title: Fatigue fracture in dual modular revision total hip arthroplasty stems: failure analysis and computed tomography diagnostics in two cases.
abstract: We report on two patients with fracture of a modular, tapered and distally fixed, uncemented titanium revision hip stem, not previously described. A failure analysis revealed that the cause of the fractures was the development of fatigue cracks in the mid-stem cobalt-chromium modular junction ending in corrosion-fatigue failure. No material defects or stress risers were found in any of the implants. The diameter of the mid-stem modular junction might be undersized for use in heavy and active patients. We also report a new way of detecting an undisplaced fracture at the modular junction, using the scout image from a computed tomography (CT) scan; a technique that can be used when plain radiographs are inconclusive.
authors.affiliation: Department of Orthopaedics, Skane University Hospital, Clinical Sciences, Lund University, Lund, Sweden.
authors.forename: Pontus
authors.initials: P
authors.lastname: Norman
authors.affiliation: Division of Materials Engineering, Lund University, Lund, Sweden.
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Iyengar
authors.affiliation: Division of Solid Mechanics, Lund University, Lund, Sweden.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Svensson
authors.affiliation: Department of Orthopaedics, Skane University Hospital, Clinical Sciences, Lund University, Lund, Sweden.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Flivik
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D001672:Biocompatible Materials; D002858:Chromium Alloys; D003343:Corrosion; D019544:Equipment Failure Analysis; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed
chemical_list: D001672:Biocompatible Materials; D002858:Chromium Alloys
keywords: CT; fatigue failure; hip prosthesis; modular