Prevalence and related clinical factors of thoracic ossification of the ligamentum flavum-a computed tomography-based cross-sectional study

BACKGROUND TEXT: Thoracic ossification of the ligamentum flavum (TOLF) is an uncommon pathology, but it may sometimes grow and cause serious neurologic manifestations. Little has been demonstrated yet about the epidemiology and etiology of TOLF. PURPOSE: This study aimed to estimate the prevalence and clinical characteristics of TOLF. DESIGN: A cross-sectional study was carried out. PATIENT SAMPLE: All individuals who had undergone chest computed tomography (CT) for the evaluation of pulmonary disease or for medical examination for 1 year at our institute comprised the patient sample. OUTCOME MEASURES: Presence of TOLF and the association of these findings with thoracic kyphosis (TK), ossification of posterior longitudinal ligament (OPLL), space available for cord (SAC), age, gender, body mass index (BMI), and diabetes were the outcome measures. METHODS: Prevalence and distribution of TOLF, TK, and concurrent OPLL were analyzed on CT scans. Through reviews of their medical records, clinical characteristics including age, gender, BMI, and diabetes were investigated. Logistic regression analysis was performed to determine the risk factors of TOLF. RESULTS: A total of 4,999 individuals (2,929 men and 2,070 women) were included for the analysis. Thoracic ossification of the ligamentum flavum was found in 1,090 individuals (674 men and 416 women. A single TOLF lesion was noted in 592 individuals and multiple lesions were noted in 498 individuals. The most commonly involved level was T10-T11. Distribution of TOLF showed two peaks: and the highest peak was at the lower thoracic spine (T10-12) and the second highest peak was at T3-T5. Thoracic kyphosis was 31.5 degrees +/- 9.5 degrees in the TOLF group and 29.7 degrees +/- 8.9 degrees in the non-TOLF group (p<.001). Space available for cord/anteroposterior canal diameter ratio in TOLF level was 0.882. Logistic regression analysis showed that gender and TK were significantly associated with TOLF. CONCLUSIONS: Incidental TOLF was found in 21.8% of the study cohort. Gender and TK were related to TOLF. (C) 2017 Elsevier Inc. All rights reserved.