Scoliosis describes an irregular spinal curve when viewed from behind. Structural scoliosis specifically refers to a fixed, three-dimensional change in the spine’s alignment. This type involves a sideways bend and rotation of the vertebrae, making it a distinct and persistent spinal deviation.
Understanding Structural Scoliosis
Structural scoliosis is characterized by a fixed, three-dimensional curvature of the spine, meaning the curve does not straighten out when a person changes position. This enduring nature differentiates it from non-structural, or functional, scoliosis, where the curve is temporary and can disappear when the underlying cause is addressed. A key feature of structural scoliosis is the rotation of the vertebrae, which accompanies the sideways bending. This rotation causes the spine to twist, leading to visible asymmetries in the body.
The spinal curve typically appears as a “C” or “S” shape when viewed from the back. This three-dimensional aspect means the spine bends to one side while also rotating along its vertical axis. The rotation can cause the rib cage to protrude on one side, a phenomenon often referred to as a rib hump. A curve of 10 degrees or more with rotation is considered scoliosis.
What Causes Structural Scoliosis?
The causes of structural scoliosis are varied, with the most common type being idiopathic scoliosis, meaning its origin is unknown. Idiopathic scoliosis accounts for approximately 80% of all scoliosis cases and typically manifests during adolescence, often coinciding with growth spurts. While the exact cause remains elusive, research suggests a genetic component, as about 30% of adolescent idiopathic scoliosis patients have a family history of the condition.
Other forms of structural scoliosis stem from identifiable causes. Congenital scoliosis, a rare type, develops before birth due to malformations of the vertebrae. These malformations can include incompletely formed vertebrae (hemivertebrae) or segments that fail to separate properly during fetal development. Children with congenital scoliosis may also have other health conditions, such as issues with their kidneys or bladder.
Neuromuscular scoliosis arises from disorders affecting the muscles and nerves, such as cerebral palsy, muscular dystrophy, or spina bifida. These conditions lead to muscle weakness or imbalance, which can prevent the spine from being properly supported and aligned. This type of scoliosis can progress rapidly, particularly in children with significant neuromuscular involvement. Syndromic scoliosis is associated with a broader genetic syndrome, like Marfan syndrome or Ehlers-Danlos syndrome, where the underlying condition affects the development of tissues throughout the body, including the spine.
Signs and Diagnosis of Structural Scoliosis
Identifying structural scoliosis begins with noticing visible changes in a person’s posture or body symmetry. Common signs include uneven shoulders or hips, where one side appears higher than the other. A prominent shoulder blade or a noticeable rib hump, especially when bending forward, can indicate structural scoliosis. The head may not appear centered over the pelvis, or the individual might lean to one side.
The diagnostic process involves a physical examination by a healthcare professional. One common screening method is the Adam’s forward bend test, where the individual bends forward at the waist with arms hanging freely. During this test, the examiner looks for any asymmetry, such as a rib hump or an uneven back, which becomes more apparent with spinal rotation.
If scoliosis is suspected, imaging tests are performed to confirm the diagnosis and assess the curve’s characteristics. X-rays are the primary tool used to visualize the spine, allowing healthcare professionals to measure the curve’s magnitude using a method called the Cobb angle. X-rays also help determine the rotational component of the curve and provide a detailed view of the vertebral alignment. In some cases, MRI or CT scans may be used to rule out other underlying conditions.