Prevalence and distribution of ossification of ligamentum flavum at the adjacent segment of the apex in patients with degenerative kyphosis / 中华骨科杂志

ABSTRACT

Objective:To evaluate the prevalence and distribution of ossification of ligamentum flavum (OLF) at the segments adjacent to the apex in patients with degenerative kyphosis.Methods:All of 74 patients with degenerative kyphosis from January 2018 to December 2021 were retrospective reviewed. All patients were taken anteroposterior and lateral radiographs, CT scan and magnetic resonance imaging (MRI) of the entire spine. Global kyphosis, the morphology of kyphosis and the occurrence of OLF at three segments adjacent to the kyphosis apex were recorded.Results:Of the 74 patients, 54 patients (73%) developed OLF in three segments adjacent to the kyphotic apex. The mean age of the 54 patients was 61.4±6.8 years, and the mean global kyphosis was 49.5°±21.2°. Among other 20 patients without OLF, the mean age was 56.1±7.5 years, and the mean kyphosis angle was 52.1°±19.1°. There was a statistically significant difference in ages ( t=2.92, P=0.005), but no statistically significant difference was observed regarding global kyphosis ( t=0.48, P=0.634). In these 74 patients, 9 patients had angular kyphosis, of which 8 (89%) developed OLF; of the 65 patients without angular kyphosis, 46 patients (71%) developed OLF. There was no significant difference between them (χ 2=1.32, P=0.251). Among the 54 patients diagnosed with OLF, 5 patients (9%) suffered ossification of the posterior longitudinal ligament (OPLL) and 20 patients (37%) suffered dural ossification; 43 patients (80%) developed OLF at proximal segments of apex, 6 patient (11%) developed OLF at distal segments of apex, and 5 patients (9%) developed OLF both at proximal and distal segments of apex. Thirty-two patients (59%) developed OLF at the first segment adjacent to the kyphotic apex, 27 patients (50%) developed OLF at the second segment, and 15 patients (28%) developed OLF at the third segment. Conclusion:Among patients with degenerative kyphosis, about 73% may development OLF within three segments adjacent to the kyphotic apex, and it mostly occurred within two segments adjacent to the apex proximally.