Predictors of surgical outcome in thoracic ossification of the ligamentum flavum: focusing on the quantitative signal intensity

Abstract

The association between intramedullary increased signal intensity (ISI) on T2-weighted magnetic resonance imaging (MRI) and surgical outcome in thoracic ossification of the ligamentum flavum (OLF) remains controversial. We aimed to determine the impact of signal change ratio (SCR) on thoracic OLF surgical outcomes. We retrospectively reviewed 96 cases of thoracic OLF surgery and investigated myelopathy severity, symptom duration, MRI and computed tomographic findings, surgical technique and postoperative recoveries. Surgical outcomes were evaluated according to the modified Japanese Orthopaedic Association (JOA) score and recovery rate. JOA recovery rate <50% was defined as a poor surgical outcome. By multivariate logistic regression analysis, we identified risk factors associated with surgical outcomes. Forty patients (41.7%) had a recovery rate of <50%. In receiver operating characteristic (ROC) curves, the optimal preoperative SCR cutoff value as a predictor of poor surgical outcome was 1.54. Multivariate logistic regression analysis revealed that a preoperative SCR ≥1.54 and symptom duration >12 months were significant risk factors for a poor surgical outcome. These findings suggest that preoperative SCR and duration of symptoms were significant risk factors of surgical outcome for patients with thoracic OLF. Patients with preoperative SCR ≥1.54 can experience poor postoperative recovery.Thoracic ossification of the ligamentum flavum (OLF) is a relatively rare cause of myelopathy that generally requires surgical treatment owing to its progressive nature and its poor response to conservative therapy. Reportedly, the prevalence of OLF ranges from 3.8% to 26% 1,2 . Patients with thoracic OLF have various symptoms, such as sensory abnormality of the trunk or lower extremities, gait disturbance, and urinary dysfunction 3 . Although decompressive surgery is an available treatment option for this disease, the surgical outcome is not always satisfactory. Prognostic guidelines are still unclear and it is very difficult for the surgeon to predict postoperative recovery.Magnetic resonance imaging (MRI) is a valuable tool before surgical decompression because it allows the visualisation not only of the magnitude of spinal cord compression but also of intramedullary signal intensity. The presence of intramedullary increased signal intensity (ISI) on T2-weighted imaging (WI) in patients with thoracic OLF reflects chronic spinal cord compression. However, the significance of ISI on T2-WI for postsurgical prognosis remains controversial [4][5][6][7][8][9][10][11][12][13][14][15] . Definitive information is not available because most descriptions of signal changes are qualitative in nature. Wang et al. 16 first used signal change ratio (SCR) as a quantifiable measure of signal intensity in cervical compressive myelopathy. This quantitative method may also be used to evaluate the signal change of the spinal cord in thoracic OLF. The purpose of this study was to assess the risk factors associated with poor surgical outcome, pa...

Clinical Outcomes and Prognostic Factors in Patients With Myelopathy Caused by Thoracic Ossification of the Ligamentum Flavum

“…With recent developments and advances in MRI techniques and software, we can quantify various signal intensities of the spinal cord using ROIs in these patients. Zhang et al [ 18 ] reported that preoperative SIR on T2WI of MRI could be potentially useful for the prediction of surgical outcomes in patients with thoracic OLF. Results of the present study corresponded with the results of an earlier study, which reported low SIR as a prognostic factor correlated with high JOA RR.…”

“…Results of the present study corresponded with the results of an earlier study, which reported low SIR as a prognostic factor correlated with high JOA RR. Furthermore, 2 previous studies reported that patients with preoperative SIR greater than or equal to 1.54 or 1.55 are likely to experience poor postoperative recovery [ 12 , 18 ]. In accordance with previous studies [ 12 , 18 ], mean SIR (1.41±0.23) was higher in the poor RR group than (1.16±0.17) in the good RR group (p=0.009) ( Table 2 ).…”

“…The modified Japanese Orthopaedic Association (JOA) scoring system was used to evaluate the neurological status of patients before and after surgical decompression, which excluded the sections regarding upper extremity function [ 10 ]. The maximum score of 11 indicates normal function, total score ≤3 was considered severe neurological impairment, 4–6 was moderate, and ≥7 was mild [ 18 ]. Postoperative improvement of symptoms was estimated on the basis of the recovery rate (RR)=(postoperative JOA score−preoperative JOA score)/(11−preoperative JOA score)×100%.…”

“…Postoperative improvement of symptoms was estimated on the basis of the recovery rate (RR)=(postoperative JOA score−preoperative JOA score)/(11−preoperative JOA score)×100%. A score of 75 to 100% was designated as excellent, 50% to 74% as good, 25% to 49% as fair and 0% to 24% as poor [ 18 - 20 ]. Therefore, the extent of recovery was defined by RR, with good (RR≥50%), poor (RR<50%).…”

The incidence and risk factors of postoperative neurological deterioration after posterior decompression with or without instrumented fusion for thoracic myelopathy

“…1), indicating that the spinal cord is in the condition of ischemia, and postoperative ND may occur due to the ischemia reperfusion. [21] As Zhang et al [22] noted that patients with preoperative signal change ratio (SCR) ≥1.54 can experience poor postoperative recovery, Li et al [23] demonstrated that intramedullary signal change on T 2 WI and preoperative severity of myelopathy were confirmed and significantly correlated with the surgical outcome. Second, for patients suffering from both ventral and dorsal compression to the dural mater, the spinal cord is vulnerable, and mild traction or only slight vibration may cause severe paralysis at the procedure of extirpation of the OPLL through 1-stage posterior approach.…”