Current Concepts in the Management of Early-onset Idiopathic Scoliosis

Ujjwal K Debnath

Disclosures

Pediatr Health. 2010;4(3):343-354. 

In This Article

Management

Nonsurgical

The traditional management of progressive EOS involved casting and bracing with subsequent fusion once sufficient growth of the spine has occurred.[43] Management principles are based on age of the child, the magnitude of the curvature and RVAD as measured on plain radiographs. Most patients are at low risk of progression if the Cobb angle is under 25° with an RVAD of less than 20°. Clinicians should observe these patients with serial radiographs at 6 months. If the progression of more than 10° was observed at any stage during the follow-up, then a referral to a scoliosis specialist should be sought. If there was minor or no progression then the curve may undergo resolution. Once curve was resolving, a biannual follow-up may be sufficient. It should be noted that there are two growth periods during a child's life when there may be deterioration of a nonprogressive curve. Orthotic treatment has no role in toddlers with severe and progressive curvatures. Patients with pulmonary involvement may be further compromised with the use of brace or cast. A long-term observation study suggested that there was no advantage of plaster treatment over physiotherapy for a good functional outcome in patients with resolving infantile idiopathic curvatures.[44]

The rib–vertebral relationship has been classified by Mehta into two phases. In phase one, there is no overlap of the rib head and vertebral body. In phase two, there is overlap of the rib head on the vertebral body. She observed that the children with phase two rib–vertebral relationship and a Cobb angle of 20–35° are at high risk of progression.[37,43] These children need to be observed and treated by a specialist until growth is completed.[45] Bracing should be considered in children with curvatures over 35°. A Milwaukee-type brace is preferred to an underarm thoraco–lumbo–sacral orthosis (TLSO) to prevent thoracic deformity and pulmonary complications. Casting can be performed in young children when bracing is difficult to achieve the outcome. Risser casting begins with application of a molded body cast with the patient under general anesthesia (Figure 3).[46,47] This is an increasingly popular method that avoids complications of surgery. The cast is changed at 6–12-week intervals until maximum correction is achieved. Patients are observed at 6-monthly intervals and the curve progression is noted. The brace is worn for at least 23 h per day and for at least 2 years until there is no evidence of curve progression. If there is progression of more than 5° in these patients then active surgical treatment should be initiated. Casting and bracing are not always successful and the possibility of early spinal surgery should be considered.[45] Sometimes there may be relapse of the curvature in patients who had less then full correction. Clinicians should be aware of such relapses and refer to spinal surgeons. Curvatures of more than 50° need to be managed surgically at any stage of life. Thoracic curves need special attention. The respiratory effects of EOS (i.e., morbidity and mortality) must take precedence over the psychological consequences of the deformity.[40]

Figure 3.

Risser casting technique in a child with early-onset scoliosis.

Surgical

The surgical management of EOS aims to correct the deformity and maintain the correction with growth. The choice of surgery depends on the age of the patient, type, severity of curve and progression of the curve. Several procedures have been described and practised at various centers around the world. The earliest described procedures aimed at halting the curve progression was posterior spinal fusion.[48,49] In his original description, Hibbs had performed uninstrumented spinal fusion and suggested that fusion prevents progression of the deformity. But the cohort of patients he treated was suffering from infantile paralysis.[48] Spinal fusion produced short and straighter spines instead of curved ones. Spinal fusion before the age of 10 years was later discouraged for fear of compromising spinal growth and final height.[3] Rarely, posterior spinal fusion produced crankshaft phenomenon due to continued anterior vertebral growth.[50] The progression of the curvature due to continued anterior growth of the spine following successful posterior fusion alone is known as crankshaft phenomenon. To avoid this complication, some surgeons preferred circumferential fusion. Other procedures that have been described were convex epiphysiodesis,[51] unilateral growth arrest,[52] segmental spinal instrumentation without fusion[53,54] or combination of the above procedures.[55] In the last decade, the trend has been towards fusionless techniques for managing the curvature as well as maintaining the growth of the spine.[56,57]

Fusion

Convex epiphysiodesis with convex laminar and vertebral body fusion was reported by Roaf.[52] He proposed that the overgrowth on the convex side produces the spinal asymmetry and progressive deformity. Therefore, a convex epiphysiodesis may address the imbalance. Only 23% patients showed significant improvement.[52]

Marks et al. had deteriorating clinical results following convex epiphysiodesis in their series of patients with progressive EOS.[58] They also suggested that addition of instrumentation could slow progression, but does not reverse the progression.

Winter suggested that patients younger than 5 years of age with a curve magnitude of 70°, would benefit most from anterior and posterior convex epiphysiodesis.[59] There are studies demonstrating that spinal fusion at an early age does not improve respiratory function.[40] Current interest in endoscopic anterior vertebral stapling to modulate the growth of curvatures is also considered for EOS.[60]

Fusionless Surgery

Many spine surgeons have been interested by fusionless surgeries to maintain the growth potential of the spine. The principle of instrumentation without fusion was first introduced by Harrington for treating paralytic scoliosis.[61] Moe et al. subsequently modified the technique by limiting subperiosteal exposure at the hook placement sites.[62] Luque introduced his technique with sublaminar wires.[25] Subsequent reports suggested that sublaminar wires created scar tissue and weakened the lamina, which made revision and definitive fusion difficult.[54,63] A study from Nottingham, UK, included 13 patients with EOS, who under went Luque trolley and convex epiphysiodesis. The Cobb angle increased in seven patients during the 5-year follow-up, remained the same in four and improved in two. The growth of the instrumented spinal segment was 32% of the curve predicted.[64]

Expandable Spinal Implants

Single Rod There are very few long-term studies of single-rod techniques to substantiate the results into regular practice. Klemme et al. reported on the outcome of 67 patients following the subcutaneous rodding described by Moe et al. A total of 65% of the patients had improved curvature (mean curve reduction by 30%) or stopped progression. The unfused segments grew by 0.08 cm per segment per annum.[56] Most of these patients had threaded Harrington rods and few had segmental instrumentation. Apical fusion to allow for spinal growth and subcutaneous rods did not change the outcome (i.e., these preserved neither cosmesis nor respiratory function).[40] A high rate of complications (24%) has been reported with the single-rod technique (Isola single submuscular instrumentation).[65] Mineiro and Weinstein concluded from their study of 11 children with EOS that subcutaneous rodding with consecutive distraction allows correction of progressive curvatures.[66] However, this conclusion was weighed against the number of procedures each child had received to achieve the results. Could we justify the amount of growth achieved at the end of the completed treatment versus the number of complications?

Another study analyzed the 3D nature of the curvature following the use of single-rod distraction technique. The observation suggested that there was increased vertebral rotation although the curvature improved significantly.[67] Sometimes, a short anterior and posterior apical fusion may improve spinal mobility and curve correction achieved concomitantly. A TLSO is worn by the patient until definitive fusion. The rods are lengthened periodically, usually when the curve has progressed 15–20°. Once the child has reached sufficient age (~10 years for girls; 12 years for boys) and size, a definitive posterior spinal fusion or perhaps a same-day or staged anterior and posterior spinal fusion, depending on severity, is performed.[68]

Dual Rod Akbarnia and Marks developed the technique of a dual growing rod (GR) with subperiosteal dissection limited to upper and lower foundation sites.[69] This technique was developed on the principles laid by Asher.[70] Foundations are assembly of at least two anchors (claws) and one or two rods that have enough strength to accept corrective loads and to resist deforming loads without anchor dislodgement. The rest of the spinal exposure is subcutaneous or subfascial to prevent any autofusion. The foundation sites may be fused with locally harvested bone grafts and synthetic grafts. The rods are placed on either side of the spine and connected with tandem connectors (Figure 4A & B). Pedicle screws add stability to the construct.[71] A distractor fitted within the longitudinal openings in the tandem connector is used for lengthening. At the onset, a modest correction of the curvature is aimed at more aggressive correction after fusion at the foundation sites. A brace is worn until fusion is achieved at the foundation sites.[72] The rods are lengthened every 6 months regardless of curve progression. A final fusion is performed when the child has cessation of spinal growth, which is usually after the pubertal growth spurt. An average of 6.8 lengthening was performed in 23 patients with EOS. The curvature improved significantly (mean preoperative of 82° to final follow-up of 36°). Spinal length improved from 23 to 32 cm, approximately. Seven patients reached final fusion. A total of 48% had complications during the whole treatment.[73] Akbarnia et al. concluded that dual rodding is a safe and effective procedure that provides stability, increases the duration of treatment period and has an acceptable rate of complications.[73]

Figure 4.

Plain radiographs of the whole spine of a 3-year-old boy with early-onset scoliosis.
(A) Preoperative antero-posterior x-rays showing a Cobb angle of 124° from T7 to L3. (B) 2-year postoperative x-rays showing Dual Growing Rod in situ with correction of the deformity.

Further studies comparing single- and dual-rod techniques in patients with EOS through to definitive surgery suggested better outcome following dual rodding.[74] Five of 28 had single rod with fusion, 16 of 28 had single rod without fusion and seven of 28 had dual rodding without fusion. Spinal growth was 0.3, 1.0 and 1.7 cm per year, respectively. Spinal curvature was significantly reduced from 92 to 26° in the dual rod group, which was much higher correction achieved versus the other two groups of single rodding. The spines with dual rods had better curve correction and allowed more growth than their single rod counterpart. The duration of the treatment has been longer than previously reported series and the complications were within acceptable limits.[74]

However, dual rods are contraindicated in obese patients and in patients with significant rigid curves. Multiple surgical procedures are also not indicated in patients with little growth potential.[73] In theory, spinal motion could be preserved at the end of the final follow-up.

Vertical Expandable Prosthetic Titanium Rib The vertical expandable prosthetic titanium rib (VEPTR™), made by Synthes Spine of West Chester (PA, USA) is a titanium alloy longitudinal rib distraction device. It has been approved for use in patients with chest wall deformities along with scoliosis, which may be either, congenital, syndromic or early-onset idiopathic types. VEPTR is indicated if a constrictive chest wall syndrome is present based on a windswept deformity of the thorax at the apex of the curve on CT.[75] The operative strategy of VEPTR is to maximize thoracic volume and symmetry of the deformed thorax by lengthening the constricted hemithorax by a transverse opening wedge thoracostomy[76] of the concave side, through an intercostal muscle lysis in EOS.[77] A thoracostomy is performed to correct the spinal curvature indirectly. Once acutely equilibrated, the thoracic reconstruction is stabilized by the addition of a rib-to-spine or rib-to-pelvis VEPTR construct medially, and another rib-to-rib VEPTR at the posterior axillary line (Figure 5). No bracing is used postoperatively. The VEPTRs are lengthened every 4–6 months. Final fusion is preferentially delayed until skeletal maturity.[77]

Figure 5.

A 4-year-old boy with early-onset scoliosis and thoracic insufficiency syndrome treated with the vertical expandable prosthetic titanium rib.

Can we Compare these Techniques?

The three expandable implants are based on different principle. It is probably justifiable to compare the single and dual rod constructs, but it is probably unwise to compare the rod techniques with VEPTR. The vertical expandable prosthetic titanium rib is not truly a GR system. It corrects the 3D deformity of the thorax due to volume depletion deformity without inhibiting spinal growth so that growth of the underlying lungs has the most potential for optimal size by skeletal maturity.[78] Complication rates for all surgical techniques for treatment of EOS remains high due to the repetitive nature of the surgeries.

The addition of the VEPTR opening wedge thoracostomy as a new treatment for thoracic insufficiency syndrome associated with EOS makes comparison between these surgical techniques difficult. In EOS, it appears to be able to correct curves, improving space available for the lungs in the coronal plane as confirmed by CT scans. The effect on pulmonary function of serial VEPTR expansion thoracoplasty was studied longitudinally in anesthetized children with thoracic insufficiency syndrome in EOS.[79] After a median of 3.2 years (1.0–6.5), their forced vital capacity was found to have increased by an average of 11.1% per year. The rate of increase was greater in children who were younger than 6 years at the start of the study than in older children (14.5 vs 6.5%; p < 0.01). This independent study confirms the speculation by Campbell et al. regarding the improved pulmonary outcome following VEPTR.

Patients treated by VEPTR or GR as a group showed a normalization of the hemoglobin level (a surrogate measure for respiratory function), suggesting a beneficial effect of surgical intervention on respiratory function. EOS patients treated with VEPTR and expansion thoracostomy demonstrated a significant improvement of their hemoglobin level.[80]

Multicenter study groups suggest a complication rate of 57–119% in GR techniques. Comparing the complications in the three techniques, one study suggested rate of 230% for GRs, 86% for hybrid devices and 237% for VEPTR.[81] The complications may include rod breakage, migrated anchors, infection, wound breakage and neurological deficit requiring implant removal.

Definitive Fusion

Definitive spinal fusion is performed to stop growth of the spine and thus achieve permanent correction. Spinal fusion becomes appropriate when the patient has achieved sufficient spinal length and thoracic volume. Timing of the procedure is controversial, but in general, patients who are at least 10 years of age have completed the greatest part of their thoracic growth, and thus are candidates for definitive fusion to finish their scoliosis treatment.

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