The Investigation of the Role of the Facet Joint Angle in the Development of L5-S1 Spondylolysis in Young Men

Abstract

Objectives: This study aims to evaluate facet tropism in younger patients with lumbar spondylolysis and to investigate the role of facet tropism in the development of spondylolysis. Patients and methods: Between February 2013 and December 2015, a total of 102 male patients with bilateral L5 pars defect including 53 with spondylolysis and 49 control subjects were included in this case-control study. The facet joint angles were measured bilaterally and axially at the level of L3-4, L4-5, L5-S1 using computed tomography (CT). The classification was made as follows: A difference between two reciprocal facet joint angles of < 6 degrees indicated no tropism, 6 degrees-12 degrees indicated moderate tropism, and > 12 degrees indicated severe tropism. Results: A total of 612 angles including 318 facet joint angles from 53 patients with spondylolysis and 294 facet joint angles from 49 control subjects were measured. L3-4 measurements in the control group showed no tropism in 87.8% (n=43), moderate tropism in 12.2% (n=6), and severe tropism in 0% (n=0). L4-5 measurements in control group showed no tropism in 79.6% (n=39), moderate tropism in 20.4% (n=10), and severe tropism in 0% (n=0). L5-S1 measurements in the control group showed no tropism in 69.4% (n=34), moderate tropism in 28.6% (n=14), and severe tropism in 2.0% (n=1). The mean facet joint angles in the spondylosis group were 32.9 +/- 5.1 degrees, 37.5 +/- 5.4 degrees, and 41.2 +/- 7.8 degrees at the levels of L3-4, L4-5, and L5-S1, respectively. The mean facet joint angles of the control group were 33.2 +/- 5.7 degrees, 39.7 +/- 4.9 degrees, and 42.2 +/- 4.9 degrees at the levels of L3-4, L4-5, and L5-S1, respectively, indicating no significant difference between the right and left mean facet joint angles between the groups (p > 0.05). The frequency of facet tropism and the difference between right and left facet joint angles for all three levels were significantly higher in the spondylolysis group (p < 0.05). Facet tropism at the level of L5-S1 was significantly more frequent than facet tropism at L3-4 level (p < 0.05). Conclusion: Our study results show that the rate of facet joint tropism is higher in the patients with spondylolysis, suggesting that facet tropism seems to play a role in the etiology of spondylolysis as a predisposing factor.