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 <6° was classified as no tropism; a difference of 6°-12°, moderate tropism; and a difference 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.