Abstract
Background Sciatic scoliosis is commonly observed in patients with lumbar disc herniation and is believed to represent a compensatory response to radicular pain. While surgical decompression has been shown to correct this deformity, the potential for nonoperative interventions to induce similar radiographic improvement remains unclear. Therefore, the present study aims to evaluate early radiographic and clinical changes in sciatic scoliosis following transforaminal epidural steroid injection (TFESI) in patients with lumbar disc herniation.
Methods A prospective cohort study was conducted, including 25 patients with lumbar disc herniation and associated sciatic scoliosis. Radiographic parameters, including lumbosacral Cobb angle, compensatory thoracic/thoracolumbar curve, and trunk shift, were assessed at baseline and at 3 weeks, and 6 weeks after intervention. Clinical outcomes included visual analog scale and Oswestry Disability Index.
Results Significant reductions in lumbosacral Cobb angle were observed at 3 and 6 weeks (12.56°–6.68° and 4.48°, respectively; P < 0.001). Compensatory thoracic/thoracolumbar curves and trunk shift also improved significantly. At 6 weeks, 84% of patients achieved normalization of the lumbosacral curve (<10°), and 88% demonstrated ≥50% improvement. Significant improvements in pain and functional outcomes were also observed.
Conclusions TFESI is associated with early improvement of pain-induced sciatic scoliosis and coronal imbalance. These findings suggest that radicular pain plays a key role in the development of this deformity and that its resolution may result in reversible postural correction. TFESI may also serve as a useful clinical tool in distinguishing flexible, pain-related deformity from structural scoliosis prior to surgical decision-making.
Clinical Relevance These findings support the use of TFESI as an effective nonoperative strategy for early correction of sciatic scoliosis and symptom improvement, potentially reducing the need for surgical intervention.
Level of Evidence 3.
Introduction
Lumbar disc herniation is a prevalent spinal disorder, particularly among young and physically active individuals. Clinical manifestations may include low back pain, radiculopathy, gait disturbance, sciatic scoliosis, and a kyphotic posture, all of which may result in limitations in daily activities.
Sciatic scoliosis has been reported to occur in association with lumbar disc herniation, particularly in young and physically active individuals. Although the exact underlying mechanism remains unclear, most authors consider sciatic scoliosis to represent a compensatory postural response aimed at alleviating nerve root irritation, thereby resulting in coronal imbalance.1–3 The direction of sciatic scoliosis has been reported to correlate with the side of disc herniation.4 Patients typically compensate by tilting the trunk away from the side of the herniation in an attempt to relieve compression of the affected nerve root.
Transforaminal epidural steroid injection (TFESI) has been proven to be an effective treatment for patients with lumbar disc herniation. It can help to reduce the pain caused by irritation of compressed nerves by its anti-inflammatory effect. This method is suitable for lumbar disc herniation patients with radicular pain who are considered surgical candidates as a surgery-sparing intervention.3
Recently, several studies have reported that sciatic scoliosis improves following relief of lumbar disc herniation-related pain after discectomy.2 However, such improvement may not occur in patients with long-standing sciatic scoliosis or in those with concomitant scoliosis unrelated to disc herniation. Therefore, the ability to predict postoperative improvement prior to surgery would be valuable for patient counseling. Several studies have attempted to identify predictors of scoliosis correction before surgical intervention. We hypothesized that TFESI, which has been shown to reduce nerve root irritation caused by disc herniation, may also improve sciatic scoliosis and potentially serve as a predictor of postoperative deformity correction following discectomy. To date, however, no study has specifically evaluated the improvement of sciatic scoliosis after TFESI.
The aim of this study was to evaluate the improvement of sciatic scoliosis and coronal imbalance after TFESI in patients with lumbar disc herniation.
Methods
This prospective cohort study was conducted at the Orthopedic Surgery Unit in the Department of Orthopedics at Thammasat University Hospital in Pathum Thani, Thailand. The approval from the Ethics Committee on Clinical Research of the Faculty of Medicine, Thammasat University, was obtained prior to the study (MTU-EC-OT-1-200/63).
Twenty-five patients who had lumbar disc herniation and sciatic scoliosis were enrolled in this study. TFESI was performed at Thammasat University Hospital between October 2020 and February 2021. Inclusion criteria included patients aged 20 to 60 years who were diagnosed with lumbar disc herniation presenting with radicular pain. Eligible participants demonstrated no clinical improvement after at least 3 months of conservative management, including physical therapy and pharmacological treatment. Additional criteria included the presence of radiographic scoliosis, defined on standing plain radiographs as a lumbar coronal Cobb angle ≥10°, and magnetic resonance imaging confirming lumbar disc herniation involving no more than 2 levels (Figure 1). Exclusion criteria included patients diagnosed with adolescent idiopathic scoliosis, spondylolisthesis, or spinal instability. Patients who had a previous history of back surgery, severe traumatic back injury, infection at the back, cancer, or allergic history to steroids and seafood were also excluded from this study. The demographic data included age, gender, history of smoking, duration of symptoms, level of disc herniation, presence of positive straight leg raising test, and presence of weakness.
Example of imaging confirming lumbar disc herniation involving no more than 2 levels. Preintervention posteroanterior standing radiograph of a 54-year-old woman with sciatic scoliosis (upper left image) and a postintervention posteroanterior standing radiograph (upper right image) are shown. T2-weighted sagittal magnetic resonance imaging (MRI; bottom left image) demonstrates disc extrusion at L5–S1 and T2-weighted axial MRI (bottom right image) demonstrates a left paracentral disc herniation with compression of the traversing left S1 nerve root.
A whole spine standing radiograph was performed and assessed during the initial visit, prior to any intervention, and subsequently at 3 weeks and 6 weeks following the intervention. The radiograph should provide adequate exposure to ensure clear visualization of key anatomical landmarks, including the second and seventh cervical vertebrae, the first and fifth lumbar vertebrae, and the first sacral vertebra. Scoliosis, which is determined by the Cobb angle, was measured between the upper and the lower ends of the vertebrae of lumbosacral and thoracic or thoracolumbar curves. Trunk shift was measured by using the horizontal distance between the central sacral vertical line and the C7 plumb line.5 All radiographic parameters were independently measured twice by 2 fellowship-trained spine surgeons, with a 2-week interval between measurements. The mean values were used for analysis. The direction of the curve, the direction of trunk shift, and the side of disc herniation were also collected to determine their relationship.
Visual analog scale (VAS) for back and radicular pain ranging from 0 (no pain at all) to 10 (the most severe pain), and back disability score using the Oswestry Disability Index (ODI), which ranges from 0% (no disability) to 100% (severe disability), were collected before the intervention was performed.6 The sample size calculation was referenced from Matsui’s study.4 The alpha and power were set at 0.05 and 0.9, respectively. The primary outcome was defined as the improvement in the coronal lumbosacral curve, compensatory thoracic or thoracolumbar coronal curve, and trunk shift at 3 and 6 weeks following the intervention, compared with the preoperative parameters. Secondary outcomes included VAS and ODI, which were collected before the intervention and 3 and 6 weeks after the intervention. In addition to mean changes of curves, a responder analysis was conducted to determine the proportion of patients achieving a normalized curve (defined as a Cobb angle <10°) or a ≥50% reduction in curve magnitude at 6 weeks postintervention.
Procedures in the operating room started with the patients lying prone on a radiolucent table. A fluoroscope was used to verify the level of injection and the clear appearance of the vertebral endplate and symmetrical oval pedicles. The operating field was prepared in a sterile fashion, and an anesthetic solution of 1 mL of 1% lidocaine was injected into the skin before the needle was inserted. The tip of a 23-gauge spinal needle was placed in the neural foramen (Figure 2). The position was confirmed by injecting 1 mL of iohexol contrast agent under fluoroscopic guidance (Figure 3). The final step was to inject the mixed solution of 40 mg of triamcinolone and 1 mL of normal saline. This process was performed at the site of the disc herniation identified on the magnetic resonance imaging. Subsequently, the patients were observed in the postoperative care unit. At 3- and 6-week intervals after the intervention, the patients were asked to perform the whole spine standing radiograph and answer questionnaires including VAS and ODI.
Posteroanterior and lateral radiographic views of the transforaminal epidural injection.
Posteroanterior and lateral radiographic views demonstrate the contrast flow pattern within the epidural space, confirming precise needle placement for transforaminal epidural steroid injection.
Data were analyzed using STATA version 17. Demographic data were represented by means and standard deviations. A linear mixed model was used to analyze data before and after TFESI, which included lumbosacral curve, thoracic or thoracolumbar curve, trunk shift, VAS, and ODI scores. The association between the side of disc herniation and the direction of the sciatic scoliotic curve and trunk shift was analyzed. Intraclass correlation coefficient reliability was used to interpret intraobserver and interobserver reliability for lumbosacral curve, thoracic or thoracolumbar curve and trunk shift measurements.
Results
The mean age of patients in the study was 45.3 years. Fifty percent of patients were men. Forty percent of patients had a smoking history. The mean duration of symptoms was 19.1 weeks. The most common location of the herniated disc was L4/L5 and L5/S1 levels. During physical examination, 56% of patients had a positive straight leg raising test and 24% had weakness in the physical examination of lower extremities. All patients demonstrated a primary lumbar Cobb angle of at least 10° as well as a compensatory thoracic or thoracolumbar Cobb angle of at least 10°.
All 25 enrolled patients completed the 6-week follow-up and were included in the final analysis. For the primary outcome, after the patients underwent TFESI, the coronal lumbosacral curve decreased with statistical significance at 3 and 6 weeks after intervention (12.56° vs 6.68° and 4.48°, respectively). The compensatory coronal thoracic or thoracolumbar curve decreased significantly at 3 and 6 weeks postintervention (13.12° vs 6.92° and 5.6°, respectively). Responder analysis at 6 weeks postintervention revealed that 84% (21/25) of patients achieved a normalized lumbosacral curve (<10°), and 88% (22/25) demonstrated a ≥50% improvement from baseline. For the compensatory thoracic/thoracolumbar curve, 84% (21/25) of patients achieved normalization, while 68% (17/25) showed ≥50% improvement. Trunk shift also decreased with statistical significance at 3 and 6 weeks after the intervention (22.99 mm vs 15.40 and 9.98 mm, respectively; Table 1). The intraclass correlation coefficient for both inter- and intraobserver reliability of the coronal lumbosacral curve and trunk shift measurements was 0.92, indicating excellent agreement.
Radiographic outcomes of transforaminal epidural steroid injection at baseline and at 3 and 6 weeks after the intervention.
For the secondary outcomes, back pain improved with statistical significance at 3 and 6 weeks (5.96 vs 3.72 and 2.88, respectively). Radicular pain improved significantly at 3 and 6 weeks (9.38 and 4.54 and 3.26, respectively). Functional outcomes (ODI) also improved with statistical significance at 3 and 6 weeks (36.56 and 22.32 and 18.96, respectively; Table 2). The relationship between the side of disc herniation, the direction of the sciatic scoliotic curve, and the trunk shift was not in conjunction (Table 3).
Clinical outcomes of transforaminal epidural steroid injection at baseline and at 3 and 6 weeks after the intervention.
Relationship between the side of the coronal curve/trunk shift and the side of disc herniation.
Discussion
Lumbar disc herniation with sciatic scoliosis is common in young patients. It can be misdiagnosed as idiopathic scoliosis.7 Most authors have considered sciatic scoliosis as a compensatory mechanism of the body to relieve nerve irritation.1,2 Conceptually, sciatic scoliosis would be improved once the painful stimulus is removed. While previous studies have demonstrated correction of sciatic scoliosis following surgical decompression, the potential for nonoperative interventions such as TFESI to achieve radiographic improvement remains unclear. The author hypothesized that TFESI, by alleviating pain caused by lumbar disc herniation, may consequently improve sciatic scoliosis. TFESI is expected to reduce nerve root inflammation, thereby relieving radicular pain. With resolution of radicular pain, the associated paraspinal muscle spasm may decrease, leading to correction of the compensatory posture, sciatic scoliosis. However, there is no single previous research that studies the improvement of sciatic scoliosis after TFESI.
The mechanism underlying the observed radiographic improvement is likely multifactorial. Sciatic scoliosis is widely considered an antalgic posture driven by radicular pain. Nerve root irritation may induce asymmetric paraspinal muscle activation and spasm, leading to trunk shift and coronal imbalance. Relief of inflammation and radicular pain following TFESI may therefore reduce muscle spasm and allow restoration of a more neutral spinal alignment. This concept supports the hypothesis that a subset of scoliotic deformities in lumbar disc herniation represents a functional and reversible condition rather than a fixed structural deformity.
TFESI is an effective treatment for patients with lumbar disc herniation. Pain reduction has been shown to be significant within 2 to 4 weeks following injection, as supported by the North American Spine Society guidelines for the diagnosis and treatment of lumbar disc herniation with radiculopathy (Recommendation A).8 Previous studies have consistently demonstrated the efficacy of epidural steroid injections in the management of lumbar radicular pain.9 Armon et al reported improvement in radicular lumbosacral pain when assessed between 2 and 6 weeks after epidural steroid injection.4 Similarly, Roberts et al found that TFESI may serve as a surgery-sparing intervention in patients with radicular pain due to lumbar disc herniation who are considered surgical candidates, consistent with findings by Kanna et al, who demonstrated that epidural steroid injection can provide sustained symptom relief for at least 1 year in patients with acute lumbar disc herniation.10,11 Furthermore, Riew et al reported that epidural steroid injections were significantly more effective than bupivacaine alone in reducing the need for surgical decompression in patients with lumbar radicular pain.12 In line with these findings, Radcliff et al observed a higher rate of crossover to nonsurgical treatment among patients initially assigned to surgical management who received epidural steroid injections.13 Previous reports have suggested that a lumbar coronal Cobb angle greater than 30° and a trunk shift exceeding 2 cm are indicative of poor coronal balance or decompensation.14–16 In the present study, the mean preintervention trunk shift was 22.99 mm, indicating that the study population exhibited coronal imbalance. Our findings demonstrated that sciatic scoliosis, as measured by the Cobb method, improved significantly following TFESI, with a magnitude of correction comparable to that reported in surgically treated cases.5 These results suggest that TFESI may achieve similar early deformity correction without the need for surgery and may serve as a surgery-sparing option for selected patients.
Furthermore, TFESI provided significant pain relief and functional improvement, as evidenced by reductions in VAS scores and improvements in ODI scores at both 3 and 6 weeks. To our knowledge, this study represents the first evidence demonstrating the potential for nonoperative correction of sciatic scoliosis.
In a previous study, Suk et al reported that the direction of sciatic scoliosis was not associated with the location of nerve root compression (medial, lateral, or beneath), although it was related to the side of disc herniation (left or right), likely as a compensatory mechanism for pain perceived by patients.4 Matsui et al conducted a retrospective study examining the relationship between the location of disc herniation and pre- and postoperative changes in sciatic scoliotic list and found that the sciatic list may indicate the side of disc herniation and assist in the preoperative prediction of scoliosis recovery.5 However, in the present study, the side of disc herniation was not significantly associated with the direction of the sciatic scoliotic curve or trunk shift. This discrepancy may be explained by differences in the location of disc herniation, as varying zones of nerve root compression may result in different patterns of compensatory mechanisms.
From a clinical perspective, the ability of TFESI to induce early radiographic improvement may have diagnostic and prognostic value. Patients demonstrating rapid correction of scoliosis following injection may be more likely to have flexible, pain-driven deformity and may respond favorably to decompression alone. Conversely, persistent deformity despite pain relief may suggest underlying structural components. Therefore, TFESI may serve not only as a therapeutic modality but also as a tool to guide surgical decision-making.
Limitations
This study has several limitations. First, the sample size was relatively small, which may limit generalizability. Second, the follow-up period was limited to 6 weeks; thus, the findings reflect early radiographic changes rather than long-term deformity correction. Third, the absence of a control group makes it difficult to distinguish the effect of TFESI from the natural course of lumbar disc herniation. Future studies with larger sample sizes, longer follow-up, and comparative groups are warranted.
Conclusion
TFESI is associated with rapid correction of sciatic scoliosis. In the present study, both the primary coronal lumbosacral curve and the compensatory thoracic or thoracolumbar curve, as well as pain scores and functional outcomes, demonstrated significant improvement following TFESI. This study also highlights that not all scoliosis associated with lumbar disc herniation is structural, and a substantial proportion may be reversible with pain control. Further well-designed, large-scale randomized controlled trials are warranted to validate these findings and further elucidate the underlying mechanisms.
Acknowledgments
We wish to thank the Department of Orthopedics, Faculty of Medicine, Thammasat University, and Thammasat University Hospital for their kind support. We also wish to thank you for your assistance from proofreaders and editors.
Footnotes
Funding The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests The authors report no conflicts of interest in this work.
Ethics Approval The approval from the Ethics Committee on Clinical Research of Faculty of Medicine, Thammasat University, was obtained prior to the study (MTU-EC-OT-1-200/63).
- This manuscript is generously published free of charge by ISASS, the International Society for the Advancement of Spine Surgery. Copyright © 2026 ISASS. To see more or order reprints or permissions, see http://ijssurgery.com.
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