Morphometric parameters of the radial head: an anatomical study

Exact anatomical description of the proximal radius is imperative for the development of radial head prostheses. The purpose of this study was to measure the anatomical parameters of the radial head.

Optosil imprints of 18 pairs of proximal radii fixed with formalin were taken. All possessed their native cartilage joint surface free of any arthritic defects. After being cut into 3 mm slices, the diameter of each slice was measured in steps of 30 degrees of rotation with the margo interosseous acting as a reference point.

Maximum radial head diameter was seen from the 0 to the 9 mm slice at a rotation of 30 degrees to full supination perpendicular to the proximal radioulnar joint. The diameter increased from the radiocapitular joint surface to the 6 mm slice, and then it decreased (P < 0.001). At the level of 6 mm the maximum radial head diameter was 24.13 mm (range 21.2-27.3 mm). The minimum diameter was seen perpendicular to the maximum; it also increased from the radiocapitular joint surface to the 6 mm slice and then decreased. There was a significant difference between the minimum and maximum diameter of each slice at a P-level of P < 0.001. Left and right sides were not significantly different at a P-level of 0.01.

Our data show that the radial head is neither round nor conical. It has a complex shape with an increasing size from the radiocapitular joint surface to the middle of the proximal radioulnar joint surface. No statistically significant differences could be observed between right and left radii.