title: Fatigue failure of an AO spiral blade.
abstract: We report an unusual case of a femoral neck stress fracture leading to the fatigue failure of an AO spiral blade. An unreamed femoral nail with a spiral blade was inserted to treat an unstable subtrochanteric femoral fracture. which lead to fracture union at 5 months. Eight months post-operatively the patient started to complain of left hip pain. Serial radiographs revealed progressive osteoporosis of the proximal femur possibly due to the stress sharing effect of a stiff intramedullary device, which continued to bear a significant amount of the transmitted load. The cause of pain was a stress fracture of the femoral neck and the AO spiral blade, which only became radiologically visible 4 months after the start of the symptoms (1 year after the initial operation). The implant was removed and replaced by a cemented hemiarthroplasty. This case reaffirms the difficulty in diagnosing a stress fracture through a metallic implant. The delay in diagnosis may be shortened if stress fracture were included as an expected complication following an intramedullary nailing.
authors.affiliation: Department of Orthopaedic Surgery, James Connolly Memorial Hospital, Blanchardstown, Dublin, Ireland.
authors.forename: A A
authors.initials: AA
authors.lastname: Syed
authors.forename: J G
authors.initials: JG
authors.lastname: Kennedy
authors.forename: H
authors.initials: H
authors.lastname: Mullet
authors.forename: J
authors.initials: J
authors.lastname: O'Flanagan
authors.forename: D
authors.initials: D
authors.lastname: Taylor
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D019544:Equipment Failure Analysis; D005260:Female; D005265:Femoral Neck Fractures / Q000000981:diagnostic imaging* / Q000601:surgery; D005500:Follow-Up Studies; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation*; D017102:Fracture Healing / Q000502:physiology; D015775:Fractures, Stress / Q000000981:diagnostic imaging* / Q000601:surgery; D006620:Hip Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D008855:Microscopy, Electron, Scanning; D011183:Postoperative Complications / Q000000981:diagnostic imaging* / Q000601:surgery; D011859:Radiography; D012086:Reoperation; D014025:Titanium
chemical_list: C070282:Ti-6Al-7Nb alloy; D014025:Titanium