Neurosurgery notes/Spine/Deformity

Deformity

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Spine
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Radiological assessment in deformity
Clinical assessment
Classification-Spinal deformity
Craniocervical deformity
Thoracic and lumbar deformity

Definition

  • Spinal deformities refer to abnormal curvatures or malalignments of the vertebral column deviating from normal anatomy
  • These deformities manifest in three dimensions (3D)

Types of deformity

  • Coronal plane deformity (eg, scoliosis or laterolisthesis)
  • Sagittal plane deformity (eg, thoracic hyperkyphosis or spondylolisthesis)
  • Axial plane deformity (eg, rotational olisthesis)
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Pathophysiology

  • Heuter-Volkmann principle
    • Increased pressure on the end plate of bone retards growth (Hueter)
    • Reduced pressure accelerates growth (Volkmann)
    • It’s not the primary cause of neuromuscular scoliosis.
      • Neuromuscular scoliosis is primarily caused by muscle weakness, paralysis, or neurological issues related to an underlying condition
  • “Life is a kyphosing event.” - D. Polly
    • Compensation potential depends greatly on the PI
      • Low PI types have little compensation potential
      • High PI types have bigger potential
        • with type 4 having the greatest potential of compensation
    • If the spine is flexible around this kyphosing event, there is an increased extension of the flexible spine above and/or below this local kyphosis.
    • If the spine is rigid, with progressive kyphosis, the gravity line moves forward and the pelvis rotates backward (retroversion) inducing a decrease in the SS

Driver for deformity

Main drivers of deformity:
  • Growing spine:
    • Gravity:
      • Excess of forces
      • Altered resistance to forces
    • Growth:
      • Speed of growth
      • Symmetry of growth
  • Aging spine:
    • Gravity:
      • Excess of forces
      • Altered resistance to forces
    • Degeneration:
      • Quality of bones and joints
      • Quality of discs, muscles, and ligaments
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Clinical assessment of spinal shape

  • Assessment of spinal shape
    • Undress patient down to their underwear.
      • Movement and clothing obscure the subtle changes in body surface shape that spinal deformity may cause.
    • Patient stands upright and still.
    • Observe for any difference in the
      • Waist creases
      • Trunk shift
      • Shoulder heights
        • Medial shoulder balance (MSB)
        • Lateral shoulder balance (LSB)
          • Measured off of clavicles, acromion, or other bony or soft-tissue landmarks lateral to the spine.
      • Asymmetry
        • of
          • Posterior chest wall
          • Loin
        • Adam’s forward bend test
            • Having the patient lean forwards, bending at the waist
            • To make asymmetries (due to rotation) more obvious.
            • In bent forward position, the spinal rotation (relative to the horizontal plane) may be measured with a scoliometer.
            notion image
        • Forward bending sitting test
          • Can eliminate leg length inequality as cause of scoliosis
      • Check that the patient is able to stand upright with the hips and knees fully extended;
        • patients with sagittal plane deformity may stand with their hips and knees flexed, allowing them to tilt the pelvis backwards and compensate for some or all of the spinal deformity.
      • There are several photographic techniques that may be used to generate a topographical spinal map of the back shape (e.g. ISIS 2— Integrated Shape Imaging System, Oxford, UK).
        • This can quantify the posterior chest wall asymmetry and may be useful for monitoring scoliotic curve progression without using ionizing radiation, and for assessing the outcomes of surgery.

Adult deformity

Definition
  • Adult spinal deformity (ASD):
    • Two- or three-dimensional change in spinal alignment
  • Threshold that defines ASD?
    • Functional impairment becomes more important over time
    • Progressive decrease of health-related quality of life (QoL)
Deformity types
Coronal plane imbalance: Adult scoliosis
  • Lateral deviation of the normal vertical line of the spine > 10 degrees
  • The coronal plane (scoliosis) deformity is relatively unimportant.
    • It is the sagittal plane and pelvic parameters that have the biggest clinical impact.
    • Focal subluxation, loss of lumbar lordosis, and global spinal imbalance have been correlated with disability.
Sagittal plane imbalance (Kyphosis/lordosis)
  • Radiographic sagittal imbalance of >5cm
  • Aetiology
    • Destructive pathologies such as trauma, tumour, and infection can all produce localized kyphosis.
      • If there is sufficient flexibility
        • across the uninvolved adjacent spinal segments for a normal global spinal balance to be maintained.
      • If there is not sufficient flexibility
        • the localized destruction may result in a global sagittal spinal imbalance, which should be considered when treating the patient.
 

Factors Influencing Deformity Correction