What are the types and causes scoliosis?

Scoliosis affects roughly 0.5 percent of men and two percent of women. The most common form of the condition, known as idiopathic scoliosis (structural scoliosis), is one that does not have a known cause but it is thought to have a genetic link. Several subtypes of idiopathic scoliosis exist and are classified based on the age at which the condition develops:

• If a child develops the condition before three years of age, this is referred to as infantile idiopathic scoliosis.
• When a child develops scoliosis between the ages of four and ten, this is known as juvenile idiopathic scoliosis (JIS).
• If scoliosis develops between the ages of 10 and 18 years old this is known as adolescent idiopathic scoliosis (AIS). Most idiopathic scoliosis cases occur in this age group.

The majority of people with idiopathic scoliosis are adolescent girls with the condition occurring most commonly in the thoracic (upper) spine.

What causes the other types of scoliosis?

As previously mentioned, idiopathic scoliosis, as well as the subtypes of this form of the condition, account for the majority of scoliosis cases. There are however, other forms of the condition which include:

• Congenital scoliosis – This form of scoliosis refers to a curvature of the spine that is the result of a birth defect, thus, the condition is present at birth. Only one in 10,000 newborn babies will have this condition³. Children who have congenital scoliosis will sometimes also have other health disorders such as bladder or kidney problems. A paediatrician will typically diagnose this disorder during an examination of the infant at birth if a spinal abnormality is noted. If the abnormality is not detected in infancy, due to the fact that scoliosis is not a painful condition, the curvature may go unnoticed until there are more obvious signs which may only appear when the child is an adolescent.
  • Spina bifida is another condition that may lead to scoliosis. This condition is present at birth and is characterised by the spinal canal and backbone of a baby not closing before birth. In severe cases, the disorder may cause the spinal cord and its protective membranes to protrude through the spinal arches and out of the infant’s back (referred to as Myelomeningocele spina bifida) or in some instances only the protective membranes protrude through an opening in the spine (Meningocele spina bifida).

• Functional scoliosis – With this form of scoliosis, also known as nonstructural scoliosis, the spine is normal, however, an abnormal curve starts to develop as a result of an issue in another part of the body. Some underlying conditions include injury, muscle spasms, a difference in leg length or an inflammatory condition such as appendicitis (this may result in muscle spasms). Practicing asymmetrical activities on a repetitive basis (such as golf or tennis) over a number of years may also contribute to the development of this condition. This form of scoliosis will be treated by detecting and addressing the underlying issue or condition.
• Neuromuscular scoliosis – With this form of scoliosis, an affected child will suffer from an irregular curvature of the spine that is the result of disorders of the spinal cord, brain and muscular system. Muscles and nerves will be unable to maintain balance and/or their alignment of the trunk and spine. Spinal curves that are neuromuscular related tend to be associated with a condition known as pelvic obliquity, this disorder results in the affected person’s pelvis tilting unevenly higher on one side. The majority of cases also have kyphosis present. This form of scoliosis, when compared to the idiopathic type, is considered a condition that results in more curves that progress into adulthood, meaning that neuromuscular scoliosis will require attention and care. 

• Degenerative lumbar scoliosis – While other forms of scoliosis are usually seen in children and adolescents, degenerative scoliosis occurs in adults of an advanced age. This type of scoliosis is a result of changes occurring in the spine due to arthritis, this is known as spondylosis. Spondylosis refers to age-related wearing down of the spinal bones. The progressive weakening of the ligaments and some other soft tissues in the spine, combined with abnormal bone spurs may lead to the abnormal curvature of the spine. The spine may also be adversely affected by osteoporosis (the development of porous and spongy bones as bones lose their strength and density) which can lead to disc degeneration and compression fractures.
  • **My Med Memo – Bone spurs refer to small bony projections that have developed along the edges of bones. They are also known as osteophytes and tend to form where the bones meet with each other (the joints) and can also form on the bones of the spine (vertebrae). Bone spurs are usually caused by the damage done by osteoarthritis.

There are several other causes of scoliosis, one of these may include tumours such as osteoid osteoma. This is a benign tumour that can occur in the spine and cause a considerable amount of pain often resulting in the sufferer leaning to one side in an attempt to reduce the pressure being applied to the tumour and the associated pain. This may lead to a deformity of the spine.

In addition, some researchers have suggested that muscle disorders, genetics, and/or an abnormal fibrillin metabolism may have a role to play in the development of scoliosis.

Scoliosis in adults

Scoliosis is commonly seen in adolescence, however, the condition may seem to develop in adulthood. This is generally as a result of childhood scoliosis progression which only becomes noticeable later in life or may be due to the development of degenerative lumbar scoliosis caused by other underlying conditions.