title: [Ex vivo microCT analysis of possible microfractures of the femoral head during implantation of a cementless hip resurfacing femoral component].
abstract: OBJECTIVE
  Microfractures of the femoral head during implantation of the femoral components are suspected to be a cause of fractures at the implant/neck junction which represent a common failure mode in hip resurfacing arthroplasty. Callus formation observed in femoral head retrievals suggests the occurrence of microfractures inside the femoral head, which might be inadvertently caused by the surgeon during implantation. The aim of this biomechanical study was to analyse whether or not the implantation of a cementless femoral component hip resurfacing system causes microfractures in the femoral head.
  
  
  METHODS
  After the preparation of 20 paired human cadaveric femoral heads, the cementless femoral component ESKA Typ BS (ESKA Implants GmbH & Co., Lübeck) was implanted on 9 specimens with an impaction device that generates 4.5 kN impaction force. On 9 specimens the femoral component was implanted by hand. One head was used as a fracture model, 1 specimen served as control without manipulation. The femoral component used for impaction was equipped with hinges to enable its removal without further interfering with the bone stock. Specimens were scanned with a microCT device before and after impaction and the microCT datasets before and after impaction were compared to identify possible microfractures.
  
  
  RESULTS
  Twenty strikes per hand or with the impaction device provided sufficient implant seating. Neither the macroscopic examination nor the 2-dimensional microCT analysis revealed any fractures of the femoral heads after impaction.
  
  
  CONCLUSIONS
  At least macroscopically and in the 2-dimensional microCT analysis, implantation of the cementless hip resurfacing femoral component ESKA Typ BS with 4.5 kN or by hand does not seem to cause fractures of the femoral head.
authors.affiliation: Orthopädische Klinik, Medizinische Hochschule Hannover. matthias.lerch@annastift.de
authors.forename: M
authors.initials: M
authors.lastname: Lerch
authors.forename: G
authors.initials: G
authors.lastname: Olender
authors.forename: N
authors.initials: N
authors.lastname: von der Höh
authors.forename: F
authors.initials: F
authors.lastname: Thorey
authors.forename: G
authors.initials: G
authors.lastname: von Lewinski
authors.forename: A
authors.initials: A
authors.lastname: Meyer-Lindenberg
authors.forename: H
authors.initials: H
authors.lastname: Windhagen
authors.forename: C
authors.initials: C
authors.lastname: Hurschler
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D005260:Female; D005270:Femur Head / Q000000981:diagnostic imaging* / Q000293:injuries*; D006622:Hip Prosthesis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D011183:Postoperative Complications / Q000000981:diagnostic imaging*; D011474:Prosthesis Design; D012307:Risk Factors; D013525:Surgical Instruments; D055114:X-Ray Microtomography