Measurement of bone electrical impedance in fracture healing.
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.
Yoshida
Takashi
T
Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 465 Kajii-cho Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-0841, Japan.
Kim
Wook-Cheol
WC
Kawamoto
Koei
K
Hirashima
Toshiko
T
Oka
Yoshinobu
Y
Kubo
Toshikazu
T
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