Surgical Correction for Adolescent Idiopathic Scoliosis : A Case Series of 139 Consecutive Patients Treated in Neurosurgical Department

Abstract

Objective

This study aimed to evaluate the clinical and radiographic results of patients with adolescent idiopathic scoliosis (AIS) operated by a single neurosurgeon.

Methods

A total of 139 consecutive patients with AIS who underwent corrective surgery by a single neurosurgeon were investigated between January 2011 and January 2024. Segmental instrumentation with pedicle screws was utilized for deformity correction. Demographic information, structural type of curve using Lenke classification, degree of correction achieved, total numbers of fusion levels, complications, and clinical/radiographic results were evaluated.

Results

Most patients were adolescent girls (105 vs. 34) with an average age of 15.9 vs. 16.0, respectively. The average duration of follow-up was 4.5 years (0.1–13.0). Nine patients (6.6%) had levoscoliosis, and the remaining 130 had dextroscoliosis. Chiari malformation with syringomyelia was incidentally diagnosed in four patients (2.8%). Of the patients having Chiari malformation, two (50%) had levoscoliosis. The mean number of fused levels was 11.2. The mean value of the Cobb angle of the major structural curvature was 63.4° (43°–125°). The major structural curve’s average percentage of correction was 78.8%. The final postoperative SRS-22 average score significantly improved to 4.3±0.4 compared with the preoperative score of 3.8±0.5 (p<0.001). After the surgery, there were no observed cases of neurological deficits or need for screw repositioning. Revision fusion extension surgery was performed on one patient to treat postoperative shoulder imbalance.

Conclusion

Patients with AIS treated by a neurosurgeon had acceptable clinical and radiographic results. However, AIS surgery necessitates a fundamental comprehension of pediatric spinal deformities, which is crucial. Furthermore, spine surgeons should be careful with patients who have levoscoliosis.

INTRODUCTION

Different clinical consequences of spinal deformities include deformity progression, neurological deterioration, and psychosocial, cardiovascular, and pulmonary issues [1]. Pediatric spinal deformity has a more significant impact because it affects growth [1]. Adolescent idiopathic scoliosis (AIS) is a distinct type of spinal deformity that accounts for a significant portion of pediatric spinal deformities. Since the Department of Neurosurgery was founded in South Korea, there has not been enough discussion about treating spinal deformities compared to other spinal disorders. However, the Korean Spinal Deformity Society (KSDS) was founded in January 2009, and the neurosurgeon members have held annual meetings to discuss related research and education on spinal deformities. Thus, Korean neurosurgeons have treated many patients with adult spinal deformities since then [8]. Neurosurgeons have broadened their scope to include complex spinal deformities, such as pediatric spinal deformities like AIS as well as congenital and neuromuscular scoliosis [5,10]. Nevertheless, neurosurgeons in South Korea have not widely performed corrective deformity surgery for AIS. We presented our early surgical experience in 2015 and the learning curve for AIS surgery in 2018 by presenting 46 consecutive patients with AIS who received corrective deformity surgery [6].

As far as current research indicates, no study has focused on the surgical and clinical outcomes of more than a hundred AIS surgical series performed by a neurosurgeon. This study aimed to assess the radiographic, surgical, and clinical results of AIS surgery by a single neurosurgeon in 139 consecutive patients.

MATERIALS AND METHODS

Details of patient and surgeon

This research involves a series of sequential case studies and a retrospective analysis. The Institutional Review Board of Seoul National University Bundang Hospital approved this single-center retrospective study (approval number : B-2404-892-108). One hundred and thirty-nine patients with AIS underwent surgical treatment by a single neurosurgeon between January 2011 and January 2024. Surgical methods were posterior segmental instrumentation and fusion, commonly used for deformity correction. Neuromuscular and congenital scoliosis resulting from formation or segmentation failure, such as unsegmented bar and hemivertebra, were not included in this study. Patients’ demographic data, curve magnitude, structural type of curve using Lenke classification, degree of correction achieved, total number of fused levels, operative duration, estimated blood loss (EBL) during surgery, radiographic and clinical results (evaluated using the Scoliosis Research Society-22 [SRS-22] questionnaire) [20], and complications were evaluated.

The spine surgeon is a board-certified neurosurgeon with specialized training in spine deformity under three senior members of the SRS, namely Dr. Rhim SC, a neurosurgeon and the founder of KSDS, and Drs. Kim YJ and LG Lenke, who are orthopedic surgeons. The index surgeon was selected and educated as a traveling fellow of the SRS.

Pre- and postoperative assessment

Thirty-six-inch whole-spine plain radiographs or wholebody stereoradiographs (EOS Imaging, Paris, France) were examined with fists positioned on the clavicle to ensure the humerus does not obstruct the view of the spine while maintaining proper balance [2]. The children’s growing organs were shielded during radiography by using gonad shields. The Lenke classification categorizes the patterns of spinal deformity curves [12]. All patients were photographed before and after the surgery, including a forward-bending image, to compare their overall clinical characteristics, such as trunk and shoulder balance [11]. A preoperative magnetic resonance imaging (MRI) was performed for a patient who had levoscoliosis with more than a 70-degree scoliotic curve. The SRS-22 questionnaire was conducted at regular intervals : preoperatively, 6 weeks postoperatively, 1 year, 2 years, and so on. Pulmonary function was assessed before and after surgery to measure forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) at 1 and 2 years post-operation. At each outpatient clinic visit, a board-certified neurosurgeon assessed surgical complications, radiologic and clinical results, and the degree of curve correction by comparing standing whole-spine plain radiographs.

Surgical procedures

All patients were put on a Jackson spine table in the prone position while under general anesthesia. During the surgery, we used monitoring for somatosensory evoked potentials and transcranial motor evoked potentials. All pedicle screws were placed using the freehand method for segmental instrumentation without the aid of radiological guidance [3,7,9]. A pedicle hook or transprocess hook was used if the pedicle was scanty of the cancellous channel. After segmental instrumentation, various deformity correction techniques, such as direct vertebral rotation, rod derotation, translation technique, and posterior column osteotomies, were utilized. However, additional thoracoplasty has never been performed. Then, the shoulder balance and junctional disc wedge angle were assessed using intraoperative portable whole-spine radiographs. The fusion process was completed with extensive bone grafting, utilizing autologous bone obtained during surgery with or without allograft bone chips. There has never been an autograft using the iliac bone.

Statistical analysis

All statistical analyses were conducted using IBM SPSS Statistics version 22.0 (IBM, Corp., Armonk, NY, USA). Categorical variables were analyzed using the Mann-Whitney test, and continuous variables were analyzed using the student t-test. The analysis of dichotomous data utilized the chi-squared test. For variables collected before and after the operation, we utilized either a paired t-test or Wilcoxon signed rank test. A p-value lower than 0.05 was considered to be statistically significant.

RESULTS

Surgical and radiographic outcomes

Most patients were adolescent girls (105 vs. 34) with an average age of 15.9 vs. 16.0, respectively. The average duration of follow-up was 4.5 years (0.1–13.0). Nine patients (6.6%) had levoscoliosis, and the remaining 130 had dextroscoliosis. Chiari malformation with syringomyelia was incidentally diagnosed in four patients (2.8%). Of the patients having Chiari malformation, two (50%) had levoscoliosis. Asymptomatic syrinx without Chiari malformation was found in four patients (2.8%). All four patients having Chiari malformation with syringomyelia underwent foramen magnum decompression (FMD) as the initial surgical treatment. The mean number of fused levels was 11.2. The mean value of the Cobb angle of the major structural curvature was 63.4° (43°–125°). The major structural curve’s average correction rate was 78.8%. The average operative time and EBL were 254.0 minutes and 502.2 mL, respectively.

Clinical results and postoperative complications

No cases of postoperative neurological deficits or screw malposition requiring revision were observed. Superficial wound infection and asymptomatic rod fracture occurred in each patient, which was treated conservatively. One patient underwent surgery to extend a fusion for shoulder imbalance. The clinical outcomes improved significantly after surgical treatment, as measured by the SRS-22 questionnaire. The final postoperative average score of the SRS-22 significantly improved to 4.3±0.4 compared with the preoperative score of 3.8±0.5 (p<0.001). Based on the analysis of sub-domains, there has been a significant improvement in self-image (2.3±0.7 and 3.9±0.3) and function scores (3.6±0.5 and 4.4±0.5) of the SRS-22 were achieved through surgery (p<0.001).

Pulmonary function test

The FVC before surgery averaged 3.0 L, while it averaged 3.8 L after surgery. (0.8 L increase, p=0.021). Preoperatively, the absolute FEV1 was 2.7 L, which increased to 3.6 L in the postoperative measurement. (0.9 L increase, p=0.018).

DISCUSSION

AIS typically develops during the menarche period in girls and is characterized by a noticeable chest wall or back deformity and shoulder imbalance [16,19]. Historically, AIS has been treated mainly by orthopedic surgeons. This could be because orthopedic surgeons have specialized experience in bone fixation for long bone and skeletal fractures. Neurosurgeons have gained experience in complex spinal surgery and realized that a fundamental knowledge of spinal deformities is crucial for optimal surgical outcomes. The literature contains several anecdotal reports of neurosurgeons treating and operating on patients with AIS [5,6,15]. Since the SRS, the World Federation of Neurosurgical Societies (WFNS), and local academic societies such as the KSDS have been teaching neurosurgeons the fundamental understanding of adult and pediatric spinal deformities, the number of AIS surgeries performed by neurosurgeons has gradually increased.

This study included 139 consecutive patients who underwent surgical treatment for AIS by a neurosurgeon. To the best of our knowledge, no study has focused on the clinical and surgical outcomes of a large surgical series AIS performed by a neurosurgeon. In the current study, there were no instances of neurological deficits or need for screw repositioning. Regarding surgical outcomes, operative duration and EBL were 254.0 minutes and 502.2 mL, respectively. Our previous study for the learning curve of AIS surgery indicated that surgical outcomes such as operative time, surgical bleeding, and the correction rate of the major structural curve could improve with more surgical experience. The more AIS surgeries a neurosurgeon performs, the more technically proficient they become. These results are consistent with earlier studies that have looked into the learning curve for spine surgeries [17,19].

Regarding radiography results, the major structural curve’s average correction rate was relatively high (78.8%), even compared with previous studies by orthopedic spinal deformity specialists. Our surgical outcomes are acceptable in terms of the EBL, operative time, and correction rate. Nonetheless, we believe a level shoulder and balanced spine are more crucial in AIS surgery than the actual correction rate. A patient who underwent revision fusion extension surgery for postoperative shoulder imbalance was the only one revision case from the present study. We suggest scoliotic curvature can be treated more effectively and thoroughly as surgeons become more proficient.

Our clinical results demonstrated significant improvement based on the SRS-22 questionnaire following the surgical correction (Fig. 1). Considering one revision surgery for postoperative shoulder imbalance and no neurological deficit cases, surgical and clinical outcomes are acceptable. Although there is an initial obstacle, AIS surgery becomes more effective and safer as neurosurgeons gain experience.

Fig. 1.

A : Preoperative whole spine plain radiograph showing scoliotic deformity with 101 degrees Lenke type 2A+ curve. B : Postoperative 2-year whole body EOS images (EOS Imaging, Paris, France) demonstrating a balanced spine after surgical correction.

In the current study, Chiari malformation with syringomyelia was incidentally diagnosed in four patients (2.8%). Of the patients having Chiari malformation, two (50%) had levoscoliosis. Chiari I malformation and syringomyelia have been associated with scoliosis in numerous studies [14,21]. Interestingly, several studies found that FMD can improve not only neurological status but also scoliotic deformity. This means that syringomyelia may exacerbate spinal alignment. If a neurosurgeon incidentally discovers Chiari malformation while treating a patient with AIS, there is a benefit to first performing FMD. This procedure allows for careful monitoring of neurological changes and the degree of spinal curvature, helping to prevent the worsening of the spinal curvature. Following this, surgical treatment for AIS can be considered in a staged manner, based on existing research evidences. However, FMD did not stop aggravating the scoliotic deformity in this series. Although all four patients having Chiari malformation with syringomyelia underwent FMD as the initial surgical treatment, the scoliotic curve progressed even after FMD in all of them. Thus, these patients underwent additional correction surgery for spinal deformities (Fig. 2).

Fig. 2.

A : Preoperative whole spine plain radiograph showing scoliotic deformity with 52.1 degrees Lenke type 1A+ curve. B : Preoperative cervical MRI confirmed cerebellar tonsil lying below the foramen magnum with cervical syringomyelia. C : Post-FMD MRI showing decreased syringomyelia. D : Follow-up whole spine plain radiograph after FMD 1 week, 7 months, 18 months showing aggravated scoliosis. E : Postoperative 2-year whole body EOS images (EOS Imaging, Paris, France) demonstrating a balanced spine after surgical correction. MRI : magnetic resonance imaging, FMD : foramen magnum decompression.

The limitation of this study is that it is not a comparative study. However, the surgical and clinical outcomes were comparable to previous studies [4,13,18,22]. Regardless of this shortcoming, we show that a neurosurgeon can perform AIS surgery with acceptable outcomes. Furthermore, we suggest a comprehensive understanding of the growing spine and pediatric spinal deformity is crucial for AIS treatment. In this regard, patient outcomes are more favorable when neurosurgeons and orthopedic surgeons collaborate on these operations, as opposed to a neurosurgeon handling them exclusively. In addition, spine surgeons, regardless of residency training, are increasingly being recognized as a unified group treating children within the SRS and spinal fellowships worldwide. Increased participation in treating spinal deformities and practice in higher-volume centers have shown clinical significance and safety in spinal deformity surgery. As a result, we highly recommend that neurosurgeons treating AIS undergo basic knowledge training and enhance their surgical skills through WFNS and SRS.

CONCLUSION

A total of 139 patients with AIS treated by the neurosurgeon had acceptable clinical and radiographic results. However, AIS surgery necessitates a fundamental comprehension of pediatric spinal deformities, which is crucial. Furthermore, spine surgeons should be careful with patients who have levoscoliosis.