Ankylosing spondylitis (AS) is a chronic inflammatory disease primarily affecting the spine, leading to pain and stiffness. Scoliosis, in contrast, is a condition marked by an abnormal lateral curvature of the spine. While both conditions involve changes to the spinal column, they have distinct origins and characteristics. This article explores the relationship between ankylosing spondylitis and scoliosis, discussing how AS can influence spinal alignment and whether it might contribute to a sideways curve.
Ankylosing Spondylitis and the Spine
Ankylosing spondylitis is a form of arthritis that mainly impacts the axial skeleton, particularly the spine and sacroiliac joints. The disease involves inflammation of these joints and the vertebrae, the bones of the spine. This inflammation can lead to pain, stiffness, and restricted movement.
As AS progresses, the body’s healing response can lead to the formation of new bone, known as syndesmophytes. These bony growths gradually bridge the gaps between vertebrae, potentially causing sections of the spine to fuse, a process called ankylosis. This fusion reduces spinal flexibility and can result in a hunched posture. The most common spinal deformity associated with advanced AS is kyphosis, an excessive forward curvature of the upper back.
Scoliosis Defined
Scoliosis is a spinal deformity characterized by a three-dimensional deviation of the spine. It involves a lateral, or sideways, curvature, often appearing as an S- or C-shape. Additionally, scoliosis includes a rotational component, where the vertebrae twist along their vertical axis. This combination of lateral curvature and vertebral rotation distinguishes scoliosis from other spinal conditions.
The causes of scoliosis vary, with the most common type being idiopathic, meaning its exact origin is unknown. Other types include congenital scoliosis, present at birth due to vertebral malformations, and neuromuscular scoliosis, resulting from conditions affecting muscles and nerves. Scoliosis differs from kyphosis, a forward curve, and lordosis, an exaggerated inward curve, as these are distinct spinal alignment issues.
How AS Relates to Scoliosis
While ankylosing spondylitis primarily causes a forward curvature (kyphosis) and spinal stiffening, it can sometimes be associated with scoliosis. This connection is often indirect, occurring through several mechanisms rather than direct causation of a sideways curve. In some cases, AS and scoliosis may simply co-exist, as both are relatively common conditions.
Severe kyphosis from AS can lead to compensatory scoliotic curves. The body attempts to maintain an upright posture and balance despite the forward spinal bend. This can cause the spine to curve sideways in other regions to offset the kyphotic deformity. Chronic inflammation, pain, and changes in muscle use due to AS can lead to muscle imbalances or asymmetry. These imbalances may contribute to spinal asymmetry and foster the development or progression of a scoliotic curve.
The stiffening and fusion of the spine in AS also alter spinal biomechanics. This can exacerbate a pre-existing mild scoliosis or contribute to new lateral curves as the spine loses its natural flexibility and shock-absorbing capacity. AS rarely causes structural scoliosis directly, unlike its more typical impact of causing kyphosis and spinal fusion. The relationship is more often one of secondary effect or co-occurrence.
Managing Spinal Changes in AS
Management of spinal changes in individuals with ankylosing spondylitis, including potential scoliosis, begins with early diagnosis and consistent monitoring. Regular assessments of spinal posture and mobility are important for tracking disease progression. Physical therapy plays a significant role in maintaining flexibility, improving posture, and strengthening muscles that support the spine. Exercise programs are tailored to the individual to help reduce stiffness and pain.
Medications control the underlying inflammation of AS, which can indirectly help prevent severe spinal deformities. Nonsteroidal anti-inflammatory drugs (NSAIDs) and biologics are commonly used to manage inflammation and slow disease progression. In rare and severe cases where deformities significantly impact quality of life, surgical intervention might be considered. Procedures like osteotomy can help realign the spine and improve posture, though they are reserved for specific circumstances.