Advances in Early Onset Scoliosis Management: A Narrative Review of Treatment Modalities

Abstract

Early-onset scoliosis (EOS) refers to a heterogeneous group of spinal deformities in children aged below 10 years. These conditions exhibit significant variations in their causes, natural progression, and available treatment options. As EOS progresses, it can lead to thoracic insufficiency syndrome, characterized by an altered thoracic structure that hinders normal respiratory function and lung development. This chapter provides an overview of the current treatment methods for EOS, focusing on nonoperative interventions, growth-friendly surgical techniques, and advanced technologies. Nonoperative approaches include bracing, casting, and physiotherapy, aiming to slow or halt curve progression. Surgical interventions are often necessary for severe cases and utilize growth-friendly techniques such as traditional or magnetically controlled growing rods. This chapter highlights the various treatment options available for EOS, emphasizing the importance of early detection and intervention. By effectively managing EOS, healthcare professionals can optimize patient outcomes, minimize complications, and improve the quality of life for affected children. Potential avenues for future research and advancements in EOS treatment are discussed, focusing on minimizing complications and maximizing functional outcomes for affected children. Furthermore, this chapter aims to guide healthcare professionals in making informed decisions regarding the management of EOS.

1. Introduction

Early-onset Scoliosis (EOS) encompasses a spectrum of spinal pathologies that arise during the growth phase, presenting in diverse forms. The intrinsic complexity of EOS has posed challenges in formulating a comprehensive and universally accepted definition, thereby affecting the consensus on diagnosis and management within the orthopedic community. The term EOS was first introduced by Ponseti and Friedman to characterize idiopathic scoliosis in patients under 10 years old [1]. Their observations highlighted a notably less favorable prognosis for these younger patients compared to their older counterparts. Subsequently, in 1954, James further refined the classification of idiopathic scoliosis, categorizing it into three distinct age-based groups: infantile (≤3 years), juvenile (4–9 years), and adolescent (10 years to skeletal maturity) [2]. However, Dickson raised concerns regarding the classification of juvenile idiopathic scoliosis, suggesting an overlap with the infantile subgroup [3]. In later years, Dickson proposed a subdivision of idiopathic scoliosis into early-onset (0–5 years) and late-onset (>5 years) categories [4]. It is noteworthy that despite the recent adoption of this classification in the literature, it has been acknowledged that the treatment approaches for children aged 5–10 years more closely resemble those employed for children under 5 years of age rather than those for children over 10 years of age. Consequently, the Growing Spine Study Group (GSSG) and the Children Spine Study Group (CSSG) defined EOS as any spinal deformity present before the age of 10 years, irrespective of its underlying cause [5, 6]. In 2014, a research team led by Vitale proposed a comprehensive definition for EOS that incorporates both age of onset and etiology. They categorized EOS into four distinct etiological groups: idiopathic, neuromuscular, congenital, and syndromic [6]. This multifaceted approach aimed to enhance the understanding and classification of EOS, thereby facilitating more precise diagnosis and tailored management strategies.

EOS is characterized by a rapid progression, underscoring the importance of expeditious clinical diagnosis and timely referral to a specialized pediatric orthopedic unit [6]. Extensive research has consistently demonstrated that the timing of EOS onset significantly influences the eventual curvature severity and prognosis, with earlier onset correlating with more adverse outcomes [7]. Furthermore, untreated EOS often culminates in substantial spinal deformities, ultimately resulting in a shortened spine, linked to heightened mortality rates and cardiopulmonary compromise [8, 9]. Historically, Scott et al. reported a linear progression rate of approximately 5° per year in EOS cases, highlighting the aggressive nature of the condition [7]. Subsequent investigations by Pehrsson et al. have elucidated the increased risk of severe scoliosis development in patients with early-onset EOS, juxtaposed with adolescent-onset scoliosis, further underscoring the significance of prompt intervention [8]. This elevated morbidity and mortality risk among early-onset EOS patients can be attributed to structural alterations constraining the thoracic cavity, leading to restrictive lung disease, cardiovascular complications, and respiratory failure [10]. Consequently, a comprehensive assessment of EOS should explore the intricate interplay between lung, spine, and thorax development. This holistic approach is imperative for a thorough understanding of EOS’s deleterious impact on cardiopulmonary function and underscores the necessity for timely clinical intervention to mitigate its adverse consequences.

The consideration of lung development plays a pivotal role in comprehending EOS’s historical and progressive aspects within the context of orthopedics. The intricate interplay between the growth of the thoracic cage, spine, and lungs has been extensively explored in existing academic literature. In humans, the skeletal system undergoes two distinct phases of rapid growth, the initial one transpiring from birth to 5 years of age and the subsequent phase occurring during puberty [11, 12]. Concomitantly, lung development exhibits a nonlinear trajectory, characterized by alveolar-capillary proliferation peaking around birth and reaching completion by the age of 2 years, with a cessation phase extending until the age of 8 years. Simultaneously, the bronchial tree’s volume undergoes augmentation with the child’s growth [13]. Consequently, any disruption within the growth dynamics of the thoracic cage-spinal complex can exert detrimental effects on alveolar number and volume as well as the overall lung growth. The simultaneous progression of spinal deformities attributable to EOS during the critical phase of pulmonary alveolar development can significantly impair pulmonary function [9, 14]. Notably, instances of lung hypoplasia, marked by diminished alveoli and arteries, have been observed in patients whose scoliosis becomes pronounced during this crucial period of lung growth, often accompanied by emphysematous alterations [15]. Furthermore, Karol et al. have elucidated a direct correlation between thoracic height and pulmonary function, establishing that a shorter thoracic spine is associated with reduced forced vital capacity (FVC) and an increased propensity for restrictive pulmonary disease. Their research highlights that, in order to avert severe restrictive lung disease (FVC < 50%), the thoracic height should measure greater than 22 cm at skeletal maturity [9]. However, Johnston et al. conducted a study to assess the relationship between pulmonary function and thoracic spine height in EOS patients who underwent corrective surgery. The study revealed that, regardless of whether the patients had a thoracic height of 18 cm or more, their pulmonary function was significantly compromised if they had residual curves exceeding 50°. This raised questions about the validity of using a fixed threshold such as 18 cm as an EOS outcome parameter [16]. The expanding understanding of lung growth dynamics and the long-term consequences of early spinal fusion in scoliosis have influenced current clinical practice. Consequently, spinal fusion procedures before the age of 8 years are now not preferred, with a preference for postponing surgery until the age of 10 years to optimize patient outcomes [17]. These findings underscore the critical role of interdisciplinary collaboration between orthopedic and pulmonary specialists in managing EOS and emphasize the importance of informed clinical decision-making based on the latest scientific insights.

The management of severe scoliosis in skeletally mature adolescents predominantly revolves around spinal fusion, a procedure known to entail the sacrifice of spinal mobility and potential impediments to longitudinal growth. Conversely, addressing severe scoliosis in pediatric patients presents a constellation of distinctive challenges, underscored by the ongoing maturation of the spine, thoracic cavity, and cardiopulmonary system, often complicated by the presence of intricate functional, cognitive, or medical comorbidities. Treatment of EOS assumes paramount importance with multifaceted goals, encompassing the arrest of progression or correction of deformity, the preservation of spinal growth, the optimization of thoracic capacity, and the enhancement of pulmonary function. These objectives are fundamentally directed toward averting cardiopulmonary compromise and optimizing the health-related quality of life [18]. The knowledge derived from extensive research elucidates the intricate interplay between the chest wall, lungs, and spinal column. This deep understanding has directed therapeutic approaches toward cultivating a well-developed thoracic cavity, augmentation of lung volume, and refinement of pulmonary function [9, 14]. Thus, a shift toward growth-friendly treatments has emerged. The therapeutic spectrum for EOS spans both nonoperative interventions and surgical approaches. While nonoperative methods, notably corrective casting and bracing, play a pivotal role in forestalling or delaying the need for spinal surgery and should be considered the cornerstone of treatment, it is essential to acknowledge their inherent limitations. In rapidly progressing curvature that necessitates surgical stabilization, innovative “growth-friendly” corrective techniques have emerged as an indispensable resource within the therapeutic arsenal.

2. Nonoperative treatment

The nonoperative management of spinal deformities encompasses a range of therapeutic modalities, such as bracing, casting, halo-gravity traction (HGT), and physiotherapy, which have demonstrated a potential for achieving favorable correction outcomes in select patient populations. These interventions often serve a dual purpose of achieving satisfactory correction and postponing the need for surgical intervention, making them valuable components of comprehensive treatment strategies. HGT frequently assumes an adjunctive role in the therapeutic landscape, commonly complementing other treatments including surgical interventions [19, 20]. Its applicability is particularly indicated for patients presenting with severe and inflexible spinal curves, those afflicted by scoliosis accompanied by kyphosis, and individuals experiencing compromised pulmonary or nutritional status. The role of physiotherapy in managing idiopathic scoliosis in skeletally immature children remains a topic of ongoing debate and necessitates further substantiation through rigorous validation studies [21]. Casting and bracing are considered two major nonoperative interventions for spinal deformity.

2.1 Casting

Serial casting represents a highly effective conservative approach to managing EOS, which can help preserve growth potential and potentially obviate the need for surgical intervention, particularly in cases of idiopathic scoliosis [22, 23]. The specific techniques employed in serial casting can vary across different studies. Typically, patients receive general anesthesia, followed by applying traction and padding placement on prominent bony areas. Subsequently, plaster is used and shaped with derotational forces to address scoliosis. Casts are scheduled for replacement every 2 to 3 months, with regular clinical and radiological evaluations to accommodate the rapid growth phase of the spine and trunk, tailored to each patient’s growth trajectory.

Serial casting is generally recommended when the curvature exceeds 25°, shows a minimum documented progression of 10°, or exhibits a rib-vertebral angle difference greater than 20° [24]. Early initiation of casting has demonstrated the ability to halt the progression and even correct EOS, yielding a durable and stable outcome in otherwise healthy children [25]. Therefore, the commencement of serial casting should occur as early as possible, as older age and more significant curvature have been identified as potential risk factors for unsuccessful casting treatments [26, 27].

In a study conducted by Gussous et al. [26], 74 consecutive patients were treated with casting therapy, comprising 41 with idiopathic scoliosis and 33 with non-idiopathic scoliosis. Their average age was 19 months, and they were followed up for an average of 11 months. The results revealed that in the idiopathic group, the Cobb angle was successfully corrected from 47° to 27°, whereas in the nonidiopathic group, it improved from 62° to 57°. Notably, the idiopathic group exhibited a higher correction rate compared to the nonidiopathic group. During the final follow-up, minor complications were observed in 8% of cases, including issues such as pressure sores, pyogenic granuloma, exacerbations of gastroesophageal reflux, and humeral fractures, which were attributed to cast-related impaction by parents. Major complications occurred in 4% of cases, including subclavian vein thrombosis, cardiac arrest during general anesthesia induction, and a tragic death due to an acute asthma attack. The study findings suggest that individuals with idiopathic scoliosis, characterized by greater flexibility and milder curvature, tend to respond more favorably to casting treatment compared to those with non-idiopathic scoliosis. Moreover, progressive idiopathic scoliosis patients achieved superior curve correction with casting compared to nonidiopathic scoliosis patients. Commencing casting before 24 months led to improved curve correction outcomes. Patients who ultimately required surgery are typically presented at an older age with a higher Cobb angle than those who transitioned to thoracolumbosacral orthosis (TLSO) treatment. Although rib-vertebral angle difference (RVAD) predicts progression in infantile idiopathic scoliosis, it did not demonstrate predictive values in response to casting for either the idiopathic or nonidiopathic scoliosis groups.

In recent times, there has been a resurgence of interest in the previously abandoned Mehta casting technique for EOS treatment. Mehta’s approach, as described in his 2005 paper [25], aimed to utilize casting to harness the growth potential in EOS and correct progressive curves that could otherwise lead to severe deformities. This method involves meticulously applying a plaster jacket on a Cotrel frame, incorporating a head halter and pelvic traction, known as elongation-derotation-flexion casting. This approach applies a three-dimensional correction force to counteract scoliotic deformity.

Mehta’s groundbreaking study involved 136 children under 4 years with progressive infantile scoliosis (diagnosed before age 3 years). Among the 94 children who received early referral at an average age of 1 year and 7 months, with an average Cobb angle of 32° (ranging from 11° to 65°), their scoliosis resolved by the mean age of 3.5 years, obviating the need for further treatment, allowing them to lead normal lives. In contrast, among the 42 children with a late referral at an average age of 2.5 years and a mean Cobb angle of 52° (ranging from 23° to 92°), casting was ineffective in reversing the deformity, leading to spinal fusion in 36% of these cases.

It’s worth noting that the nonidiopathic population did not exhibit the same promising results in significantly reducing morphologic deformity; however, it did delay the need for surgical intervention [28]. Nonetheless, if young patients can tolerate the associated complications, casting remains a viable and effective treatment option for EOS.

2.2 Bracing

The effectiveness of bracing in treating adolescent idiopathic scoliosis has yielded promising results, particularly for patients with curves ranging from 25 to 40° [29, 30].

However, the use of bracing for EOS remains a topic of debate, with limited research available [31, 32, 33].

Recent investigations by Thometz et al. have shown encouraging outcomes when employing an elongation-bending-derotation brace (EBDB) in children with infantile or juvenile scoliosis, including neuromuscular, congenital, and idiopathic cases [31, 32]. During a 12-month follow-up, the juvenile group exhibited a 25.7% curve correction and 42.9% stabilization, whereas the infantile group showed a remarkable 50% curve correction and 32.1% stabilization. Notably, no patients required surgery during this follow-up period. Additionally, the authors focused on nine infants with idiopathic scoliosis (average age: 11 months) treated with EBDB for a minimum of 2 years. Four patients achieved complete correction with bracing alone (final curve ≤10°), whereas five patients with more rigid curves demonstrated improvement from an average of 57° to 21°.

However, it is important to acknowledge the relatively short follow-up duration and the absence of a second growth spurt assessment in these studies [31, 32]. While bracing offers convenience by allowing removal as needed, casting provides continuous corrective force because it cannot be removed. While bracing may be an effective treatment option for EOS, further research is required to directly compare the efficacy of bracing versus casting in this patient population.

3. Operative treatment

Performing long spinal fusion procedures in patients with early-onset scoliosis (EOS) can pose risks to thoracic growth and pulmonary function. It may increase the likelihood of complications such as the crankshaft phenomenon or decompensation.

However, the introduction of growth-sparing spinal surgery has revolutionized the management of EOS patients. These innovative surgical approaches can correct severe spinal deformities while preserving the potential for thoracic cage and spinal complex growth until the child nears skeletal maturity [34]. The primary objective of these nonfusion surgical techniques is to achieve the appropriate spine length, specifically a T1–T12 length of at least 18 cm at the time of skeletal maturation. This achievement provides access to approximately 45% of normal lung volume (vital capacity) and helps mitigate the long-term repercussions associated with traditional spinal fusion procedures [9].

There is remarkably little information in the literature depicting the impact of these newer expandable devices on lung function in children with EOS after the initial implantation, during expansion, and after spine fusion—no randomized controlled trials state whose devices and surgical strategies provide the greatest respiratory benefit to patients. In addition, most series describing preoperative and postoperative changes in lung function among children with EOS include small numbers of subjects [3, 7, 25]. Most reports have studied children receiving vertical expandable prosthetic titanium ribs but not other growth-sparing or modulating devices [25, 26, 27].

Growth-friendly surgical techniques for EOS were classified by Skaggs et al. based on the applied correction force [35]. These techniques fall into three categories:

1. Distraction-based implants encompass traditional growing rods (TGR), vertical expandable prosthetic titanium rib (VEPTR), and magnetically controlled growing rod (MCGR). This approach applies mechanical distractive forces to the spine segments, ribs, and/or pelvis.

2. Compression-based implants include vertebral body stapling (VBS) and vertebral body tethers (VBT). This method involves applying a compressive force to the convex side of the deformity, resulting in growth inhibition on the ipsilateral side.

3. Guided growth systems, such as the Luque Trolley and Shilla techniques, anchor the end and apical vertebrae, allowing the spine to slide along the rod.

While growth-friendly surgeries maintain growth potential in EOS patients, they come with a high complication rate, extended treatment duration, and additional costs.

3.1 Distraction-based systems

3.1.1 Traditional growing rods

Traditional growing rods (TGRs) are the preferred technique and are considered the standard of care for treating EOS characterized by long curves [36]. These rods achieve correction through distraction and maintain it through proximal and distal instrumentation and fusion. This approach preserves growth potential, particularly lung growth, by leaving spine segments unfused and allowing for lengthening procedures. The concept of using rods for distraction to correct scoliosis, as an alternative to spinal fusion, was initially introduced by Harrington [37]. Subsequently, Moe et al. attempted a modification with a “subcutaneous rod” technique, but it yielded unsatisfactory results and a high rate of complications [38, 39]. Akbarnia et al. later demonstrated improved outcomes by implementing the dual-growing rod technique over a single rod [40]. While there is a consensus that growing-rod surgery is primarily indicated when bracing or casting treatments fail and the curvature exceeds 60° in patients younger than 10 years old, theoretically, TGRs can be considered for any patient with ongoing skeletal immaturity [41].

Performing TGR surgeries involves a series of procedures under general anesthesia every 6 months to lengthen the rod throughout a child’s development. Unfortunately, this technique comes with a substantial risk of complications, often necessitating unplanned surgeries for management. These complications encompass rod fracture, anchor failure, deep surgical site infections, repeated exposure to anesthesia, neurological issues, proximal junctional kyphosis, and prolonged postoperative recovery. Moreover, this method carries both direct and indirect financial burdens for families and the healthcare system, making it a significant concern in its application [42, 43]. Multiple studies have reported a high rate of complications, with as many as 77% of patients experiencing at least one complication [40, 42, 44, 45]. Notably, the reported complication rates can vary due to differences in fixation methods, types of growing rods, and surgical strategies [46, 47]. This variation has led to ongoing controversy regarding the ideal approach for TGR surgeries.

Several well-recognized risk factors contribute to complications associated with growing rods, including younger age at the initial surgery, using a single rod, longer lengthening intervals, thoracic hyperkyphosis, and the placement of rods subcutaneously. The elevated incidence of complications in treating EOS with traditional growing rods (TGRs) can be attributed to the extended treatment duration, primarily due to the young age of patients when the initial rod placement occurs and the substantial number of surgical procedures needed throughout the treatment period. Research has demonstrated that the likelihood of complications increases by 24% for each additional surgical procedure. Additionally, for every year following surgery, complications decreased by 13% [42].

In a 2010 study by Bess et al. [42], the effects of TGRs were compared in 140 children with EOS. Participants were divided into two groups based on the type of growing rods used, with 51% receiving single TGRs and 49% receiving dual TGRs. Among the 140 participants, 81 experienced at least one complication, resulting in a 57% complication rate. For those using single TGRs, this rate was slightly higher at 60.6%. A total of 177 episodes of complications were observed, with 94 occurring in 43 participants in the single TGRs group and 83 in 38 participants in the dual TGRs group. Among these complications, 74 necessitated unplanned surgeries for management (41.8%), with 42 occurring in participants with single TGRs (46.7%) and 32 in participants with dual TGRs (38.5%). However, statistically, none of these differences were significant. Interestingly, the study revealed that the use of dual TGRs, compared to single TGRs, was associated with a lower risk of implant-related complications and a reduced likelihood of hook dislodgments and unplanned implant-related surgeries (P ≤ .05).

While previous literature has highlighted the superiority and cost-effectiveness of dual TGRs [48, 49], it is important to acknowledge that using dual TGRs may not always be a feasible or preferred option. Factors such as patient size, the amount of supporting soft tissue, and the nature of the spinal deformity can limit their applicability.

In a 2021 study by Luhmann et al., it was demonstrated that the use of single-growing rod structures, particularly in children aged 4–8 years, can yield acceptable outcomes for EOS patients, especially when dual rods are not considered feasible due to factors such as curve rotation, magnitude, kyphosis, and inadequate soft tissue coverage for a convex spinal rod. The study suggests that single TGRs and MCGRs can serve as bridging treatments for patients aged 3–7 years with low body weight and short T1–T12 distances. These rods can be employed until the patient attains the necessary weight and height growth, at this point, the surgical construct can be converted to dual TGRs or MCGRs [50].

Nematian et al. [45] conducted a study involving 35 cases of EOS treated with single TGR insertion, encompassing 162 lengthening episodes and 42 unplanned surgeries. Their findings revealed that a substantial 77.1% of patients encountered at least one complication during the course of treatment. The mean preoperative Cobb angle for the major curve was 59.2° ± 5.8°, and this was corrected to 38.2° ± 6.0° at the final follow-up, demonstrating a significant improvement (P < .001). However, no statistically significant difference was noted in pre- and postoperative T1–T12 kyphosis measurements. It is worth noting that the relatively higher complication rate observed in this study, compared to previous literature, could be attributed to the nature of the study population. Case selection in this study was not random, and the children treated were of low socio-economic status, referred late, and tended to have more complicated conditions. The study’s conclusions suggest that even when dual TGRs are not feasible or preferred due to the patient’s physical condition and the specific characteristics of the deformity, the use of single TGRs should be minimized. Conservative treatments and early fusion are recommended as alternatives. The long-term results and complications associated with single TGRs indicate that their disadvantages may outweigh their advantages even when used as a bridge treatment. To reduce the incidence of complications in growing rod treatment, the study recommends personalized treatment plans based on the etiology of EOS and the patient’s physical condition (including age, respiratory status, and degree of deformity). Delaying treatment initiation based on the rate of progression, utilizing dual rods with appropriate diameters, and employing screws as anchors in sufficient numbers to secure foundation sites whenever feasible are also suggested strategies.

In conclusion, while TGRs remain the standard for EOS treatment, dual TGRs are preferred, but patient-specific factors may limit their use. MCGRs offer convenience but introduce unique risks. Single TGRs should be used cautiously, with alternative treatments considered when appropriate. Personalized treatment and careful patient selection are crucial for minimizing complications.

3.1.2 Magnetically controlled growing rods

In 2015, the FDA granted approval for the use of MCGR in treating EOS [36]. MCGR represents a more recent method of distraction surgery designed to address the issues associated with TGR. MCGR incorporates telescopic distraction actuators within each rod, and these actuators can be magnetically adjusted externally using a remote control for lengthening, eliminating the need for repeated surgeries. Surgical placement and fixation of the rods using screws or hooks are similar to TGR constructs. Notably, the initial surgery in the MCGR method is the sole planned surgery until the completion of the growing rod treatment [51]. While there is no consensus on the ideal lengthening intervals or number of distractions, most surgeons opt for more frequent rod lengthening compared to TGRs, typically occurring every 3–6 months [52, 53]. Theoretically, the indications for MCGRs should align with those for TGRs; however, MCGRs are not officially approved in all regions.

Akbarnia et al. [53] conducted a study involving 14 EOS patients (mean age: 8 years and 10 months) who received MCGRs, with an average follow-up period of 10 months. The study demonstrated a 50% correction rate after the initial surgery, which was well-maintained at the final follow-up. Additionally, spine height increased from 292 to 322  mm post-surgery and reached 338  mm at the final follow-up. On average, each patient underwent 4.9 distraction procedures. Complications included one case of superficial infection, one instance of a prominent implant, and three losses of initial distraction after the index procedure. The study concluded that MCGRs serve as a viable alternative treatment option, providing comparable results to TGRs but without the anticipated complications. La Rosa et al. [52] reported that MCGRs offer benefits over TGRs by preventing surgical scarring, surgical site infections, and psychological distress typically associated with the multiple surgeries required by TGRs. This reduction in infections and wound healing issues benefits patients and reduces medical costs. Akbarnia et al. [54] also demonstrated that MCGRs achieve similar results to TGRs regarding major curve correction and spinal and thoracic height. MCGRs are proposed to minimize the need for planned surgical interventions by avoiding repeated open lengthening procedures, thereby reducing the risk of complications. However, concerns about unplanned surgical revisions due to complications remain. In addition, Teoh et al. [34] found that, while MCGRs were linked to lower rates of both deep and superficial infections compared to TGRs, they were associated with a significantly increased risk of metalwork problems and unplanned revisions (OR = 4.67). Their study also indicated a higher overall complication rate compared to conventional growing rods [33]. In summary, MCGRs offer advantages in terms of reduced infections and improved patient experience but come with a higher risk of metalwork issues and unplanned revisions. Aslan et al. [55] conducted a study assessing the psychological effects of multiple surgeries on patients’ mental health. They found that MCGRs did not improve psychological effects on patient mental health compared to TGRs. Despite the noninvasiveness of the MCGR procedure, it did not yield the anticipated benefits in terms of psychological well-being and health-related quality of life, as compared to TGR [56].

While MCGRs offer the advantage of avoiding repetitive surgical procedures for lengthening, they still share many complications with TGRs and introduce a few novel ones. Coupled with their high cost and limited availability, particularly in developing countries, MCGRs have lost some of their initial appeal. They are now viewed as merely one of several therapeutic options alongside TGR [34, 57]. In conclusion, further research involving larger sample sizes and longer follow-up periods is essential to better understand this relatively new technique and its optimal utilization.

In summary, MCGRs offer advantages in terms of convenience but come with increased risks and psychological outcomes similar to TGRs. Further research with larger sample sizes and longer follow-up periods is needed to better understand and utilize this technique effectively.

3.1.3 Vertical expandable prosthetic titanium rib

VEPTR devices are constructed from titanium alloy longitudinal rods that function as distraction devices. These rods are equipped with anchors placed at the ribs and spine, allowing for the comprehensive management of three-dimensional thoracic deformities, with or without expansion thoracoplasty [58].

VEPTRs were originally developed by Dr. Robert Cambell and Melvin Smith with the primary aim of treating thoracic insufficiency syndrome (TIS) linked to congenital scoliosis and fused ribs [59]. While their main indication is for patients with TIS, they are occasionally employed for individuals with EOS who are at risk of developing secondary TIS [60].

Initial studies exhibited promising results, including Cobb angle corrections, increased lung expansion space, and overall spine growth [59, 61]. However, subsequent research has failed to consistently support these initial findings. A 15-year study by Ramirez et al. [62] revealed that respiratory function did not improve significantly, spine growth was moderate, and Cobb angle correction fell short of expectations. Additionally, VEPTRs have been associated with notable complication rates, with proximal fixation failure being the most common issue. Lengthening of VEPTRs is typically performed every 4–6 months, and the complication rate can be as high as 100%, limiting their widespread application [63].

Studies by Campbell et al. reported complication rates as high as 163% in patients with congenital scoliosis, Hasler et al. documented 100% complication rates in non-congenital scoliosis patients, and Ramirez et al. observed rates as high as 73.1% in neuromuscular scoliosis patients [61, 64, 65]. Consequently, doubts have arisen regarding the benefits of VEPTRs, and when they are considered, there is a consensus to approach their use with caution, favoring a multidisciplinary approach.

In summary, VEPTR devices were initially promising for managing thoracic deformities but have faced challenges with complications and limited benefits in subsequent research. Their use is now approached cautiously, with a preference for multidisciplinary evaluation.

3.2 Compression-based implants

Compression-based implants function by addressing spinal deformities by applying a compressive force to the convex side of the curve, which hinders its growth while allowing the development of the concave side, aligning with the Hueter-Volkmann principle. This principle suggests that physeal growth can be regulated through mechanical compression, promoting growth by reducing mechanical load [66].

However, concerns related to overcorrection of the curve, particularly in immature patients, have been associated with compression-based implants. Consequently, some surgeons recommend reserving this technique for patients with limited remaining growth potential, typically in the 9- to 10-year-old age range [18].

Despite these strict indications and limited applications, the primary advantage of vertical body tethering (VBT) and vertebral body stapling (VBS) is their ability to preserve growth potential and spinal segment mobility. On the downside, these techniques can be associated with surgical approach complications, including pulmonary and bowel issues resulting from anterior surgeries.

As VBS and VBT are relatively recent methods for treating spinal deformities, the available literature is limited. Because of the absence of long-term results and discrepancies in complication rates or adverse events reported in studies, further research is needed to comprehensively assess their effectiveness, safety profile, and the optimal age range for patients to benefit from these techniques.

3.2.1 Vertebral staples techniques

The concept of VBS was initially proposed by Nachlas et al. [67]; however, early attempts showed poor results [68]. In Guille et al. introduced a modern nitinol C-shaped staple that improved compression across the growth plate [69].

VBS entails the placement of metal staples to selectively inhibit spinal growth on the convex side while preserving motion segments throughout the spine without fusion. The procedure involves thoracoscopic stapling for thoracic curves and a mini-open retroperitoneal approach for motion segments below the diaphragm, specifically at the T12–L1 level and below [70, 71].

Traditionally, moderate immature curves have been managed with bracing; however, when bracing is no longer effective, VBS becomes a viable option [30]. The current indications for VBS are quite stringent and include idiopathic scoliosis, a Risser sign of 0–2, a curvature degree ranging from 25° to 40°, and failure of brace treatment [72].

Cahill et al. conducted a review involving 63 patients who underwent VBS at a mean age of 10.78 years, with a mean follow-up duration of 3.62 years. Their findings demonstrated the effectiveness of VBS in preventing progression and fusion in thoracic and lumbar curves with mean Cobb angles of 29.5° and 31.1°, respectively. Seventy-four percent of patients with thoracic VBS and eighty-two percent of those with lumbar VBS did not exhibit progression and/or fusion [73].

In summary, VBS has evolved with modern techniques and has shown promise in managing scoliosis in select patient populations, particularly when bracing is no longer effective.

3.2.2 Vertebral tethering techniques

VBT is a recent compression-based implant technique introduced by Crawford et al. [74]. It involves the thoracoscopic placement of anterior vertebral body screw anchors with a tightened flexible tether between them. This method achieves correction through both tether tension and spinal translation, all performed via an endoscopic approach.

Indications for VBT include thoracic curves within the range of 30°–70° and thoracolumbar or lumbar curves ranging from 30° to 60° in skeletally immature patients. However, the presence of hyperkyphosis (>40°) in the thoracic region is considered a relative contraindication due to the use of anterior instrumentation [36].

In a study conducted by Samdani et al. thoracic curve correction was reported in 32 patients, reducing from an average of 42.8°–21.0° on the initial erect radiograph and 17.9° at the latest follow-up. Additionally, the non-instrumented lumbar curve exhibited significant spontaneous correction, decreasing from 25° to 18° at the first follow-up and 13° at the final follow-up [75]. In Hoernschemeyer et al. [76] presented the results of a study involving skeletally immature patients treated with VBT, achieving a success rate of 74% in attaining curve magnitudes less than 30° at skeletal maturity.

In summary, VBT represents a promising approach for correcting certain spinal deformities in skeletally immature patients, demonstrating favorable outcomes in select cases.

3.3 Guided growth systems

3.3.1 Luque trolley technique

The Luque trolley technique utilizes sublaminar wires to segmentally fix rods to the spine, aiming to limit subperiosteal dissection to prevent unintentional spinal fusion [29]. However, this approach is not commonly employed due to documented issues such as spontaneous spinal fusion, limited spinal growth, and control of spinal deformity [77].

A more recent development is the Modern Luque Trolley (MLT) system, introduced by Ouellet et al., who published a 5-year retrospective study involving five patients. The study showed that MLT successfully corrected primary curves, reducing them from 60 to 21°, with the maintenance of correction observed during a 2-year follow-up period. Notably, MLT does not rely on sublaminar or cerclage wires. Instead, it employs gliding spinal anchors that travel along fixed, overlapping rods. This technique can effectively halt the progression of spinal deformities while still allowing for relatively normal spinal growth. While concerns about spinal fusion may persist, the study reported fewer implant failures compared to the original trolley technique [78].

Indications for MLT include a Cobb angle exceeding 40°, failed conservative treatment, and significant growth potential [79]. It is important to note that MLT is a relatively new technique and has yet to receive official approval in many regions.

In summary, MLT represents a promising advancement in the treatment of spinal deformities, addressing some of the limitations associated with traditional Luque trolley methods.

3.3.2 Shilla technique

The Shilla technique, introduced by McCarthy and colleagues [80], represents a relatively recent procedure that adheres to the growth principles of guided growth systems. It involves the fixation of dual rods using pedicle screws at the apex of the spinal curve, with proximal and distal gliding screws employed to minimize subperiosteal dissection, thereby preventing spontaneous fusion at these segments [35].

In the Shilla technique, the initial correction focuses on the apical deformity, aligning it toward a neutral position. Subsequently, the upper and lower growth guidance segments extend into the distal and proximal regions of the curve using polyaxial screws. These specialized screws feature locking caps that attach to the top of the screws (rather than the rod), capturing the rod and allowing it to slide longitudinally with growth. This approach eliminates the need for multiple open lengthening surgeries similar to MCGRs. Present indications for the Shilla technique include cases where bracing has proven ineffective and when dealing with coronal curves exceeding 50° [80].

In McCarthy et al. [81] reported findings from a study involving 40 patients with a minimum 5-year follow-up, encompassing various scoliosis types (nine idiopathic, one congenital, 16 neuromuscular, and 14 syndromic). The average preoperative curve measured 69°, which was reduced to 25° following the index procedures, and at the most recent follow-up or prior to definitive spinal fusion, the curve averaged 38.4°.

In Luhmann et al. [82] compared the Shilla technique and TGRs radiographically. They observed that preoperative curves with mean values of 61° and 65° in the two groups had corrected to 27° and 29°, respectively, at the latest follow-up. The growth of the T1–T12 segment increased by 4.6 cm for the Shilla technique and 5.2 cm for TGR. Both methods demonstrated favorable radiographic outcomes regarding growth, curve correction, and complications. A notable distinction was the Shilla technique’s threefold reduction in overall surgeries.

However, despite the advantage of reducing the total number of surgeries, concerns about complication rates, particularly implant-related complications, persist similar to MCGR and TGR. These complications have been reported to reach as high as 73%, leading to return surgeries due to secondary infections, alignment issues, and implant-related problems [81]. Wilkinson et al. [83] noted that the apex of the fused primary curve shifted in approximately 62% of patients, with nearly all of these cases (92%) involving distal migration.

In summary, the Shilla technique is a promising approach for spinal deformity correction, showing advantages in terms of reduced surgeries compared to TGRs. However, complications, especially implant-related problems, remain a significant concern, and long-term studies are needed to better assess its effectiveness and safety.

3.4 Other alternatives

3.4.1 Vertebral column resection

Vertebrectomy for severe scoliosis was initially introduced by MacLennan [84]. Over time, this technique has evolved into vertebral column resection (VCR), which now involves a three-column circumferential osteotomy encompassing the vertebral body, adjacent disks, pedicles, and all dorsal elements. This creates a segmental defect, inducing instability and necessitating provisional instrumentation [85].

Current indications for VCR mainly involve addressing short angular deformities, especially in cases where other methods are technically unfeasible, often seen in congenital scoliosis (CS) or early-onset congenital kyphosis [86]. Hemivertebrae, a common pathology in CS, often results in a wedge-shaped deformity that progresses with spinal growth. Hemivertebrae resection has emerged as the gold standard treatment for CS caused by hemivertebrae, yielding excellent curve correction results [87].

Traditionally, this procedure was performed via an anterior-posterior approach. However, due to prolonged operative times, substantial blood loss, and elevated complication rates, there has been a shift toward adopting a posterolateral approach more recently [86]. Despite improvements in surgical duration and blood loss with this approach, concerns persist regarding its technical complexity, potential blood loss, and heightened complication rates, especially concerning neurologic complications. Therefore, when considering VCR, it should be cautiously approached by an experienced surgical team [85].

A study by Wang and Zhang [88] focused on 36 CS patients (mean age: 59 months; mean follow-up: 62.3 months) with hemivertebrae who underwent hemivertebra resection and segmental fusion. They achieved significant correction of segmental scoliosis (from 36.6° to 5.1°) and segmental kyphosis (from 21.2° to 5.8°) at the last follow-up. Complications included one case of delayed wound healing, two cases of pedicle fractures, and one case of progressive deformity. These patients, typically very young with poor bone quality and thin, soft tissue coverage, face higher risks of wound healing issues and screw displacements than adults. However, satisfactory outcomes and prognoses can be achieved with careful management, malformation correction, and solid fusion.

In summary, VCR is valuable for addressing severe scoliosis and congenital spinal deformities. It is especially effective in cases of hemivertebrae-related deformities, although it comes with potential complications, requiring a skilled surgical team for optimal outcomes.

3.4.2 Convex hemiepiphysiodesis

Convex hemiepiphysiodesis, also referred to as convex growth arrest, was once a commonly employed technique for managing congenital scoliosis in children [89]. This method was primarily used to address multilevel congenital deformities, and while it was considered safe and straightforward, its ability to guide and regulate spinal growth was somewhat unpredictable [90].

In a 2020 study by Rizkallah et al. [89], 22 patients with congenital scoliosis underwent a 1-staged double approach hemiepiphysiodesis involving bone grafting of the convex side without instrumentation. The study concluded that limited convex hemiepiphysiodesis remains a viable option in the treatment of congenital scoliosis, especially in patients ≤3 years old, with curves ≤35°, and isolated hemivertebra. This approach offers certain advantages, sparing patients the risks associated with vertebral resection and instrumentation while achieving fusion across the same number of levels.

4. Future directions

The current approach to treating EOS prioritizes addressing spinal and thoracic cage deformities, improving cardiopulmonary function, addressing psychological impact and enhancing health-related quality of life. Over recent years, substantial advancements have been in comprehending EOS’s natural progression and long-term consequences. Moreover, technological innovations have expanded the treatment options available to EOS patients. However, despite these advances, EOS remains a complex challenge, marked by a lack of consensus among experts in the field [91]. The proliferation of treatment options has outpaced the availability of evidence-based literature, leading to uncertainties in managing EOS effectively. Additionally, various obstacles hinder the acquisition of high-level evidence in EOS treatment. These obstacles include the small and diverse patient population, the need for extended follow-up periods, the absence of reliable prognostic classifications, and the difficulties in assessing pulmonary outcomes in this specific patient group.

Classification systems serve as crucial tools in healthcare, allowing the characterization of medical conditions, suggesting potential prognoses, and guiding treatment decisions. However, a significant challenge arises when it comes to early-onset scoliosis (EOS)—the existing classification systems are not reliably prognostic. This issue highlights the pressing need for further research in this field to enhance the utility of classification systems in identifying trends of successful and unsuccessful treatment options for EOS patients. To address this limitation and improve the efficacy of EOS treatment, the integration of artificial intelligence (AI) holds significant promise. With its remarkable ability in data analysis and pattern recognition, AI can help create more practical and accurate classifications for EOS. By leveraging AI algorithms, classification systems can be refined to categorize EOS cases and predict their likely treatment outcomes. Furthermore, the application of AI in EOS research can benefit from big data and multicentric studies. Gathering extensive patient data from various medical centers and incorporating it into AI-driven analyses can lead to more comprehensive and accurate classification systems. This approach ensures that a narrow dataset does not limit classification systems but encompasses a diverse range of EOS cases.

Although evidence supports the effectiveness of treatments in correcting spinal curvature and promoting spinal growth in early-onset scoliosis (EOS), concerns persist regarding their impact on enhancing pulmonary function. It has become evident that conventional radiographic assessments are insufficient for adequately gauging respiratory outcomes in EOS patients. The development of advanced imaging techniques capable of providing three-dimensional dynamic measurements, in conjunction with other assessment modalities, holds the potential to enhance our understanding of pulmonary outcomes in children undergoing treatment. These advancements are promising in improving the evaluation of the intricate relationship between the spine, thorax, and pulmonary function. Progress in these areas is crucial because it can lead to a more comprehensive understanding of how to prevent the progression of EOS to thoracic insufficiency syndrome (TIS), which ultimately results in cardiopulmonary compromise [92, 93].

5. Conclusion

EOS encompasses a spectrum of spinal growth pathologies with diverse causes and presentations, demanding a multifaceted approach to treatment. Successful management should prioritize the correction of spinal and thoracic cage deformities, enhancing respiratory function, and improving health-related quality of life for affected children. Addressing EOS poses significant challenges, with treatment strategies necessitating tailored approaches considering the specific deformity type, underlying causes, and potential coexisting medical conditions. Despite our abundant knowledge of EOS, it remains a condition without a definitive, one-size-fits-all solution. The early identification and accurate classification of EOS are of utmost importance in providing effective treatment strategies. Each case warrants a personalized plan tailored to its unique characteristics and underlying etiology. Conservative treatments should be explored as the initial course of action whenever possible.

Recent advancements have spurred growing interest in applying Mehta’s casting method for treating idiopathic scoliosis. This promising approach is gaining recognition and acceptance within the medical community as an effective treatment option for idiopathic cases, showcasing its potential to provide positive patient outcomes. For other cases, a meticulous and multidisciplinary approach is indispensable. A dedicated team of healthcare professionals, including pediatricians, nutritionists, physiotherapists, orthopedic specialists, and orthotics experts, must work collaboratively in managing these complex cases. This comprehensive approach acknowledges that scoliosis often accompanies other health concerns in children, necessitating holistic care that addresses various facets of their well-being.

Recognizing that spinal deformity represents just one aspect of a child’s broader health issues is crucial. Therefore, comprehensive care should encompass all aspects of their physical, medical, and developmental needs. This multidisciplinary approach empowers healthcare providers to provide the highest quality of care and support for children with scoliosis, addressing their spinal health and overall well-being.

Moving forward, future efforts should prioritize technological advancements and treatment refinement. These include the development of prognostic classifications, enhancing pulmonary function assessment methodologies, conducting high-level clinical research, and ultimately improving the quality of life for EOS patients.

Acknowledgments

This research received no specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Conflict of interest

The authors declare no conflict of interest.