Local factor
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Segmental angle [11]
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Angle between the perpendicular line of the lower endplate of the upper vertebra and upper endplate of the lower vertebra
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Segmental translation [11]
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Forward or backward slippage on a lateral radiograph
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Lumbar factor
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Short lumbar lordosis [5]
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Cobb angle between the upper endplate of the fused vertebra and lower endplate of the fused vertebra
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Whole lumbar lordosis [5]
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Cobb angle between the upper endplate of L1 and the lower endplate of L5
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Spinopelvic factor
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Pelvic incidence [12]
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Angle between the perpendicular line to the mid-point of the upper sacral endplate and mid-point of both femoral heads
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Pelvic tilt [12]
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Angle between the vertical line from the femoral head and center of the sacral endplate
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Sacral slope [12]
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Angle between the vertical line and superior sacral endplate
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Global sagittal balance
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Thoracic kyphosis [12]
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Angle between the T4 upper endplate and T12 lower endplate
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Sagittal vertical axis [12]
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Distance from the vertical line of the C7 body to the inferior lateral corner of the L5 body
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Sagittal balance [12]
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Sagittal vertical axis line located within 5 cm
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Implant failure
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Subsidence [13]
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Greater or equal to 2 mm loss of height
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Pseudoarthrosis [6]
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Bony non-union between two vertebrae
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Proximal junctional kyphosis [6]
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Proximal junction Cobb angle of at least 10° greater than the preoperative angle
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Screw malposition [6]
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Perforated pedicular screw
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