Variation in the position and orientation of the elbow flexion axis

We analysed the axis of movement in the normal elbow during flexion in vivo using radiostereometric analysis (RSA). The results show an intraindividual variation in the inclination of the axis ranging from 2.1degrees to 14.3degrees in the frontal and from 1.6degrees to 9.8degrees in the horizontal plane analysed at 30degrees increments. The inclination of the mean axis of rotation varied within a range of 12.7degrees in the frontal and 4.6degrees in the horizontal plane. In both planes, the mean axes were located close to a line joining the centres of the trochlea and capitellum. The intra- and interindividual variations of the axes of flexion of the elbow were greater than previously reported. These factors should be considered in the development of elbow prostheses.