Measurement of bone electrical impedance in fracture healing

• Published in: Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association 2009-05, Vol.14 (3), p.320-329
• Main Authors: Yoshida, Takashi, Kim, Wook-Cheol, Kawamoto, Koei, Hirashima, Toshiko, Oka, Yoshinobu, Kubo, Toshikazu
• Format: Article
• Language: English
• Subjects: Animals; Electric Impedance; External Fixators; Fracture Healing - physiology; Male; Medicine; Medicine & Public Health; Original Article; Orthopedics; Rabbits; Rheumatology; Stress, Mechanical; Tensile Strength; Tibial Fractures - physiopathology; Tibial Fractures - therapy
• ISSN: 0949-2658; 1436-2023
• DOI: 10.1007/s00776-009-1333-z

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. 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 (Ρ) 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. 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 Ρ values and FrA in group F decreased through 5 weeks; while Bmax increased, reaching a plateau at 5 weeks. 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.