Structured oral examination question 4: Scoliosis
EXAMINER : What can you see? (Figure 5.5.)
CANDIDATE: This is an AP radiograph showing the spine, ribs and iliac crests. There is a left-sided, lumbar scoliosis.
EXAMINER: What different types of scoliosis do you know? What type of scoliosis is this?
CANDIDATE: The radiograph shows a congenital scoliosis. There is a hemivertebra within the lumbar spine producing the scoliosis.
Scoliosis occurs in different groups of patients and can be classified according to aetiology. Scoliosis may be idiopathic, congenital, neuromuscular or associated with other conditions such as Marfan’s syndrome or neurofibromatosis.
EXAMINER: Why might you treat a scoliosis?
Anteroposterior ( AP ) radiograph of the thoracic and lumbar spine demonstrating a left-sided lumbar scoliosis.
CANDIDATE: The primary indication for treating a scoliosis is progressive deformity. Additionally, patients with ‘early-onset’ scoliosis and some types of neuromuscular scoliosis are at risk of progressive cardiorespiratory compromise as the curve deteriorates.
EXAMINER: How might you treat this scoliosis?
CANDIDATE: I would refer this patient to a specialist centre for treatment. I suspect that, if after monitoring the curve, it shows signs of progression they might consider excising the hemivertebra.
EXAMINER: The vertebra could be excised using an anterior, posterior or combined approach. Can you describe the thoraco-abdominal (Hodgson’s) approach that might be used to approach this vertebra?
CANDIDATE: The patient is positioned in the lateral position with the limbs and trunk supported. The table is ‘broken’ with apex at the thoracolumbar junction. A skin incision is made over the 10th rib and curved distally to run longitudinally along the lateral border of rectus abdominus. Skin and fat are incised, as are serratus anterior, external oblique and latissimus dorsi. The rib is removed subperiosteally. The parietal pleura is incised exposing the lung and diaphragm.
A key step in this procedure is splitting the costal cartilage to enter the retroperitoneum. Retroperitoneal fascia is swept away with swabs. The diaphragm is divided 2 cm from its origin down to the vertebrae using marking stitches. Segmental vessels are ligated and the discs above and below the vertebrae excised.
Scoliosis background knowledge
Scoliosis is defined as a lateral curvature of the spine in the coronal plane that measures more than 10 using the Cobb method. When present it usually forms part of a three-dimensional spinal deformity. It is sometimes described as a four-dimensional deformity (the fourth dimension being time, emphasizing the progressive nature of the condition).
The key to treating scoliosis is knowledge of the natural history of the condition in order to predict curves that are likely to deteriorate rapidly so that they can be detected and treated at an early stage. Scoliosis has been classified according to severity, location, aetiology and age of onset.
Severity – The Cobb angle also defines the magnitude of the curve with minor (small) curves measuring between 10 and 25, moderate curves between 25 and 50 and severe (large) curves measuring over 50.
Location – The ‘side’ of a scoliosis is the side of the patient to which the spine deviates away from the midline, it is the side of the convexity of the curve. A scoliosis is also described by the region of the spine that it affects. The Scoliosis Research Society have defined a ‘thoracic’ scoliosis as having its apex between T2 and the T11–T12 disc, a ‘thoracolumbar’ curve as having its apex between the T12 and L1 vertebrae and a lumbar scoliosis as having its apex between the L1–2 disc space and L4. The apex of the curve is located by the most laterally deviated vertebra. Curves can be single, double or triple ‘major’ curves depending on whether the curves above and below the main curve are flexible or structural (flexible curves reduce to less than 25 on lateral bending).
Aetiology – Scoliosis is classified according to its aetiology and pathogenesis.
|
|
Idiopathic (the largest group – 70%). In this group the scoliosis is produced by an imbalance in the growth of the spine with the convexity of the curve growing at a faster rate than the concavity. |
|
|
Congenital scoliosis. In this group abnormalities of one or more vertebrae are present at birth. The subsequent growth of these abnormal vertebrae cause the scoliosis. (The name might be confusing as it is the vertebral abnormalities that are present at birth and the scoliosis develops later with growth.) |
|
|
Neuromuscular (cerebral palsy, Duchenne muscular dystrophy, spinal muscular atrophy). In this group the scoliosis is produced by a lack of support to the spine causing the spine to collapse to one side. |
|
|
Miscellaneous conditions associated with scoliosis (5% – e.g. Marfan syndrome, |
neurofibromatosis).
Age of onset – Idiopathic scoliosis has been classified by age into infantile (age 0–3 years), juvenile (3–10 years) and adolescent (10–maturity) idiopathic scoliosis. An alternative classification divides scoliosis into early-onset scoliosis (associated with a high risk of cardiorespiratory compromise as the developing heart and lungs may be affected) which has its onset before the age of 7 and late-onset scoliosis which has its onset after the age of 7. (The age of 7 is used by the AO group – others have suggested 5.)1,2
The assessment of a spinal deformity
The assessment of spinal deformity should aim to detect conditions that might mimic (leg length discrepancy, disc prolapse) or be associated with a scoliosis. It should also characterize the patient in terms of skeletal maturity and fitness for anaesthetic as well as characterizing the scoliosis itself. Finally it should formulate a treatment plan.
History – key features
Curve onset and progression.
Maturity (age, menarche, height relative to parental height, recent growth).
General health/fitness for anaesthesia ( especially in neuromuscular group). Although patients with scoliosis do experience back pain, scoliosis is not typically thought of as a painful condition. Severe pain may indicate the possibility of an underlying cause (prolapsed disc, osteoid osteoma, spondylolisthesis).
Examination – key features
Height, arm span, weight and assessment of maturity (secondary sexual characteristics).
Assessment of the curve (location and severity).
Common associated problems (rib prominence, shoulder height, pelvic asymmetry, skin creases, hairline and neck shape).
How flexible is the curve and the remainder of the spine?
Features of spinal dysraphism such as hairy patches on the back overlying the spine.
Neurological examination – abnormal abdominal reflexes are most commonly associated with intraspinal anomalies.
Adam’s forward bend test.
Investigations
X-ray: Full-length standing AP and lateral plane radiographs showing the ribs, iliac crests and hip joints. Risser’s sign grades the progression of development and fusion of the iliac apophysis, is visible on plain X-rays and is a useful indication of maturity.
MRI scanning of the spine can be used to detect underlying intraspinal anomalies such as diastomatomyelia, syringomyelia and Arnold–Chiari malformations (particularly in atypical curves).
Surface topography is also frequently used to assess scoliosis. This can produce an objective assessment of the results of surgery but in some circumstances can also be used instead of frequent X-ray when following up the progression of curves.
Pattern recognition
The most common type of curve seen is a late-onset adolescent idiopathic scoliosis with a ‘right thoracic’ curve presenting in a girl just after menarche. Atypical features indicate possible underlying pathology (e.g. left-sided curves, severe pain, rapid progression and short angular deformities.)
Late-onset (adolescent idiopathic) scoliosis
Late-onset (adolescent) idiopathic scoliosis is the most common form of scoliosis (70%).
Prevalence of curves over 10 is 2% (female 1 : 1 male).
Prevalence of curves over 20 is 0.2% ( female 5.4 : 1 male).
There is a genetic tendency to develop scoliosis with 20% of affected individuals having at least one affected family member.
The development and progression of scoliosis is related to skeletal growth, typically deteriorating most rapidly during the adolescent growth spurt. Features that indicate an increased likelihood of curve progression are therefore associated with but not limited to immaturity. They are:
Young age at onset.
Premenarchal status. Physical immaturity.
Large curves.
Female gender.
Once skeletal maturity is reached the scoliosis tends to stabilize and progress less rapidly (1 per year).
Treatment
Bracing
|
|
Applied for progressive curves measuring 25–40. Not thought of as corrective but aims to prevent progression of the curve whilst growth continues aiming to reduce the need for surgery. |
|
|
To be effective, a brace needs to be worn 23 hours a day. |
|
|
Not without morbidity. |
Surgery
The aim of surgery is to (partially) correct and stabilize the curve, reducing the deformity and the risk of further progression. Instrumentation is used to correct and stabilize the curve whilst bone graft stimulates fusion of the spine. Indications:
|
|
Unacceptable deformity.Progressive curves.Usually reserved for curves with a magnitude > 50. |
|
|
Earlier intervention is indicated in curves with greater potential for progression.Approaches: |
|
|
With ‘third-generation’ instrumentation(segmental pedicle screws), there has been a recent trend towards the posterior approach. |
|
|
Consider anterior approach for thoracolumbar curves. |
When selecting which levels to fuse, the first question to ask is, is there just one curve to fuse or more than one? This is the same as asking: are the curves above and below the primary curve sufficiently correctable/flexible? If on the lateral bending X-ray the ‘compensatory’ curve bends down to less than 25, it does not need to be included in the construct.
Early-onset scoliosis
Applies to patients under the age of 7 years with an idiopathic scoliosis.
The developing heart and lungs may be affected by the scoliosis.
Cardiorespiratory compromise may result from a progressive curve resulting in decreased life expectancy.
Patients that present with an idiopathic scoliosis below the age of 3 (infantile scoliosis) have the most heterogeneous prognosis. A significant number (80– 90% of curves) will resolve before the age of 2 years. However, those that do not resolve go on to develop extremely severe curves that cause major deformity and affect cardiac and respiratory function leading to death in early adult life. Treatment is problematic and prolonged. The most common forms of treatment are serial plaster jackets (localizer casts), subsequently bracing and eventually growing rods.
Neuromuscular scoliosis
Occurs in association with a neuromuscular condition.
Typical collapsing long ‘C’ shaped curve ( other patterns have been described).
Classified into upper motor neurone, lower motor neurone and myopathic.
The two most frequently encountered neuromuscular conditions causing scoliosis are cerebral palsy and Duchenne muscular dystrophy.
Duchenne muscular dystrophy: In almost all patients with Duchenne muscular dystrophy (90%) a scoliosis will develop 1–2 years after the loss of ambulatory function.
Cerebral palsy: The likelihood of developing a curvature is related to its severity. Overall 25–30 % of patients with cerebral palsy develop a scoliosis but in four-limb cerebral palsy the incidence of scoliosis increases to 75%. In cerebral palsy the average age of onset of a scoliosis is approximately 10 years.
In this group the problems associated with scoliosis include:
|
|
Pressure sores.Pain from costo-pelvic impingement.Problems with sitting balance causing patients to become hand-dependent sitters, which in turn limits upper limb function. |
|
|
Reflux and swallowing difficulty and associated chest complications. |
Treatment
The goals of treatment in neuromuscular scoliosis are improved quality of life, maintenance of function, maintenance of respiratory function and sitting balance. Treatments include:
Bracing/total contact orthoses ( permanent/ continuous).
Wheelchair modifications.
Surgery – posterior spinal fusion.
In cerebral palsy high levels of care-giver satisfaction following surgery have been reported.3 Similar benefits are seen in Duchenne muscular dystrophy and surgery may also allow patients to live for longer, having an additive effect with nocturnal ventilation in delaying the deterioration of respiratory function.
Congenital scoliosis
|
|
Scoliosis develops as a result of the growth of vertebral anomalies present at birth. |
|
|
The vertebral anomalies may be part of the VATER or VACTERL associations. |
|
|
Multiple vertebral anomalies are often hereditary. Isolated anomalies are mostly sporadic.No single genetic or environmental cause has been identified. |
Classification: Anomalies present can be failures of formation or segmentation. More common congenital vertebral anomalies include the unilateral unsegmented bar, the hemivertebra (either fully segmented, semi-segmented or incarcerated), wedge vertebra and block vertebra. A fully segmented hemivertebra is one that has growth plates cranial and caudal to it.
Progression of congenital curves depends on growth potential and whether that growth is balanced. Thus a fully segmented hemivertebra in connection with a contralateral unsegmented bar has the least balanced growth and the worst prognosis. A block vertebra on the other hand has benign prognosis rarely leading to a curve beyond 20.
-
Aebi M, Arlet V, Webb J. AO Spine Manual. New York: Theime Publishing, 2007.
-
Dickson RA. Early-onset scoliosis. In Weinstein SL (Ed.), The Paediatric Spine: Principles and Practice. New York: Raven Press, 1994.
-
Tsirikos AI, Chang WN, Dabney KW et al. Comparison of parents’ and caregivers’ satisfaction after spinal fusion in children with cerebral palsy. J Ped Orthop 2004; 24(1):54–58.
