J Korean Orthop Assoc.  2012 Jun;47(3):198-204. 10.4055/jkoa.2012.47.3.198.

Measurement Discrepancy of Sagittal Parameters between Plain Radiography and 3D Computed Tomography in Thoracolumbar and Lumbar Fractures

• Kim DS
• Kim YM
• Choi ES
• Shon HC
• Park KJ
• Cho BK
• Park JK
• Lee HC

• KMID: 2106648
• DOI: http://doi.org/10.4055/jkoa.2012.47.3.198

Abstract

PURPOSE
For decision making in the management of vertebral fractures such as operation or not, sagittal parameters like Cobb angle and wedge compression ratio are important. Plain radiography had been the only image tool for measuring such parameters until 3D computed tomography (CT) became popular recently. In this study, we investigated the measurement discrepancy between plain radiography and 3D CT.
MATERIALS AND METHODS
Plain radiography and 3D CT of 45 thoracolumbar and lumbar fracture patients (male=21, female=24) were evaluated. We measured sagittal angle and vertebral height on lateral radiography and sagittal CT. Sagittal angle was measured between the upper body and lower body of fractured vertebrae. Anterior and posterior heights were measured to assess anteriorposterior (AP) wedge ratio.
RESULTS
The sagittal angle of plain radiography (13.1+/-14.3degrees) was significantly larger than that of 3D CT (8.2+/-13.0degrees) by 4.9degrees (p<0.001). AP wedge ratio of plain radiography was on average 65+/-17%, which was significantly lower than the 3D CT (73+/-17%) by 8% (p<0.001). The severer the initial kyphotic deformity, the more discrepancy of results between the two methods was observed.
CONCLUSION
Significant discrepancy was observed in sagittal features of fractured vertebra between plain radiography and 3D CT. Measured values of plain radiography showed more kyphotic features of the fractured body.

Keyword

thoracolumbar and lumbar fracture; plain radiography; 3D CT; sagittal angle; AP wedge ratio

MeSH Terms

Congenital Abnormalities
Decision Making
Humans
Spine

Figure

• 

  Figure 1 Measurement method of sagittal angle and AP wedge ratio in plain radiograph (A), mid-sagittal plane of 3D CT (B) and schematic illustration (C). Sagittal angle is Cobb angle between upper end plate of upper body and lower end plate of lower body. AP wedge ratio is anterior body height divided by posterior body height (Ha/Hp) of fractured vertebra. AP, anterior-posterior; CT, computed tomography; Ha, anterior height; Hp, posterior height.

• 

  Figure 2 Comparison between plain radiography and 3D CT in sagittal angle. The sagittal angle of plain radiography (13.1±14.3°) was significantly larger than that of 3D CT (8.2±13.0°) by 4.9° (p<0.001). CT, computed tomography.

• 

  Figure 3 Plain radiograph (A) and sagittal CT (B) of a 28-year-old female patient. In plain radiograph, sagittal angle is 29.3° and AP wedge ratio is 57%. Sagittal angle and AP wedge ratio of 3D CT are 21.2° and 67% respectively. Sagittal parameters of plain radiograph are more kyphotic than 3D CT. CT, computed tomography; AP, anterior-posterior.

• 

  Figure 4 Discrepancy between plain radiograph and 3D CT in AP wedge ratio. AP wedge ratio of plain radiograph is lower than 3D CT (p<0.001). CT, computed tomography; AP, anterior-posterior.

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  Figure 5 Schematic illustrations and photographs of position when obtaining plain lateral radiography (A, B) and 3D computed tomography (C, D).

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