Ann Rehabil Med.  2016 Apr;40(2):237-243. 10.5535/arm.2016.40.2.237.

The Availability of Radiological Measurement of Femoral Anteversion Angle: Three-Dimensional Computed Tomography Reconstruction

• Byun HY
• Shin H
• Lee ES
• Kong MS
• Lee SH
• Lee CH

• KMID: 2309922
• DOI: http://doi.org/10.5535/arm.2016.40.2.237

Abstract

OBJECTIVE
To assess the intra-rater and inter-rater reliability for measuring femoral anteversion angle (FAA) by a radiographic method using three-dimensional computed tomography reconstruction (3D-CT).
METHODS
The study included 82 children who presented with intoeing gait. 3D-CT data taken between 2006 and 2014 were retrospectively reviewed. FAA was measured by 3D-CT. FAA is defined as the angle between the long axis of the femur neck and condylar axis of the distal femur. FAA measurement was performed twice at both lower extremities by each rater. The intra-rater and inter-rater reliability were calculated by intraclass correlation coefficient (ICC).
RESULTS
One hundred and sixty-four lower limbs of 82 children (31 boys and 51 girls, 6.3±3.2 years old) were included. The ICCs of intra-rater measurement for the angle of femoral neck axis (NA) were 0.89 for rater A and 0.96 for rater B, and those of condylar axis (CA) were 0.99 for rater A and 0.99 for rater B, respectively. The ICC of inter-rater measurement for the angle of NA was 0.89 and that of CA was 0.92. By each rater, the ICCs of the intrarater measurement for FAA were 0.97 for rater A and 0.95 for rater B, respectively and the ICC of the inter-rater measurement for FAA was 0.89.
CONCLUSION
The 3D-CT measures for FAA are reliable within individual raters and between different raters. The 3D-CT measures of FAA can be a useful method for accurate diagnosis and follow-up of femoral anteversion.

Keyword

Three-dimensional imaging; Bone anteversion; Gait

MeSH Terms

Axis, Cervical Vertebra
Bone Anteversion
Child
Diagnosis
Female
Femur
Femur Neck
Follow-Up Studies
Gait
Humans
Imaging, Three-Dimensional
Lower Extremity
Retrospective Studies

Figure

• 

  Fig. 1 (A) Anteroposterior view was acquired from 3-dimensional computed tomography. (B) Ninety degrees of rotation by the program resulted in the horizontal view, which is the looking down view of the femur. To measure each FAA, left side femur was eliminated (C) and the remaining right femur was rotated as vertically as possible in a view that hides the femur shaft (D). Upside down view of the femur was rotated to make femur neck as the most linear, for the straightest line (E). R, right; L, left; FAA, femoral anteversion angle.

• 

  Fig. 2 The angle between the long axis of the femur neck and horizontal line is defined as femoral neck angle. R, right.

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  Fig. 3 Definition of femur neck axis. From superior view of 3-dimensional computed tomography, a diagram was constructed. Femur was hypothesized as a circle, and a line that links two points of the circle and passed the center of the circle was drawn (A). Femur neck was hypothesized as a cylinder, and two lines extended from cylinder were drawn. Then, one horizontal line that was closest to the greater trochanter from femur neck and tangential to the two extended lines, was drawn. A point that bisected this line is the center of neck (B). Femur neck axis (thick red line) was defined as a line that connected the two central points (C). FH, femur head; FN, femur neck; GT, greater trochanter.

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  Fig. 4 The angle between the intercondylar axis of the distal femur and horizontal line is defined as condylar angle. R, right.

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  Fig. 5 Femoral anteversion angle was calculated as subtraction of the femoral neck and condylar angles when the two horizontal axis were in the same direction (A), and as summation when the two angles were in the opposite direction (B). H, horizontal axis; NA, femoral neck axis; CA, condylar axis.

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