title: Biomechanical evaluation of periprosthetic refractures following distal femur locking plate fixation.
abstract: BACKGROUND
  Distal femur fractures proximal to total knee femoral component constitutes the most prevalent type of periprosthetic fracture, and plate fixation treatment is associated with a 7.7% incidence of refracture proximal to the plate. The primary objective of this study was to compare proximal fixation techniques of a periprosthetic distal femur fracture plate in an osteoporotic bone model. The secondary objective was to determine the subsequent periprosthetic plate fracture pattern and/or complexity associated with each proximal plate fixation configuration.
  
  
  METHODS
  A segmental defect was created in 21 synthetic osteoporotic adult femurs 6 cm proximal to the distal femur and all specimens were stabilised with a 246 mm locking femur plate. Fixation in the most proximal hole was varied by use of either a cerclage cable, unicortical locking screw, or a bicortical locking screw. Specimens were tested to failure in simultaneous eccentric compression and torsion.
  
  
  RESULTS
  Proximal cerclage fixation demonstrated higher mean maximum axial force at failure (4142.67±178.71 N, p<0.001), stiffness (443.8±61.64 N/mm), and maximum torque (20.9±0.93 N m, p<0.001). Unicortical and bicortical screw refractures occurred at the screw, cerclage wire refractures occurred at the first proximal screw distal to the cerclage.
  
  
  CONCLUSIONS
  In periprosthetic distal femur fracture locking plate fixation, proximal hole stabilization with a cerclage wire tolerates significantly higher failure forces while distributing forces distal to the area within the plate fixation. Cerclage wiring may be an option in distal femur periprosthetic fractures to alleviate stress risers in vulnerable bone.
authors.affiliation: The University of Texas Medical Branch, 301 University Boulevard, Route 0165, Galveston, TX 77555, United States. Electronic address: jjalexan@utmb.edu.
authors.forename: Jamie
authors.initials: J
authors.lastname: Alexander
authors.affiliation: The University of Texas Medical Branch, 301 University Boulevard, Route 0165, Galveston, TX 77555, United States. Electronic address: rmorris@utmb.edu.
authors.forename: Randal P
authors.initials: RP
authors.lastname: Morris
authors.affiliation: Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Department of Research, 4300 Alton Road, Miami Beach, FL 33140, United States. Electronic address: dkaimraj@msmc.com.
authors.forename: David
authors.initials: D
authors.lastname: Kaimrajh
authors.affiliation: Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Department of Research, 4300 Alton Road, Miami Beach, FL 33140, United States. Electronic address: tmilne@msmc.com.
authors.forename: Edward
authors.initials: E
authors.lastname: Milne
authors.affiliation: Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Department of Research, 4300 Alton Road, Miami Beach, FL 33140, United States. Electronic address: llatta@msmc.com.
authors.forename: Loren
authors.initials: L
authors.lastname: Latta
authors.affiliation: The University of Texas Medical Branch, 301 University Boulevard, Route 0165, Galveston, TX 77555, United States. Electronic address: adflink@utmb.edu.
authors.forename: Adam
authors.initials: A
authors.lastname: Flink
authors.affiliation: The University of Texas Medical Branch, 301 University Boulevard, Route 0165, Galveston, TX 77555, United States. Electronic address: rlindsey@utmb.edu.
authors.forename: Ronald W
authors.initials: RW
authors.lastname: Lindsey
mesh_terms: D001696:Biomechanical Phenomena; D001860:Bone Plates; D001864:Bone Wires; D005264:Femoral Fractures / Q000601:surgery*; D005593:Fracture Fixation, Internal; D006801:Humans; D008422:Materials Testing; D057068:Periprosthetic Fractures / Q000601:surgery*; D011474:Prosthesis Design; D013314:Stress, Mechanical; D013718:Tensile Strength
keywords: Biomechanics; Cerclage wiring; Locking plate fixation; Periprosthetic fixation; Refractures