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Localized bioimpedance reactance as a biophysical parameter of muscle recovery following total knee arthroplasty: a
Gloria Pedemonte-Parramón1,2, Lexa Nescolarde3, Ester García-Oltra1,2
1Department of Orthopedic Surgery and Traumatology, Hospital Universitari Germans Trias i Pujol, Barcelona, Spain.
Background:
Quadriceps weakness and atrophy are common in patients with knee osteoarthritis and can persist after total knee arthroplasty (TKA), affecting functional recovery. Localized bioelectrical impedance analysis (L-BIA) allows non-invasive assessment of muscle status through resistance (R) and reactance (Xc), reflecting muscle composition and cell integrity. This study investigated longitudinal changes in quadriceps Xc following TKA and their association with functional outcomes.
Methods:
Twenty-five patients undergoing unilateral TKA were evaluated preoperatively and at 6 and 12 months postoperatively. L-BIA parameters (R and Xc) were measured in the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF). Functional outcomes were assessed using the Knee Society Score (KSS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Interlimb comparisons and predictive performance of Xc for functional recovery were analyzed using ROC curves, Gini indices, and Kolmogorov-Smirnov statistics.
Results:
R values remained stable across all muscles postoperatively (P > 0.05). Xc values significantly decreased at 6 months in VM and RF: P < 0.01; VL: P = 0.04 and recovered by 12 months to pre-TKA levels, with greater percentage changes in VM and VL than RF. Also, pre-TKA, Xc was lower in the operated limb compared to the contralateral side (P < 0.01). By 12 months, Xc in VM and RF was similar between limbs, while VL remained slightly lower in the operated leg. ROC analysis showed excellent predictive performance of Xc for WOMAC outcomes (VM and VL Gini = 0.909; K-S = 0.955), with optimal cut-offs of 15.65 Ω and 14.3 Ω, respectively. Functional improvements were most pronounced in the first 6 months and correlated with Xc recovery, particularly in VM at 12 months.
Conclusion:
Quadriceps Xc measured by L-BIA decreases initially after TKA but recovers by 12 months, paralleling improvements in pain and function. Xc provides a sensitive, non-invasive biophysical parameter for monitoring quadriceps muscle recovery and may inform individualized rehabilitation strategies.
