Christopher J. Cleary1, Bryan G. Vopat2, Ashley A. Herda1

1University of Kansas Edwards Campus, Overland Park, Kansas, 2 University of Kansas Health Systems, Overland Park, Kansas

Phase angle (PhA) is derived from bioelectrical impedance analysis (BIA), representative of cell membrane integrity and thought to be a surrogate for muscle function. Therefore, PhA may be a useful, easily assessed outcome to track in times when traditional muscle function tests are contraindicated, such as after anterior cruciate ligament reconstruction surgery. PURPOSE: The purpose of this project was to assess differences in segmental PhA between the operative (OP) and non-operative (NO) legs in knee surgery patients and their relationships with whole-body and segmental lean mass. METHODS: Twenty (13 M, 7 F, mean±SD: 18.2±4.6 years; 177.1±9.9 m; 80.8±19.7 kg) knee surgery patients were assessed two-weeks after surgery as part of their normal physical therapy visits. BIA assessed whole-body and segmental (OP and NO leg) PhA and lean muscle masses. Data were analyzed using paired-samples t-test to assess any differences between OP and NO legs and Pearson’s correlations assessed the relationships between OP and NO leg PhA and whole body and segmental (OP and NO) lean masses. Data were considered significant at p<0.05. RESULTS: For PhA, the NO leg (6.8±0.7°) was significantly greater (p<0.001) than the OP leg (5.5±0.9°). However, OP leg lean mass (9.7±2.0 kg) was estimated as greater (p<0.001) than NO leg lean mass (9.4±1.9 kg). There was no significant relationship between OP PhA and OP lean mass (r=0.34, p=0.14), while NO PhA significantly correlated with NO lean mass (r=0.47, p=0.039). PhA of both legs was significantly related to total body lean mass, but NO PhA was more strongly related (r=0.58, p=0.008) than the OP leg (r=0.49, p=0.027). CONCLUSION: PhA was significantly greater in the NO leg by approximately 22% two-weeks after knee surgery, while NO leg lean mass was less than the OP leg by approximately 3%. The estimate of OP lean muscle and differences between legs may be representative of intra-and extracellular swelling post-surgery. These differences in PhA may represent altered cellular integrity, and potentially function, in the OP leg. Bioelectrical impedance therefore may be an advantageous way to non-invasively interpret muscle function early after surgery.

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