A comparative study between proximal radial morphology and the floating radial head prosthesis.

A morphometric study of the proximal radius was performed with computed tomography scanning in 51 healthy adults. These dimensions were then compared with those of a commercially available floating radial head prosthesis. Results were expressed as mean values, SD, and minimum and maximum values. The minimum and maximum diameters of the radial head were 21.9 +/- 1.9 mm and 22.9 +/- 1.9 mm, respectively. The minimum and maximum intramedullary diameters of the radial neck were 8.3 +/- 1.3 mm and 9.3 +/- 1.5 mm, respectively. The combined length of the radial head and neck was 22.47 +/- 2.84 mm. The implications for prosthetic design are as follows: the small floating cup (19 mm in diameter) is too small for the large majority of adults, the large floating cup (22 mm in diameter) is closer to the radial anatomy, the mean values are significantly different between male and female patients, and a single component would suffice for right and left elbows.