Intraoperative Neurophysiological Monitoring Alerts During Three-Column Osteotomy: Incidence and Risk Factors

Assessing Neurological Complications in Thoracic Three-Column Osteotomy: A Clinical Application of a Novel MRI-Based Classification Approach

STUDY DESIGN

Retrospective comparative study.

OBJECTIVE

To investigate the occurrence of neurological complications in patients undergoing thoracic three-column osteotomy (3CO) utilizing an magnetic resonance imaging (MRI)-based classification that assesses spinal cord shape and the presence of cerebrospinal fluid at the curve apex and evaluate its prognostic capacity for postoperative neurological deficits.

SUMMARY OF BACKGROUND DATA

Recent advancements in correction techniques have improved outcomes for severe spinal deformity patients undergoing 3CO. A novel MRI-based spinal cord classification system was introduced, but its validation and association with postoperative complications remain unexplored.

MATERIALS AND METHODS

Between September 2012 and September 2018, a retrospective analysis was conducted on 158 adult patients with spinal deformities undergoing 3CO. Radiographic parameters were measured. T2-weighted axial MRI was used to describe spinal cord morphology at the apex. Intraoperative neurophysiological monitoring alerts were recorded, and preoperative and postoperative neurological functions were assessed using the Frankel score. Categorical data were compared using the χ 2 or the Fisher exact test. The paired t test was utilized to assess the mean difference between preoperative and postoperative measurements, while the one-way analysis of variance and independent t test were used for comparative analyses among the different spinal cord types.

RESULTS

Patients were categorized into three groups: type 1, type 2, and type 3, consisting of 12, 85, and 61 patients. Patients with type 3 morphology exhibited larger Cobb angles of the main curve ( P <0.001). This disparity persisted both postoperatively and during follow-up ( P <0.05). Intraoperative neurophysiological monitoring alerts were triggered in 32 patients (20.3%), with a distribution of one case in type 1, six cases in type 2, and 22 cases in type 3 morphologies ( P <0.001). New neurological deficits were observed in 15 patients (9.5%), with 1, 3, and 11 cases in type 1, 2, and 3 morphologies, respectively.

CONCLUSIONS

Patients with type 3 morphology exhibited greater spinal deformity severity, a higher likelihood of preoperative neurological deficits, and an elevated risk of postoperative neurological complications. This underscores the utility of the classification as a tool for predicting postoperative neurological complications in patients undergoing thoracic 3CO.

LEVEL OF EVIDENCE

4.

The Role of Spinal Cord Compression in Predicting Intraoperative Neurophysiological Monitoring Events in Patients With Kyphotic Deformity: A Magnetic Resonance Imaging-Based Study

OBJECTIVE

To establish a novel classification system for predicting the risk of intraoperative neurophysiological monitoring (IONM) events in surgically-treated patients with kyphotic deformity.

METHODS

Patients with kyphotic deformity who underwent surgical correction of cervicothoracic, thoracic, or thoracolumbar kyphosis in our center from July 2005 to December 2020 were recruited. We proposed a classification system to describe the morphology of the spinal cord on T2-weighted sagittal magnetic resonance imaging: type A, circular/symmetric cord with visible cerebrospinal fluid (CSF) between the cord and vertebral body; type B, circular/oval/symmetric cord with no visible CSF between the cord and vertebral body; type C, spinal cord that is fattened/deformed by the vertebral body, with no visible CSF between the cord and vertebral body. Furthermore, based on type C, the spinal cord compression ratio (CR) < 50% was defined as the subtype C-, while the spinal cord CR ≥ 50% was defined as the subtype C+. IONM event was documented, and a comparative analysis was made to evaluate the prevalence of IONM events among patients with diverse spinal cord types.

RESULTS

A total of 294 patients were reviewed, including 73 in type A; 153 in type B; 53 in subtype C- and 15 in subtype C+. Lower extremity transcranial motor-evoked potentials and/or somatosensory evoked potentials were lost intraoperatively in 41 cases (13.9%), among which 4 patients with type C showed no return of spinal cord monitoring data. The 14 subtype C+ patients (93.3%) had IONM events. Univariate logistic regression analysis showed that patients with a type C spinal cord (subtype C-: odds ratio [OR], 10.390; 95% confidence interval [CI], 2.215-48.735; p = 0.003; subtype C+, OR, 497.000; 95% CI, 42.126- 5,863.611; p < 0.001) are at significantly higher risk of a positive IONM event during deformity correction compared to those with a type A. In further multiple logistic regression analysis, the spinal cord classification (OR, 5.371; 95% CI, 2.966-9.727; p < 0.001) was confirmed as an independent risk factor for IONM events.

CONCLUSION

We presented a new spinal cord classification system based on the relative position of the spinal cord and vertebrae to predict the risk of IONM events in patients with kyphotic deformity. In patients with type C spinal cord, especially those in C+ cases, it is essential to be aware of potential IONM events, and adopt standard operating procedures to facilitate neurological recovery.

Potential impairment of spinal cord around the apical vertebral level in hyperkyphotic patients: findings from diffusion tensor imaging

PURPOSE

To evaluate the neuronal metrics/microstructure of the spinal cord around apical region in patients with hyperkyphosis using diffusion tensor imaging (DTI).

METHODS

Thirty-seven patients with hyperkyphosis aged 45.5 ± 19.6 years old who underwent 3.0 T magnetic resonance imaging (MRI) examination with DTI sequence were prospectively enrolled from July 2022 to July 2023. Patients were divided into three groups according to spinal cord/ cerebrospinal fluid (CSF) architecture on sagittal-T2 MRI of the thoracic apex (the axial spinal cord classification): Group A-circular cord with visible CSF, Group B-circular cord without visible CSF at apical dorsal, and Group C-spinal cord deformed without intervening CSF. The fractional anisotropy (FA) values acquired from DTI were compared among different groups. Correlations between DTI parameters and global kyphosis (GK)/sagittal deformity angular ratio (sagittal DAR) were evaluated using Pearson correlation coefficients.

RESULTS

In all patients, FA values were significantly lower at apical level as compared with those at one level above or below the apex (0.548 ± 0.070 vs. 0.627 ± 0.056 versus 0.624 ± 0.039, P < 0.001). At the apical level, FA values were significantly lower in Group C than those in Group B (0.501 ± 0.052 vs. 0.598 ± 0.061, P < 0.001) and Group A (0.501 ± 0.052 vs. 0.597 ± 0.019, P < 0.001). Moreover, FA values were significantly lower in symptomatic group than those in non-symptomatic group (0.498 ± 0.049 v. 0.578 ± 0.065, P < 0.001). Pearson correlation analysis showed that GK (r2 = 0.3945, P < 0.001) and sagittal DAR (r2 = 0.3079, P < 0.001) were significantly correlation with FA values at apical level.

CONCLUSION

In patients with hyperkyphosis, the FA of spinal cord at apical level was associated with the neuronal metrics/microstructure of the spinal cord. Furthermore, the DTI parameter of FA at apical level was associated with GK and sagittal DAR.

LEVEL OF EVIDENCE: 4