Scoliosis: a review

SYMPOSIUM: SURGERY & ORTHOPAEDICS

Scoliosis: a review

thoracolumbar or lumbosacral) has the apical vertebra at the interface between these 2 areas. The apical vertebra is the most rotated vertebra in the curve. The end vertebra are the most cephalad and caudad vertebrae whose superior and inferior surfaces respectively, tilt maximally towards the concavity of the curve. The curve size is assessed by measurement of the Cobb angle (Figure 1) which is usually described in the direction of the concavity. This is done by drawing lines perpendicular to the transverse axes of the upper and lower end vertebrae. Where these lines intersect is the cobb angle. Previously this was done using a device called the cobbometer but can now be done with computer software. The different curves are indicated below:  Cervical C1-C6  Cervicothoracic C7-T1  Thoracic T2-T12  Thoracolumbar T12-L1  Lumbar L2-L4  Lumbosacral L5-S1 The successful treatment of scoliosis to a large extent depends on a good understanding of the natural history of the curve and the consequences of not treating it. This must be tempered by an appreciation of there being no single natural history but rather a multitude of natural histories depending on the type of curve.

Colin Nnadi Jeremy Fairbank

Abstract The normal spine has a straight profile when seen from behind. Scoliosis occurs when this profile is deformed by a curvature which may appear in one or more segments. This curvature is associated with rotation and wedging of the vertebrae. Outwardly, in addition to the curve there may be prominence of the thorax or lop-sidedness of the shoulders or pelvis. The majority of cases present in adolescent females with no obvious cause. Spinal deformity presenting in younger children is much more likely to have an identifiable cause. Because of the risk of progression and the consequences these curves need to be monitored and treated if necessary. These treatments and indications are discussed along with the different types of scoliosis.

Keywords classification; investigation; natural history; risk factors; scoliosis; surgery

Introduction Scoliosis is a structural three dimensional deformity of the spine which is related to growth. Non-structural deformity can be caused by lower limb disorders resulting in limb length discrepancy such as hip dysplasia, limb deficiency syndromes and herniated discs in the older child. This type of spinal deformity is dealt with by treating the primary cause. Scoliosis can also be classified by cause into idiopathic or secondary. Idiopathic scoliosis is further classified into infantile, juvenile and adolescent types or early and late onset. Scoliosis can also be secondary to congenital disorders, neuromuscular conditions, tumours, trauma or syndromic. The prevalence of scoliosis in the UK has been established in a survey of 10,000 children in Edinburgh as 1.3/1000 in those under 8 years and 1.8/1000 in those over 8 years of age. In the former group the incidence was similar in both sexes but in the latter group girls outnumbered boys by almost 3 to 1. These figures are similar across the world with a few exceptions.

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Terminology A scoliosis has a primary curve and a secondary curve. Each curve has a convex side and a concave side. The primary curve is usually stiffer. The curve site is classified according to the location of the apical vertebra in the coronal plane e cervical, thoracic or lumbar. A junctional curve (cervicothoracic,

Figure 1 Cobb angle. The two ‘end’ vertebrae are the last vertebrae whose end plates are tilted into the concavity. The Cobb angle is measured between a line drawn along the upper end plate of the superior vertebra and another along the lower end plate of the inferior vertebra. Rotation may be estimated from pedicle asymmetry, the more marked the asymmetry the greater the vertebral rotation (normally maximal at the apex).

Colin Nnadi FRCS(ORTH) Consultant Orthopaedic Spine Surgeon, Nuffield Orthopaedic Centre, Windmill Rd, Headington, Oxford, OX3 7LD, UK. Jeremy Fairbank FRCS Consultant Orthopaedic Spine Surgeon, Nuffield Orthopaedic Centre, Windmill Rd, Headington, Oxford, OX3 7LD, UK.

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deceleration after onset of menarche in girls and puberty in boys the incidence of progression decreases.

Scoliosis is a 3-dimensional deformity F:M Prevalence > over 8 years Curve site dependent on location of apical vertebra

Congenital curves Generally, the worst curves occur with unilateral defects in segmentation. Other factors include the type of anomaly, site of anomaly and age of onset. These curves should be referred early for specialist opinion. These anomolies are commonly associated with neuraxis, cardiac and urogenital anomalies. These are increasingly identified during prenatal ultrasound examinations. Congenital scoliosis ranges from the trivial to catastrophic depending on the capacity to progress (and in kyphosis, the capacity to cause spinal cord compression and paralysis). It is wise to ask for an MR scan of the neuraxis when the child is old enough to lie still, as about 20% are associated with neuraxis anomalies.

Natural history of scoliosis This is based on long term follow up of untreated cases. Most studies involve a mixed group of patients and therefore the observations may not be wholly accurate but the general trend is that in severe curves (greater than 90 degrees) there is an increased risk of morbidity and mortality. There is also a reduced self-image leading to psychological disturbance in later life. In congenital or early onset curves these consequences can be devastating if not treated early. Adult scoliosis can either develop de novo usually secondary to degenerative disease or result from untreated or missed adolescent deformity. The aim of treatment in all cases is to prevent curve progression. Factors which influence the natural history of the different curves are smmarised below:

Neuromuscular curves (Figure 4) Most of our knowledge and practice of scoliosis came from the polio era, when so many children developed aggressive and malignant scoliosis. Now the most common neuromuscular cause of scoliosis is cerebral palsy(CP). The more severe the CP, the greater the likelihood of scoliosis appearing in childhood. Gross Motor Function Classification (GMFC) 4 and 5 children need close scrutiny by paediatricians and physiotherapists to detect scoliosis. Specialist surgeons use sitting (or when possible, standing) X-rays to monitor progress. As this is difficult to do by clinical examination. Scoliosis surgeons include muscular dystrophies in this group, including Duchenne, Beckers, SMA and other rarer varieties. In general the more wheelchair dependent is a child, the more likely they are to develop scoliosis.

Infantile idiopathic curves Many of these curves resolve. Progressive curves are identified by measuring the rib-vertebral angle difference (RVAD) (Diagram 1). This is assessed by the angle formed by the intersection of a line perpendicular to the apical vertebra with a line drawn from the midneck to midhead of the corresponding convex and concave rib. If the difference between the 2 sides is more than 20 degrees this indicates a likelihood of progression. This measurement reflects rotation and asymmetry of the thoracic cavity and thus indicates the potential risk to pulmonary function. Arborisation of the bronchial tree continues to around age 7. Thereafter the lungs enlarge. Early onset scoliosis can have a profound effect on lung development that in turn has an impact on life expectancy. Early intervention on scoliotic spines are primarily aimed at enhancing lung development, encouraging normal spine growth and preventing progression of deformity.

Syndromal scoliosis There are numerous syndromes where scoliosis is a feature. The most common include neurofibromatosis and Marfans, although the list is very long.

Neurofibromatosis(NF) Scoliosis is very rare in type 2 NF but occurs in 10-40% of patients with type I NF. There are two types of curve: 1. Dystrophic curve which is a short severe curve often with a marked kyphosis. 2. Non-dystrophic curve which is similar to an idiopathic curve. MRI is required to exclude an intraspinal neurofibroma which is more common in dystrophic curves. A combined approach may be required. Pseudoarthrosis is a known complication.

Adolescent idiopathic curves As a general rule, the larger the curve at initial presentation the greater likelihood of progression. A double curve is more likely to progress than a single curve. Premenarchal status and skeletal immaturity increase the potential for progression. With growth

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Awareness of risk factors for progression Early specialist opinion

Assessment Diagram 1 The rib-vertebra angle difference(RVAD). A line is drawn perpendicular to the transverse axis of the apical vertebra. The angle subtended by this line and a line which connects the neck and head of the convex rib is then subtracted from the angle calculated by the same method on the concave side. If the difference is greater than 20 degrees this curve is likely to progress.

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It is important to take a detailed history. Estabilish the date of onset and who first noticed the curve. A history of progression should be noted. A history of pain is important as this may indicate underlying pathology such as tumours, neurological or syndromic conditions like Arnold chiari malformation or cord tethering.

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Idiopathic curves are seldom painful. Onset of menarche in females and features of puberty in males are important in predicting likelihood of progression and also timing of interventions. Details of secondary effects of the deformity should be obtained. Functional restrictions at school may indicate problems with coordination due to neurological anomalies or cardio-respiratory problems. Urinary or bowel symptoms should be noted. A birth history should be recorded to exclude congenital or syndromic causes. A family history should also be taken. Clinical examination should include height and weight measurements. Disproportionate stature in skeletal dysplasias can be associated with scoliosis. Skin stigmata such as cafe´ au lait spots, hairy patches or skin dimpling must be noted. Lower limb anomalies in the form of calf asymmetry and foot deformities should also be noted as should dysmorphic facial features. In the coronal plane observe for shoulder or pelvic asymmetry in addition to spinal curvature. With normal truncal balance a plumb line dropped from the spinous process of C7 should bisect the natal cleft. Where there is truncal imbalance this line falls either side of the cleft. The forward bend test (Adam’s test) performed by asking the child to clasp their hands and place them between the knees on bending forwards allows assessment of scapular prominence. This is indicative of a structural deformity. The flexibility of the curve can be assessed by side bending to view the amount of correction. This helps with treatment planning. In the sagittal plane a flattening of the normal thoracic kyphosis is not uncommon. A hyperkyphosis or hyperlordosis may signify a congenital cause. Palpation for tenderness and range of motion should be assessed. The gait pattern should be observed. A full neurological examination should be performed. Asymmetrical abdominal reflexes may indicate a neuroaxial anomaly. It should be remembered that in the younger child it may not be possible to complete a full examination. The spine in these situations can be assessed by suspending the child in the air to observe flexibility as well as pelvic obliquity. It is also useful to examine normal functional activities such as walking and squatting. Always remember to evaluate the lower extremities for deformity or discrepancies in length.

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Other specialised views include the ferguson view which allows assessment of the L5-S1 junction. In wheelchair bound patients sitting films will reveal pelvic obliquity and spinal deformity. The magnitude of the curve and its progression over time is measured by the cobb angle. Ossification of the iliac apophysis from front to back allows an estimation of skeletal maturity (see Figure 2) This is graded 1-5. Risser 5 represents skeletal maturity. Grades 0-2 have the highest risk of progression. It is important to minimise radiation exposure and therefore requests for x-rays should reflect clinical need. A PA film minimises radiation. In the authors institution surface topography of the back to monitor curves is used instead of x-rays to lower radiation exposure. Magnetic resonance imaging MRI of the whole spine is advisable in all infantile and juvenile groups with large or progressive curves. Approximately a quarter of these will have neuro-axial anomalies. MRI in the adolescent group is more controversial due to the very small pick up rate of abnormalities. Indications for MRI are as follows:  Left sided thoracic curve  Pain  Rapid curve progression  Congenital scoliosis  Neurofibromatosis The scan should encompass the whole spine including the cranio-cervical junction. Computed tomography This is useful in pre-operative planning for complex cases to define bony anatomy. Other investigations As part of the pre-operative work up all congenital cases should have an echocardiogram and renal ultrasound. There is a significant incidence of renal and cardiac anomalies in these children. Bronchio-alveolar development continues up to the age of 7 years. It is therefore important to assess respiratory function in the younger child. In the older more co-operative patient forced

Detailed history & examination Evaluate deformity and secondary effects Always examine lower limbs

Investigations Plain X-ray In the community and at first presentation, the plain x-ray forms the basis of initial assessment apart from physical examination. It is cheap and readily available. It is also useful for curve monitoring. Standard cassettes are inadequate for providing useful information in adolescent scoliosis. Standing AP and lateral views of the whole spine are needed at the first visit. Subsequent visits require only an AP view. Lateral views allow assessment of the sagittal profile and also help diagnose any congenital deformity. Additional views include supine active bending films to assess curve flexibility and traction views in the neuromuscular or syndromic patient unable to actively bend. Hyperextension views can be used to assess flexibility in a kyphotic deformity.

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Figure 2 Risser grade. The iliac apophysis appears anteriorly and moves backwards, as illustrated on the right hemi-pelvis. By dividing the iliac crest into four quadrants, increasing skeletal maturity is indicated from Risser grades 1}4. Risser grade 0 is an absent iliac apophysis, and Risser grade 5, when the apophysis has fused along its entire length correlates with the end of growth in height.

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The objective is to contain the curve until skeletal maturity. The outcome of bracing however is less predictable than surgery. In the younger child with a flexible curve a cast is first applied which needs to be changed regularly(3-4 monthly) to keep up with growth. When control of the curve has been achieved which usually takes 6-12 months a moulded brace is applied for long term control. The brace is worn for up to 2 years. If the curve is controlled the brace can be weaned off but clinical follow up must proceed to maturity. Surgery should be considered with failure of bracing. The main difficulty with bracing is compliance as the brace needs to be worn for up to 23 hours a day.

vital capacity measurement as a percentage of normal is a simple yet effective guide to pulmonary function. Occupational therapy/Physiotherapy review It is important that any social requirements such as wheelchair adaptation or modifications of the home environment which may impact on recovery from surgery are identified early to ensure smooth passage of treatment. Certain groups may require intensive physiotherapy input to aid recovery. Dietary support Nutritional requirements should be assessed prior to surgery as nutritional status plays a significant role in infection control. If necessary supplementation should be given prior to surgery.

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X-ray is initial investigation of choice > 20 curve under 10 years should have MRI CT useful in pre-op planning Cardiac/renal anomalies in 20% of congenital cases

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Indications for treatment As a general rule any curve over 20 degrees in all groups requires a minimum of further follow up. Significant progression is deemed to occur with a 5 increase in curve size within 6 months or 10 within 1 year. Treatment must start when there is evidence of progression or if the curve is of a large size on initial presentation. In cases where progression with serious consequences is predictable such as in congenital deformity, surgery may be the initial treatment of choice. In the older child with curves between 20-40 observation or bracing is a reasonable option. Risk factors for progression  Growth Spurt  Growth potential (age, menarchal status, Risser sign <2)  Curve pattern (Double curve > Single curve)  Curve magnitude (larger curves more likely to progress)  Unusual curve pattern i.e Left thoracic curve  Thoracic hypokyphosis Aims of Treatment  Prevent curve progression  Achieve good correction in coronal and sagittal planes  Improve cosmetic appearance  Achieve solid fusion  Prevent long term disability

Treatment Surgery In general terms, the more immature the patient the more aggressive the treatment strategy. This is because scoliosis is a growth related disorder. Also certain curves (i.e congenital and neuromuscular) are more likely to require surgery. The goal of surgery is to halt progression of the curve and correct the deformity in the coronal and sagittal planes. In such cases a short segment or long segment fusion may be performed. It is important to consider the effect of a fusion on the growth potential of the spine. There are two periods of rapid spinal growth. Namely, 0-5 years and 10-16 years. In between these periods spinal growth is steady. A formula has been devised for determining the amount of potential shortening after spinal fusion e0.07 multiplied by the number of segments fused multiplied by the number of years of remaining growth. This enables a rough estimate of how much shortening can be expected from surgery. The surgical treatment options in the early onset group (Infantile and Juvenile) and late onset groups (adolescent) are listed below: Early onset  Fusionless surgery with growing rods  Vertical Expandable Titanium Rib Device (VEPTR)  Growth modulation (Epiphysiodesis)  Definitive fusion Late onset  Anterior fusion  Posterior fusion  Combined Anterior and Posterior fusion The decision whether to fuse anteriorly or posteriorly will depend on the location of the curve, size and degree of stiffness. Historically, Harrington rods were used to achieve spinal fusion. These have now been superseded by newer segmental instrumentation techniques.

Classification systems for idiopathic scoliosis (Figure 3) These classification systems have been devised to help with diagnosis, prognosis and management. No system has proven entirely adequate. Infantile curves are resolving or progressive. Juvenile curves have been more difficult to classify. The adolescent curve is the most commonly described and we briefly discuss these classifications below. The King & Moe classification system for adolescent idiopathic scoliosis was devised in the early 1980’s. It describes five distinct curve patterns based on standing radiographs of the spine. The aim of this system was to determine a reliable method for selection of fusion area. The curve types were stratified from I-V with II and III being the commonest types. Type III is a thoracic curve while type II is a thoracolumbar curve. There is poor intra/

Bracing and casting Indications for bracing are stronger in younger children and more controversial in adolescents.

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Bracing is for curve ‘containment’ Surgery is to halt curve progression Ideal time for surgery is around skeletal maturity Surgery in younger child for aggressive curves

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inter observer reliability with this system. It also only assesses the curve in the coronal plane and does not take into account the 3-dimensional scope of the deformity. A new classification called the Lenke system has been developed. This is a triad system which combines 6 curve types with coronal and sagittal plane modifiers. This system identifies minor and major structural curves. A major curve is the largest curve and a structural curve is one which does not correct to less than 25 cobb angle on bending radiographs. This system is said to be treatment based in that all structural curves are included in the fusion. It is beyond the scope of this article to discuss the pros and cons of these assertions but the authors would caution that not all curves fall into the groups mentioned in either classification system. Each curve should be treated on merit as it may on occasion be necessary to combine treatment approaches. Classification of congenital scoliosis (Figure 4) These are classified into failure of formation, failure of segmentation and mixed groups. They are further sub-divided into anterior formation failure, posterior formation failure, lateral formation failure, anterolateral formation failure and anterocentral formation failure depending on site of pathology. The classification provides a guide regarding the natural history of these curves in that as a general principle failures of

Figure 4 Neuromuscular scoliosis. This 19-year-old female has Cerebral Palsy with total body involvement. The sitting radiograph demonstrates marked pelvic obliquity and an unbalanced spine. Note how different the long, single curve appears from that typically seen in idiopathic scoliosis (Figure 3).

segmentation have a more benign prognosis whilst failures of formation and mixed anomalies have a poorer prognosis. Anomalies at junctional areas e.g thoracolumbar junction also tend to fare worse. A

FURTHER READING Akbarnia BA. Management themes in early onset scoliosis. J Bone Joint Surg Am 2007; 89(Suppl. I). Bergofsky EH, Turino GM, Fishman AP. Cardio-respiratory failure in kyphoscoliosis. Medicine 1959; 38: 263e317. Bradford DS, Heithoff KB, Cohen M. Intraspinal abnormalities and congenital spine deformities: a radiographic and MRI study. J Pediatr Orthop 1991; 11: 36e41. British Scoliosis Society. Available at: www.britscoliosissoc.org.uk. Chaglassian JH, Riseborough EJ, HallNeurofibromatosis JE. Natural history and results of treatment in 37 cases. J Bone Joint Surg Am 1976; 58: 695e702. Cobb JR. Outline for the study of scoliosis. In: Edwards JW, ed. Instructional course lectures, Vol. 5. Ann Arbor, MI: The American Academy of Orthopaedic Surgeons, 1948.

Figure 3 Adolescent idiopathic scoliosis. This 14-year-old female has a typical right thoracic scoliosis. Cobb angle 70 degrees. By convention, scoliosis radiographs are viewed as if observing the patient from behind.

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Conrad RW, Richardson WJ, Oakes WJ. Left thoracic curves can be different. Orthop Trans 1985; 9: 126e7. Dobbs MB, Lenke LG. Prevalence of neural axis abnormalities in patients with infantile idiopathic scoliosis. J Bone Joint Surg Am 2002; 84: 2230e4. Evans SC, Edgar MA, Hall-Craggs M, Powell MP, Taylor BA, Noordeen HH. MRI of ‘idiopathic’ juvenile scoliosis. J Bone Jt Surg 1996; 78B: 314e7. Frymoyer JW, et al. The adult and paediatric spine. 3rd edn. 2004; I: 337e90. Hefti FL, McMaster MJ. The effect of the adolescent growth spurt on early posterior spinal fusion in infantile and juvenile idiopathic scoliosis. J Bone Jt Surg 1983; 65B: 247e54. Lonstein JE, Carlson JM. The prediction of curve progression in untreated idiopathic scoliosis during growth. J Bone Jt Surg 1984; 66A: 1061e71. Lonstein JE, et al. Moe’s textbook of scoliosis and other spinal deformities. 3rd edn., 1995. Mehta MH. The rib vertebral angle in the early diagnosis between resolving and progressive infantile scoliosis. J Bone Jt Surg 1972; 54B: 230e43. Nachemson AL, Peterson LE. Effectiveness of treatment with a brace in girls who have adolescent idiopathic scoliosis. J Bone Jt Surg 1995; 77A: 815e22. Nash CL, Gregg EC, Brown RH, Pillia MS. Risk of exposure to X-rays in patients undergoing long term treatment for scoliosis. J Bone Jt Surg 1979; 61A: 371e80. Nuwer MR, Dawson EG, Carlson LG, Kanim LE, Sherman JE. Somatosensory evoked potential spinal cord monitoring reduces neurologic deficits after scoliosis surgery: results of a large multicenter survey. Electroencephalogr Clin Neurophysiol 1995; 96: 6e11.

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Risser JC. The Iliac apophysis: an invaluable sign in the management of scoliosis. Clin Orthop 1958; 11: 111e9. Sarwark J, Aubin E. Growth considerations of the immature spine. J Bone Joint Surg Am 2007; 89: 8e13. Scoliosis Research Society. Available at: www.srs.org. Segal LS. Current concepts in neuromuscular scoliosis. Current Opin Orthop 2004; 15: 439e46. Winter RB, Lonstein JE, Drogt J, et al. The effectiveness of bracing in the nonoperative treatment of idiopathic scoliosis. Spine 1986; 11: 790e1. Zadeh HG, Sakka SA, Powell MP, Mehta MH. Absent superficial abdominal reflexes in children with scoliosis as an early indicator of syringomyelia. Spine 1995; 77-B: 762e7.

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A basic understanding of features of scoliosis is essential Idiopathic scoliosis is a diagnosis of exclusion There is a mixture of natural histories depending on type of scoliosis There are risk factors for curve progression Treatment is aimed at halting curve progression Treatment involves bracing or surgery In the young child growth modulation is the aim of treatment Definitive surgery is best at skeletal maturity

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