Monitoring of Callus Maturation and Measurement of Resistance Rates Using Bioelectrical Impedance for Patients Treated With an External Fixator

: Evaluation of callus maturation and the decision to remove an external fixator depend on radiographic and clinical findings, which are subjective. Callus fracture or recurrent deformity may occur after premature removal of a fixator. The authors applied a technique to measure bioelectrical impedance to assess callus maturation. This study included 27 limbs that underwent deformity correction or callus distraction using a fixator. Mean patient age at the time of surgery was 17.2 years. Overall impedance during callus maturation was measured from after completion of correction or distraction to removal of the fixator. Temporal changes in impedance values were measured, and maximum and final values were compared with initial values. The resistance rates were compared by age (<15 or ≥15 years), correction site (femur or tibia), and treatment method (noncontact or contact). Mean overall impedance increased gradually. Compared with initial values, maximum and final impedance values were 1.21 times and 1.15 times higher, respectively. Resistance rates by age, correction site, and treatment method were significantly higher in patients 15 years and older, in the tibia, and in the contact group, respectively. Overall impedance tended to increase during callus maturation but varied among patients. Therefore, resistance rates were calculated to classify differences for individual patients. Age and treatment method were important predictors of resistance rates. These data by age, correction site, and treatment method, which assume overall impedance from after completion of correction or distraction, can serve as a useful index to determine when a fixator should be removed. [Orthopedics. 2018; 41(1):54-58.].