Normal radiographic angulation in the 4th and 5th metacarpal: a reference guide.

Accurate radiographic interpretation of deformities is of value during treatment of disorders of the 4th and 5th metacarpal. A uniform and simple measurement technique and a matching reference standard of the normal radiographic anatomy is indispensable to do so. Reports representing the normal radiographic angulations of these metacarpals are as yet not available. In 225 plain hand radiographs taken in PA and oblique directions, the capital- and subcapital angulations, the proximal articular inclination angle and the shaft bending angle, have been measured. A simple but effective measurement technique was developed to define their 'normal values'. The reproducibility of this technique was confirmed in a cadaver study. The obtained values were not dependent on sex, age, the involved side or the manual dominance. Increased subcapital inclination in one metacarpal was often accompanied by the same trend in the other. The values reveal some variation, but provide an applicable reference table. They can be used on an individual base for reliable determination of fracture angulation in the 4th and 5th metacarpal in persons over 14 years old with closed growth plates.