The assessment of the postoperative spinal alignment: MRI adds up on accuracy

Supine Imaging Is a Superior Predictor of Long-Term Alignment Following Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To investigate correlations between preoperative supine imaging and postoperative alignment.

METHODS

A retrospective review was conducted of a single-institution database of patients with adult spinal deformity (ASD). Patients were stratified by fusion location in the lumbar or thoracic spine. Outcomes of interest were postoperative lumbar lordosis (LL) and thoracic kyphosis (TK). Sagittal alignment parameters were compared and correlation analyses were performed. Multilinear stepwise regression was conducted to identify independent predictors of postoperative LL or TK. Regression analyses were repeated within the lumbar and thoracic fusion cohorts.

RESULTS

A total of 99 patients were included (mean age 63.2 years, 83.1% female, mean body mass index 27.3 kg/m²). Scoliosis Research Society classification demonstrated moderate to severe sagittal and/or coronal deformity (pelvic tile modifier, 18.2% ++; sagittal vertical axis, 27.3% ++, pelvic incidence minus lumbar lordosis mismatch, 29.3% ++, SRS type, 29.3% N type curve and 68.7% L or D type curve). A total of 73 patients (73.7%) underwent lumbar fusion and 50 (50.5%) underwent thoracic fusion. Correlation analyses demonstrated a significant association between pre- and postoperative LL and TK. Multilinear regression demonstrated that LL supine and pelvic incidence were significant predictors of postoperative LL (r² = 0.568, P < .001). LL supine, TK supine, and age were significant predictors of postoperative TK (r² = 0.490, P < .001).

CONCLUSION

Preoperative supine films are superior to standing in predicting postoperative alignment at 1-year follow-up. Anticipation of undesired alignment changes through supine imaging may be useful in mitigating the risk of iatrogenic malalignment.

Correlation and Differences in Lumbopelvic Sagittal Alignment Parameters Between Lumbar Radiographs and Magnetic Resonance Images

STUDY DESIGN

Imaging parameter study.

OBJECTIVE

Though lumbar alignment is better evaluated using standing radiograph than supine magnetic resonance imaging (MRI), few studies have researched this. Our study aimed to observe the correlation and difference in alignment between standing radiograph and supine MRI, and assess whether the change of position affects the lumbopelvic parameters.

METHODS

We analyzed 105 patients, measuring lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI). Inter- and intraparameter analyses were performed to identify any difference between standing radiograph and supine MRI. Statistical differences between the lumbopelvic parameters were compared.

RESULTS

There was excellent interobserver agreement for each parameter (interclass correlation coefficient > 0.75), and significant differences were observed in each parameter between radiograph and MRI (P < .05). Strong correlations were noted between the equivalent parameters in radiograph and MRI, both SS and PI were strongly correlated with LL in radiograph and MRI image, both PT and SS were strongly correlated with PI in radiograph and MRI image (r = -1.0 to -0.5 or 0.5 to 1.0).

CONCLUSION

Supine MRI obviously underestimated the measurements of lumbopelvic sagittal alignment parameters in standing radiograph. Therefore, standing lumbar radiographs should be obtained preoperatively in all surgical patients, not only supine MRI. In addition, we observed that PI was not a constant morphological parameter.

The utility of supine radiographs in the assessment of thoracic flexibility and risk of proximal junctional kyphosis

OBJECTIVE

Supine radiographs have successfully been used for preoperative planning of lumbar deformity corrections. However, they have not been used to assess thoracic flexibility, which has recently garnered attention as a potential contributor to proximal junctional kyphosis (PJK). The purpose of this study was to compare supine to standing radiographs to assess thoracic flexibility and to determine whether thoracic flexibility is associated with PJK.

METHODS

A retrospective study was conducted of a single-institution database of patients with adult spinal deformity (ASD). Sagittal alignment parameters were compared between standing and supine and between pre- and postoperative radiographs. Thoracic flexibility was determined as the change between preoperative standing thoracic kyphosis (TK) and preoperative supine TK, and these changes were measured over the overall thoracic spine and the fused portion of the thoracic spine (i.e., TK fused). A case-control analysis was performed to compare thoracic flexibility between patients with PJK and those without (no PJK). The cohort was also stratified into three groups based on thoracic flexibility: kyphotic change (increased TK), lordotic change (decreased TK), and no change. The PJK rate was compared between the cohorts.

RESULTS

A total of 101 patients (mean 63 years old, 82.2% female, mean BMI 27.4 kg/m2) were included. Preoperative Scoliosis Research Society-Schwab ASD classification showed moderate preoperative deformity (pelvic tilt 27.7% [score ++]; pelvic incidence-lumbar lordosis mismatch 44.6% [score ++]; sagittal vertical axis 42.6% [score ++]). Postoperatively, the average offset from age-adjusted alignment goals demonstrated slight overcorrection in the study sample (-8.5° ± 15.6° pelvic incidence-lumbar lordosis mismatch, -29.2 ± 53.1 mm sagittal vertical axis, -5.4 ± 10.8 pelvic tilt, and -7.6 ± 11.7 T1 pelvic angle). TK decreased between standing and supine radiographs and increased postoperatively (TK fused: -25.3° vs -19.6° vs -29.9°; all p < 0.001). The overall rate of radiographic PJK was 23.8%. Comparisons between PJK and no PJK demonstrated that offsets from age-adjusted alignment goals were similar (p > 0.05 for all). There was a significant difference in the PJK rate when stratified by thoracic flexibility cohorts (kyphotic: 0.0% vs no change: 18.4% vs lordotic: 35.0%; p = 0.049). Logistic regression revealed thoracic flexibility (p = 0.045) as the only independent correlate of PJK.

CONCLUSIONS

Half of patients with ASD experienced significant changes in TK during supine positioning, a quality that may influence surgical strategy. Increased thoracic flexibility is associated with PJK, possibly secondary to fusing the patient's spine in a flattened position intraoperatively.

Association of postoperative covert stroke and cognitive dysfunction among elderly patients undergoing non-cardiac surgery: protocol for a prospective cohort study (PRECISION study)

INTRODUCTION

The incidence of covert stroke and cognitive dysfunction has gradually increased due to an ageing population. Recently, a prospective cohort study reported perioperative covert stroke was associated with an increased risk of postoperative cognitive dysfunction (POCD) 1 year after non-cardiac surgery. However, the mechanism remains unclear.

METHODS AND ANALYSIS

This is a prospective observational trial aiming to investigate the cumulative incidence of perioperative covert stroke and test the hypothesis that perioperative covert stroke associates with POCD in elderly patients undergoing non-cardiac and non-neurological surgery. Data on risk factors, brain MRI, cognitive function evaluation and serum immune-inflammatory cytokines will be collected and analysed.

ETHICS AND DISSEMINATION

Ethical approval has been granted by the Medical Ethics Committee of Beijing Tiantan Hospital, Capital Medical University (reference number: KY2017-027-02). The results of this study will be disseminated through presentations at scientific conferences and publication in scientific journals.

TRIAL REGISTRATION NUMBER

NCT03081429.

Correlation of cervical and thoracic inlet sagittal parameters by MRI and radiography in patients with cervical spondylosis

To investigate the relationship between cervical and thoracic sagittal alignment parameters measured by magnetic resonance imaging (MRI) and x-ray in patients with cervical spondylosisData from 120 symptomatic patients who presented with cervical spondylosis between April 2015 and January 2016 were retrospectively analyzed. Patients received both a cervical MRI and a cervical radiograph during a single visit. The thoracic inlet angle (TIA), T1 slope (T1S), neck tilt (NT), C2-C7 angle (C2-C7), and C2-C7 sagittal vertical axis (C2-7 SVA) were assessed. Pearson correlation coefficient, paired t test, and linear regression models were used to analyze parameters obtained by cervical MRI and radiography.The difference in mean thoracic inlet angle x-ray (TIAX) and thoracic inlet angle MRI (TIAM) (TIAM-TIAX) (0.72 ± 5.82°) was not significant (P > .05). There were significant differences in mean T1 slope x-ray (T1SX) and T1 slope MRI (T1SM) (T1SM-T1SX) (-2.55 ± 6.14°), mean neck tilt x-ray (NTX) and neck tilt MRI (NTM) (NTM-NTX) (3.26 ± 6.01°), mean C2-C7 angle x-ray (C2-7X) and C2-C7 angle MRI (C2-7 M) (C2-7M-C2-7X) (-3.57 ± 10.00°), and mean C2-C7 sagittal vertical axis X ray (C2-7 SVAX) and C2-C7 sagittal vertical axis MRI (C2-7 SVAM) (C2-7 SVAM-C2-7 SVAX) (-4.50 ± 1.26 mm) (all P ≤ .001). There were positive correlations between TIAM and TIAX (r = 0.807), T1SM and T1SX (r = 0.581), NTM and NTX (r = 0.759), cervical loidosis MRI and cervical loidosis x-ray (r = 0.666), and SVAM and SVAX (r = 0.226).MRI may be useful to evaluate thoracic inlet and sagittal alignment parameters in patients with cervical spondylosis. Patients with cervical spondylosis may have a relatively low capacity for compensation in the cervical region.

Grayscale Inversion View Can Improve the Reliability for Measuring Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis

BACKGROUND

Proximal junctional kyphosis (PJK) is a common phenomenon after long segmental fusion surgery of adolescent idiopathic scoliosis. However, the inability to reliably identify vertebral endplates on lateral upright radiographs has made an accurate measurement of proximal junctional angle (PJA) technically impossible in many patients. The aim of this study was to determine whether a grayscale inversion view is more reliable to measure PJA and to assess PJK accurately.

METHODS

A total of 162 patients with adolescent idiopathic scoliosis who underwent posterior spinal fusion surgeries were included in this study. PJA was measured on preoperative lateral standing films using 3 methods (upper-instrumented vertebrae [UIV] + 1, UIV + 2, and UIV to T2) on both standard view and grayscale inversion view. Two physicians independently measured the PJA twice at a 1-month interval. Intra- and interobserver reliabilities were compared between the 2 radiographic views. Forty patients with preoperative magnetic resonance imaging (MRI) scans were randomly selected. PJA was measured for these patients on both views of lateral standing films and MRI images. The correlation coefficients between PJA obtained on MRI and PJA obtained on radiographs with different views were calculated respectively.

RESULTS

The intraclass correlation coefficients were greater in a grayscale inversion view than in a standard view in all 3 methods for both observers, and the intraclass correlation coefficients of interobserver reliabilities also were greater in a grayscale inversion view. The correlation coefficient between PJA obtained on grayscale inversion view and preoperative MRI was greater in all methods compared with standard view.

CONCLUSIONS

Grayscale inversion view can be a more reliable tool for the evaluation of PJK as compared with the conventional measurement. We recommend the application of a grayscale inversion view to measure PJA and assess PJK in clinical practice, particularly for patients instrumented to the upper thoracic spine.

Evaluation of the influence of kyphosis and scoliosis on intervertebral disc extrusion in French bulldogs

BACKGROUND

Although thoracic vertebral malformations with kyphosis and scoliosis are often considered incidental findings on diagnostic imaging studies of screw-tailed brachycephalic breeds, they have been suggested to interfere with spinal biomechanics and intervertebral disc degeneration. It is however unknown if an abnormal spinal curvature also predisposes dogs to develop clinically relevant intervertebral disc herniations. The aim of this study was to evaluate if the occurrence of thoracic vertebral malformations, kyphosis or scoliosis would be associated with a higher prevalence of cervical or thoracolumbar intervertebral disc extrusion in French bulldogs.

RESULTS

French bulldogs that underwent computed tomography for reasons unrelated to spinal disease (n = 101), and French bulldogs with thoracolumbar (n = 47) or cervical intervertebral disc extrusion (n = 30) that underwent magnetic resonance imaging were included. There was a significant association between the presence of kyphosis and the occurrence of intervertebral disc extrusion, particularly in the thoracolumbar region. Dogs with kyphosis were at nearly a two times increased odds of being affected by intervertebral disc extrusion than those without kyphosis [(OR = 1.98 (95% CI: 1.04-3.78)]. There was also an association between the presence of scoliosis and the anatomical distribution of intervertebral disc extrusions, with dogs with scoliosis more likely to have more caudal lumbar intervertebral disc extrusions. Presence of scoliosis was not associated with an increased odds of being affected by intervertebral disc extrusion.

CONCLUSIONS

Although thoracic vertebral malformations with kyphosis only rarely cause spinal cord dysfunction in itself, French bulldogs with kyphosis appear to be at higher risk to develop thoracolumbar intervertebral disc extrusion.

Magnetic resonance imaging: A possible alternative to a standing lateral radiograph for evaluating cervical sagittal alignment in patients with cervical disc herniation?

BACKGROUND AND OBJECTIVES

Convincing evidence supporting the use of magnetic resonance imaging (MRI) as an effective tool for evaluating cervical sagittal alignment is lacking. This study aims to analyze the differences and correlations between cervical sagittal parameters on x-ray and MRI in patients with cervical disc herniation and to determine whether MRI could substitute for cervical x-ray for measurement of cervical sagittal parameters.

METHODS

One hundred forty-three adults with cervical disc herniation were recruited. Each patient had both an x-ray and MRI examination of the cervical spine. The cervical sagittal parameters were measured and compared on x-ray and MRI including: C2-C7 Cobb angle, C2-C7 sagittal vertical axis (C2-C7 SVA), cervical tilt (CT), T1 Slope (T1S), and neck tilt (NT). The data were analyzed using a paired-samples t test, a Pearson correlation test, and linear regression.

RESULTS

The values of C2-C7 Cobb angle, C2-C7 SVA, CT and T1S on X-ray were larger than those on MRI (P < .05) and NT on X-ray was smaller than that on MRI (P < .05). Each of the cervical sagittal parameters had a significant correlation with the corresponding one on MRI (r = 0.699, 0.585, 0.574, 0.579 and 0.613, respectively) (C2-C7 Cobb MRI = 0.957 + 0.721 C2-C7 Cobb X, C2-C7 SVA MRI = 6.423 + 0.500 C2-C7 SVAX, CT MRI = 3.121 + 0.718 CTX, T1S MRI = 7.416 + 0.613 T1SX, NT MRI = 22.548 + 0.601 NTX).

CONCLUSION

Although MRI and x-ray measurements of cervical sagittal parameters were different, there were significant correlations between the results. MRI could be used to evaluate the sagittal balance of the cervical spine with great reliability.

The Assessment of Upright Cervical Spinal Alignment Using Supine MRI Studies

STUDY DESIGN

This is a prospective, single-centre study.

OBJECTIVE

The purpose of this study is researching whether there is a correlation or not between the cervical alignment in the examinations of magnetic resonance imaging (MRI) in lying position and the alignment in the cervical direct radiography and whether the cervical alignment in standing position could be estimated or not through MRI measurements in the supine position.

SUMMARY OF BACKGROUND DATA

Cervical spinal alignment is a parameter required for deciding the surgical procedure particularly in patients with cervical myelopathy and deformity. However, cervical alignment angles change according to lying and standing positions. Therefore, the direct standing radiograph is taken as basis for this examination.

METHODS

Cervical alignments were measured with 3 different methods with the standing lateral radiographies and lying MRI of 51 patients with cervical disorder.

RESULTS

A high correlation was found between the measurements in standing and lying positions for the spinal alignments measured through the Cobb angle and posterior tangent method. It was found that standing Cobb angle (in plain graphy)=Cobb angle (in MRI)×0.489+7.13 and posterior tangent angle (in plain graphy)=posterior tangent angle (in MRI)×0.54+9.37.

CONCLUSIONS

It is possible to estimate the spinal alignment in standing position with the measurements of cervical spinal alignment in the MRI at supine position. And this may render having cervical graphy in standing position unnecessary.

Can MRI Predict Flexibility in Scheuermann Kyphosis Patients?

STUDY DESIGN

Retrospective, blinded analysis of imaging studies.

OBJECTIVE

The aim of this study is compare the use of magnetic resonance imaging (MRI) to lateral radiograph using bolster in the evaluation of Scheuermann kyphosis (SK) curve flexibility measurement.

SUMMARY AND BACKGROUND DATA

The flexibility of the thoracic curve [thoracic kyphosis (TK)] in SK is of primary importance in its preoperative planning. Several methods have been described for SK curve flexibility measurement. The most commonly used method is lateral hyperextension radiography on hard bolster [hyperextension radiograph (HE)]. No current methods use MRI for flexibility assessment.

MATERIALS AND METHODS

Flexibility of TK in SK patients was measured as a difference between standing radiograph and bolster-assisted lateral HE or supine MRI. The sagittal Cobb angle of the TK was measured between the superior endplate of T4 and the inferior endplate of T12 vertebral body. Flexibilities measured by these 2 methods were compared and analyzed using the generalized estimating equation analysis and the correlation analysis.

RESULTS

We assessed 18 SK patients (14 males and 4 females) with mean age of 20.06±6.03 years. The standing TK x-rays showed 83.8±6.1 degrees. On HE, TK curve reduced by 39.3 degrees (95% confidence interval, 35.8-42.9) to 44.5±6.2 degrees (P<0.001). Preoperative MRI images showed TK of 53.8±5.9 degrees which means reduction by 30 degrees (95% confidence interval, 26.6-33.4) from the standing radiographs (P<0.001). Linear dependency between HE and MRI flexibility with a mean difference of 9.3 degrees was found (R=0.61, P<0.001).

CONCLUSIONS

Our study shows that preoperative MRI can be used for SK flexibility assessment with similar predictive value as routinely used bolster-assisted hyperextension lateral radiograph. Consequently, patient exposure to preoperative hyperextension ionizing radiation may be reduced.

Measurement of Thoracic Inlet Alignment on MRI: Reliability and the Influence of Body Position

STUDY DESIGN

A retrospective radiographic study.

OBJECTIVE

To investigate the reliability of using magnetic resonance imaging (MRI) to measure thoracic outlet parameters and whether supine MRI could supersede upright x-ray in measuring these parameters.

SUMMARY OF BACKGROUND DATA

On x-ray, overlapped soft and bony tissues make sternum contour invisible. Thus, measuring thoracic inlet (TI) alignment on x-ray may be inaccurate. MRI could clearly show anatomy around TI.

METHODS

A total of 124 adolescents with idiopathic thoracolumbar/lumbar scoliosis were recruited. The visibility of T1 upper endplate and the upper end of sternum on the lateral standing x-ray films was rated. For patients with moderate or good clarity forT1 upper endplate and the upper end of sternum on x-ray films, thoracic inlet angle (TIA), T1 slope (T1S), and neck tilt (NT) were measured by 3 observers on standing x-ray films and supine MR images, respectively. Intraclass correlation coefficients (ICC) were used to determine the intraobserver, interobserver, and method reliability. The paired t test was performed to compare the measurements between the 2 methods. The correlation coefficients between the 2 methods were analyzed by regression analysis.

RESULTS

The visibility of TI region on x-ray films was unsatisfactory, whereas all the landmarks were clear on MR images. Only 81 patients' x-ray films were graded as moderate or good visibility in the TI region. Both the intraobserver ICC and interobserver ICC were better in the MRI set than in the x-ray set among all the observers for 3 TI parameters. The paired t test demonstrated that no significant difference was noted in terms of TIA, T1S, and NT (P=0.572, 0.203, and 0.637, respectively). Regression analysis demonstrated high correlation coefficients for TIA, T1S, and NT (R=0.612, 0.629, and 0.722, respectively).

CONCLUSIONS

MRI serves as a good substitute for x-ray scans with regard to the measurement of TI alignment, with superior reliability.

MRI May Serve as a Valid Alternative to Standing Radiography in Evaluating the Sagittal Alignment of the Upper Thoracic Spine

STUDY DESIGN

This study is of a retrospective radiographic design.

OBJECTIVE

The objective of the study was to compare supine magnetic resonance images (MRI) with standing x-ray scanning in the evaluation of the sagittal alignment of the upper thoracic spine.

SUMMARY OF BACKGROUND DATA

X-ray films have been reported to be inaccurate in evaluating the proximal thoracic sagittal alignment because of poor visibility of the upper thoracic region. Previous studies have demonstrated the feasibility of supine MRI in evaluating spinal deformities in the coronal plane. However, no study has addressed the use of MRI for evaluating the sagittal alignment of the upper thoracic region.

METHODS

Ninety-six adolescents with idiopathic thoracolumbar/lumbar scoliosis were enrolled. The visibility of the upper thoracic spine landmarks from C7 to T6 in the lateral standing x-ray films was first graded. For patients with moderate or good clarity of the landmarks of each vertebra from C7 to T6 on x-ray films, the vertebral sagittal angles from T1 to T5 and the angle of T2-T5 kyphosis were measured by 3 observers on standing x-ray films and supine MRI images, respectively. Intraclass correlation coefficients were used to determine the intraobserver, interobserver, and method reliability. The paired t test was performed to compare the measurements between the 2 methods.

RESULTS

The visibility of the upper thoracic region in x-ray films was generally unsatisfactory, especially for T1 and T2, whereas all the vertebrae were clear in MRI images. Only 50 patients' x-ray films were graded as moderate or good visibility in the upper thoracic spine. Measurements on MRI images gave excellent intraobserver and interobserver reliability (0.914-0.924 and 0.838-0.920, respectively), which were better than that on x-ray films (0.767-0.891 and 0.713-0.883, respectively). No significant difference was found between the 2 modalities in terms of sagittal angles of T3, T4, and T5 (P=0.680, 0.595, and 0.239, respectively) and T2-T5 kyphosis (P=0.105).

CONCLUSIONS

With excellent measurement reproducibility, a supine MRI image may serve as a valid alternative to a standing x-ray film for the measurement for T3, T4, and T5 sagittal angles and for the evaluation of upper thoracic kyphosis.

Magnetic resonance imaging assessment of degenerative cervical myelopathy: a review of structural changes and measurement techniques

Degenerative cervical myelopathy encompasses a spectrum of age-related structural changes of the cervical spine that result in static and dynamic injury to the spinal cord and collectively represent the most common cause of myelopathy in adults. Although cervical myelopathy is determined clinically, the diagnosis requires confirmation via imaging, and MRI is the preferred modality. Because of the heterogeneity of the condition and evolution of MRI technology, multiple techniques have been developed over the years in an attempt to quantify the degree of baseline severity and potential for neurological recovery. In this review, these techniques are categorized anatomically into those that focus on bone, ligaments, discs, and the spinal cord. In addition, measurements for the cervical spine canal size and sagittal alignment are also described briefly. These tools have resulted collectively in the identification of numerous useful parameters. However, the development of multiple techniques for assessing the same feature, such as cord compression, has also resulted in a number of challenges, including introducing ambiguity in terms of which methods to use and hindering effective comparisons of analysis in the literature. In addition, newer techniques that use advanced MRI are emerging and providing exciting new tools for assessing the spinal cord in patients with degenerative cervical myelopathy.

Upright, prone, and supine spinal morphology and alignment in adolescent idiopathic scoliosis

BACKGROUND

Patients with adolescent idiopathic scoliosis (AIS) are usually investigated by serial imaging studies during the course of treatment, some imaging involves ionizing radiation, and the radiation doses are cumulative. Few studies have addressed the correlation of spinal deformity captured by these different imaging modalities, for which patient positioning are different. To the best of our knowledge, this is the first study to compare the coronal, axial, and sagittal morphology of the scoliotic spine in three different body positions (upright, prone, and supine) and between three different imaging modalities (X-ray, CT, and MRI).

METHODS

Sixty-two AIS patients scheduled for scoliosis surgery, and having undergone standard pre-operative work-up, were included. This work-up included upright full-spine radiographs, supine bending radiographs, supine MRI, and prone CT as is the routine in one of our institutions. In all three positions, Cobb angles, thoracic kyphosis (TK), lumbar lordosis (LL), and vertebral rotation were determined. The relationship among three positions (upright X-ray, prone CT, and supine MRI) was investigated according to the Bland-Altman test, whereas the correlation was described by the intraclass correlation coefficient (ICC).

RESULTS

Thoracic and lumbar Cobb angles correlated significantly between conventional radiographs (68° ± 15° and 44° ± 17°), prone CT (54° ± 15° and 33° ± 15°), and supine MRI (57° ± 14° and 35° ± 16°; ICC ≥0.96; P < 0.001). The thoracic and lumbar apical vertebral rotation showed a good correlation among three positions (upright, 22° ± 12° and 11° ± 13°; prone, 20° ± 9° and 8° ± 11°; supine, 16° ± 11° and 6° ± 14°; ICC ≥0.82; P < 0.001). The TK and LL correlated well among three different positions (TK 26° ± 11°, 22° ± 12°, and 17° ± 10°; P ≤ 0.004; LL 49° ± 12°, 45° ± 11°, and 44° ± 12°; P < 0.006; ICC 0.87 and 0.85).

CONCLUSIONS

Although there is a generalized underestimation of morphological parameters of the scoliotic deformity in the supine and prone positions as compared to the upright position, a significant correlation of these parameters is still evident among different body positions by different imaging modalities. Findings of this study suggest that severity of scoliotic deformity in AIS patients can be largely represented by different imaging modalities despite the difference in body positioning.

How Does the Supine MRI Correlate With Standing Radiographs of Different Curve Severity in Adolescent Idiopathic Scoliosis?

STUDY DESIGN

A retrospective study.

OBJECTIVE

To study how the supine magnetic resonance image (MRI) correlates with standing radiographs of different curve severity in adolescent idiopathic scoliosis (AIS).

SUMMARY OF BACKGROUND DATA

Linear correlation between Cobb angles measured on supine MRI and standing radiographs has been identified. However, the effects of different curve severity on the correlation have not been studied in depth.

METHODS

Girls with AIS with standing radiographs and supine MRI were reviewed. From standing radiographs, all structural and nonstructural Cobb angles were measured. For those with simultaneous lateral radiographs, thoracic kyphosis (TK) and lumbar lordosis (LL) angles were measured. On supine MRI, the coronal Cobb angles, TK and LL were measured accordingly. The coronal Cobb angles were divided into 3 groups based on values measured on standing radiographs: mild group for Cobb angles less than 20°, moderate group for 20° to 40°, and severe group for more than 40°. Correlation was analyzed using scatter plot.

RESULTS

Eighty patients with AIS with 122 coronal curves were reviewed. On standing radiographs, the coronal Cobb angles were 14.7°± 3.2°, 28.2°± 5.1°, and 54.9°± 11.3° for mild, moderate, and severe groups. On supine MRI, the Cobb angles averaged 10.1°± 5.6°, 20.0°± 6.3°, and 49.4 ± 12.3° for each group, respectively. TK were 16.3 ± 9.1° and 11.8 ± 6.1° for radiographs and MRI (P < 0.001), whereas the LL averaged 45.5 ± 12.2° and 39.5 ± 10.5° for radiographs and MRI (P < 0.001). Cobb angles measured on standing radiographs and supine MRI were linearly correlated with the adjusted R being 0.0627, 0.2118, and 0.7999 for the mild, moderate, and severe groups.

CONCLUSION

Cobb angles measured on supine MRI were linearly correlated with Cobb angles measured on standing radiographs and the correlation was more reliable in those with Cobb angles more than 40°. Therefore, the supine MRI could serve as a reliable alternative to standing radiographs in the assessment of Cobb angles more than 40° in AIS.

LEVEL OF EVIDENCE

3.

Thoracal flat back is a risk factor for lumbar disc degeneration after scoliosis surgery

BACKGROUND CONTEXT

Lumbar segments below fused scoliotic spines are thought to be exposed to extraordinary stress. Although positive sagittal imbalance has come into focus, reports about factors influencing the outcome of these segments remain inconclusive.

PURPOSE

Our study aimed at identifying spinal risk factors for the development of lumbar degenerative disc disease (DDD) in surgically treated patients with adolescent idiopathic scoliosis (AIS).

STUDY DESIGN/SETTING

Retrospective comparative prognostic study (Level III) was conducted. Thirty-three patients were seen at an average follow-up of 7.5 years after either isolated selective anterior (n=18) or long combined anterior-posterior fusion (n=15) for AIS.

OUTCOME MEASURES

Self-reported Scoliosis Research Society 22 questionnaire, physical examination including the detection of segmental pain and unspecific back pain, preoperative and postoperative whole-spine standing radiographs, and magnetic resonance imaging were obtained.

METHODS

Radiographic evaluation included the measurement of regional, coronal, and sagittal curve parameters and the assessment of spinal balance. Magnetic resonance imaging evaluation was done for preoperative and postoperative lumbar discs, according to the classification of Pfirrmann.

RESULTS

Patients with low DDD (Pfirrmann grading <3) had a significantly higher thoracal kyphosis angle (mean 28°) than patients with advanced DDD (mean 15°). There was a trend toward a more flat-type lumbar lordosis in patients with severe DDD. Positive sagittal imbalance was associated with advanced DDD. Follow-up coronal parameters, trunk imbalance, instrumentation length, and lowest instrumented vertebra selection had no influence on DDD. Specific segmental pain could be attributed to a significantly higher coronal trunk imbalance (21 vs. 11 mm).

CONCLUSIONS

This study establishes thoracal flat back as a risk factor for lumbar DDD after spinal fusion and supports the pathogenetic role of positive sagittal imbalance in this process.

Epidural neural fibrolipoma of the thoracic vertebral canal

Neural fibrolipoma is a benign tumor that most frequently infiltrates the median nerve. The authors describe a patient with spinal cord compression syndrome caused by a neural fibrolipoma. The tumor originated in the thoracic nerve at the T6–7 extradural level in the left conjugate foramen and extended into the thoracic cavity. Total removal was achieved by a combined posterior and costotransversectomy approach. Postoperatively, the patient's spinal cord compression syndrome resolved. No tumor recurrence has been observed in medium-term follow-up. This is the second case of an extradural spinal neural fibrolipoma to be reported in the literature.