17.6% ( n  = 9), and severe tropism in 1.9% ( n  = 1). For L5-S1, there was no tropism in 68.6% ( n  = 35), moderate tropism in 29.4% ( n  = 15), and severe tropism in 1.9% ( n  = 1). Conclusions Facet angle tropism is seen in a high proportion of patients with IS and seems to be a predisposing factor in the etiology of IS.