Aetiological classification
Aebi classification - types of adult deformity
Type 1 adult scoliosis
- Aka: Primary degenerative scoliosis; (‘‘de novo’’ scoliosis)
- Mostly lumbar or thoracolumbar curve
- Apex at L2/3 or L/4 most frequently
- Develops after the age of 50
- Greater the age, higher the incidence
- Incidence 6%
- A 4 dimensional deformity:
- Axial deformity
- Sagittal deformity
- Coronal deformity
- Time
- Types of deformity
- Bi-dimensional:
- Degenerative spinal changes and sagittal malalignment
- Muscular dystrophy, camptocormia, osteoporosis
- Secondary postoperative deformity
- Three-dimensional:
- De novo scoliosis
- Degenerative scoliosis
- Neuromuscular, Parkinson
- Pathophysiology
- Asymmetric disc and facet joint degeneration:
- The process often begins with degeneration of the intervertebral discs and/or facet joints, which occurs unevenly on either side of the spine.
- This asymmetric breakdown leads to abnormal loading in specific spinal segments.
- Vicious cycle of deformity progression:
- The resulting asymmetric loading furthers the degeneration, leading to a self-perpetuating “vicious cycle.”
- As the structural integrity of the vertebrae, discs, and facet joints worsens, the spinal curve (scoliosis and/or kyphosis) progresses.
- Instability:
- Destruction of the discs, facet joints, and joint capsules causes instability, both in the sagittal and frontal planes.
- This instability can be segmental (affecting specific segments) or multisegmental, ultimately leading to spondylolisthesis (slippage) or rotational/translational dislocations.
- Osteophyte formation and ligamentous changes:
- The body attempts to compensate for instability with the formation of osteophytes (bone spurs) on the facet joints and vertebral endplates.
- Ligamentum flavum and joint capsules also thicken and may calcify, further narrowing the spinal canal and contributing to central and foraminal (lateral) spinal stenosis.
- Role of osteoporosis:
- In postmenopausal women especially, reduced bone density (osteoporosis) increases the risk for asymmetric vertebral collapse, amplifying progression of the scoliotic curve.
- Muscular imbalance and pain:
- The abnormal spinal alignment overloads certain musculature, particularly the paraspinal muscles.
- Chronic muscular fatigue and pain further reduce spinal stability and functional compensation, worsening the deformity.
- Associated with
- Disk degeneration
- Facet arthritis
- Thickening/hypertrophy of the ligamentum flava
- Loss of lumbar lordosis
- Lateral listhesis
Type 2 adult scoliosis
- General
- Idiopathic adolescent scoliosis → into Adulthood (AdIS)
- Progression due to mechanical reasons or bony and/or degenerative changes
- Unlike the paediatric patients, adult patients present with
- Pain
- Radicular symptoms.
- Mortality rate of untreated adult patients with adolescent idiopathic scoliosis is comparable with that of the general population
Classification
Types of deformity
- Bi-dimensional:
- Kyphosis, Scheuermann disease
- Congenital kyphosis
- Coronal deformity linked to leg-length discrepancy
- Three-dimensional:
- Early onset scoliosis (EOS) at skeletal maturity
- Adolescent idiopathic scoliosis (AIS) at skeletal maturity
- Congenital scoliosis
- Neuromuscular or syndromic scoliosis
Progression of deformity over time: Degenerative change and curve progression in adolescent idiopathic scoliosis
- As young adults
- Clinical trunk imbalance
- Mainly self-image altered
- Low-level of functional impairment
- Progression risk during adulthood
- In adulthood
- Lumbar curve dislocation
- Increase in trunk asymmetry
- Coronal and sagittal malalignment
- Degenerative lumbar changes
Surgery
- Fusion levels
- For thoracic and lumbar curves
- >35 deg and graded as structural require them to be included in the arthrodesis
- Non structural curve < 30 deg can be excluded from the fusion.
- Fusion of Lumbar sacral cruves
- depends on
- Presence of radiculopathy
- Age
- Bone density
- presence of significant degeneration on MRI
Type 3 adult scoliosis
- Aka secondary adult scoliosis
- Subtype
- 3a Due to pelvic obliquity
- Eg: leg length discrepancy, hip pathology, etc.
- Most located at thoracolumbar, lumbar-sacral
- 3b Due to metabolic bone disease
- Eg: osteoporosis + arthritic disease/fractures; Metabolic bone disease
Scoliosis classification:
Adult
Location of deformity
Paediatric
- Evolution of AIS Classification
Year | Classification |
1902 | Schulthess |
1950 | Ponseti and Friedman |
1983 | King-Moe |
2001 | Lenke |
2005 | PUMC |
2025 | SRS 3D classification |
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