Mechanical failure of a Thompson’s hemiarthoplasty stem 28 years post-implantation: an investigation with electron microscopy

Abstract

Τhe authors would like to report a mechanical failure of a Thompson’s prosthesis, 28 years post-implantation. A detailed examination of the specimen revealed no defects in the prosthesis and a dominating ‘brittle component’ fracture of the stem. In this context the detailed fractographic study by scanning electron microscopy (SEM) revealed no detrimental manufactural defects that may have produced microcracks and consequently risked initiating the fracture propagation. In contrast, the fracture was mainly a fatigue one with a mixed mode of microscopic trans- and intergranular crack propagation. To the best of our knowledge, such a mechanism of implant failure in a cementless stem has never before reached 28 years neither in a Thompson’s nor any other type of prosthesis, and in the already reported case, it exceeded 30 years [N. Wolson and J. P. Waadell, Can. J. Surg. 38(6) (1995) 542], however the stem’s ultrastructure has never been investigated under electron microscopy, which arguably can provide a useful assessment of a fatigue fracture. Τhe authors introduce the question of revising our standards when evaluating the newly designed and expensive implants and propose re-focusing on surgical technique, rather than purely on implant properties.