Scoliosis: Classification and Causes
Scoliosis (scoliosis) is a lateral deviation of the spinal axis by more than 10 degrees. The pathology is broadly divided into two major groups.
Congenital scoliosis (congenital scoliosis) is caused by developmental and segmentation defects of the spinal column. It is frequently accompanied by the presence of hemivertebrae (hemivertebrae), butterfly vertebrae (butterfly vertebrae), or their fusion (block vertebrae). This form is often associated with genetic disorders:
- Syndromes: Klippel-Feil (Klippel-Feil), Goldenhar (Goldenhar), VACTERL;
- Dysostoses: spondylocostal and spondylothoracic;
- Connective tissue diseases: Marfan and Ehlers-Danlos syndromes, homocystinuria;
- Neurological pathologies: cerebral palsy, neurofibromatosis, tethered cord syndrome (tethered cord).
Idiopathic scoliosis (idiopathic scoliosis) has a pronounced hereditary character (candidate genes identified on chromosomes 6, 9, 10, and 16). Depending on the patient's age at diagnosis, it is classified into:
- Infantile (under 3 years old);
- Juvenile (from 3 to 10 years old);
- Adolescent (developing after 10 years old and until skeletal growth is complete) — this is the most common variant of the pathology.
Progression Assessment and Diagnostic Imaging
The likelihood of further curve deterioration directly depends on the severity of the deformity, the patient's sex (girls have a worse prognosis), and remaining growth potential.
Curve severity is assessed on radiographs by measuring the Cobb angle (Cobb angle). To determine growth potential, the clinical Tanner stage (Tanner stage) and the radiological Risser scale (Risser grade) are used, which are based on the ossification stages of the iliac crest apophysis:
- Grade 0: no ossification;
- Grades 1–4: sequential increase in ossification volume in 25% increments (e.g., grade 4 indicates a process close to complete fusion);
- Grade 5: complete skeletal maturity is reached.
Magnetic resonance imaging and computed tomography are indicated when occult spinal cord or vertebral anomalies are suspected (syringomyelia, spondylolisthesis, tumors). Absolute indications for scanning include left thoracic scoliosis, neurological deficit, pain, and any atypical clinical findings. CT is also informative in Klippel-Feil syndrome for visualizing high scapular elevation, upper thoracic spine defects, and detecting the omovertebral bone (omovertebral bone).
Spinal Changes in Neurocutaneous Syndromes
Skeletal anomalies are frequently part of multisystem genetic diseases.
In neurofibromatosis (neurofibromatosis), angular kyphoscoliosis (angular kyphoscoliosis) develops in the spine. Posterior scalloping of the vertebral bodies indicates dural ectasia. In addition to café-au-lait spots, focal gigantism, and axillary freckling, radiographs may reveal:
- Hourglass neurofibromas and lateral meningoceles;
- Cranial vault defects and ribbon-like eroded ribs (due to mesodermal dysplasia);
- Sphenoid wing aplasia or hypoplasia ("empty orbit" sign);
- Orbital wall hypoplasia leading to pulsating exophthalmos;
- Intraosseous cysts, cortical defects, and pseudarthrosis of the clavicle or leg bones. Tibial bowing is characteristic.
In tuberous sclerosis (tuberous sclerosis), specific bone changes are detected in addition to facial angiofibromas, shagreen patches, and cystic visceral lesions. The most common sign is sclerotic bone islands in the vertebral bodies and pedicles. Cyst-like defects of the phalanges and wave-like periosteal reactions on the tubular bones of the hand are also characteristic.
Skeletal Manifestations of Juvenile Idiopathic Arthritis
Juvenile idiopathic arthritis (juvenile idiopathic arthritis) is an inflammatory joint disease of unknown etiology developing in children under 16 years of age.
Depending on the pattern of musculoskeletal involvement in the first 6 months, several subtypes of the disease are distinguished:
- Oligoarthritis (oligoarthritis): inflammation affects 1 to 4 joints.
- Polyarthritis (polyarthritis): more than 4 joints are involved.
- Systemic arthritis (systemic arthritis): formerly known as Still's disease, characterized by a systemic response and a salmon-pink rash.
- Psoriatic arthritis and enthesitis-related arthritis (the latter is often associated with the carriage of specific HLA antigens).
Briefly: answers to topical questions
How to geometrically and correctly measure the Cobb angle on a spine radiograph?
To measure the Cobb angle (Cobb angle), it is necessary to draw straight lines along the endplates of the end vertebrae of the curve and construct perpendiculars to them.
Construction steps:
- First line — drawn strictly along the cranial endplate of the upper end (neutral) vertebra.
- Second line — drawn along the caudal endplate of the lower end vertebra.
If the endplates are poorly visualized, lines can be drawn through the upper or lower margins of the pedicle shadows. If the lines intersect outside the film, it is necessary to construct perpendiculars to both lines. The angle formed at the intersection of these perpendiculars determines the desired magnitude of the scoliotic deformity.
What is an omovertebral bone and what anatomical structures does it connect?
The omovertebral bone (omovertebral bone) is an additional bone formation between the scapula and the spine.
It is considered in congenital high scapula (Sprengel's deformity), particularly in its osseous form. When bone formations are present between the scapula and the spine, marked muscular changes occur; shoulder movements, especially elevation, are sharply restricted due to the lack of scapular mobility. CT and MRI are informative for visualizing the omovertebral bone, if present, as well as associated vertebral segmentation defects.
To remember the Risser scale: each of the 4 intermediate stages adds exactly 25% to apophyseal ossification (Grade 1 — 25%, Grade 2 — 50%, Grade 3 — 75%, Grade 4 — 100% without fusion), until final bone fusion occurs at Grade 5.
Class and exam questions
What anomalies of the vertebrae themselves are characteristic of congenital scoliosis?
Segmentation and development disorders are typical for the congenital form: formation of hemivertebrae, butterfly vertebrae, and fusion of adjacent vertebrae.
In what cases are CT or MRI mandatory for scoliosis?
Tomography must be performed in cases of left thoracic scoliosis, pronounced pain syndrome, neurological symptoms, or any unexpected clinical findings.
Which radiological sign of the spine is most typical for tuberous sclerosis?
The most common skeletal sign in this disease is the appearance of sclerotic bone islands in the vertebral bodies and pedicles.
What else to study on this topic
- Features of measuring the Cobb angle on radiographs
- Skeletal manifestations of Klippel-Feil syndrome
- Differential diagnosis of types of juvenile idiopathic arthritis
- Radiological presentation of pseudarthroses in neurofibromatosis
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