title: Measurement of bone electrical impedance in fracture healing.
abstract: BACKGROUND
  Although external fixation is widely used for fractures and limb lengthening, evaluation of the time for removing the external fixator is dependent upon radiographic examinations and clinical findings, and a useful method has yet to be established clinically. This study aimed to measure the bone electrical impedance (Z values) non-invasively by using external fixation pins as electrodes, and clarify the relationship with bone union.
  
  
  METHODS
  Thirty rabbits received the external fixation at the right tibia and were assigned to a control group (group C; n = 5) and a fractured group (group F; n = 25). Z values were measured once a week following surgery. The animals of group F were assigned to 5 groups (weeks 2, 3, 4, 5, and 6 after osteotomy, each n = 5). The resistivity (rho) of the electrical property between electrodes was measured prior to euthanasia, and fracture cross-sectional area (FrA) of the conduction pathway and maximum bending stress (Bmax) were measured following excision of the tibia.
  
  
  RESULTS
  Although Z values in group F increased through 5 weeks after surgery, Z values in group C remained constant at 3 weeks, and significant differences were observed between groups at 4, 5, and 6 weeks. The rho values and FrA in group F decreased through 5 weeks; while Bmax increased, reaching a plateau at 5 weeks.
  
  
  CONCLUSIONS
  Narrowing of conduction pathway due to the decrease in the contour of fracture area accompanying bone remodeling resulted in an increase of Z values. Both Z values and Bmax in group F reached a peak at 5 weeks, this was believed to be the optimal time for removal of external fixation. These results suggest that measurement of Z values makes it possible to evaluate bone union.
authors.affiliation: Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 465 Kajii-cho Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-0841, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yoshida
authors.forename: Wook-Cheol
authors.initials: WC
authors.lastname: Kim
authors.forename: Koei
authors.initials: K
authors.lastname: Kawamoto
authors.forename: Toshiko
authors.initials: T
authors.lastname: Hirashima
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Oka
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Kubo
mesh_terms: D000818:Animals; D017097:Electric Impedance; D016267:External Fixators; D017102:Fracture Healing / Q000502:physiology*; D008297:Male; D011817:Rabbits; D013314:Stress, Mechanical; D013718:Tensile Strength; D013978:Tibial Fractures / Q000503:physiopathology* / Q000628:therapy