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Measurement of torsion angles of long finger bones using computed tomography
L D Berthold1, A Peter, N Ishaque
1Department of Pediatric Radiology, Justus Liebig University, Giessen, Germany.
Objective:
Rotational dislocation at the fracture site is a complication of long finger bone fractures of the metacarpals and phalanges. To evaluate such deformities, we performed CT of the articular surfaces of these bones to demonstrate the torsion angles.
Design:
We evaluated 10 pairs of cadaver hands. These were placed flat, with the bones of interest perpendicular to the gantry to acquire axial images. The torsion of the long bone axes was defined as the angle between a tangent positioned parallel to the proximal articular surface and a tangent parallel to the distal articular surface of individual bones.
Results:
The maximum difference between repeated measurements was 4 degrees. Intraobserver differences measured between right and left hands are less than 3 degrees.
Conclusion:
Side differences in torsion angles exceeding 3 degrees are strongly suspicious of a malrotation after fracture. These measurements might help to plan derotational osteotomy and assess the results of therapy.