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Table 1 Descriptions of the measurements and implant failure

From: Can posterior stand-alone expandable cages safely restore lumbar lordosis? A minimum 5-year follow-up study

Category

Parameter

Definition

Local factor

Segmental angle [11]

Angle between the perpendicular line of the lower endplate of the upper vertebra and upper endplate of the lower vertebra

Segmental translation [11]

Forward or backward slippage on a lateral radiograph

Lumbar factor

Short lumbar lordosis [5]

Cobb angle between the upper endplate of the fused vertebra and lower endplate of the fused vertebra

Whole lumbar lordosis [5]

Cobb angle between the upper endplate of L1 and the lower endplate of L5

Spinopelvic factor

Pelvic incidence [12]

Angle between the perpendicular line to the mid-point of the upper sacral endplate and mid-point of both femoral heads

Pelvic tilt [12]

Angle between the vertical line from the femoral head and center of the sacral endplate

Sacral slope [12]

Angle between the vertical line and superior sacral endplate

Global sagittal balance

Thoracic kyphosis [12]

Angle between the T4 upper endplate and T12 lower endplate

Sagittal vertical axis [12]

Distance from the vertical line of the C7 body to the inferior lateral corner of the L5 body

Sagittal balance [12]

Sagittal vertical axis line located within 5 cm

Implant failure

Subsidence [13]

Greater or equal to 2 mm loss of height

Pseudoarthrosis [6]

Bony non-union between two vertebrae

Proximal junctional kyphosis [6]

Proximal junction Cobb angle of at least 10° greater than the preoperative angle

Screw malposition [6]

Perforated pedicular screw