- General
- Increases workload and therefore pain and poor quality of life
Compensatory measurements
- Full-body x-rays with lower extremity measurements:
- Sagittal compensatory mechanism
- Spine changes
- Thoracic spine
- Reduction of thoracic kyphosis
- Hyperextension of adjacent segments
- This exposes to the risk of retrolisthesis and may result in accelerated facet joints arthritis, inter-spinous hyperpressure (Baastrup’s disease) and sometimes isthmic lysis.
- Difference between ageing and compensatory hyperextension
- Retrolisthesis
- Retrolisthesis is typically limited to 2–3 mm slippage in the lumbar spine and result in severe foraminal stenosis and more rarely in central stenosis
- Observed at lower or upper adjacent segments of the kyphotic degenerative disease:
- L5-S1 is a common site.
- Retrolisthesis is typically underestimated on lying down radiological imaging techniques (MRI and CT scan).
- They can be suspected on MRI imaging with the presence of loss of coaptation of facet joints with fluid collection and frequent synovial facet cysts
- Lumbar spine
- Lordosis loss
- Common primary disturbance; patients tend to lose normal lumbar curve (hypolordosis or even kyphosis).
- Local extension at segments above the deformity is a spine-based compensation targeted to reduce forward lean.
- Sometimes, the cervical spine develops hyperlordosis (increased backward curve) to maintain horizontal gaze when thoracolumbar kyphosis is pronounced.
- Pelvic Retroversion: The pelvis tilts backward (increases pelvic tilt) as the first and main compensation for loss of lordosis.
- Pelvic Tilt (PT):
- Increases with age
- Compensation of malalignment
- Used as a marker for pelvic retroversion compensation. PT > 25°–30° often indicates overcompensation.
- Pelvic incidence (PI):
- Increases during growth
- Remains constant in adulthood
- Sacral slope (SS):
- Smaller changes over time
- Sacroiliac joint degeneration
- Hip Extension:
- Pelvic retroversion is associated with hip extension to realign the trunk’s center of mass over the hips.
- Knee Flexion:
- When pelvic compensation is insufficient, patients may flex their knees to stay upright. This is typically a late compensation and signals advanced imbalance.
- Progression:
- There is a typical sequence: spine → pelvis → hips → knees.
- Sagittal changes with age:
- Measurements by
- Femoral obliquity angle: (Grey)
- Angle between vertical and femoral axis
- Knee flexion angle: (White)
- Angle between femoral axis and tibial axis
- Global sagittal axis
- Aka Global tilt
- Angle between the line from midst of C7 to midpoint of femoral condyles and the line from this point to the mid point of S1
- Coronal compensatory mechanism
- Limb-length discrepancy
- Pelvic obliquity
- Compensatory lumbar curve
- Flexible deformity that can become structural over time
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