Predictive Risk Factors of Poor Preliminary Postoperative Outcome for Thoracic Ossification of the Ligamentum Flavum

The aim of the present study was to ascertain the independent risk factors of poor preliminary outcome and to reveal the value of these factors in predicting the postoperative prognosis.

A total of 165 patients diagnosed with thoracic myelopathy because of thoracic ossification of the ligamentum flavum (TOLF) were enrolled in this retrospective study. All of them underwent posterior decompressive laminectomy surgery in our hospital from May 2016 to June 2019. The postoperative improvement of symptoms was evaluated using the modified Japanese Orthopaedic Association (mJOA) scoring system. Clinical data, such as age, sex, body mass index (BMI), duration of symptoms, history of hypertension and diabetes, tobacco use, history of drinking, symptoms of incontinence, number of compressed segments, and preoperative mJOA score, were respectively recorded. Radiologic features data included sagittal maximum spinal cord compression (MSCC), axial spinal canal occupation ratio (SCOR), grades and extension of increased signal on sagittal T2-weighted images (ISST2I), types of increased signal on axial T2-weighted images (ISAT2I), and the classification of ossification on axial CT scan and sagittal MRI. The t-test, the χ² -test, Fisher's exact test, binary logistic regression analyses, receiver operating characteristic (ROC) curves, and subgroup analyses were used to evaluate the effects of individual risk predictors on surgical outcomes.

A total of 76 men and 89 women were enrolled in this study. The mean age of all patients was 58.53 years. After comparison between two groups, we found some risk factors that may be associated with postoperative outcomes, such as age, preoperative mJOA score, BMI, history of hypertension, MSCC, SCOR, grade and extension of ISST2I, type of ISAT2I, axial type of ossification, and sagittal type of ossification (P < 0.05, respectively). Binary logistic regression analysis revealed that older age (odds ratio [OR] = 1.062, 95% confidence interval [CI] = 1.006-1.121, P = 0.030), number of compressed segments (OR = 1.916, 95% CI = 1.250-2.937, P = 0.003), bilateral and bridged types of ossification (OR = 4 314, 95% CI = 1.454-8.657, P = 0.019; OR = 6.630, 95% CI = 2.580-17.530, P = 0.004), and grade 1 and 2 ISST2I (OR = 8.986, 95% CI =3.056-20.294, P < 0.001; OR = 7.552, 95% CI = 3.529-16.004, P < 0.001) were independent risk factors for a poor preliminary postoperative outcome. ROC curve analysis showed that the grade of ISST2I had an excellent discriminative power (area under the curve [AUC] = 0.817). In addition, risk factors have different values for predicting the clinical outcome in each subgroup.

Age, duration of symptoms, number of compressed segments, SCOR, grade, and extension of ISST2I and classification of ossification were associated with the preliminary prognosis, and the intramedullary increased signal on sagittal T2-weighted MRI was highly predictive of poor postoperative outcome.