Thoracolumbar kyphosis in postmenopausal osteoporosis patients without vertebral compression fractures

BACKGROUND: To investigate whether thoracolumbar kyphosis (TLK) of the spine is related to the reduction of bone mineral density (BMD) in postmenopausal osteoporosis women, and whether BMD of postmenopausal osteoporosis women can predict the occurrence of TLK. METHODS: This retrospective cohort study included 224 postmenopausal female patients hospitalized for osteoporosis from December 2017 to December 2020, and the control group included 270 postmenopausal female patients hospitalized for thoracolumbar degenerative diseases. The age, body mass index (BMI), visual analogue scale (VAS), and BMD of the lumbar spine [BMD(L)] and femoral neck [BMD(F)] of all patients during admission were recorded. We measured and recorded the Cobb angle of thoracolumbar and the height of the thoracolumbar intervertebral space in the spinal X-ray lateral radiograph. The Pearson and Spearman correlation coefficients were used to calculate the correlation between each parameter in the group. The Chi-square test was used for categorical variables, the independent-sample t-test was used for normally distributed continuous variables, and two-sample non-parametric tests were used for non-normally distributed variables. Binary logistic regression analysis and receiver operating characteristic (ROC) curves were applied to determine independent risk factors and cut-off values, respectively. RESULTS: There were significant differences in the BMD(L), BMD(F), thoracolumbar junction Cobb angle, lumbar spine Cobb angle, T11/12-L1/2 height difference of the posterior and anterior edge of intervertebral space (HDPAIS), single vertebra Cobb angle (SVC), procollagen type 1 N-terminal propeptide (PINP) and 25-hydroxyvitamin D [25-(OH)D] between the study and control groups. Through binary logistic regression analysis, we found that BMD(L), PINP, bone alkaline phosphatase, and 25-(OH)D were independent risk factors for future TLK in postmenopausal women. According to the ROC curve, the prediction accuracy of BMD(L) was the highest. By calculating the critical value, we found that when the BMD(L) T-score <−1.65, postmenopausal women were more likely to develop TLK. CONCLUSIONS: In postmenopausal osteoporosis patients, TLK will occur even if there is no compression fracture, and when the BMD(L) T-score <−1.65, postmenopausal women are more likely to develop TLK in the future.