title: Comparative assessment of different reconstructive techniques of distal femur in revision total knee arthroplasty.
abstract: OBJECTIVE
  Bone loss is often encountered in revision total knee arthroplasty. In particular, when the cortex of distal femur is breached, the surgical decision on the reconstructive options to be taken is challenging due to the variety of defects and the lack of data from clinical or experimental studies that can support it. The aim of the present work was to test the hypothesis that for an identical defect and bone condition, each reconstructive technique option has a dissimilar stress and stability behaviour, which may be related to differing longevity of the revision procedure.
  
  
  METHODS
  Triaxial strain gauges and video extensometer were used to measure distal cortex strains and implant stability in eight reconstructive techniques replicated with synthetic femur under a load of 2030N. To assess the cancellous bone strains, finite element models were developed and validated.
  
  
  RESULTS
  The measured strains showed that the distal cortex is not immune to the different reconstructive techniques, when applied to an identical defect; however, significant differences (P < 0.05) were found only between bone graft and metal augment on the 12-mm larger distal defect. The stem addition improves the stability of all reconstructive techniques; however, significant differences (P = 0.03) were found only on the bone-graft technique.
  
  
  CONCLUSIONS
  Cement-fill and metal-augment techniques, applied to the 4-mm smaller defect, are not associated with different structural behaviour, while for the 12-mm larger defect, the metal-augment and bone-graft techniques presented distinct biomechanical effects. These effects, by themselves, may not be sufficient to be associated with a different longevity of the revision procedure among techniques, when the stem is added to the bone-graft technique. These findings, based on independent scientific understanding and advanced prediction tools, can improve the surgical decision-making process, when the peripheral cortex of the distal femur is breached.
authors.affiliation: Department of Mechanical Engineering, University of Aveiro, 3810-193, Aveiro, Portugal. completo@ua.pt.
authors.forename: A
authors.initials: A
authors.lastname: Completo
authors.affiliation: Department of Orthopaedics, Coimbra University Hospital, 3000-075, Coimbra, Portugal.
authors.forename: F
authors.initials: F
authors.lastname: Fonseca
authors.affiliation: Department of Mechanical Engineering, University of Aveiro, 3810-193, Aveiro, Portugal.
authors.forename: A
authors.initials: A
authors.lastname: Ramos
authors.affiliation: Department of Mechanical Engineering, University of Aveiro, 3810-193, Aveiro, Portugal.
authors.forename: J
authors.initials: J
authors.lastname: Simões
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001843:Bone Cements; D016025:Bone Transplantation; D005269:Femur / Q000601:surgery*; D006801:Humans; D008297:Male; D011474:Prosthesis Design; D012086:Reoperation
chemical_list: D001843:Bone Cements
keywords: Experimental strains; Modular augments; Press-fit stem; Revision total knee arthroplasty; Structural allograft