Failure at the Taper Lock of a Modular Stemmed Femoral Implant in Revision Knee Arthroplasty

Abstract

The Optetrak total knee arthroplasty system (Exactech, Gainesville, Florida) is the fifth in a series of total knee arthroplasty designs developed at the Hospital for Special Surgery1-3. The Optetrak implant retains the design concepts of the previous posterior stabilized Insall-Burstein-I (IB-I PS; Johnson and Johnson, Braintree, Massachusetts; Zimmer, Warsaw, Indiana) and Insall-Burstein-II (IB-II PS; Zimmer) posterior stabilized total knee implants2,4-7. A constrained condylar knee version of the Optetrak design has an elevated tibial post that, because of its higher and more squared design in comparison with standard posterior stabilized designs, provides greater varus-valgus and anteroposterior stability. The modular femoral and tibial components can accommodate stems through a taper junction. Traditionally, constrained condylar devices have been used with stem extensions to augment component fixation. The stem transfers the bending and torsion loads to the diaphysis and unloads the epiphyseal cancellous bone. From 1995 to 2006, 3886 of these constrained condylar stems were implanted at our institution. We report the cases of two patients who had failure in the male portion of the taper junction of the femoral component and stem extension. This study was performed under a protocol approved by the institutional review board of the Hospital for Special Surgery. Both patients were informed that data concerning the cases would be submitted for publication, and they consented. Case 1. A man underwent a right total knee arthroplasty for osteoarthritis in 1993 with use of the Insall-Burstein-II posterior stabilized knee prosthesis. The patient was sixty-three-years old, weighed 91 kg, and was 1.6 m tall at the time of the operation. He did well for nine years, until 2002, at which time aseptic loosening necessitated revision total knee arthroplasty with use of an Optetrak stemmed constrained condylar knee prosthesis. A constrained insert …