Canal preparation for prosthetic radial head replacement: Rasping versus reaming

Background: While many design-specific features of radial head prostheses have been studied (ie, geometry and surface coating), the optimum technique for canal preparation has not been determined. We hypothesized that preparation of the radial canal with a reamer would allow for the accommodation of a larger stem diameter versus following canal preparation with a rasp, and would provide acceptable stem-bone micromotion. Methods: Paired proximal radii from 7 cadavers were prepared by a rasp on one side and a reamer on the contralateral side. Cementless radial head stems of increasing diameter were sequentially implanted up to the maximum size or until a fracture occurred and the micromotion between the stem and bone was recorded. Results: In 3 of 5 pairs, at least a 1mm larger stem size fit into the canal after reaming versus after rasping (P=.04). 5 of 7 radii fractured secondary to intentional stem oversizing. For the optimally-sized stems, similar micromotion values were observed whether the canal was rasped (41±6μm) or reamed (44±6μm) (P=.72). Discussion: This study investigated an aspect of radial head arthroplasty technique about which little has currently been published. It is possible that use of a reamer rather than a rasp, while providing similar initial stability, might expand the stem size options for initial press-fit stability, and decrease the risk of fracture. Conclusion: Radial canal preparation with a reamer allows for implantation of a 1mm larger stem diameter versus rasping, while providing comparable initial stability to that achieved after rasping.