Idiopathic Scoliosis
Scoliosis is defined as a coronal spinal curvature of at least 10° with rotation of the vertebral bodies of unknown origin.
Epidemiology
Idiopathic scoliosis is the most common structural spinal deformity in children and adolescents. It affects about 2-3% of adolescents, but only 0.1-0.3% for curvatures greater than 30°. The most common scoliosis is a thoracic curve to the right side. The primary age of onset is 10 to 15 years.
With small curves there is an equal prevalence of affected males and females. However there is a female predominance with increasing curve magnitude.
In the infantile form, which presents at 0-3 years of age, there is a predominance in males at 3:2. At 3-6 the female to male ratio is 1:1; at 3-10 it is 2:1 to 4:1; at 10 years the ratio is 8:1.
Aetiology
The exact aetiology is unknown. There appears to be asymmetrical growth of anterior column of the vertebrae with resulting tethering of the posterior elements. The underlying cause for this imbalance of growth is unknown.
There are thought to be genetic factors controlling for scoliosis. This has been indicated by population and twin studies. However no specific gene or genes have been found. There is variable expression and so environmental factors also contribute to the pathogenesis.
There has been interesting research done on platelets as both skeletal muscle and platelets have myosin/actin contractile systems. There is an association with scoliosis and a defective contractile system in platelets.
Calmodulin and melatonin interact with the actin/myosin system with calmodulin regulating calcium influx from the sacroplasmic reticulum and melatonin binding to calmodulin as an antagonist. Research has suggested abnormal levels of these substances in scoliotic individuals.
Classification
Age Based Classification
The Scoliosis Research Society (SRS) classifies idiopathic scoliosis based on age
| Infantile | 0-3 years | IIS | |
| Juvenile | 3-10 years | JIS | |
| Adolescent | 10-18 years | AIS | |
| Adult | >18 years |
The adult form is differentiated from primary degenerative scoliosis. The adult idiopathic type is an idiopathic scoliosis that was present at the end of growth and has progressive secondary degenerative changes.
Radiological Classification
The SRS classifies a curve as thoracic if the apex is at the T2 to T11/12 disc, thoracolumbar if the apex is at T12 or L1, and lumbar if the apex is at the L1/2 to L4 disc.
King and Lenke are other classification systems. There is a problem with reliability of grading systems.
Clinical Assessment
History
Scoliosis can cause visible back and rib deformities, emotional and psychological distress, and back pain.
Enquire about family history of scoliosis, bowel and bladder dysfunction, weight loss or constitutional symptoms, neurological symptoms. Asking about age of menarche and secondary sex characteristics can help ascertain the level of skeletal maturation. Pain is often a feature but is usually low grade.
Examination
Examine the patients spine for asymmetries including shoulder height asymmetry, scapula prominence, rib hump, and uneven iliac crests. Look for whether the midline of the occiput is over the centre of the pelvis.
Assess the scoliotic curve. 90% of adolescent idiopathic scoliosis curves are right thoracic, left lumbar curves, i.e. the curve is convex towards the right.
The Adam's forward bend test is used to confirm scoliosis. The patient stands and bends forward at the waist. The examiner assesses for symmetry of the back from behind and beside the patient while looking for any back or rib cage abnormalities such as a rib hump. Non-structural causes can be assessed by examining the patient sitting on the bed and bending forward. Structural scoliosis persists in this position, while a non-structural scoliosis (e.g. due to leg length discrepancy) disappears.
Assess the chest for deformities including pectus excavatum and carninatum, and teh skin for manifestations of neurofibromatosis.
Restrictive lung disease may become a serious health issue with thoracic curves larger than 70°.
Differential Diagnosis
Child and adolescent idiopathic scoliosis accounts for approximately 80% of cases. It is a diagnosis of exclusion and is differentiated from neuromuscular and congenital scoliosis. In adults degenerative scoliosis is a consideration. Also non-structural causes such as leg-length discrepancy occurs.
- Idiopathic Scoliosis
- Neuromuscular Scoliosis
- Congenital Scoliosis
- Adult Degenerative Scoliosis
- Non-Structural Scoliosis
Imaging
Anteroposterior and lateral radiographs of the whole spine
Management
Risk factors for curve progression are young age, pre-menarchal state, large curve size at the first presentation, and left thoracic curve (convex towards the left). Curves between 50-70° are most likely to progress in adulthood.
Curves up to 25°: observation every 6 months until skeletally mature including sequential photographs, sitting height.
Curves between 25-40°: bracing
Larger curves: surgery
Surgery
The goal of surgery is prevention of curve progression and correction of the deformity. It usually involves curve correction and spinal instrumentation and fusion. The lower lumbar motion segments tend to be left unfused.
References
Spinal disorders fundamental of diagnosis and treatment - Boos
