Article Figures & Data
Figures
- Figure 1
Figure 1 is a schematic of the technique used for variable X-ray beam acquisition. With the X-ray tube aiming parallel to the floor, the angle subtended between the X-ray beam and the device center was decreased from 15°, 10°, 5°, and 0° in the sagittal plane by sequentially lowering the X-ray beam without changing the distance between the tube and the device (black arrow).
- Figure 2
Sawbones model (Pacific Research Laboratories, Inc., Vashon, Washington) with lumbar total disc replacement (ProDisc-L, Synthes Spine, West Chester, Pennsylvania) implanted at the L4-5 interbody space in flexion. With the X-ray beam in the neutral position (A), the edges of the endplates are clearly identifiable. With increasing superior movement of the X-ray beam at 5° (B), 10° (C), and 15° (D), notice the increasingly distorted projection of the footplates. The keel method, using lines drawn along the superior and inferior aspects of the keels, was used to determine Cobb measurements from which range of measurements were calculated.8 A comparison of (A: neutral beam angle) and (D: 15° beam angle) reveals a difference of only 0.3° despite an X-ray beam angle of 15°.
ILA: index level angle
- Figure 3
Minimal variation in mean ROM measurement as beam angle increases.
- Figure 4
Minimal variation in median intra-observer ROM error as beam angle increases.
Tables
- Table 1
Inter- and Intraobserver Precision and Accuracy of Radiographic Range of Motion Measurement Using the Keel Method at Increasing Beam Angles
Comparison Calculation n 0° 5° 10° 15° P Interobserver precisiona ROM observations 1 and 2 combined 16 24.7 ± 4.6 23.8 ± 3.4 24.1 ± 3.3 24.2 ± 3.9 .92 Intraobserver accuracya ROM error observations 1 and 2 combined 16 4.3 ± 4.6 3.2 ± 3.3 3.8 ± 3.3 3.3 ± 3.9 .86 Interobserver precisionb ROM observation 1 - ROM observation 2 8 2.0 (0.0 - 10.0) 3.0 (1.0 - 10.0) 1.5 (0.0 - 10.0) 1.0 (0.0 - 3.0) .09 Intraobserver accuracyb ROM error observation 1 - ROM error observation 2 8 2.0 (0.0 - 10.0) 3.0 (0.2 - 10.0) 1.5 (0.0 - 9.4) 1.0 (0.0 - 3.0) .07
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