Lumbar apophyseal ring fracture: Prevalence and relationship with spina bifida occulta.

Purpose: To investigate the prevalence of apophyseal ring fracture and its association with spina bifida occulta (SBO).

Methods: A total of 973 patients (mean age 62 years [range 21-90]) with abdominal and pelvic computed tomography scans available were retrospectively evaluated. The prevalence of apophyseal ring fracture and of SBO and the association between these two entities were evaluated.

Results: The prevalence of apophyseal ring fracture was 3.8 % (n = 22) in men and 2.8 % (n = 11) in women; the difference was not statistically significant (p = 0.53). The incidence was highest at L5 in both men (58.3 %, n = 14) and women (38.5 %, n = 5). SBO was found in 92 patients (9.5 %), who comprised 75 men (12.9 %) and 17 women (4.4 %). The prevalence of SBO was 2.95-fold higher in men than in women (p < 0.0001). Apophyseal ring fracture was 2.6 times more frequent in patients who had SBO than in those who did not (7.6 % vs 3.0 %, p = 0.019).

Conclusions: This study identified the lower lumbar levels as the anatomical locations where apophyseal ring fracture was more likely to occur, particularly involving the anterior portion of the cephalad endplate at L3 and L4 and the posterior portion of the cephalad endplate at S1. This finding will be helpful for understanding the site of origin of apophyseal ring fractures, which can be easily overlooked. In addition, apophyseal ring fractures were more frequent in the presence of SBO, which may contribute to understanding their etiology.