The purpose of this study was to determine the normal angle of rotation of the axis of each finger using digital image analysis, whether the rotation of the digits is symmetrical in the two hands of an individual, and the reliability of this method.

Standardised digital photographic images were taken of thirty healthy volunteers. The palm of each hand was placed on a flat bench top with their fingers held in extension and adducted, to give an end-on image of all four fingers. Three independent observers analysed the images using Adobe Photoshop software. The rotational angle of each finger was defined as the angle created by a straight line connecting the radial and ulnar border of the nail plate and the bench top horizon.

The three observers showed Inter-Rater Reliability of 92%. The mean angles of rotation were: Index 13°, Middle 10°, Ring 5°, Little 12°. The differences in angle of rotation of the index and middle finger between the left and right hand were statistically significant (p=0.003, and p=0.002 respectively), demonstrating asymmetry between the two sides. The differences in angle of rotation of the ring and little finger of the left and right hand were not significantly significant (p= 0.312 and p=0.716 respectively).

In conclusion, symmetry was seen in the little and ring but not in the index and middle fingers. Digital image analysis provides a non-invasive and reproducible method of quantifying the rotation of normal fingers and may be of use as a diagnostic tool in the assessment and management of hand injuries.

Templates are used in the preoperative planning of many orthopaedic procedures. The magnification of the bones on preoperative radiographs can vary despite using standardised radiological techniques. Templates will give misleading measurements unless this magnification is quantified.

A coin may be used to calculate the magnification, with significant improvement in the accuracy of templating (p = 0.05). A group of patients undergoing uncemented arthroplasty of the hip was at high risk for intraoperative fracture of the femur because the magnification of the radiograph was larger than that of the template.