The spine is structurally normal with a lateral curvature, no spinal rotation, and no truncal asymmetry.
Types of nonstructural scoliosis:
- Postural– This curvature is due to prolonged use of a wrong posture. It resolves when the child is lies down.
- Compensatory – It is caused by leg-length discrepancy. There is no rotation of the vertebrae and it usually goes off on sitting.
- Sciatic This curve results from trying to avoid pain from an irritated sciatic nerve
- Inflammatory: Here a curvature in the spine is caused by an infective process such as an appendicitis. The body curves in response to the disease or abdominal muscle spasm.
- Hysterical – very rare and has an underlying psychological component
Most common type of scoliosis is idiopathic where the cause is not known. Idiopathic scoliosis is classified based on the age when scoliosis develops. For example in a person less than 3 years old, it is called infantile idiopathic scoliosis.
It is caused by an abnormal development of the bones of the spine for example hemivertebra or due to other paralytic disorders.
Degenerative scoliosis occurs in older adults. Degenerative changes may lead to weakening of the normal ligaments and other soft tissues of the spine. In presence of arthritic changes abnormal curvature may result
Any pathology in the spine like spine tumors may cause people to lean to the opposite side to reduce discomfort. Prolonged posturing may lead to scoliosis.
Most common causes in this group are neuromuscular diseases such as cerebral palsy, poliomyelitis or muscular dystrophy or birth defects such as hemivertebra. Injury may be another cause. Infections or tumors also might give rise to curvature of the spine.
Here is the list of causes of non idiopathic structural scoliosis.
- Cerebral palsy
- Spinocerebellar degeneration
- Friedreich’s ataxia
- Hereditary Motor and Sensory Neuropathies
- Spinal tumor
- Spinal muscular atrophy I-IV (usually right sided curve)
- Muscular dystrophies
- Duchenne and Becker’s
- Limb girdle
- Fibre type disproportion
- Congenital hypotonia
- Myotonia dystrophica
- Achondroplasia and hypochondroplasia – mainly lordosis or thoracolumbar kyphosis.
- Mesenchymal disorders like Marfan’s syndrome or Ehler’s-Danlos syndrome
- Spina bifida especially thoracic type
- Rheumatoid disease
- Osteoid osteoma
- Eosinophilic granuloma
- Intraspinal tumours like ependymoma, astrocytoma, epidermoid cyst
Scoliosis in patients with spondylolisthesis
It is of three types
Sciatic scoliosis is caused by muscle spasm. It is mostly not structural and resolves with lying down or on relief of symptoms.
Olisthetic scoliosis is a torsional lumbar curve in association with spondylolisthesis and results from asymmetrical slipping of the vertebra. These resolve after treatment of the spondylolisthesis.
However in severe cases the curves may become structural.
Lastly idiopathic scoliosis and spondylolisthesis may occur together.
Neuromuscular Scoliosis and Its Types
Neuromuscular scoliosis develops at a younger age than idiopathic curves and a larger percentage of neuromuscular curves are progressive. Usually neuromuscular curves are long, C-shaped curves and associated pelvic obliquity is common.
The basic treatment methods are similar – observation, orthotic treatment, and surgery.
The goal of treatment is to maintain a spine balanced in the coronal and sagittal planes over a level pelvis.
These patients generally are less compliant with orthotic management and surgery is associated complications like increased bleeding, less satisfactory bone stock, longer fusions, and the necessity for fusion to the pelvis.
Upper motor neuron
- Cerebral palsy
- Spinocerebellar degeneration
- Friedreich ataxia
- Charcot-Marie-Tooth Disease
- Roussy-Levy Syndrome
- Spinal cord tumor
- Spinal cord trauma
Lower motor neuron
- Other viral myelitides
- Spinal muscle atrophy
- Dysautonomia (Riley-Day syndrome)
Congenital scoliosis is the curvature due to the imbalance of growth of the spine caused by the presence of vertebral defects. Most of these defects develop during the first 6 weeks of embryological life.
Classification of Congenital Scoliosis
Failure of formation
- Partial failure of formation (wedge vertebra)
- Complete failure of formation (hemivertebra)
Failure of segmentation
- Unilateral failure of segmentation (unilateral unsegmented bar)
- Bilateral failure of segmentation (block vertebra)
In addition to this regions of the spine involved are also mentioned in the classification like the cervicothoracic spine, thoracic spine, thoracolumbar spine, and lumbosacral spine.
The deformity produced by a failure of formation is much more difficult to predict than that caused by the failure of segmentation.
The patient is evaluated as per routine spinal evaluation first. In addition, specific findings should be looked for in congenital scoliosis
Problems in Congenital Scoliosis
The five major problems in congenital scoliosis are
- Trunk deformation
- Trunk decompensation
- Truncal shortening
- Altered neurology
- Other congenital anomalies
The major target site for deformation in congenital scoliosis is the vertebral bone itself.
- Presence of wedge or hemivertebrae on one side of the spine
- Presence of an unsegmented bony bar with or without contralateral hemivertebrae.
Unilateral unsegmented bar with a convex hemivertebra produces the most progressive curve followed by unilateral unsegmented bar and a double convex hemivertebra. Thoracolumbar curves have maximum progression, followed by lower thoracic and upper thoracic regions. The least severe scoliosis is caused by a block vertebra.
The site of the bony anomaly is important as lower thoracic and thoracolumbar curves have a larger propensity to increase. Upper thoracic or cervical scoliosis has a high visibility and becomes a cosmetic problem much earlier.
Hence it is important to identify the structural defect responsible for the spinal deformity.
A solitary hemivertebra located strategically may give rise to truncal decompensation. This happens at the junctional zones e.g. the lumbosacral junction (patient has oblique take off), the thoracolumbar or cervicothoracic junction.
Large rigid curves may show poor compensation above or below the curve.
Trunk balance is an important aspect to be considered in treatment planning.
Due to reduced growth potential truncal shortening may be visible. Secondarily due to early spinal fusion the truncal height may be reduced. However, a short straight trunk is better than a deformed one. We have currently no means available to increase truncal height and this remains a research area
Congenital scoliosis is characterised by a high incidence of intraspinal problems ranging upto 30% in some series. These comprise pathologies like those of diastematomyelia, fibrous splitting of the cord, low filum terminale, cord or root tethering etc. These may be responsible for altered neurological signs prior to treatment. They also have important implications for surgical treatment e.g. distraction instrumentation. This may demand rectification of the intraspinal pathology prior or along with the definitive surgical treatmen
Other congenital anomalies
The VATER association and presence of other anomalies e.g. cardiac or genitourinary may have a bearing on treatment and all congenital scolioses need to be evaluated for presence of other congenital problems.
Diastematomyelia, tethered cord, spinal cord tumor, kyphosis, arnold chiari malformation and syringomyelia in spine are frequent associated abnormalities. Apart from this congenital heart defects, pulmonary dysfunction,cor pulmonale and back pain can be associated.
The patient presents with deformity of the back. Subtle deformities may not be seen unless patient is evaluated for some other reason.
In addition to the routine spinal evaluation, some specific physical findings should be sought in patients with congenital scoliosis.
- Hair patches, lipomata, dimples, and scars may indicate an underlying vertebral defect and should be looked for.
- A complete neurological evaluation should be done.
- Clubfoot, calf atrophy, absent reflexes, and limb atrophy could be signs of neurological involvement or associated anomalies
Age, remaining growth, presence of other congenital defects and neurological status are important in clinical examination. A thorough clinical and radiological evaluation should include analysis of the type and site of vertebral anomaly, trunk balance, presence of laminar defects and signs of occult dysraphism etc.
Imaging in Congenital Scoliosis
Anteroposterior and lateral radiographs are the basic imaging studies required for this. Sserial radiographic investigation would tell about the progression of the curve.The radiograph also let us know if the curve is due to failure of segmentation or a failure of formation.
Growth potential of the curves should be estimated to better determine the possibility of curve progression.
Myelography or MRI should be considered if diastematomyelia or a neurological abnormality is suspected. Some authors recommend urological evaluation of all patients with congenital scoliosis with ultrasound.
Treatment of Congenital Scoliosis
The treatment options when faced with a patient of congenital scoliosis are either non operative or operative.
Nonoperative treatment has a limited role in congenital scoliosis.
- Small curves
- Initially to determine progression
- Long, flexible curves
- Curves correctable on traction or on side bending
- Curves with a mixture of anomalous and nonanomalous vertebrae.
- Curve < 40° with flexibility of 50%
- Where better trunk balance can be obtained by bracing
- Post operative management of curves where localised apical fusion is carried out.
Nonprogressive curves require regular observation with six monthly xrays. 75% of congenital curves are progressive and only 5% to 10% can be treated with bracing. Therefore bracing has limited role in congenital scoliosis
Surgery remains the main treatment in congenital scoliosis.
Operative management is indicated for congenital scoliosis in the following situations
- Progressive increase in deformity
- Trunk decompensation
- Neural deficit
Following operative procedures are used in treatment of congenital scoliosis
- Posterior fusion without instrumentation
- Posterior fusion with instrumentation
- Combined anterior and posterior fusion
- Combined anterior and posterior convex hemiepiphysiodesis
- Hemivertebra excision
- Instrumentation without fusion
Infantile Idiopathic Scoliosis
A scoliotic curve in patients younger than 3 years is termed as infantile idiopathic scoliosis. Infantile idiopathic scoliosis is more frequent in boys than in girls, the curves are primarily in thoracic spine and generally convex to the left.
Infantile idiopathic scoliosis may be progressive, usually increasing rapidly, or resolve spontaneously within a few years with or without treatment. The resolving type occurs in 70% to 90% of patients.
However, till now it is very difficult to differentiate between the two especially when the curve is mild. There are different observations by different researchers that favor the likelihood of resolving type but there is no certain criteria. These observations are
- Deformity noted before 1 year of age
- Smaller curves at presentation
- No compensatory curves.
- Curves associated with plagiocephaly[a condition characterized by an asymmetrical distortion (flattening of one side) of the skull]
Based on measurement of the rib vertebral angle, Mehta developed a method to differentiate resolving from progressive curves and this is quite helpful in predicting curve progression.
Cause of Infantile Idiopathic Scoliosis
Though the exact cause is not yet identified, few researchers suggested that the position in which an infant is laid may be the causative factor for the scoliosis. During the first few months of life, all infants have a natural tendency to turn toward their right side when laid supine and gravity causes plastic deformation of the immature thorax. Making child lie prone has been suggested as a measure to reduce the chances of this development.
Treatment of Infantile Idiopathic Scoliosis
For treatment it is important to identify the progressive type from resolving type.If the rib vertebral angle difference (RVAD) is more than 20 degrees and the curve is not flexible on clinical examination, it is considered progressive until proved otherwise.
Overall, treatment options include
- Serial casting followed by bracing and later fusion if needed
- Preoperative traction to correct the curve followed by fusion
- Subcutaneous instrumentation without fusion.
Non Operative Treatment
In a very young child, serial casting with general anesthesia may be needed until the child is large enough for fitting an orthosis satisfactorily with a change usually required every 2 to 3 months. When the brace is given for full time untill the curve stability has been maintained for at least 2 years and gradually reducing thereafter.
A thoracic-lumbar-sacral orthosis (TLSO) or cervical-thoracic-lumbar-sacral orthosis (CTLSO) are usually required depending upon the size of the curves.
Significant improvement can be obtained with the use of a well-fitting orthosis during the early period of skeletal growth.
If a curve is severe or increases despite the use of an orthosis, surgical stabilization is needed. Effort should be made to delay surgical procedures long as possible to optimize spinal growth, but if the curve progression is substantial, it would need to be operated.
Ideally, surgery should not only stop progression of the curve but also allow continued growth of the thorax. But if fusion is necessary, it should be done spanning short length so as to preserve maximum number of motion segments and growth plates.
Anterior release and fusion followed by posterior spinal fusion with instrumentation is considered to be the functional treatment but If it is technically possible, subcutaneous growth rods should be preferred.
Juvenile idiopathic scoliosis
appears between the ages of 4 and 10 years. Usually the convexity of the curve is towards right in thoracic region. Juvenile idiopathic scoliosis is considered to be more progressive than adolescent idiopathic scoliosis. The risk of progression increases if the curve has an angle greater than 20 degrees.
There is a high incidence of neural axis [Brain and spine] abnormalities in children of juvenile idiopathic scoliosis.
Anteroposterior and lateral xrays are the basic investigations to know types of curves and the severity. Magnetic resonance imaging is able to reveal neural axis abnormalities which have been reported as high as abut 27% in patients considered for surgery and who were considered neurologically normal preoperatively.Image Credit: drerrico
MRI has been recommended as part of a preoperative workup in any juvenile idiopathic scoliosis. Other reasons for ordering an MRI are
- Rapid progression
- Deformity of left thorax
- Neurological abnormalities
If the Rib vertebral angle difference angle of the curve is less than 20 degrees, it is recommended for observation and follow up with an xray every 4-6 months. A progression is indicated by change in angle. A change by 5-7 degrees needs treatment by bracing like Milwaukee brace or thoracolumbosacral orthosis.
Initially, the brace is worn at least 22 hours of 24 hours [called full time bracing].If the curve shows improvement after one year of full time bracing, the time of wearing of brace is decreased gradually to only night time bracing. However, if the progression is noted after decreasing the brace time, a full-time brace program is resumed.
If the curve is not progressing, observation is continued until skeletal maturity.
Part time Milwaukee bracing program has been found successful in patients with curve curvature less than 35 degrees and rib vertebral angle difference of less than 20 degrees had excellent prognoses with treatment in a part-time Milwaukee brace program. Part-time brace treatment may afford these children the social and psychological benefits not provided by a full-time Milwaukee brace program.
The part-time brace program consisted of wearing the brace after school and all night for approximately a year. The patients were then kept in the brace at night only for another 2.5 years. The brace was at that point worn every other night for an average of 1.2 years. Individually, however, the numbers of hours spent wearing the brace depended on the amount of improvement and stability of the curvature.
Bracing is discontinued at skeletal maturity.
If the rib vertebral angle difference progresses above 10 degrees during brace wear, progression can be expected.
However, even if the curve progresses, bracing should be continued as it may slow progression and delay surgery until the child is older.
In case of failure of treatment by orthosis, surgery is considered type of which would depend on the age of the child.
If the child is younger than 8 years and small, the ideal treatment is subcutaneous rod insertion, also termed as growing rod instrumentation..
If the child is larger and 9 or 10 years of age, instrumentation and fusion may be done, but combined anterior and posterior spinal fusions should be considered to avoid a crankshaft phenomenon.
Surgery For Juvenile Idiopathic Scoliosis
There are two kinds of surgeries for Juvenile idiopathic scoliosis.
- Growing rod instrumentation
- Instrumentation with fusion of vertebrae
Growing rod instrumentation allow growth of vertebral column as the vertebrae are not fused and gain in length acquired by natural growth is maintained whereas fusion is contemplated in older children or where the conditions/requirements of growing rod instrumentation cannot be met with.
Growing Rod Instrumentation
This technique isconsidered in a cooperative patient and whose family is able to understand the procedure and its demands.
A multihook segmental instrumentation system is used.
Surgery is required every 6 months to lengthen the construct. A TLSO is needed for at least the first 6 months to protect the instrumentation.
The orthosis can be discontinued if the hook sites are solidly fused. The rods are lengthened every 6 months. At a point where no further distraction can be achieved, final arthrodesis is done and usually instrumentation is removed.
Instrumentation with Fusion
Instrumentation and spinal fusion is considered for children older than 9 or 10 years or are non cooperative.
A combined anterior and posterior procedure should be considered if the patient is deemed at risk for the crankshaft phenomenon.
A multihook segmental system is used or pedicle screw fixation can be considered if it is feasible.
Idiopathic Adolescent Scoliosis
Idiopathic adolescent scoliosis is 10 to 20 years and females are affected six times more as compared to boys. In idiopathic adolescent scoliosis,right thoracic curve is more predominant. There is a low risk of cardiovascular compromise and overall risk of progression is 23%.
Cause of Idiopathic Adolescent Scoliosis
Lately, the researchers have pointed a multifactorial causation of idiopathic adolescent scoliosis that include following
- Genetic predisposition
- Connective tissue abnormality
- Neurophysilogical disposition
- Abnormal biomechanical forces
Curve Progression in Idiopathic Adolescent Scoliosis
Less than 10% of children with curves of 10 degrees or more require treatment. What is more important is probability of the curve progression. Progression is defined as an increase of 5 degrees or more measured by the Cobb angle over two or more visits.
Following factors have been found to be related to curve progression in idiopathic adolescent scoliosis
- Progression is more likely in girls than in boys.
- There is progression risk associated with the rapid adolescent growth spurt before the onset of menses. The incidence of progression decreases as the child gets older.
- A Risser Sign of has higher risk for progression than Risser signs of 3 or 4.
- Double curves are more likely to progress than single curves
- Single thoracic curves tend to be more progressive than single lumbar curves.
- More severe curves have a higher progression
The effect of progressive curves on adults are
- Back pain
- Pulmonary function [affected only in patents with thoracic curves and there is a direct correlation was between decreasing vital capacity and increasing curve severity.]
- Psychosocial effects
- Mortality (usually in thoracic curves >100 degrees)
Diagnosis of Idiopathic Adolescent Scoliosis
The evaluation begins with a thorough history and is followed by complete physical examination and neurological examination. This is followed by radiographic evaluation.
In physical examination, after the general physical examination, the spine is examined and characteristics of the deformity are recorded.
The height of the patient while standing and while sitting should be measured and recorded. These measurements can be compared with future measurements in follow up to determine changes in the patient’s total height and whether any change is caused by growth of the lower extremities or by an increase or a decrease in the height of the trunk.
Radiographic Evaluation in Idiopathic Adolescent Scoliosis
Posteroanterior and lateral radiographs of the spine with patient in standing position are made and should also include iliac crest iliac crest distally and most of the cervical spine proximally. The use of posteroanterior view in comparison to anteroposterior view lessens the radiation dose to maturing breasts which sustain the most at risk from radiation
If patient is being considered for surgery a right and left bending films usually are obtained.
Due to vertebral rotation in scoliosis, standard anteroposterior views of scoliosis curves significantly underestimate the magnitude of the curve and also give the erroneous impression of kyphosis. Stagnara radiographic technique eliminate this rotational component of the curve , allowing a much more accurate measurement of the curve size and better evaluation of vertebral anatomy.
In this technique, an oblique radiograph is made with the cassette parallel to the medial aspect of the rotational rib prominence and the x-ray beam positioned at right angles to the cassette. This provides modified posteroanterior view. A film made at 90 degrees to this provides the true lateral view.
MRI of the whole spine is required for assessment if there is an unusual curve, a very rapid progression and a very large curve at presentation.
Treatment For Adolescent Idiopathic Scoliosis
Observation is the primary treatment of all curves. Few degree of scoliosis is frequent in the population and most of these do not require a treatment. Only the progressive curves would require treatment. There is no definitive method Unfortunately, no method is reliable for accurately predicting at the initial evaluation for progression of the curve.
Therefore, periodic evaluation of the spine with radiographs still is necessary.
- Young patients with less than 20 degrees can be examined every 6 to 12 months.
- Adolescents with larger degrees of curvature should be examined every 3 to 4 months.
- Skeletally mature patients with curves of less than 20 degrees generally do not require further evaluation.
Depending on type of curve and age of the patient, furthrer treatment options are considered
- If progression of the curve (an increase of 5 degrees during 6 months) beyond 25 degrees is noted – orthotic treatment is considered.
- For curves of 30 to 40 degrees in a skeletally immature patient, orthotic treatment is recommended at the initial evaluation.
- Curves of 30 to 40 degrees in skeletally mature patients generally do not require treatment, but there being a potential for progression, these patients should be observed with yearly for 2-3 years after skeletal maturity, then every 5 years for life.
Orthotic treatment of adolescent idiopathic scoliosis is indicated in following situations
- A flexible curve of 20 to 30 degrees in a growing child with documented progression of 5 degrees or more.
- Curves in children between the 30 to 40 degree range at the initial evaluation. Although surgery usually is indicated for curves in the 40- to 50-degree range in growing children, orthotic treatment may be considered for some curves, such as a cosmetically acceptable double major curve of 40 to 45 degrees. Orthotic treatment is not used in patients with curves of more than 50 degrees.
Initially, the orthoses were to be worn 23 hours a day at least. Due to poor compliance, newer and more patient friendlyeen introduced which require wearing for 16 hours only and obviate the need for wearing the brace to the school. regimes have . If the curve is less than 35 degrees and does not show significant vertebral wedging, part-time brace wear is certainly reasonable to attempt first. if the curve progresses in spite of it, full-time bracing can be started.
The Charleston and Boston braces are frequently used braces for scoliosis.
Operative Treatment of Adolescent Idiopathic Scoliosis
The goals of surgery for spinal deformity are
- To correct or to improve the deformity
- Maintain sagittal balance
- To preserve or to improve pulmonary function
- To minimize morbidity or pain
- To maximize postoperative function
- Improve or maintain the function of the lumbar spine.
The operative treatment of scoliosis aims at correction of the deformity and is mot meant for every scoliotic curve. Most of the surgeries are indicated if there are potential consequences of significant deformity and pain.
In children and adolescents, surgery is considered if the curve can be expected to become troublesome in adulthood.
Following are common indications for surgery in Idiopathic adolescent scoliosis
- A progressive curve despite non operative treatment
- Severe deformity (>50 degrees) and asymmetry of trunk in adolescent
- Pain not relieved by nonoperative treatment
- Thoracic lordosis – Thoracic lordosis has a detrimental effect on pulmonary function, and bracing worsens thoracic lordosis.
- Significant cosmetic deformity
Surgery is indicated more in single curves than double curves as double curves are cosmetically more acceptable.
The surgical techniques may include anterior, posterior, or combined anterior and posterior procedures.
Scoliosis Curves Measurements
Vertebral rotation is measured by following methods
- Nash and Moe
- Perdriolle and Vidal.
Nash and Moe
In this method the distance of the pedicle is noted from the sides of vertebral bodies.Vertebral body is divided into six segments and grades 0 to 4+ are assigned, depending on location of pedicle within segments. Because pedicle on concave side disappears early in rotation, pedicle on convex side, easily visible through wide range of rotation, is used as standard.
The rotation by this method is calculated by analyzing the AP radiograph.
Stage 0 Rotation – Both the pedicles are at equidistant and there is no asymmetry
Stage I Rotation – The pedicle on the convex side migrates within first segment and the pedicle on the concave side may start disppearring.
Stage II Rotation – The pedicle on the convex side moves to second segment and the other pedicle disappears.
Stage III Rotation – The pedicle on the convex side migrates to third segment and other pedicle is not visible
Stage IV Rotation – The pedicle on the convex side moves past the midline
Perdriolle method uses a template called torsion meter that measures the amount of vertebral rotation on a spinal radiograph.
CT scan is also a good and reliable method to measure rotation but is not don on routine basis.
If a plumb line is dropped from the dens, it usually falls anterior to the thoracic spine, posterior to the lumbar spine, and through the posterior superior corner of S1. However because on the standing long lateral films, the dens is not easily seen and therefore, the plumb line is dropped from the middle of the C7 vertebral body. This plumb line is called the saggittal vertebral axis.
A positive sagittal vertebral axis is considered present when the plumb line is anterior to the anterior aspect of S1. A negative sagittal vertebral axis occurs when this plumb line passes posterior to the anterior body of S1.
For sagittal balance to be maintained, lumbar lordosis should measure 20 to 30 degrees more than the kyphosis.
In the thoracic spine, the normal sagittal curvature is kyphotic and the normal regional lumbar sagittal alignment is lordotic.
The thoracolumbar junction is the transition area from a relatively rigid kyphotic thoracic spine to a relatively mobile lordotic lumbar spine. Bernhardt and Bridwell showed that the thoracolumbar junction is nearly straight. This relationship must be maintained during reconstructive procedures to prevent a junctional kyphosis.
If there exists sagittal plane imbalance, it must also be corrected so that there is no undue stress on unfused vertebrae when the segments are fused.
Classification of Scoliosis Curves
Ponseti and Friedman Classification
1. Single major lumbar curve.
The lumbar curve has its apex between the L1-2 disc and L4 producing an asymmetry of the waistline with prominence of the contralateral hip.
2. Single major thoracolumbar curve.
The thoracolumbar curve apex is at T12 or L1 and tends to produce more trunk imbalance than other curves. It often produces a severe cosmetic deformity.
3. Combined thoracic and lumbar curves (double major curves).
Cause less visible deformities because the the trunk usually is well balanced.
4. Single major thoracic curve.
Generally is a convex right pattern. The curve produces prominence of the ribs on the convex side, depression of the ribs on the concave side, and elevation of one shoulder.
5. Single major high thoracic curve.
The apex of the curve usually is at T3, and the curve extending from C7 or T1 to T4 or T5.
6. Double major thoracic curve.
There is a short upper thoracic curve, often extending from T1 to T5 or T6, with considerable rotation of the vertebrae and other structural changes and a lower thoracic curve extending from T6 to T12 or L1.
The upper curve usually is convex to the left, and the lower usually is convex to the right.
This classification system is used to describe thoracic curves.
1. Type I curve
Lumbar curve is larger than the thoracic curve or nearly equal, but the lumbar curve is less flexible on side bending.
2. Type II curves
A combined thoracic and lumbar curve and thoracic curve is larger than or equal to the lumbar. On supine side-bending radiographs, the lumbar curve is more flexible than the thoracic curve.
3. Type III curve
Thoracic scoliosis with the lumbar curve not crossing the midline.
4. Type IV curve
Single long thoracic curve, with L4 tilted into the curve and L5 balanced over the pelvis.
5. Type V curve
A double structural thoracic curve. The first thoracic vertebra is tilted into the concavity of the upper curve, which is structural. An elevation of the left shoulder is a frequent finding. There is an upper left thoracic rib hump and a lower right thoracic rib prominence.
Surgery for Scoliosis
Perioperative Preparation In Scoliosis Surgery
Proper preparation of the patient is very necessary for the scoliosis surgery. If patient is on any nonsteroidal antiinflammatory agent, it should be discontinued before surgery. In case of females birth control pills should be discontinued 1 month before surgery [Increase the possibility of thrombophlebitis in the postoperative period].
Patient should be evaluated with x-rays, computed tomography, magnetic resonance imaging, and myelography for evaluation of spinal levels and to rule out conditions such as syringomyelia, diastematomyelia, and tethered cord.
In patients with severe curves pulmonary function studies usually are indicated.
Autologous blood donation in preoperative period in patients who are fit for autodonation is good option. Autologous donation reduces the the risks of homologous blood transfusion. Erythropoietin is another good but costly option.
Following routine gadgets are used for patient monitoring in scoliosis surgery
- Arterial line- continuous monitoring of blood pressure.
- Indwelling urinary catheter – monitor urinary output.
- Blood pressure cuff
- Esophageal stethoscope
- A pulse oximeter
Hypotensive anesthesia is the one in which arterial blood pressure is kept at 65 mm Hg. Hypointensive anesthesia is an effective way to reduce the loss of blood during surgery.
The cell saver is another method where one is able to save 50% of the red cell mass. However, cost could be a deterring factor.
Acute normovolemic hemodilution is another option to decrease loss of red cells. The maximum quantity of blood is withdrawn to reach to a level of 9 g/dL or higher after hemodilution and volume is maintained by crystalloid replacement. The surgery is conducted at normal blood pressure and diuresis of excess fluid is performed after surgery is finished followed by the transfusion of initially removed blood .
Somatosensory evoked potentials involve stimulation of distal sensory proximal to the surgical area and can alert the surgeon to possible alteration of spinal cord transmission. Preoperative baseline can be compared with one during the surgery. As it measures only the integrity of the sensory system, the use of motor evoked potentials has increased. The combination of motor evoked potentials and somatosensory evoked potentials can provide important information regarding the primary motor and sensory tracts within the spinal cord.
Stagnara wake-up test
Stagnara wake-up test, the anesthesia is decreased or reversed after correction of the spinal deformity. The patient is brought to a conscious level and asked to move both lower extremities. Once voluntary movement is noted, anesthesia is returned to the appropriate level, and the surgical procedure is completed.
Posterior Scoliosis Surgery
Posterior approach to the spinal column is the most commonly used for surgeries of idiopathic scoliosis. [Posterior means that incision is put on the back]
Following types of surgeries are performed on the scoliotic spine.
The long-term success of any operative procedure for scoliosis depends on a good arthrodesis.
The success of spinal arthrodesis depends on ability of the graft material to stimulate a healing process which in turn depends on
Surgical preparation of the fusion site
- Soft-tissue trauma should be minimal.
- Bed for grafting should be prepared well and avascular tissue should be removed
- Bone surfaces should be decorticated
A good bed exposes maximum surface area for vascular ingrowth and allows delivery of more osteoprogenitor cells [Cells that form bone cell precursors]
Systemic and local factors
- Good nutrition provides optimum condition for graft union.
- Any medical problem should be controlled.
- Smoking has been found to inhibit fusion significantly and should be stopped.
Autografts provide the best chances of union as it combines the osteogenic, osteoinductive and osteoconductive properties. Autograft taken from iliac crest is considered as “Gold Standard”. Another excellent source is rib obtained from a thoracoplasty.
Allografts have been shown to produce results equal to those of autogenous iliac crest graft in young patients.
They are routinely used in cases of paralytic scoliosis [Large amounts of bone graft are needed and the iliac crests often are small.
There are several graft substitutes like tricalcium phosphate, hydroxyapatite, and demineralized bone matrix but they are still under investigation
Bone graft generally does better under compression and is less effective with distraction.
Psuedorthrosis [literally -false joint] is failure of spinal fusion. But with modern surgical techniques, pseudarthrosis rate has been decreased.
Posterior Spinal Instrumentation
The goals of instrumentation in scoliosis surgery are to correct the deformity as much as possible and to stabilize the spine in the corrected position while the fusion mass becomes solid.
The fusion mass in a well-corrected spine is subjected to lower bending and tensile forces than is the fusion mass in an uncorrected spine
Spinal Instrumentation System
No Single device is the best choice for every surgeon or every patient.
Due to its disadvantages of need for distraction, laminar fractures, and loss of saggital contour, other instrumentation system have replaced it.
Multihook or posterior segmental instrumentation system with screws are are more commonly used now.
Posterior segmental spinal instrumentation systems have following advantages
- Multiple points of fixation to the spine
- Apply compression, distraction, and rotation forces through the same rod.
- Do not require any postoperative immobilization in most of the cases
- Better coronal plane correction and better control in the sagittal plane.
- Preserves normal contours of spine to good extent
The systems have, however, potential disadvantage of being bulky and complex and not many surgeons have much experience with them.
Posterior Thoracoplasty For Rib Hump In Scoliosis
Posterior thoracoplasty is a surgery for correction of rib hump in scoliosis though with newer surgical techniques and newer instrumentation, it is now done rarely.
The procedure is performed in prone position and the approach used is midline posterior. The procedure involves cutting of the ribs at the site of deformity.
Anterior thoracoplasty also aims at same correction.
Anterior Scoliosis Surgery
Anterior instrumentation and fusion is used in thoracolumbar and lumbar curves. It provides excellent derotation and correction of the curve in the coronal plane.
At some occasions, the deformity correction requires lesser number of motion segments to be fused than if done posteriorly.
For treatment to be effective the thoracolumbar or lumbar curve should be flexible. The thoracic curve should be nonstructural and reducible to 25 degrees or less on the bending films.
The child should be around 9 years of age.
Anterior instrumentation and fusion in thoracic curves is controversial.
In case of thoracolumbar curve, a thoracoabdominal approach is required. However in lumbar curves, a lumbar extraperitoneal approach can be used. Pedicle screws are used to instrument the spine.
Complications of Anterior Scoliosis Surgery
- Chylothorax – Collection of lymphatic fluid in pleural cavity following injury to lymphatics
- Injury to the ureter, spleen, or great vessels
- Retroperitoneal fibrosis
- Screw dislodgment
- Respiratory insufficiency requiring ventilatory support
- Collapse of lung alveoli
- Pneumothorax, hemothorax
- Urinary tract infection
Video Assisted Thoracoscopic Surgery
In this, the surgery is done with the help of thoracoscope [An endoscope that is inserted in the thorax from a portal and its imaging is used to guide the surgeon.
The Advantages of thoracoscopic surgery over open thoracotomy are
- Better illumination and magnification
- Lesser injury to the anatomical structures
- Decreased blood loss
- Better cosmesis
- Shorter recovery time
- Improved postoperative pulmonary function
- Shorter hospital stays.
The disadvantages are – technically demanding procedure, steep learning curve and requirement of the specialized equipment.
Video-assisted thoracoscopic surgery is indicated in
- Patients with compromised pulmonary function requiring anterior release
- Rigid curves requiring anterior release and posterior fusion
- When surgery is needed in young children to prevent crankshaft phenomenon
- and skeletal immaturity in patients in whom anterior surgery is needed to prevent the crankshaft phenomenon.
- Rigid thoracic idiopathic curves
Video-assisted thoracoscopic surgery is contraindicated in
- Inability to tolerate single-lung ventilation
- Respiratory insufficiency
- High airway pressures with positive-pressure ventilation
- Previous thoracotomy
Complications of video assisted thracoscopic surgery are
- Damage to lung tissue
- Dural tear
- Lymphatic injury [ Injury to thoracic duct]
Endoscopic Anterior Instrumentation
This technique allows anterior instrumentation of thoracic spine using a thoracoscopic approach. These technique are still being developed for getting results comparable to that of open thoracotomy.
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