Do metal implants for total hip arthroplasty affect bioelectrical impedance analysis? A retrospective study

Abstract

Abstract Background: Evaluation of body composition after total hip arthroplasty (THA) is essential because it can be used to evaluate muscle and functional recovery. Muscle volume and degeneration are evaluated using computed tomography (CT). However, CT evaluation of muscle volume has several limitations, such as radiation exposure and high medical cost. Bioelectrical impedance analysis (BIA) has gained attention for resolving these limitations of CT. BIA takes advantage of the microelectric current; thus, metal implants may affect the results. Therefore, this study aimed to elucidate the effects of metal implants on BIA after THA. Methods: Two types of patients were assessed (group 1: 70 patients who underwent unilateral THA and BIA after THA; group 2: 35 patients who underwent THA and BIA before and after THA. Electric impedance (resistance and reactance) of the operated and non-operated lower limbs was compared in group 1. The pre- andpostoperative impedances of the operated ipsilateral limbs were compared in group 2. To evaluate the effects of sex and age on BIA, the postoperative electrical impedances of men and women were also compared. The correlations between age and electrical impedance were also compared. Results: Regarding electric impedance in group 1, no significant differences were observed in electrical resistance and reactance between the operated and non-operated lower limbs. Concerning electric impedance in group 2, no significant difference was seen in electric resistance and reactance preoperatively and postoperatively. Electrical resistance was significantly lower in men than in women. A significant negative correlation was observed between age and electrical reactance. Conclusions:Electrical resistance and reactance did not change significantly after THA. BIA is useful for measuring body composition after THA.