Figure 2

Lumbar lordosis and segmental angle measurements, radiographies on end-plate angle measurements and pelvic tilt and pelvic incidence measurements. (A) Measurement of lumbar lordosis, upper and lower lumbar lordosis, and segmental angles. (c) The lumbar lordotic angle is the angle between the upper plate of the first lumbar and first sacral vertebral bodies. (a) The upper lumbar lordosis is the angle between the upper plate of the first and fourth lumbar vertebral bodies. (b) The lower lumbar lordosis is the angle between the upper plate of the fourth lumbar and first sacral vertebral bodies. Each segmental angle was measured as the angle between the upper plates of two adjacent vertebral bodies. (B) Measurement references for end-plate angle based on radiography. In the standing position, lumbar lordosis (angle between ⓐ and ⓒ), upper lumbar lordosis (angle between ⓐ and ⓑ), and lower lumbar lordosis (angle between ⓑ and ⓒ) were 59.09°, 17.46°, and 44.82°, respectively. After position was changed to sitting with the seat back at 60°, lumbar lordosis, upper lumbar lordosis, and lower lumbar lordosis changed to 8.26°, -5.15°, and 15.03°, respectively. (C) Radiography showing the measurement of pelvic tilt (PT) and pelvic incidence (PI). PT is defined as the angle between the line joining the hip axis and the midpoint of the S1 end plate and the reference vertical line. PI is defined as the angle between the line joining the hip axis and the midpoint of the S1 endplate and the line orthogonal to the S1 end plate.