Effect of Radial Head Implant Shape on Radiocapitellar Joint Congruency

Purpose Radial head arthroplasty is indicated in displaced fractures in which comminution precludes successful internal fixation. Many types of radial head implants have been developed varying in material, methods of fixation, and degrees of modularity and geometry. The purpose of this study was to investigate the effect of radial head implant shape on radiocapitellar joint congruency. Methods Joint congruency was quantified in 7 cadaveric specimens employing a registration and inter-surface distance algorithm and 3-dimensional models obtained using computed tomography. Forearm rotation was simulated after computer-guided implantation of an axisymmetric radial head, a population-based quasi-anatomic radial head implant, and a reverse-engineered anatomic radial head implant. Inter-surface distances were measured to investigate the relative position of the radial head implant and displayed on 3-dimensional color-contour maps. Surface area was measured for inter-surface distances (1.5 mm) and compared for each radial head geometry. Results There were no statistical differences in the contact surface area between radial head implants during active or passive forearm rotation. The joint was more congruent (larger contact surface area) during active forearm rotation compared with passive forearm rotation. Conclusions This study investigated the effect of implant geometry on the radiocapitellar joint contact mechanics by examining a commercially available radial head system (axisymmetric), a quasi-anatomic design, and an anatomic reverse-engineered radial head implant. We found no statistical differences in radiocapitellar joint contact mechanics as measured by 3-dimensional joint congruency in cadaveric specimens undergoing continuous simulated forearm rotation. Copyright (C) 2017 by the American Society for Surgery of the Hand. All rights reserved.