A radiographic method of measuring axial rotation of bone in vivo.

Present techniques of assessing rotational alignment in bone are limited to gross anatomical and radiographic observations made at a single point in time. Because of these quantitative limitations, this paper describes a radiographic technique devised to give precise information elucidating the direction, magnitude and site of rotational change. This technique is based on the radiographic monitoring of a positional change, in vivo, of biologically inert marker pins in the long bones. Animal investigations have demonstrated the validity of the in vivo angular assessments and have also shown morphologic and biomechanical compatibility. Laboratory experiments simulating an in vivo deflection were performed with a correlation of 0.999 found between the calculated angles and those measured in vitro.