Congenital Scoliosis

Introduction

Congenital scoliosis is a lateral curvature of the spine due to congenital vertebral anomalies. These anomalies are present at birth but usually do not manifest until later in life. Congenital scoliosis is estimated to occur in approximately 1 in 1,000 live births.^1,2

Anatomy

Scoliosis is a three-dimensional deformity involving the coronal plane, sagittal plane, and axial plane of the spinal column. The curve location is based on the apex of curve:

Cervical: C2-C6
Cervicothoracic: C7-T1
Thoracic: T2-T11
Thoracolumbar: T12-L1
Lumbar: L2-L4

Pathogenesis

Congenital scoliosis results from abnormal vertebral development during the 4th to 6th week of gestation, leading to asymmetric growth of the spine. The cause of these vertebral anomalies is unknown. Isolated anomalies are likely sporadic, but multiple vertebral anomalies may carry a 5% to 10% risk in future siblings.^2,7 Studies in mice suggests that maternal exposure to toxins, such as carbon monoxide, may cause congenital scoliosis.^3,4 Maternal diabetes and use of anti-epileptic drugs during pregnancy have also been postulated as possible causes.^5,6

Classification

Congenital scoliosis is categorized into 3 main groups:

Failure of segmentation
Failure of formation
Mixed form⁹

Approximately 80% of anomalies are failures of segmentation or formation, with 20% being the mixed form.

An incomplete failure of formation leads to a wedge vertebra with bilateral pedicles; one side is hypoplastic. A complete failure of formation results in a hemivertebra, with the absence of one pedicle and a region of the vertebral body. Hemivertebra are further classified by the presence or the absence of fusion to the vertebral bodies above and/or below:

An unsegmented hemivertebra is fused to the vertebral body above and below
A partially segmented hemivertebra is fused to the vertebral body either above or below
A fully segmented hemivertebra is separated from the body above and below by disc space¹⁰

The defects of segmentation result in abnormal bony connections between vertebrae. These bony connections may be bilateral and symmetrical resulting in a block vertebra, or may be unilateral resulting in bars.

Mixed deformities are common. One example occurs when a segmentation defect spans an ipsilateral formation defect, resulting in a unilateral bar and a contralateral hemivertebra.¹¹

Natural History

In general, 25% of curves are nonprogressive, 25% progress slowly, and 50% progress rapidly. The determinants of curve progression are based on the age of the patient, the type of anomaly, and its location. Progression occurs most rapidly during growth periods such as adolescence and continues until skeletal maturity.

The most severe anomaly is a unilateral bar with a contralateral hemivertebra (progressing 5º-10º per year), followed by a unilateral bar (about 5º), a hemivertebra (2º-5º), a wedge vertebra, and finally a block vertebra (no healthy intervening discs prevent asymmetric growth).⁸ Curves in the thoracolumbar region tend to progress more rapidly than those in the thoracic spine.

Clinical Presentation

A thorough history and physical are important when diagnosing congenital scoliosis due to the high incidence of associated anomalies. Check the patient’s height and weight, head tilt, shoulder elevation, pelvic obliquity, overall trunk balance, rib cage deformities, and the skin for any stigmata that may represent an underlying pathologic condition. A thorough neurologic exam — including strength, sensation, and reflexes — is required. The inspiratory and expiratory capacity of the chest wall should also be evaluated.

The spine develops between 4 and 6 weeks of gestation, along with the genitourinary, musculoskeletal, and cardiovascular systems. As a result, patients with congenital scoliosis often present with abnormalities of these organ systems. These anomalies may be associated with VACTERL syndrome:

Vertebral anomalies
Anorectal atresia
Cardiac anomalies
Tracheoesophageal fistula
Renal and limb anomalies¹³

Neural axis abnormalities such as diastematomyelia, syringomyelia, cord tethering, Chiari malformations, and intradural lipomas are present in up to 35% of patients with congenital scoliosis.¹² Clinical indicators include skin stigmata (hairy patch and skin dimple) and foot and leg abnormalities (cavus feet, vertical talus, and calf atrophy).

Congenital heart disease is observed in up to 25% of patients with congenital scoliosis.¹³ The cardiac defects range from atrial and ventricular septal defects (the most common) to complex congenital heart defects (tetralogy of Fallot, transposition of the great vessels).

Genitourinary anomalies such as horseshoe kidney, renal aplasia, duplicate ureters, and hypospadias are observed in up to 20% of patients with congenital scoliosis.¹³

Musculoskeletal anomalies such as clubfoot, Sprengel deformity, Klippel-Feil deformity, developmental dysplasia of the hip, and upper and lower limb deformities are commonly associated with congenital spinal deformity.

Imaging and Diagnostic Studies:

Anteroposterior and lateral films are taken of all patients suspected of congenital scoliosis. These are initially done supine (up to about 4 years of age) since the child has poor postural mechanisms. Once the child is able to stand, radiographs are done supine and standing for comparison and to obtain a new baseline.

The Cobb angle is measured at every visit, but there is a 10º intraobserver error due to difficulty of determining radiographic landmarks.¹⁴ Lateral bend films are used to determine flexibility.

A CT with 3-dimensional reconstruction may be used to better determine the anatomy before surgery. An MRI is often done to rule out any intraspinal anomaly.

An echocardiogram and renal ultrasound should be performed to look for underlying cardiac and renal abnormalities.

Nonsurgical Treatment

After diagnosis, children are usually assessed every 3 months for curve progression. If the curve is stable and the anomaly is one that is not likely to progress, they may be followed every 6 months. However, during adolescence patients are followed every 3-4 months.

Bracing

Bracing is rarely used to treat congenital scoliosis since these curves are usually inflexible.¹⁵ Bracing is occasionally used to control the more flexible compensatory curves, or after surgery until solid fusion is achieved.

Traction

Halo gravity traction allows gradual correction of a large rigid curve, and is often used before or after surgery. There is a gradual increase in traction weight (up to 50% of the patient’s weight).

Surgical Treatment

The treatment of congenital scoliosis is primarily surgical; it is indicated for curve progression or when an anomaly is thought to have a high risk of progressing.

Spinal Instrumentation

Spinal instrumentation was first described by Hall et al in 1982 for the treatment of congenital spine deformities.²⁶ Newer, downsized implants are now available, and titanium implants have allowed for increased MRI compatibility.

In Situ Fusion

In situ fusion is used to stabilize the main curve before the development of a major deformity and can be done anteriorly, posteriorly, or combined. The fusion should extend one level above and below the deformity.¹⁷ Isolated posterior fusion may result in the crankshaft phenomenon due to continued anterior growth.¹⁸

Convex Epiphysiodesis and Posterior Arthrodesis

This procedure provides stabilization and may even correct medium-sized curves due to growth of the concave side.19 The ideal patient is less than 5 years of age with a curve less than 40º involving 5 segments or less. The procedure is contraindicated in patients with no growth potential.

Hemivertebra Excision

Hemivertebra fusion may be done through a posterior-only or anterior/posterior approach. The best indication is for an isolated fully segmented hemivertebra at the lumbosacral junction.

Growing Rods

This procedure allows the child to attain maximal truncal height. It was first described by Harrington et al in 1963, using a subperiosteal approach with placement of a single distraction rod connected to hooks at the distal ends.²² High rates of hook dislodgement and rod breakage led to Akbarnia et al developing a dual rod.²³

Vertical Expandable Prosthetic Titanium Rib (VEPTR)

Developed by Campbell and Hell-Vocke^2,24 to address spinal and chest wall deformity without the need for fusion, the VEPTR requires an opening wedge thoracostomy and implantation. It can be attached rib to rib, rib to spine, or rib to pelvis.

Outcome

Sink et al reported no permanent neurologic deficits with the use of traction on patients with congenital scoliosis.²⁵
Hedequist et al studied the use of downsized instrumentation in patients with congenital spine deformities and concluded that instrumentation was safe and effective in congenital scoliosis, even in the youngest of patients.²⁷
Winter et al reported that 38% of their patients treated with convex epiphysiodesis and posterior arthrodesis were corrected an average of 10º, and 54% were stabilized.²⁰
Ruf et al reported excellent results with the posterior-only excision of hemivertebra in 28 patients.²¹
Thompson et al compared the dual-rod technique with the single growth rod technique and found that the dual rod produced better initial correction and allowed more growth with equal complication rates (48%).²³
Campbell and Hell-Vocke reported on patients with congenital scoliosis and fused ribs treated with the VEPTR and noted longitudinal growth of the thoracic spine to be 7.1 mm per year, compared to a normal longitudinal growth of 6 mm per year.²³

Complications

Intra-operative Complications

Blood loss
Neurologic injury
Vascular injury
Direct trauma
Ischemia
Pneumothorax

Post-operative Complications

Infection
Hematoma
Neurologic deterioration
Pneumonia
Ileus
Pulmonary embolism

Delayed Complications

Pseudarthrosis
Failed instrumentation
Loss of correction
Adjacent level degeneration
Back pain

Pearls and Pitfalls

All patients with the diagnosis of congenital scoliosis need an MRI of the spinal axis and a screening evaluation for renal and cardiac anomalies.
Surgical treatment is recommended early for congenital scoliosis patients with rapidly progressive or large curves.
Neurologic monitoring is an important tool to help prevent neurological injury during surgery.¹⁶
Thoracic insufficiency syndrome associated with congenital scoliosis and fused ribs can be managed during growth by an expansion thoracostomy and insertion of a VEPTR device.
Further investigation of the growing spine is necessary to improve outcomes in patients with congenital scoliosis.

References

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Giampietro PF, Blank RD, Raggio CL, et al. Congenital and idiopathic scoliosis: clinical and genetic aspects. Clin Med Res. 2003;1:125-136.
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