Ossification of the ligamentum flavum of the lumbosacral spine in the polish hospitalized population : a prospective cohort study

The aim of this study was to assess the prevalence, clinical features and distribution of lumbosacral ossifications of the ligamentum flavum (OLF), using MRI, CT and microCT, in hospitalized Polish patients. Patients were recruited prospectively between January 2011 and January 2013. Patients were further qualified to the study group only if CT or MRI of the lumbosacral region detected OLF. Level of OLF excision was determined by the localization of spinal stenosis. After excision the LF fragments containing OLF were stored in a 4% solution of formaldehyde until microCT assessment. A total of 184 agreed to take part in the study. In 50 patients (27.2%) OLF were found. Thus, the study group consisted of 17 women (34%) and 33 men, with a mean age of 55.4 \pm 17.2 years. OLF occurred more often in men (66%) than in women (34%) (p = 0.0014). The most common site for the localization of OLF in women, as well as in men was the L5/S1 level (60% and 53.3% respectively). The mean volume of OLF was 3.87\pm 5.27 mm^{3}\left ( 4.66 \pm 5.71 mm^{3} vs. 1.27 \pm 2.19 mm^{3}, in men and women respectively; p = 0.023 \right ). The LF were thickened in 21 (42%) patients. The mean volume of OLF in patients with normal LF was 4.78\pm 5.95 mm^{3} and in patients with thickened LF 5.33\pm 6.10 mm^{3} (p = 0.75). The prevalence of lumbosacral OLF in the Polish hospitalized population is very high. The most common site of their localization is the L5/S1 level. LF thickening is not associated with OLF formation.