Scoliosis: Types and Causes

• Scoliosis is defined as a lateral curvature of the spine measuring 10 degrees or greater, as determined by the Cobb angle.
• Curvatures less than 10 degrees are not classified as scoliosis.
• Neuromuscular, congenital, acquired, and idiopathic scoliosis are the four categories to classify the causes and etiologies of scoliosis.

Neuromuscular Scoliosis

• Results from conditions causing spasticity or muscle weakness
• Cerebral palsy causes spasticity, leading to high neuromuscular tone that can contort the spine.
• Duchenne muscular dystrophy, poliomyelitis, and meningomyelocele all cause muscle weakness, which can contribute to scoliosis
• Neuromuscular scoliosis accounts for about 10% of all scoliosis cases.

Congenital Scoliosis

• Largely attributed to vertebral malformations.
• This can include spina bifida occulta, sacralization of lumbar segments, lumbarization of the sacrum, and facet tropism.
• Facet tropism, asymmetrical facet development, can cause side bending and rotation, leading to compensatory curves.
• Congenital scoliosis is rare, making up approximately 1-4% of all scoliosis cases.
• A block vertebra involves multiple fused segments, whereas a bar vertebra involves fusion at the transverse process across multiple segments
• Hemi vertebra indicates a vertebra with a side wall on one side only
• Wedge vertebra has a side wall and a short side wall
• Hemi vertebrae can be fully segmented (disc above and below) or semi-segmented (disc on only one side).
• Fully segmented hemi vertebrae are considered worse due to potential growth and increased curve severity as the patient ages.

Acquired Scoliosis

• Caused by spinal tumors, spinal infections, osteomalacia, sciatic irritation, or psoas syndrome.
• Short leg syndrome, connective tissue diseases (Marfan Syndrome, Ehlers-Danlos), juvenile rheumatoid arthritis, and certain types of dwarfism can also lead to scoliosis.
• Acquired scoliosis accounts for less than 10% of all scoliosis cases.
• Tumor and infection rarely cause scoliosis, making up less than 1% each of all scoliosis cases.
• Short leg syndrome is common but rarely severe enough to cause scoliosis (greater than 10 degrees).

Idiopathic Scoliosis

• Refers to cases with no identifiable cause for the scoliotic curve.
• Infantile (under 3 years), juvenile (3-9 years), and adolescent (10 years and older) are the subcategories
• Idiopathic scoliosis is the most common type, accounting for 80-85% of all scoliosis cases.
• These scoliosis can be structural/rigid or functional/flexible.
• Higher incidence in some families suggests a possible genetic component.
• Infantile scoliosis makes up 1% of all childhood idiopathic scoliosis, with 60% of these patients being males.
• Adolescent idiopathic scoliosis is the most common type overall, affecting males and females equally
• Females have a 10 times higher risk of curve progression and need for treatment
• Scoliosis affects about 3% of the population.
• It affects females more than males, and females develop it earlier.
• Females are more likely to develop severe scoliosis (greater than 40 degrees).
• The most common manifestation is a double major curve (thoracic and lumbar).
• Thoracic spine curves are the second most common, typically convex right.
• Lumbar spine curves are the third most common, typically convex left.
• Thoracolumbar scoliosis commonly has its apex at T11 or T12 and is convex right.