Scoliosis

What is Scoliosis?

Scoliosis is routinely defined as a simple lateral curvature of the spine in the coronal plane. However, this is a relatively rare finding other than in occasional non-structural and congenital curves. In most situations, scoliosis is a 3-dimensional deformity, better described as a lordoscoliosis. As well as the lateral curvature of the spine, there is associated vertebral rotation. Scoliosis is pathological when the lateral curvature exceeds 10° as measured by the Cobb method on standing PA radiographs. Below 10° it is classed as spinal asymmetry, which is not pathological. The description of a scoliosis is based on the region of the curve (the site of the greatest curve angle), side of convexity (not the concavity), and Cobb angle e.g. 60° thoracic curve convex to right with the apex at T8. Descriptive terms such as major, minor, primary or secondary are not used in relation to a double curve. Curves are simply single or double.

The following descriptions are mainly concerning scolioses other than degenerative scoliosis. Degenerative scoliosis is a (normally thoracolumbar) curve that occurs generally in an adult secondary to massive wear and tear in the spine. This will generally be treated differently from a childhood scoliosis as the two are massively different in all aspects of management.

How do you get Scoliosis?

Scoliosis is either structural or non-structural. 

A non-structural scoliosis is a bend in the spine when the spine is actually really straight. It is generally a mild, non-rotated scoliosis that has the potential to be fully correctable by active or passive bending and to resolve completely after correcting the underlying cause. The cause is likely to be non-spinal in origin such as postural, hysterical, sciatic (possibly from a “slipped disc”, inflammatory, or compensatory (possibly from legs that are different lengths).

Idiopathic scoliosis(of unknown origin) occurs in up to 85% of structural curves.

The patients are divided into two groups:

 

Early onset  (alternative nomenclature: Infantile (birth to 3 years) and early Juvenile (4 to 10 years))

• Birth to 5 years
• Left thoracic curve more common (90%)
• More common in males
• More common in UK
• 60-70% resolve spontaneously (in this group the scoliosis generally appears in the first 6 months of life and resolves by 2 years)

 Late onset (alternative nomenclature: late Juvenile (4 to 10 years) and Adolescent (over 10 years))

• 6 years and older
• Right thoracic curve more common.
• More common in females (5:1)
• Worse prognosis if the curve appears early and patient matures late, as there is more time over which the curve can progress. Also curves can progress rapidly during the adolescent growth spurt

A scoliosis of neuromuscular aetiology tends to be a long, C-shaped curve with a potential for pelvic obliquity and hip contractures. Major respiratory impairment is possible in this group of patients.

Upper motor neurone

• Cerebral palsy
• Spinocerebellar degeneration
  • Friedreich’s ataxia
  • Hereditary Motor and Sensory Neuropathies
• Trauma
• Spinal tumour
• Syringomyelia

Lower motor neurone

• Poliomyelitis
• Trauma
• Spinal muscular atrophy I-IV (usually right sided curve)
• Dysautonomia

Myopathies

• Arthrogryposis
• Muscular dystrophies
  • Duchenne and Becker’s
  • Limb girdle
  • Facio-scapulo-humeral
• Fibre type disproportion
• Congenital hypotonia
• Myotonia dystrophica

The neural axis and spinal column develop simultaneously and there is therefore a risk of cord abnormalities in congenital scoliosis. An MRI scan is therefore always needed. In addition, a congenital scoliosis doesn’t always have a major rotational component.

Other Causes of Scoliosis

• Achondroplasia and hypochondroplasia – mainly lordosis or thoracolumbar kyphosis.
• Spondylolisthesis is the non-anatomical alignment of one vertebra on another. The vertebra may slip anteriorly, posteriorly or laterally. This most commonly involves the lumbosacral junction but it may affect the mid-lumbar spine, cervical spine or rarely the thoracic spine. It has been classified by Wiltse as congenital (Type IA,B,C), isthmic (Type IIA,B), degenerative, post-traumatic, pathologic, and  post-surgical (Fig.4).
• Mesenchymal disorders e.g. Marfan’s syndrome (75% may have spinal involvement), Ehler’s-Danlos syndrome
• Spina bifida (all patients with thoracic level paraplegia will develop scoliosis as opposed to 60% of those with an L4 level)
• Neurofibromatosis (2-30% have a spinal deformity; typically associated with a sharp lower right thoracic scoliosis (dysplastic type) or may be more like an idiopathic curve (idiopathic type); an MRI can be useful to exclude a neurofibroma when surgery is planned)
• Rheumatoid disease
• Infection normally causes a painful scoliosis and the patient is generally systemically unwell. Scintigraphy is helpful to confirm the diagnosis.
• Tumours (osteoid osteoma, osteoblastoma, eosinophilic granuloma, intraspinal tumours e.g. ependymoma, astrocytoma, epidermoid cyst)

How is Scoliosis diagnosed?

Initially the scoliosis is diagnosed clinically but xrays help to quantify the degree and sometimes the cause of the scoliosis. They also help to monitor the progression of the scoliosis.

MRI scan, ultrasound, and other techniques are sometimes required to find a cause of the deformity. However it must be understood that sometimes a cause cannot be found.

Initial plain films vary and include standing posteroanterior (PA) plain films of entire spine to include iliac crests; side-bending PA’s are useful as a pre-operative investigation only for selection of fusion levels; lateral films are not always necessary unless the patient has a suspected congenital scoliosis; a painful scoliosis or a sagittal plane deformity e.g. kyphosis or spondylolisthesis, bone age films are necessary in selected cases; and 3-Dimensional CT allows visualisation of vertebral deformity in complex congenital abnormalities but in general is not necessary.

An MRI study is indicated for selected cases patients with a congenital scoliosis, with excessive kyphosis, with early onset scoliosis, left thoracic curves, or associated syndromes, with rapid progression of curve magnitude, with neurological symptoms or signs, any patient with a painful scoliosis.
In this selected population, MRI demonstrates abnormalities in approximately one third of cases.

How is Scoliosis treated?

The aims of surgery for scoliosis prevent progression of curve and maintain balance. Balance is more important than curve correction. Other aims are to  maintain respiratory function, reduce pain and preserve neurological status, and cosmesis.

Although cosmesis is last on the list of surgical priorities, it is often the most important to the patient. Patients are often ambivalent to their scoliosis, but any rib prominence is poorly tolerated. This is often surgically rectified by a partial thoracoplasty, where the ribs involved in the prominence are resected and used as bone graft for the spinal fusion. The periosteum of the ribs is preserved to allow the ribs to regrow in a more acceptable position.