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Early Onset Idiopathic Scoliosis Abstract Children with early onset scoliosis typically present before age 5 years. Radiographic criteria help to distinguish progressive cases from those that will spontaneously resolve. Severe cardiopulmonary problems may occur in untreated progressive cases. A comprehensive evaluation should be performed to identify commonly associated conditions, such as plagiocephaly, congenital heart disease, inguinal hernia, and hip dysplasia. For curves >20°, magnetic resonance imaging of the neural axis is indicated to rule out occult central nervous system lesions. Surgical management should be considered when nonsurgical measures, including bracing and casting, fail to arrest progression. Surgical methods continue to evolve and are primarily directed at obtaining and maintaining curve correction while simultaneously preserving spinal and trunk growth. T reatment of children with progressive scoliosis occurring before age 5 years is challenging. Left untreated, progressive curves may produce significant thoracic deformity, leading to deleterious effects on the cardiopulmonary system. As James et al 1 observed in 1959, progressive early onset scoliosis “devel- ops rapidly and relentlessly, causing the severest form of orthopaedic cripple with dreadful deformity, marked dwarfing and shortening of life.” Standard treatment options for adolescent scoliosis, including bracing and spinal fusion, have limited use in much younger children because of potential adverse effects on the developing spine, chest wall, and lungs. Successful management of idiopathic scoliosis requires understanding the etiology, natural history, evaluation, and available nonsurgical and surgical management options for these patients. In 1954, James 2 described three categories of idiopathic scoliosis ac- cording to the age of onset: infantile, with curves present before age 3 years; juvenile, with curves appearing between the ages of 4 and 9 years; and adolescent, in which curves present from age 10 years until the end of growth. These three periods were thought to correspond to distinct periods of increased growth velocity during childhood and ado- lescence. In fact, during the juvenile period, there is a deceleration in spinal growth, and onset of scoliosis is uncommon. 3,4 More recently, the term “early onset” has been used to reflect the presence of scoliosis of all etiologies by age 5 years; “late onset” is used to describe the appearance of scoliosis after age 5 years. 5 These terms more accurately reflect the physiologic basis of and clinical experience with this condition. The distinction between early and late Bruce L. Gillingham, MD, CAPT, MC, USN Ryan A. Fan, MD, LT, MC, USNR Behrooz A. Akbarnia, MD Dr. Gillingham is Director, Surgical Services, Naval Medical Center, San Diego, CA, and Assistant Professor of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD. Dr. Fan is Resident, Orthopaedic Surgery, Naval Medical Center, San Diego. Dr. Akbarnia is Clinical Professor of Orthopaedic Surgery, University of California, San Diego, and Medical Director, San Diego Center for Spinal Disorders, La Jolla, CA. None of the following authors or the departments with which they are affiliated has received anything of value from or owns stock in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Gillingham and Dr. Fan. Dr. Akbarnia or the departments with which he is affiliated has received royalties from DePuy Spine. Dr. Akbarnia or the departments with which he is affiliated serves as a consultant to or is an employee of DePuy Spine. Reprint requests: Dr. Akbarnia, San Diego Center for Spinal Disorders, Suite 300, 4130 La Jolla Village Drive, La Jolla, CA 92037-1481. J Am Acad Orthop Surg 2006;14:101- 112 Copyright 2006 by the American Academy of Orthopaedic Surgeons. Volume 14, Number 2, February 2006 101 onset is important because of the potential for serious cardiopulmonary compromise in patients in whom scoliosis appears before age 5 years. Basic Science Anatomy, Growth, and Development Knowledge of the normal growth of the chest, spine, and pulmonary system is essential in understanding the effect of scoliosis on these struc- tures. The number of alveoli in the terminal respiratory unit rapidly increases in number and volume during the first year of life. The number of alveoli increases more than 10- fold between birth and adulthood, primarily during the first 8 years of life. 6 In addition, the number of respiratory branches increases from 21 at age 3 months to 23 at age 8 years. 7 The significant increase in growth of the lung parenchyma is paralleled by corresponding growth of the spine and chest. Two thirds of the final sitting height is achieved by age 5 years. 3 The growth velocity of the T1 to L5 segment is greatest from birth to age 5 years, averaging >2 cm per year, with marked deceleration between ages 5 and 10 years. Growth velocity increases again at age 10 years and after but does not equal the velocity occurring before age 5 years 3 (Figure 1). Overall, the height of the thoracic spine doubles between birth and skeletal maturity. Thoracic volume is approximately 6% of adult volume at birth, reach- ing roughly 30% of adult volume by age 5 years and 50% by age 10 years. Final thoracic volume is achieved by age 15 years in both boys and girls. 3 Etiology Several causes have been identified for early onset scoliosis, including congenital vertebral anomalies, neuromuscular conditions (eg, cere- bral palsy, myelomeningocele, mus- cular dystrophies), associated syndromes (eg, neurofibromatosis), and structural lesions of the central nervous system (eg, diastematomyelia, syrinx, tethered cord). Patients with no obvious associated abnormalities are considered to have early onset idiopathic scoliosis. Natural History In contrast with late-onset disease, early onset idiopathic scoliosis, specifically infantile idiopathic scoliosis, spontaneously resolves in a large number of patients. Although early series reported a low incidence of resolution, later reports demon- strate a much more favorable outcome. 8-11 Magnetic resonance imaging (MRI) evaluation of the neural axis was unavailable at the time of these reports, however. In 1951, James 8 identified a pattern of scoliosis he termed “infantile idiopathic scoliosis,” involving primarily infant boys with a left mid or lower thoracic curve. Only 4 of 33 patients (12%) resolved. In contrast, Lloyd- Roberts and Pilcher 10 reported on 100 patients with structural curves diagnosed within the first year of life. Ninety-two percent of the curves resolved spontaneously. In their study of 99 infants, Ceballos et al 11 reported progression in 26%. The original hypothesis that infantile cases were caused by intra- uterine molding was refuted by the absence of scoliosis at birth. Scott and Morgan 9 compared the incidence of idiopathic scoliosis in En- gland and the United States, as reported by the Research Committee of the American Orthopaedic Asso- ciation in 1941. Twenty-eight of 218 patients from England presented with idiopathic scoliosis before age 2 years, compared with only 1 of 404 patients in the United States. Mau 12 subsequently proposed that postna- tal pressure caused by constant ob- lique supine positioning in European infants (compared with prone positioning in North American babies) was responsible for this difference in incidence. He also noted associated ipsilateral plagiocephaly (an asymmetric and twisted head in reference to the spine), pelvic flattening and obliquity, and hip adduction. This proposed correlation between infant positioning and early onset scoliotic deformities is disquieting and war- rants fur ther research in light of the current trend in American pediatrics to recommend positioning infants supine to reduce the risk of sudden infant death syndrome. 13 Several factors, such as age of onset; location, type and magnitude of the scoliotic curve; associated developmental anomalies; sex; and fami- Figure 1 cm/year 2.5 2 1.5 1 0.5 0 Age 1 Age 5 Age 10 Age 15 2 2 1.25 1.25 1.25 0.75 0.75 0.75 1 1.75 0.5 .25 T1-L5 T1-T12 L1-L5 Spinal growth velocity from ages 1 through 15 years. (Adapted with permission from Dimeglio A: Growth of the spine before age 5 years. J Pediatr Orthop B 1993;1:102-107.) Early Onset Idiopathic Scoliosis 102 Journal of the American Academy of Orthopaedic Surgeons ly history, have been proposed as predictors of curve progression. The most reliable indicator, however, is the rib-vertebra angle difference (RVAD), reported by Mehta 14 in 1972 (Figure 2). Progressive scoliosis during the first 5 years of life may negatively af- fect the normal development of the lungs, chest wall, and spine. The primary effect of scoliosis on the developing lung is its inhibition of the growth of both alveoli and pulmonary arterioles. This incomplete maturation of the lung and pulmonary vasculature is the primary cause of the ventilation defect seen in patients with early onset scoliosis. 15 Although progressive distortion of the pulmonary architecture by increasing deformity of the spine and thorax would be thought to compress the developing alveoli, this has not been observed. Histolog- ic studies of lung tissue in patients with early onset scoliosis demon- strate alveoli that are normal in shape and outline but diminished in number. In addition, the number of alveoli for a given lung volume was diminished more than could be ac- counted for by limitation of space. 16 This effect is directly related to the age of onset. The most hypoplastic lungs are found in patients with the earliest onset of scoliosis. 17 Patients with scoliosis demon- strate a restrictive pattern of lung disease, with reduction in vital capacity and total lung capacity along with increased residual volume. This reflects decreased compliance of both the lung and chest wall. In children with early onset curves, the amount by which vital capacity is reduced depends on the severity of the deformity. This severity has little or no effect on vital capacity in patients whose curves begin in ado- lescence. 15 Ultimately, severe restrictive lung disease causes alveolar hypoventilation, hypoxic vasocon- striction, and, eventually, pulmonary arterial hypertension and cor pulmonale. Arterial hypoxemia in scoliosis patients is primarily caused by a decrease in minute ventilation secondary to small tidal volumes rather than an impairment in gas ex- change. 18 The smallest tidal volumes and greatest decreases in minute ventilation are seen in patients with the highest Cobb angles. Cardiorespiratory failure does not develop when the vital capacity re- mains >40% of the predicted normal value. Clinically, there is a far greater risk of cardiorespiratory complication when scoliosis is apparent before age 5 years. Even in the absence of associated disease, disabling or life-threatening respiratory failure is relatively common and is likely to present at or before late middle age. 17,19 Physical Examination The evaluation of a child with sus- pected spinal deformity should begin with a comprehensive history and physical examination. Given that the presence of cognitive delay has been shown to correlate with curve progression, particular attention should be paid to whether the child has appropriately reached developmental milestones. 20,21 It is also important to obtain a birth history; early onset idiopathic scoliosis has been noted to occur more frequently with breech presentation and in premature, low-birth-weight males. 21 A thorough physical examination should be performed, beginning with a search for cutaneous markers of systemic disorders, such as the café au lait spots and axillary freckling observed in neurofibromatosis and the hairy patch associated with occult spinal dysraphism. Evidence of chest wall and shoulder height asymmetry, trunk imbalance, and pelvic obliquity are sought. Flexibil- ity of the scoliosis should be as- sessed: the patient is laid horizontal- ly over the examiner’s knee with the convex side downward, or by hold- ing the infant suspended under the arms, looking for correction of cur- vature with lateral pressure. Curves that correct are considered to be flex- ible; those that do not are termed rigid. The relative rigidity of the curve is an approximate clinical indicator of the likelihood of scoliosis progression and should be correlated with the RVAD and Cobb angle. 22 Figure 2 To measure the rib-vertebra angle difference, a line is drawn perpendicular to the end plate of the apical vertebrae (a). Next, a line is drawn from the midpoint of the neck of the rib through the midpoint of the head of the rib to the perpendicular on the convex side (b). The resultant angle is calculated. The angle on the concave side is calculated in a similar manner. Concave − convex = rib-vertebra angle difference. (Adapted with permission from Mehta MH: The rib-vertebra angle in the early diagnosis between resolving and progressive infantile scoliosis. J Bone Joint Surg Br 1972;54:230-243.) Bruce L. Gillingham, MD, CAPT, MC, USN, et al Volume 14, Number 2, February 2006 103 Lower extremity limb-length equal- ity is verified to rule out nonstruc- tural scoliosis, particularly in the ambulatory child with a predomi- nant lumbar curve. Following this focused evaluation of the scoliotic curve and its secondary manifestations, the patient is examined for conditions associated with early onset idiopathic scoliosis. Plagiocephaly, which is extremely common, is found in most patients with early onset idiopathic scoliosis. Developmental dysplasia of the hip, inguinal hernia, and congenital heart disease are found at a higher frequen- cy in patients with early onset idiopathic scoliosis than in children without scoliosis. 20,21,23 Finally, a careful neurologic examination, including assessment of muscle tone and reflexes, is imper- ative to detect occult central nervous system abnormalities. Superfi- cial abdominal reflex also should be examined for abnormalities because it may be the only clue to an under- lying syringomyelia with an associated Chiari I malformation. The superficial abdominal reflex is char- acteristically absent on the same side as the curve convexity. 24 Consideration should be given to obtaining a pediatric pulmonology evaluation, at least at the beginning and again at the end of treatment. In the presence of significant chest wall and rib asymmetry and respiratory insufficiencies, more frequent pulmonary function tests may be required. Pulmonary function tests are difficult to obtain before age 5 years. Other techniques to assess lung function and volume, such as three- dimensional computed tomography, provide valuable information in de- termining the severity of the patient’s condition and the timing and effect of surgical intervention. 25 Radiographic Evaluation Anteroposterior and lateral radiographs with full-length spinal views should be obtained to evaluate both the Cobb angle and the RVAD. 14 These radiographs are also helpful in ruling out other associated vertebral, lumbosacral, and hip joint abnormalities. The RVAD (Figure 2) is useful in predicting curve progression when there is no overlap of the rib heads on the apical vertebra (phase 1 relationship) 14 (Figure 3, A). An RVAD >20° indicates a high likelihood of curve progression; curves with RVAD measuring <20° are more likely to resolve. A phase 2 relationship, in which a rib head over- laps the apical vertebra, implies that progression is certain; thus, the RVAD is not measured 14 (Figure 3, B). In the Mehta study, 14 46 of the 86 phase 1 curves resolved. Of those that resolved, 83% had an RVAD <20°, with a mean RVAD of 11.7°. The progressive group demonstrated a mean RVAD of 25.5°; 84% had an RVAD >20°. In a series of 132 patients, Ferrei- ra et al 26 confirmed these findings, reporting that 67 of 68 resolving curves had an angle difference <20°; all were in a phase 1 relationship, and only two had a Cobb angle >30°. Of the progressive curves in that study, 37 of 40 had an RVAD ≥20°, with two of the remaining three dis- playing an increased RVAD to >21° by the first year. The RVAD is also useful in detecting the lumbar component of early double curves. Detecting double curves is important because they are highly likely to progress. 11 Meh- ta 14 noted key radiographic features of the early double curve: the near symmetric alignment of the apical ribs with a resultant low RVAD of the thoracic curve, downward obliquity of the twelfth rib on the concave side of the curve, and vertebral rotation in opposite directions in the thoracic and lumbar vertebrae. Recent attention has focused on defining the role of special imaging for patients with early onset scoliosis. In contrast to patients with late- onset scoliosis, the incidence of occult central nervous system ab- Figure 3 AB Convex Concave Convex Concave A, Phase 1 rib-vertebrae relationship demonstrating no overlap of the rib head and vertebral body. B, Phase 2 rib-vertebrae relationship. The overlap of the rib head on the vertebral body is indicative of curve progression. (Adapted with permission from Mehta MH: The rib-vertebra angle in the early diagnosis between resolving and progressive infantile scoliosis. J Bone Joint Surg Br 1972;54:230-243.) Early Onset Idiopathic Scoliosis 104 Journal of the American Academy of Orthopaedic Surgeons normalities is high in otherwise healthy-appearing patients with early onset scoliosis. In a prospec- tive study of 34 patients younger than age 10 years who presented with cur ves measuring >20° and a normal neurologic examination, Gupta et al 27 reported a 17.6% incidence of neural axis abnormalities. Occult abnormalities were discov- ered in three of the six patients younger than age 4 years. Two of these patients demonstrated caudal displacement of the cerebellar ton- sils below the foramen magnum (Chiari type I malformation), with an associated cervicothoracic syrinx requiring surgical decompression. The MRI of the third patient dis- closed diffuse dural ectasia. A more recent, larger study retro- spectively reviewed 46 patients with a Cobb angle ≥20°, normal neurologic examination, no associated syndromes, and no congenital abnormality. The mean age at presentation was 17 months (range, 2 to 37 months). Neural axis abnormality was demonstrated on MRI in 10 patients (21.7%), 8 of whom required neurosurgical intervention. Based on these findings, the authors recommended performing total spine MRI in patients with early onset curves measuring ≥20°. 28 Management Nonsurgical The treatment of children with early onset scoliosis is based on an- ticipated or actual curve progression (Figure 4). Mehta’s prognostic criteria have proved to be very helpful in differentiating between resolving and progressive curves. Curves with Cobb angles <25° with an RVAD <20° are at low risk for progression. These patients may be observed and should be reevaluated with serial radiographs every 4 to 6 months. Ac- tive treatment should be initiated with curve progression >10°. Upon curve resolution, follow-up at 1- to 2-year intervals until maturity is prudent to ensure that there is no re- currence during the adolescent growth spurt. A recent long-term study of resolving curves validated the use of the RVAD and demonstrated that there was no advantage of supine plaster bed treatment over physiotherapy in regard to either time to resolution or functional outcome. 29 Infants with an RVAD >20° or a phase 2 rib-vertebral relationship and a Cobb angle between 20° and 35° have a high likelihood of progression. When a child presents with a curve >35°, immediate treatment should be seriously considered. These patients should be followed closely at 4- to 6-month intervals, with active treatment initiated in the presence of >5° of Cobb angle progression. Traditional nonsurgical management for early onset scoliosis in- cludes casting, bracing, or a combi- nation of both. Cast application is usually done under anesthesia. The cast is changed at 6- to 12-week intervals until maximum correction is achieved. Following this, the cast may be replaced by a Milwaukee brace with full-time implementa- Figure 4 Early onset scoliosis (< age 5) Comprehensive history and physical examination and scoliosis radiographs MRI of spinal cord, positive finding Specialty referral for nonorthopaedic conditions Continue with nonsurgical orthopaedic management; progression to Cobb angle >25°, RVAD >20°, or positive phase 2 rib relationship Significant nonorthopaedic findings Absent abdominal reflexes or Cobb angle >20° Serial observation every 4-6 months Good response Yes No Possible removal of instrumentation and continued observation Annual clinical examination until skeletal maturity Progression of curve Neurosurgery specialty evaluation Casting/bracing Consider surgical intervention Definitive fusion Growing rod ± anterior release Serial lengthenings every 4-6 months Yes Yes No No No Yes Yes Yes No No Other emerging techniques Treatment algorithm for early onset (<5 years) idiopathic scoliosis. MRI = magnetic resonance imaging, RVAD = rib-vertebra angle difference Bruce L. Gillingham, MD, CAPT, MC, USN, et al Volume 14, Number 2, February 2006 105 tion (23 h/day). The Milwaukee brace is preferred over a thoracolumbar orthosis because of the rib cage distortion and pulmonary function reduction reported with the circum- ferentially fitting thoracolumbar brace. In addition, the immature rib cage often deforms before significant correction is transmitted to the spine. Bracing is generally continued for a minimum of 2 years until there is no further evidence of progression, as indicated by an unchanging Cobb angle and RVAD. Mehta and Morel 22 studied 21 patients with infantile idiopathic scoliosis who were treated nonsurgically. They reported that with total correction before the prepubertal growth spurt, there is no relapse during ad- olescence. Without full correction, however, small relapses may occur. These patients may require surgical intervention if further progression occurs during the adolescent growth spurt. They should be followed until skeletal maturity. Surgical Fusion Several surgical procedures have been used to manage progressive curves in skeletally immature patients. Early procedures focused on slowing or halting curve progression with spinal fusion, with the ratio- nale that a short, straight spine was preferable to a long, crooked one. Continued anterior growth following posterior fusion alone, known as the crankshaft phenomenon, 30 ne- cessitates circumferential fusion in preadolescents. Although effective in halting curve progression, this approach prevents future spinal growth and has deleterious effects on the developing thorax and lungs. The effectiveness of hemiepiphysiodesis in correcting lower extremity axial malalignment led to the application of this technique to the growing spine. In 1963, Roaf 31 proposed that the spinal deformity was produced by growth asymmetry, with overgrowth on the convex side of the spine and inhibition of growth on the concave side of the curve. He recommended and performed convex spinal epiphysiodesis to address this imbalance. Twenty-three percent of his patients showed significant improvement. However, 40% were stationary or showed very little improvement (<10°). In a recent study reviewing long- term results, Marks et al 32 found that convex spinal epiphysiodesis with or without Harrington instrumentation did not significantly re- verse the established deformity. Thirteen patients with infantile idiopathic scoliosis were treated with anterior and posterior convex epiphysiodesis alone (four received Har- rington instrumentation 2 to 4 years later); a further nine patients were treated with convex epiphysiodesis and concurrent Harrington instrumentation. Radiographic progression, mirrored by a deteriorating clinical result, occurred in all but one patient. The best results were noted with epiphysiodesis and si- multaneous Harrington instrumentation placement, which controlled but did not improve the degree of the primary curve. Single Rod Instrumentation Instrumentation without arthro- desis has been performed in an at- tempt to preserve spinal growth, obtain initial scoliosis correction, and control ongoing deformity. Har- rington 33 first reported this technique in 27 idiopathic and post-polio patients in 1962. Using a subperiosteal approach, Harrington placed on the curve concavity a single distraction rod connected to hooks at the upper and lower end vertebrae. These patients were a subset of the 129 patients he initially treated with his implant. No longitudinal results were reported. Complications included hook dislocation and rod breakage. Based on this early experience, Harrington believed that children younger than age 10 years with progressive scoliosis could be managed with instr umentation alone, whereas children age 10 years and older should be fused initially. Re- gardless of patient age, treatment should not be considered definitive. 33 Moe et al 34 subsequently modified Harrington’s technique by limit- ing subperiosteal exposure to the area of hook placement. The hook sites were not fused. The rod itself was placed subcutaneously. Moe et al 34 also modified the Harrington rod to have a smooth, thicker central portion to prevent scar adhesion to threads and to allow sagittal con- touring. Patients were placed in a Milwaukee brace postoperatively; the construct was lengthened when >10° loss of correction occurred. There was an average increase of 2.9 cm in the length of the instrumented portion for all 20 patients and of 3.8 cm (compared with a predicted growth of 4.5 cm) in the 9 patients who went on to fusion. Nota- ble decrease in curve magnitude was reported in the two patients with progressive early onset curves. Com- plications occurred in 50% of patients. Rod breakage, although less common with the modified thicker rod, still occurred. The authors also reported hook dislodgement from the rod and dislocation from the lamina. Klemme et al 35 in 1997 reported the results of a 20-year experience with the Moe technique. An average of 6.1 procedures were performed from initial instrumentation to definitive fusion in 67 patients. In 44 of the 67 patients, curve progression was arrested or improved over the course of treatment, with an average curve reduction of 30%. In the remaining 23 patients, including 12 with neuromuscular scoliosis, curves progressed an average of 33%. The overall growth rate of instrumented but unfused spinal segments was 0.08 cm per segment per year. Implant-related problems, including hook dislocation and rod breakage, were reported in 33 of 402 procedures (8%). Early Onset Idiopathic Scoliosis 106 Journal of the American Academy of Orthopaedic Surgeons Marchetti and Faldini 36 in 1978 reported on what they termed the “end fusion technique.” Fourteen patients underwent staged procedures in which the vertebrae at each end of the curve were initially fused. Five to 6 months later, hook placement was performed along with subperiosteal rod placement. Finally, at a third procedure 6 to 8 weeks later, the upper hook was distracted. Serial lengthening was performed until definitive fusion at maturity. Four of the 14 patients had completed treatment at the time of publication of their report, with “most satisfactory” results. In 1977, Luque and Cardoso 37 reported on their technique for segmen- tal spinal instrumentation (SSI) without ar throdesis. In 1982, Luque 38 reported the results of adding sublaminar wiring to a Harrington rod in 47 paralytic patients. The immobilized area grew an average of 4.6 cm, with curve correction of 78%. Smooth, L-shaped rods were subsequently sub- stituted for the Harrington rod in a construct that became known as the Luque trolley. Initial enthusiasm based on these perceived advantages was tempered by reports that the subperiosteal exposure and sublaminar wire passage created scar tissue and weakened the lamina, which made revision and later definitive fusion difficult. In addition, premature spontaneous fusion was noted in several patients. In subsequent reports by other authors, growth preservation was demonstrated to be substantially less than expected. 39,40 Patterson et al 41 combined SSI with anterior apical convex growth arrest and fusion in 9 of 13 patients who had previously undergone surgery at an average age of 5 years 5 months. At 2-year follow-up, curve correction averaged 46%. Patients with anterior apical growth arrest combined with SSI without fusion had less curve deterioration than did those who had SSI alone. No spontaneous fusions were reported. Pratt et al 42 performed a retrospec- tive analysis of Luque trolley instrumentation with and without convex epiphysiodesis in 26 patients. Curve deterioration was observed in all eight patients treated with the Luque trolley alone. In curves managed with combined convex epiphysiodesis and Luque instrumentation, the Cobb angle worsened in 7 of 13 patients, was unchanged in 4, and improved in 2. Growth of the instrumented spinal segment was 49% of the curve predicted in patients treated with the Luque trolley alone, and 32% of the curve predicted in patients undergo- ing the combined procedure. More recently, Blakemore et al 43 reported periodic lengthening with a submuscular rod with and without limited apical fusion in 29 children with scoliosis. Ten of the curves were idiopathic. The single rod was placed within the muscle above the spinal periosteum. This approach placed the rod closer to the spine for better contour and alignment without causing spontaneous posterior fusion. Apical fusion was performed in curves >70° and in those that were stiff on side bending radiographs. All patients were placed in a Milwaukee brace postoperatively. Curves improved from a mean preoperative Cobb angle of 66° to a mean of 38° on initial postoperative radiographs. Slight deterioration to a mean of 47° was observed on the most recent radiographs. Spinal growth had not been calculated for the entire group at the time of publication. Compli- cations occurred in 24%, including five hook displacements, three rod breakages, and one superficial infec- tion. The authors concluded that, despite the frequent but manageable complications, their technique is useful for managing severe spinal deformities in young children who have failed, or who have a contrain- dication to, orthotic management. Emerging Techniques Dual Growing Rod Instrumentation Dissatisfied with the unpredict- ability and implant-related complications of single rod distraction techniques, Akbarnia and Marks 44 developed a dual growing rod technique, building on concepts formu- lated by Asher. 45 We currently prefer this technique. Subperiosteal dissec- tion is limited to upper and lower anchor sites (foundations) (Figure 5). Hooks or screws are placed on both sides of the spine in so-called claw patterns over two to three spinal lev- els to avoid hook crowding. Pedicle screws seem to add stability to the construct. 46 A transverse rod connector is positioned adjacent to or in the middle of the claw constructs at both foundations. Foundation sites may be fused with local bone graft supplemented with synthetic graft. Upper and lower contoured 3/16- inch-diameter rods are placed subcutaneously on both sides of the spine. The rods are joined on each side with extended tandem connectors placed at the thoracolumbar junction to avoid disturbing sagittal balance. 44 Lengthening is perfor med with a distractor designed to fit within the longitudinal openings in the tandem connector. The intent of initial lengthening during implant insertion is to achieve modest correction of the scoliotic curve without plac- ing undue stress on the foundations. More aggressive correction is at- tempted at the first lengthening after fusion of the foundation sites. Serial lengthening occurs at approximately 6-month intervals. Somatosensory evoked potential monitoring is performed during each lengthening, which is generally done as an outpa- tient surgery. Bracing is performed until the foundation sites are fused. Encouraging results were obtained from a multicenter study at minimum 2-year follow-up (range, 24 to 111 months) of 23 patients, including 7 with early onset idiopathic curves. 47 The average age at initial surgery was 5 years 5 months; patients had an average of 6.6 lengthenings. The mean Cobb angle improved from 82° to 38° following the initial surgery; it was 36° at the lat- Bruce L. Gillingham, MD, CAPT, MC, USN, et al Volume 14, Number 2, February 2006 107 est follow-up. Growth of the T1-S1 segment averaged 1.21 cm per year. The seven patients who completed treatment at an average age of 10 years 3 months achieved a total T1- S1 length increase of 11.8 cm from preoperative status to postoperative final fusion (1.66 cm growth per year). In 14 patients with thoracic curves, the space available for lung ratio, as described by Campbell et al, 48 improved from 0.87 preopera- tively to normal (1.00) at latest follow-up or after final fusion. 47 Complications occurred in 11 of 23 patients between initial surgery and final fusion. The complications included three anchor (hook or screw) displacements, two rod breakages, two deep wound infections, four superficial wound problems, one crankshaft, and one junctional kyphosis requiring an extension of instrumentation. These results indicate that the dual rod technique is safe and effective and provides increased implant stability. Although the complication rate is high, this procedure has few- er complications compared with single rod systems (Figures 6 and 7). A recent study by Thompson et al 49 of- fers additional support for the use of the dual growing rod technique. The authors compared the results of single and dual growing rod techniques in 28 patients followed through definitive surgery. Five patients had single rod with anterior and posteri- or apical fusion, 16 had single rod without apical fusion, and 7 had dual rod without fusion. The mean Cobb angle respectively improved from 85° to 65°, 61° to 39°, and 92° to 26°. Spinal growth respectively was 0.3, 1.0, and 1.7 cm per year . The authors concluded that growing rod techniques using single or dual rods are effective in establishing and maintaining curve correction and allow- ing spinal growth. On the basis of its greater strength and more frequent lengthening, however, dual rod instrumentation produced better initial correction and maintenance of correction and allowed more growth than did single rod instrumentation. Although the numbers were small, the least favorable outcomes were in patients who underwent short apical fusion. This technique appeared to lead to stiffening of the curve, crankshaft phenomenon, less correction, and a higher incidence of complications. The authors indicated that apical fusion may not be helpful. 49 Other Emerging Techniques Although still evolving, current surgical techniques using instrumentation with minimal or no ar- throdesis in the treatment of early onset idiopathic scoliosis are capable of significant initial curve correction and prevention of subsequent curve decompensation. This allows definitive fusion to be delayed until ado- lescence. In addition, it is possible to preserve nearly normal growth within the area of instrumentation. It is hoped that growing rod instrumentation may be removed at maturity in some patients, avoiding fusion completely and preserving spinal motion. The search continues, however, for methods that will achieve curve correction and prevent subsequent curve decompensation in a less invasive fashion and minimize the need for repeat surgical proce- Figure 5 Upper foundation Extended tandem connectors Lower foundation Extended tandem connectors AB Dual growing rod instrumentation. A, Anteroposterior view. The upper and lower rods are joined at the thoracolumbar junction by extended tandem connectors. B, Lateral view. The rods are contoured to maintain sagittal alignment. Extended tandem connectors are placed at the thoracolumbar junction to minimize adverse effects on thoracic kyphosis and lumbar lordosis. (Reproduced with permission from Bagheri R, Akbarnia BA: Pediatric ISOLA [DePuy Spine] instrumentation, in Kim DH, Vaccaro AR, Fessler RG [eds]: Spinal Instrumentation: Surgical Techniques. New York, NY: Thieme, 2005, pp 636-643.) Early Onset Idiopathic Scoliosis 108 Journal of the American Academy of Orthopaedic Surgeons Figure 6 Radiographs and photographs of a girl aged 5 years 10 months old with infantile idiopathic scoliosis who was followed for 7 years and eventually had final fusion. Preoperative anteroposterior (A) and lateral (B) radiographs of the spine. Anteroposterior (C) and lateral (D) radiographs taken after the initial surgery. Anteroposterior (E) and lateral (F) radiographs taken 5 years after initial surgery. G and H, Clinical appearance at 5-year follow-up. Note the correction of scoliotic curve and the linear scar (G). Patient kyphosis fell within normal limits (~50°) at the time of radiographs and clinical photographs. Bruce L. Gillingham, MD, CAPT, MC, USN, et al Volume 14, Number 2, February 2006 109 dures. The ideal implant would require minimally invasive insertion; would be durable, rarely requiring revision or replacement; would have a minimal effect on adjacent tissue; and, if required, would be easily in- corporated into the definitive fusion. One intriguing possibility is the development of an implant that can be lengthened by remote control. In 1998, Takaso et al 50 reported on the development of a rod containing a direct-current motor attached to a radio-controlled receiver . Successful serial correction of experimental scoliosis was achieved in beagles. The main problems encountered were the relatively large size of the rod (16 mm) and the receiver, which necessitated placement in the abdominal cavity. Recently, interest has returned to attempts at modulating the growth of the scoliotic spine with anterior asymmetric growth arrest performed with staples placed endoscopically. Historically, this technique had some failures, in part because of loss of staple fixation. 51 Improved staple designs promise better fixation, however. Betz et al 51 recently reviewed 21 patients with adolescent idiopathic scoliosis who were treated with vertebral body stapling. No patients with either infantile or juvenile scoliosis were included. Six of 10 patients with curves between 28° and 40° re- mained stable or improved at 1-year follow-up. Four patients progressed. Further investigation is needed to de- termine the efficacy of this technique in early onset scoliosis. The technique of expansion tho- racoplasty for managing thoracic in- sufficiency syndrome with the vertically expandable prosthetic titanium rib has recently been described. 48,52 This device was designed to manage thoracic deformities resulting from absent and fused ribs in congenital and syndromic conditions, such as Jeune’s asphyxiating thoracic dystro- phy and Jarcho-Levin syndrome. This effort has resulted in a broader and deeper understanding of the central role that the spine plays in the architecture and function of the chest wall and thorax. This new awareness emphasizes the impor- tance of evaluating thoracic volume in addition to the standard assessment of anteroposterior and sagittal spinal alignment. Restoring this “fourth dimension,” thereby maxi- mizing the potential for pulmonary development, is emerging as an important goal in the treatment of patients with congenital spine and rib anomalies or with thoracic insuffi- ciency syndrome. 48 Summary Treating progressive early onset idiopathic scoliosis is challenging. Un- treated curves may cause significant disturbance of normal trunk and spine growth, with severely deleterious effects on the cardiopulmonary system. Surgical treatment is indicated in patients whose curves progress despite nonsurgical treatment. Spinal fusion at an early age also may lead to a shorter trunk, a smaller thorax, and resultant pulmonary complications. Other techniques, such as hemiepiphysiodesis, single growing rod methods, and SSI, have yielded satisfactory results in this patient population. New, more effective techniques, such as the dual growing rod technique, anterior non- fusion techniques, and the vertically expandable prosthetic titanium rib, have emerged with the goal of preserving spinal growth and maintaining scoliosis correction. Even though they often require the patient to undergo multiple operations through- out childhood, these techniques promise to be less invasive in the future and more valuable in treating patients with early onset scoliosis. Acknowledgment The authors wish to acknowledge Sarah Canale, BS, for her assistance with the editorial process. Figure 7 Graphic representation of the improvement in length of implant, T1-S1 length, and Cobb angle magnitude in the patient shown in Figure 6.5+10=5years 10 months; 13+6=13years 6 months. Early Onset Idiopathic Scoliosis 110 Journal of the American Academy of Orthopaedic Surgeons

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