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Cause of an implant fracture: material- or fabrication failure?

  • Intramedullary hip screws (IMHSs) are implanted for the fixture of pertrochanteric femoral fractures (thigh bone). The present work investigates the failure of an IMHS implant after the rehabilitation period which required a revision surgery where the upper femur had to be replaced by a hip endoprosthesis. Due to litigation the corresponding failure analysis was conducted at BAM Federal Institute for Materials Research and Testing and is the subject of this article. By order of the customer failure causes due to material and fabrication failures should be particularly investigated. Therefore, thorough fractographic, chemical as well as metallographic investigations were carried out. In order to assess possible fabrication failures selected dimensions of the components were compared with the technical drawings and the surface topography was analysed. The investigation revealed several causes for the fracture of the lag screw which is the implant component intended to fix the positionIntramedullary hip screws (IMHSs) are implanted for the fixture of pertrochanteric femoral fractures (thigh bone). The present work investigates the failure of an IMHS implant after the rehabilitation period which required a revision surgery where the upper femur had to be replaced by a hip endoprosthesis. Due to litigation the corresponding failure analysis was conducted at BAM Federal Institute for Materials Research and Testing and is the subject of this article. By order of the customer failure causes due to material and fabrication failures should be particularly investigated. Therefore, thorough fractographic, chemical as well as metallographic investigations were carried out. In order to assess possible fabrication failures selected dimensions of the components were compared with the technical drawings and the surface topography was analysed. The investigation revealed several causes for the fracture of the lag screw which is the implant component intended to fix the position of the femoral head. These are in descending order of relevance: (1) the screw was placed incorrectly and therefore had a smaller bending stiffness, (2) the femoral fracture zone was not stable, i.e., the lag screw 'moved out' of its proper position and (3) the laser marking on the lag screw was relatively large and led to a metallurgical notch at the now, because of the above mentioned points, severely stressed region. A material- or fabrication failure was not the root cause for the fracture of the lag screw. It was mainly due to its incorrect placement during surgery and the instability of the bone fracture. Furthermore, the implant geometry with 130° was not well-suited for the patient's anatomy. A 135°-IMHS might have been biomechanically preferable. Based on the determined failure causes and influences a relative lifetime estimation led to about 10% of the lifetime of a correctly placed 135°-IMHS assuming a sufficiently stable bone fracture zone.zeige mehrzeige weniger

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Metadaten
Autor*innen:Ronald Wallstabe, Christian Klinger
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Engineering failure analysis
Jahr der Erstveröffentlichung:2012
Verlag:Elsevier Science Publ.
Verlagsort:Oxford
Jahrgang/Band:25
Erste Seite:261
Letzte Seite:270
Freie Schlagwörter:Austenitic steel; Implant fracture; Implant placement; Intramedullary hip screw (IMHS); Laser-marking
DOI:10.1016/j.engfailanal.2012.05.010
ISSN:1350-6307
ISSN:1873-1961
Verfügbarkeit des Dokuments:Physisches Exemplar in der Bibliothek der BAM vorhanden ("Hardcopy Access")
Bibliotheksstandort:Sonderstandort: Publica-Schrank
Datum der Freischaltung:19.02.2016
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:06.08.2012
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