Etiology of idiopathic scoliosis: current trends in research

Current population studies characterize idiopathic scoliosis as a single-gene disorder that follows the patterns of mendelian genetics, including variable penetrance and heterogeneity. The role of melatonin and calmodulin in the development of idiopathic scoliosis is likely secondary, with indirect effects on growth mechanisms. Reported abnormalities of connective tissue, skeletal muscle, platelets, the spinal column, and the rib cage are all thought to be secondary to the deformity itself. Although no consistent neurological abnormalities have been identified in patients with idiopathic scoliosis, it is possible that a defect in processing by the central nervous system affects the growing spine. The true etiology of idiopathic scoliosis remains unknown; however, it appears to be multifactorial.     

Idiopathic scoliosis in families of children with congenital scoliosis

Although most cases of congenital scoliosis are thought to be of sporadic etiology, it is not known whether other types of spinal deformity occur in families of individuals with this type of scoliosis. Children with congenital scoliosis were identified through a review of health records and radiographic report databases. Of 237 children with congenital scoliosis investigated, 49 (20.7%) reported a family history of spinal deformity. Detailed pedigrees were done, which showed a history of idiopathic scoliosis in 17.3% of the 237 families. This is a higher than expected rate of spinal deformity in families of children with congenital scoliosis, and the strong association of idiopathic scoliosis in families of children with congenital scoliosis has not been reported previously. Although this finding could be related to the chance occurrence of multiple genetic abnormalities or sporadic events in these families, it does raise the possibility that one genetic defect at least predisposes these families to having different types of spinal deformity develop.     

KASS内固定治疗胸腰段脊柱侧凸畸形

[目的]评价应用Kaneda脊柱前路矫形系统(Kaneda anterior scoliosis system,KASS)治疗胸腰椎侧凸畸形的临床疗效。[方法]回顾分析43例脊柱侧凸畸形通过前路椎间盘摘除、松解、椎间植骨融合及KASS内固定矫正侧凸畸形的临床资料,男性17例,女26例。年龄11~24岁(平均14.6岁)。侧弯病因:特发性35例,先天性8例。[结果]所有患者均达到满意矫正效果,平均随访时间为22个月(6个月~4年)。胸腰椎术前侧凸Cobb s角平均为66°(43°~98°),术后矫正至18°(0°~32°),畸形矫正率为91.7%。无明显并发症出现。术后随访3例出现矫正度部分丢失。[结论]KASS内固定系统治疗脊柱侧凸具有能早期矫正畸形,创伤小,融合固定节段少,矫形效果好,维持术后矫正度理想等优点,是一种值得推广的手术方法。     

Anterior and thoracoscopic scoliosis surgery for idiopathic scoliosis

Surgical management of idiopathic scoliosis is based on the natural history of this spinal disorder and on the likelihood of developing a worsening deformity. Anterior surgical treatments continue to evolve and provide advantages over posterior procedures in specific instances. Open and thoracoscopic anterior approaches allow direct access to the anterior stabilizing structures of the spine, enable mobilization of a rigid deformity, and provide a large surface area for arthrodesis. Thoracoscopic procedures provide a more cosmetically appealing alternative to a large midline posterior or anterolateral thoracotomy scar. Although the indications and contraindications for anterior versus posterior surgical intervention (for thoracic and thoracolumbar curve patterns) have been defined to some degree, there remains appropriate flexibility in the decision-making process, allowing the surgeon to make an optimal recommendation for each patient based on surgeon experience and patient needs.     

Congenital scoliosis

The congenital scoliosis is a deformity of the spine in the frontal plane caused by abnormal development of the vertebral bodies during the first 6 weeks of fetal life. More than 75 percent of all congenital scolioses are progressive. Degree and speed of progression can usually be predetermined by the type and location of the anomaly. Corset treatment is inefficient in the treatment of congenital deformities. Operation is the treatment of choice. Operative techniques are posterior fusions in situ with or without instrumentation and combined anterior and posterior arthrodeses. Since the best results can be expected in an early stage when only few segments have to be fused, operation should be performed as soon as possible. Manifestations of dysrhaphia or tethered cord must be identified prior to surgery. Spur removal or release operation should be performed during the first session.     

Congenital scoliosis

Congenital scoliosis is caused by early embryologic errors in vertebral column formation. Defining the deformity, predicting the natural history, and applying the correct treatment can help ensure successful management. Most congenital spine anomalies can be classified, and many have a predictable natural history. Because the deformities are associated with other organ system anomalies in more than half of patients, the surgeon should look for cardiac, auditory, genitourinary, and renal anomalies. Intraspinal abnormalities are present in approximately one third of patients with congenital spine deformities. Curve progression is best documented by measuring identical landmarks on sequential radiographs. Magnetic resonance imaging is warranted when curve progression is established or when surgical intervention is planned. Management of progressive deformity is generally by early in situ fusion because orthotic treatment is rarely appropriate. Other surgical techniques include combined anterior and posterior epiphysiodesis, hemivertebra resection, and reconstructive osteotomies.     

Congenital scoliosis

Congenital scoliosis is the most frequent congenital deformity of the spine. Congenital curvatures are due to anomalous development of the vertebrae (failure of formation and/or segmentation). Congenital scoliosis is believed to be related to an insult to the fetus during spine embryological development, and associated malformations (heart, spinal cord, kidney.) are frequently observed. A perfect understanding of the natural history of the deformity and the treatment principles will allow best management of these complex spine deformities. New imaging techniques like three-dimensional computed tomography (CT) and magnetic resonance imaging (MRI) are important tools for analyzing the underlying deformity and understanding the evolution of the complex deformities. The mainstay of treatment is either observation or, in case of curve progression (>10 degrees /year), surgery. Different surgeries are described with two main principles: (1) prophylactic surgeries like hemiepiphysiodesis or in situ fusions that will prevent worsening or allow progressive correction over time, and (2) corrective surgeries, with spinal fusion with or without spinal resection. Exceptional procedures (e.g. spinal column resection or halo distraction) can be attempted in cases of very severe deformity. Congenital curves must be carefully observed to choose the least invasive procedure at the right time and to minimize spinal cord risks.     

Heritability of scoliosis

Purpose

To estimate the heritability of scoliosis in the Swedish Twin Registry.

Methods

Self-reported data on scoliosis from 64,578 twins in the Swedish Twin Registry were analysed. Prevalence, pair- and probandwise concordances and tetrachoric correlations in mono- and dizygotic same-sex twins were calculated. The relative importance of genetic variance, i.e. the heritability, and unique and shared environmental variance was estimated using structural equation modelling in Mx software. In addition, all twins in the twin registry were matched against the Swedish Inpatient Register on the primary diagnosis idiopathic scoliosis.

Results

The prevalence of scoliosis was 4%. Pair- and probandwise concordance was 0.11/0.17 for mono- and 0.04/0.08 for same-sex dizygotic twins. The tetrachoric correlation (95% CI) was 0.41 (0.33–0.49) in mono- and 0.18 (0.09–0.29) in dizygotic twins. The most favourable model in the Mx analyses estimated the additive genetic effects (95% CI) to 0.38 (0.18–0.46) and the unique environmental effects to 0.62 (0.54–0.70). Shared environmental effects were not significant. The pairwise/probandwise concordance for idiopathic scoliosis in the Swedish Inpatient Register was 0.08/0.15 for monozygotic and zero/zero for same-sex dizygotic twins.

Conclusion

Using self-reported data on scoliosis from the Swedish Twin Registry, we estimate that 38% of the variance in the liability to develop scoliosis is due to additive genetic effects and 62% to unique environmental effects. This is the first study of sufficient size to make heritability estimates of scoliosis.