Abstract
Background:
The increasing utilization of magnetic resonance imaging has facilitated the detection of intraspinal abnormalities in congenital scoliosis (CS) caused by hemivertebra. However, the risk of intraspinal abnormalities across different hemivertebra patterns remains unclear. The aim of this study was to compare the prevalence of intraspinal abnormalities between single hemivertebra and multiple hemivertebra and identify key associated risk factors.
Methods:
A total of 1,048 patients with CS caused by hemivertebra who received surgical correction were included. The radiographic and clinical data for each patient were collected and analyzed.
Results:
Intraspinal abnormalities were present in 16.5% of patients, including syringomyelia (9.2%), lipoma filum terminale (6.0%), low-lying conus medullaris (3.1%), tethered spinal cord (2.9%), diastematomyelia (2.4%), and Chiari malformation (1.9%). Patients with multiple hemivertebra demonstrated a significantly higher intraspinal abnormalities incidence than those with single hemivertebra (24.4% vs. 14.1%, p < 0.001). In single hemivertebra (HV), 51 of 114 patients (44.7%) have intraspinal abnormalities located outside the region of bony HV, while the figure is 26 of 59 (44.1%) in patients with multiple HVs. Multivariate logistic regression showed that female sex [odds ratio (OR) = 1.800, p = 0.001], semisegmented/nonsegmented morphology (OR = 1.499, p = 0.003), and multiple hemivertebra (OR = 1.957, p = 0.001) are the risk factors of intraspinal abnormalities in all cases. Although 12.1% of all patients with intraspinal abnormalities had positive neurological findings, this was not statistically significant compared with those without intraspinal abnormalities (9.0%).
Conclusion:
Patients with multiple hemivertebra have a 1.96-fold higher risk of intraspinal abnormalities compared with those with a single hemivertebra. Importantly, intraspinal abnormalities are associated with female sex, multiple hemivertebra, and nonsegmented morphology, but not neurological symptoms, and caution should be paid to the intraspinal abnormalities outside of the bony lesions.
Introduction
Congenital scoliosis (CS) is a vertebral developmental disorder, affecting 0.05% to 0.1% of live births1. CS arises from failure of vertebral formation, segmentation, or mixed anomalies2. Since vertebral development is closely linked to neural tube and sclerotome differentiation, intraspinal abnormalities frequently coexist with spinal malformations. Reported intraspinal abnormalities incidence in patients with CS ranges widely (15%-53.6%)3-5. These subclinical abnormalities may accelerate deformity progression and heighten neurological risks during surgery6-9.
Hemivertebra demonstrate heterogeneous intraspinal abnormalities risk across morphological patterns. Higher prevalence of intraspinal abnormalities was reported in patients with segmentation failures and mixed hemivertebra compared with those with failure of formation5. Early investigations in small cohorts (n = 76) reported intraspinal abnormalities in 38% (8/21) of isolated hemivertebra and 21% (10/47) of complex HV cases10, while subsequent studies found that multiple hemivertebra is more prevalent among intraspinal abnormalities–positive patients (23%, 10/44)11. However, the limited sample sizes can hardly lead to definitive conclusions. The precise incidence and clinical relevance of intraspinal abnormalities across different hemivertebra patterns remains poorly characterized12.
Despite the practical challenges of magnetic resonance imaging (MRI) usage in children aged younger than 6 years which requires sedation, MRI are been increasingly accepted as standard protocol among Asian and Asian-American populations to identify intraspinal abnormalities13. Previous study recommends whole-spine MRI for CS patients with segmentation failures or neurological symptoms during outpatient evaluation14. Although segmentation failures are known to carry high risk5, the relative prevalence of intraspinal abnormalities between single versus multiple hemivertebra configurations remains poorly characterized. In addition, it remains largely unknown whether intraspinal anomalies are more likely to occur outside the region of the bony anomaly in patients with multiple hemivertebra.
Therefore, the purpose of our study was to investigate the prevalence of intraspinal abnormalities in single hemivertebra and those with multiple hemivertebra and determine the radiographic features associated with the presence of intraspinal abnormalities in these patients. Our hypothesis is that patients with multiple hemivertebra have a significantly higher prevalence of intraspinal abnormalities compared with patients with a single hemivertebra.
Materials and Methods
Subjects
This study is a retrospective study conducted under the institutional ethics committee. The surgical database for spine deformities in our institution was reviewed. All cases are reviewed by the same surgical team who are highly specialized in spine deformities, and the diagnosis is made by group consensus, and the entry of the cases is documented according to etiology. The inclusion criteria were as follows: (1) congenital scoliosis, (2) with single or multiple hemivertebra formation, and (3) received surgical treatment for hemivertebra. The surgical indications for congenital scoliosis include severe structural scoliosis, scoliosis that is unresponsive to brace treatment and progresses rapidly, severe neurological symptoms, and scoliosis with a poor prognosis (including shoulder, neck, or trunk tilt caused by an isolated hemivertebra). Patients were excluded if they presented with radiographic evidence of segmentation failure or mixed type of CS, neuromuscular scoliosis, or secondary scoliosis following trauma and infection. We enrolled a total of 1,048 patients with congenital scoliosis who received surgical treatment from 2004 to 2024 at our institution.
Clinical Data Collection
The types of congenital scoliosis including formation failure, segmentation failure, and mixed types were determined through radiograph and computed tomography scans. The presence of intraspinal abnormalities was determined by whole-spine MRI. The MRI systems used were Philips Healthcare company, including Intera 1.5T MRI, Multiva 1.5T, and Ingenia CX. Syringomyelia was diagnosed when the syrinx diameter was >2 mm, and the syrinx length was >2 vertebral levels. The presence of rib anomalies included variation in number and structural changes (fused, bifid, and widened/irregular ribs)15. A low-lying conus was diagnosed when the spinal cord terminated below the L1-L2 disk space16. The segmentation of the hemivertebra was classified as nonsegmented, partially segmented, and fully segmented. The Cobb angle of the main curve was measured, and the presence of kyphosis was documented if the regional kyphosis >30°. Echocardiogram, urogenital ultrasound was undertaken to screen for other organ abnormalities, including cardiac and urogenital malformation. Detailed physical examination was performed, and the presence of neurological findings including the sensory deficit, muscle strength of the 4 extremities, and abdominal reflexes were documented.
Statistical Analysis
Statistical analysis was performed with SPSS software (version 17.0; SPSS). Continuous variables are presented as mean ± standard deviation, while categorical variables are presented as frequency and percentages. Independent sample t test was used to determine the difference between groups. The χ2 test was used to assess differences between groups for categorical variables. A p-value of <0.05 was considered statistically significant.
Results
A total of 1,048 cases with hemivertebra were enrolled in our study, including 578 male patients and 470 female patients. The selection of patients and exclusion due to loss of imaging, poor quality images, and loss of data is specified in Figure S1. The average age was 11.61 ± 8.62 years, ranging from 2 to 36 years. Among these cases, 806 (76.9%) had single hemivertebra and 242 (23.1%) had multiple hemivertebra. Among all cases, 762 had corrective and fusion surgery with hemivertebra resection (3-column osteotomy, 3-CO), 249 patients had correction and fusion surgery without 3-CO, and 19 had epiphysiodesis. Three patients had growing rods implantation. One thousand nineteen cases were treated with posterior approach, 26 with anterior approach, and 9 with combined approach.
In patients with a single hemivertebra, the majority were located in the lumbar spine (56.4%, n = 455), followed by the thoracic spine (43.3%, n = 349). By contrast, among those with multiple HVs, 46.7% (n = 113) had lesions confined to the thoracic spine, while 35.1% (n = 83) involved both thoracic and lumbar regions. Combined cervical-thoracic (C+T) and cervicothoracolumbar (C+T+L) involvement was rare, occurring in only 5 and 1 case(s), respectively.
Among all cases, a total of 173 patients (16.5%) had intraspinal abnormalities, including 96 with syringomyelia (9.2%), 63 with lipoma filum terminale (6.0%), 30 with tethered spinal cord (2.9%), 25 with diastematomyelia (2.4%), 20 with Chiari malformation (1.9%), and 32 with low-lying conus medullaris (3.1%). For diastematomyelia, 18 were fibrous and 4 were bone septum, and 3 were mixed type. Rib abnormalities were identified in 56 patients (5.3%) (Table I). A total of 26 patients had more than 1 abnormality, including 8 with syringomyelia and tethered spinal cord, 6 with diastematomyelia and syringomyelia, 3 with diastematomyelia and tethered spinal cord, 3 with syringomyelia and lipoma filum terminale, 3 with syringomyelia and Chiari malformation, and 3 patients were found to have 3 intraspinal abnormalities. In addition, 2 cases have concurrent neural tube defects, including 1 patient diagnosed with myelomeningocele.
TABLE I.
Demographic Data
| No. of cases | 1,048 |
| Age at surgery | 11.61 ± 8.62 |
| Male: female ratio (no. of patients) | 578:470 |
| The no. of hemivertebra | |
| Single HV | 806 (76.9%) |
| Multiple HV | 242 (23.1%) |
| The no. of intraspinal abnormalities | |
| Total number (%) | 173 (17.0) |
| Syringomyelia (%) | 96 (9.2) |
| Diastematomyelia (%) | 25 (2.4) |
| Tethered spinal cord (%) | 30 (2.9) |
| Chiari malformation (%) | 20 (1.9) |
| Lipoma filum terminale (%) | 63 (6.0) |
| Low-lying conus medullaris (%) | 32 (3.1) |
| Rid deformity (%) | |
| Yes | 56 (5.3) |
| No | 992 (94.7) |
A total of 24.4% of the patients with multiple hemivertebra had intraspinal abnormalities, showing a significantly higher incidence than that in the single hemivertebra group (24.4% vs. 14.1%, p < 0.001). In patients with single hemivertebra, we observed that 67 of 114 (58.75%) of the IA occurs in the same spinal region of the hemivertebra, though the occurrence did not differ significantly by hemivertebra spinal location. In patients with multiple hemivertebra, we found a similar incidence of intraspinal abnormalities in those with hemivertebra in T, L, or TL group. Of note, 3 of 5 patients (60%) who have hemivertebra located at C+T have intraspinal abnormalities (Fig. S2). Two typical cases illustrated in Figures 1 and 2. Through further analysis, we found in single HV, 51 of 114 patients (44.7%) have intraspinal abnormalities located outside the region of bony HV, while the figure is 26 of 59 (44.1%) in patients with multiple HVs. Patients in the multiple hemivertebra groups had a significantly higher incidence of syringomyelia (13.6% vs. 7.8%, p = 0.003), tethered spinal cord (5.0% vs. 2.2%, p = 0.026), and lipoma of the filum terminale (10.3% vs. 4.7%, p = 0.001) (Table II).
Fig. 1.
A 8-year-old female CS patient with HV at L3 level (Figs. 1-A, 1-B and 1-C). MRI showed syringomyelia at T12 level and diastematomyelia at lumber spine region (Figs. 1-D and 1-E). CS = congenital scoliosis, and MRI = magnetic resonance imaging.
Fig. 2.
A 7-year-old female CS patient with multiple HV thoracic and lumbar region (Figs. 2-A, 2-B and 2-C). MRI showed spinal cord tethering at the lumbar region and syringomyelia at thoracic spine (Figs. 2-D and 2-E). MRI = magnetic resonance imaging.
TABLE II.
Comparison of IA Between Single and Multiple HV
| Single HV (n = 806) | Multiple HV (n = 242) | p | |
|---|---|---|---|
| Age | 11.95 ± 9.04 | 10.43 ± 6.94 | p < 0.001 |
| Gender (male: female) | 442:364 | 139:103 | 0.456 |
| Intraspinal abnormalities | |||
| With abnormalities | 114 (14.1%) | 59 (24.4%) | p < 0.001 |
| Without abnormalities | 692 (85.9%) | 183 (75.6%) | |
| Type of intraspinal abnormalities | |||
| Syringomyelia (%) | 63 (7.8) | 33 (13.6) | 0.003 |
| Diastematomyelia (%) | 17 (2.1) | 8 (3.3) | 0.285 |
| Tethered spinal cord (%) | 18 (2.2) | 12(5.0) | 0.026 |
| Chiari malformation (%) | 12 (1.5) | 8 (3.3) | 0.075 |
| Lipoma filum terminale (%) | 38 (4.7) | 25 (10.3) | 0.001 |
| Low-lying conus medullaris (%) | 21 (2.6) | 11 (4.5) | 0.124 |
| Presence of rib deformities | |||
| Yes | 26 | 30 | p < 0.001 |
| No | 780 | 212 | |
| The location of the HV | |||
| C | 2 | - | |
| T | 349 | 113 | |
| L | 455 | 38 | |
| C+T | 0 | 5 | |
| T+L | 0 | 85 | |
| C+T+L | 0 | 1 |
The presence of intraspinal abnormalities was significantly associated with female sex than male (p = 0.0004). The segmentation of the hemivertebra was presented in Table III. Patients with intraspinal abnormalities exhibited different presentations of hemivertebra, including a higher incidence of semisegmented or nonsegmented hemivertebra (p = 0.0022). Notably, patients with intraspinal abnormalities had a significantly higher occurrence of rib deformities (p < 0.001) (Table III). Multivariate logistic regression showed female sex [odds ratio (OR) = 1.800, p = 0.001], presentation of hemivertebra toward semisegmented/nonsegmented morphology (OR = 1.499, p = 0.003), and multiple hemivertebra (OR = 1.957, p = 0.001) are the risk factors of intraspinal abnormalities in all cases (Table S1, Fig. S3)
TABLE III.
Comparison of Clinical and Radiographic Parameters Between Those with IA and Those Without
| Intraspinal Abnormalities (n = 173) | No Intraspinal Abnormalities (n = 875) | p | |
|---|---|---|---|
| Gender (F/M) | 99/74 | 373/502 | 0.0004 |
| HV patterns | <0.001 | ||
| Single | 114 | 692 | |
| Multiple HV | 59 | 183 | |
| Presentations of HV | 0.0022 | ||
| Fully segmented | 87 (50.29%) | 533 (60.91%) | |
| Semisegmented | 66 (38.15%) | 295 (33.71%) | |
| Nonsegmented | 20 (11.56%) | 47 (5.37%) | |
| Cobb angle (°) | 43.6 ± 16.7 | 41.25 ± 15.5 | 0.080 |
| Kyphosis >20° | 0.6408 | ||
| Yes | 86 | 418 | |
| No | 87 | 457 | |
| Pain | 0.5202 | ||
| Yes | 10 | 125 | |
| No | 163 | 750 | |
| Neurological symptoms | 0.1712 | ||
| Yes | 21 | 77 | |
| No | 152 | 798 | |
| Rib deformities | <0.001 | ||
| Yes | 19 | 37 | |
| No | 154 | 838 | |
| Other organ defects | 0.1059 | ||
| Yes | 9 | 78 | |
| No | 164 | 797 |
Through physical examination, we identified 98 with abnormal neurological findings in all cases, including reduced muscle strength or hypesthesia, abnormal abdominal reflex, and muscle atrophy. We found that 3 patients had clonus signs and 4 had diminished sensation in the perineal area, but no bowel or bladder problems were found. No patients have positive Babinski, Hoffman signs. The presence of positive neurological findings does not differ significantly between those with or without intraspinal abnormalities. Surgically, 4 patients underwent neurosurgical intervention, including 2 patients with tethered cord release, 1 patient with myelomeningocele repair, and another 1 had posterior fossa decompression for Chiari malformation.
Discussion
This study of 1,048 CS patients with hemivertebra, the largest cohort of its kind, reveals that multiple hemivertebra cases show 1.7-fold higher risk than single hemivertebra (24.4% vs. 14.1%). Importantly, female patients and nonsegmented hemivertebra morphology showed significantly higher risk of intraspinal abnormalities. Notably, 87.9% of affected patients showed no neurological symptoms. These findings underscore the critical need for preoperative MRI screening in high-risk cases to prevent surgical complications, regardless of symptom presentation.
Belmont et al. found a 28% incidence of intraspinal abnormalities in single hemivertebra compared with 21% in complex deformities10. However, later studies showed a higher incidence of intraspinal abnormalities in patients with segmentation failure or mixed types than formation failure14,17. Recent meta-analysis on diverse ethnic populations found no significant association between CS type and incidence of intraspinal abnormalities18. Ghandhari et al. revealed that multivertebra was associated with a higher risk of intraspinal abnormalities, but the sample size of 26 CS patients with multiple vertebrae may not be representative11. Given the established high risk of abnormalities for those with segmentation failure or mixed type of deformity, we primarily focus on surgically treated CS caused by hemivertebra and reveal the key indicators for intraspinal abnormalities. Our study represents the largest sample size in consecutive hemivertebra cases from single population.
Reportedly, the most common intraspinal abnormalities are diastematomyelia (4%-36.4%), syringomyelia (3.75%-40.69%), and tethered cord (4.1%-28.32%)4,5,10,11,18-20. In our study with exclusively hemivertebra, the prevalence was syringomyelia (8.3%) and it was within the range of reported rates, while the incidence of tethered spinal cord (2.9%) and diastematomyelia (2.2%) were below the reported range. Segmentation failure occurs more frequently in male patients, whereas mixed anomalies are more commonly observed in female patients11. In this study, intraspinal abnormalities were significantly associated with female sex in patients, which is possibly attributed to the longer duration of cranial neural tube closure in female patients and sex differences in genetic factors21.
Reportedly, the location of spinal defects at cervical or thoracic spine (33.8%) and thoracic spine (33.4%) is higher than that of the lumbar spine (20.7%)14. Shen et al. reported a 60.4% incidence in those with thoracic hemivertebra than lumbar HV of 35.3%5. By contrast, the occurrence of intraspinal abnormalities in single hemivertebra group is evenly distributed. Moreover, over 40% of intraspinal abnormalities was identified in regions outside the bony lesions, highlighting the significance of whole-spine MRI in cases with both single and multiple HVs. Intriguingly, we found 3 of 5 patients with multiple hemivertebra located at C+T have intraspinal abnormalities, including 2 with diastematomyelia and 1 with syringomyelia.
In this study, we found that patients with intraspinal abnormalities exhibited a higher incidence of semisegmented or nonsegmented hemivertebra. This finding differs from existing literature with segmentation failure or mixed deformities. In CS patients with hemivertebra, we did not observe any correlation between sagittal kyphosis and intraspinal abnormalities. By contrast, the absence of typical thoracic hypokyphosis in adolescent idiopathic patients (AIS) is an indicator for possible intraspinal abnormalities in AIS22. In consistent with previous studies, we found positive association between rib deformities and intraspinal abnormalities17, potentially because ribs develop from the somite sides during segmentation23.
The accuracy of physical examinations in diagnosing intraspinal abnormalities varies from 53.9% to 65% in CS5,10. In our study, the presence of a positive physical examination can detect intraspinal abnormalities with a low sensitivity of 12.1%, and the incidence of positive physical examination findings is also lower than the reported rate of 47%5. Our findings support previous studies that physical examination is not reliable as a predictor for intraspinal abnormalities. Despite positive findings on MRI, accumulating evidence suggest that prophylactic detethering may not be necessary in cases with asymptomatic tethered spinal cord and diastematomyelia before surgical correction24,25. Hence, the aftermath of these MRI findings requires coordination with neurosurgeons.
This study has several limitations. First, as a retrospective analysis focused exclusively on surgically treated hemivertebra, the findings may not generalize to nonsurgical cases. Second, the single-center design and exclusive Chinese patient population may limit broader applicability. Given the retrospective design of this study, patient-related selection bias must be acknowledged, as the study cohort included may not accurately reflect the broader target population of interest. Future multicenter studies involving diverse ethnic groups are needed to validate these results.
In conclusion, our findings indicated a significantly elevated risk of intraspinal abnormalities in patients with multiple hemivertebra than single hemivertebra. Care should be taken to female patients with nonsegmented or semisegmented hemivertebra. Physical examination provides limited prediction of those intraspinal abnormalities. Preoperative spinal MRI is important to identify the intraspinal abnormalities, and caution should be paid to the region outside of the bony lesions.
Source of Funding
This work was supported by the Natural Science Foundation of Jiangsu Province (Grants No BK20240241); and Nanjing Medical Science and Technology Development Key Project (ZKX22017). Jiangsu Provincial Medical Innovation Center of Orthopedic Surgery (CXZX202214).
Appendix
Supporting material provided by the authors is posted with the online version of this article as a data supplement at jbjs.org (http://links.lww.com/JBJSOA/B33). This content was not copyedited or verified by JBJS.
Footnotes
Investigation performed at Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, People’s Republic of China
Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSOA/B32).
Contributor Information
Li Jie, Email: lijiesurg@126.com.
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