Bone Stresses before and after Insertion of Two Commercially Available Distal Ulnar Implants Using Finite Element Analysis

Distal ulnar arthroplasty is becoming a popular treatment option for disorders of the distal radioulnar joint; however, few studies have investigated how load transfer in the ulna is altered after insertion of an implant. The purpose of our study was to compare bone stresses before and after insertion of two commercially available cemented distal ulnar implants: an implant with a titanium stem and an implant with a cobalt chrome stem. Appropriately sized implants of both types were inserted into eight previously validated subject-specific finite element models, which were created by using information derived from computed tomography scans. The von Mises stresses were compared at eight different regions pre- and post-implantation. The bone stresses with the titanium stem were consistently closer to the pre-implantation stresses than with the cobalt chrome stem. For the loading situation and parameters investigated, results of these models show that insertion of the E-Centrix (R) ulnar Head may result in less stress shielding than the SBI uHead (TM) stem. Future studies are required to investigate other implant design parameters and loading conditions that may affect the predicted amount of stress shielding. (C) 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1418-1423, 2011