Etiology and mechanisms of development
Degenerative scoliosis is most commonly secondary in nature. Its development is inextricably linked with biomechanical and structural disorders of the spinal column.
The main causes of the pathology include:
- Asymmetric degenerative changes. Intervertebral discs and facet joints (facet joints) are primarily affected, leading to uneven load distribution.
- Metabolic diseases. The most frequent trigger is osteoporosis, against which asymmetric collapse (subsidence or compression fracture) of the vertebral bodies occurs.
- Associated pathologies. Scoliosis is often combined with asymmetric joint involvement, particularly arthritis, which further exacerbates the deformity.
Standard imaging protocol
A strict radiographic protocol is used for accurate diagnosis and monitoring of curve progression.
The mandatory minimum is standing full-spine radiography. Images must be taken in two projections: postero-anterior (postero-anterior) and lateral (lateral). These studies must be regularly repeated to track the dynamics of the disease.
The Cobb angle (Cobb angle) is used to assess the degree of deformity. It is measured directly on radiographs: the physician identifies the most tilted vertebrae forming the curve arc and draws perpendicular lines to their end plates (end plates). The intersection of these perpendiculars forms the target angle.
Assessment of sagittal balance
Analysis of sagittal balance (sagittal alignment) is a crucial stage of diagnosis. This procedure is performed on lateral radiographs.
The physician draws a plumb line (plumb line) through the middle of the body of the seventh cervical vertebra (C7) downwards through the L5/S1 disc space.
Norm criteria: In a balanced spine, this plumb line should pass strictly through the posterior third of the superior end plate of the sacrum (S1). If the line shifts anteriorly, it may indicate imbalance, although a plumb line passing up to 4 centimeters anterior to the specified point is also accepted as a variant of normal.
Dynamic tests and advanced diagnostics
Functional studies are used in cases where it is necessary to assess spinal stability. Dynamic radiography includes images in maximum flexion and extension (flexion/extension), as well as lateral bending (lateral bending). This allows for diagnosing spinal motion segment instability or identifying spondylolisthesis (spondylolisthesis).
CT (CT) or MRI (MR) are prescribed for an advanced assessment of soft tissue state and bone anatomy. They are indispensable for:
- Detailed visualization of bone structures;
- Detecting spinal canal stenosis (spinal canal stenosis);
- Diagnosing intervertebral foraminal stenosis (foraminal stenosis);
- Assessing the degree of nerve compression.
Degenerative spinal canal stenosis
Degenerative scoliosis is often accompanied by narrowing of the spinal canal. The causes of this stenosis include degeneration of vertebral bodies and facet joints, herniated intervertebral discs (herniated discs), as well as ligamentous thickening (ligamentous thickening).
At the lumbar level, marked stenosis can lead to a specific phenomenon — elongation of nerve roots, which in English-language medical literature is termed redundant nerve roots syndrome (redundant nerve roots).
In addition, stenosis of the transverse foramina (transverse foramina) may be observed. It is most commonly caused by the formation of bone outgrowths — osteophytes (osteophytic spurs), as well as hypertrophy of the superior articular process (superior articular facet).
Briefly: answers to topical questions
What surgical treatment methods are used for severe forms of degenerative scoliosis?
In grade III and IV kyphoscoliosis, surgical interventions on various spinal structures are used, combined with posterior bone-plastic fixation.
Types of surgical interventions:
- On the tendon-ligament apparatus of the spine — transection of the supraspinous and interspinous ligaments, incision of the facet joint capsule.
- On the intervertebral discs — discectomy, enucleation of discs at the apex of the deformity.
- On the vertebral bodies — wedge resection, epiphysiodesis.
- Additional interventions — resection of the most prominent ribs or thoracoplasty in the presence of a rib hump.
Metal constructs are used for corrective surgeries: Kazmin, Harrington, Rodnyansky (self-correcting) distractors, transpedicular, as well as other dorsal and ventral constructs.
To assess sagittal balance, remember the 'C7 Plumb Line Rule': the line falls on the posterior third of S1. Tolerance — no more than 4 cm anteriorly.
Class and exam questions
How to correctly calculate the Cobb angle on a radiograph?
It is necessary to determine the most tilted vertebrae of the curve arc, draw lines along their end plates (end plates), and construct perpendiculars to them. The angle between the perpendiculars is the Cobb angle.
What is the redundant nerve roots syndrome?
This is a pathological elongation of nerve roots (redundant nerve roots) that occurs at the lumbar level as a consequence of prolonged degenerative spinal canal stenosis.
Why is flexion and extension radiography prescribed?
Dynamic images (flexion/extension) are necessary to detect occult instability of spinal motion segments and diagnose spondylolisthesis (spondylolisthesis).
What else to study on this topic
- Technique of correctly performing the plumb line and errors in assessing sagittal balance
- CT and MRI semiotics of foraminal stenosis (foraminal stenosis)
- Biomechanics of osteophyte formation and facet joint hypertrophy
- The relationship between osteoporosis, compression fractures, and secondary scoliosis
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