Evaluation of raw segmental bioelectrical impedance variables throughout anterior cruciate ligament reconstruction rehabilitation

Background. Raw bioelectrical impedance analysis (BIA) variables are related to physical function in healthy and diseased populations. Therefore, BIA may be an insightful, noninvasive method of assessment to track following anterior cruciate ligament reconstruction (ACLR). Objectives. Evaluate phase angle, reactance and impedance at 50 kHz (PhA50, Xc50, and Z 50, respectively) in the operative (OP) and non-operative (NOP) limbs during ACLR rehabilitation. Approach. Seventeen patient (12 M, 5 F; 18.8 ± 4.8 years) clinic reports were evaluated prior to ACLR (PRE), two- (2 W), six- (6 W), and twelve-weeks (12 W) post-ACLR and at return to sport testing (RTS). Setting. All observations occurred during the participant’s physical therapy visits. Measurements. A multi-frequency BIA device measured segmental PhA, Xc, and Z. Linear mixed effects models were used to assess any leg and time interaction and changes over leg and time, independently. Any interactions or main effects were considered significant at p < 0.05. Main results. Significant leg x time interactions were observed for each variable. PhA50 and Xc50 of NOP were higher (p < 0.001) than OP at each time point by an average of by 0.9° and 4.9 Ω, respectively. In OP, PhA50 and Xc50 decreased from PRE to 2 W and increased from 6 to 12 W and 12 W to RTS (p < 0.01, for all). At RTS, PhA50 and Xc50 were similar to PRE in OP (p > 0.05). For Z 50, the OP leg did not change over time (p > 0.05). Z 50 was greater in NOP at 2 and 6 W (p < 0.01, for both). There were differences in PhA50 in NOP between PRE and 6 W and from 6 W to RTS (p < 0.05 for both). Xc50 did not change (p > 0.05), and Z 50 PRE was lower than at 2 W (p < 0.05). Significance. A multi-frequency BIA device can detect changes in segmental BIA variables following ACLR.