Quantitation of Acute Extremity Compartment Syndrome in Rabbits Using Shear-wave Elastography to Assess Viscoelasticity.

Abstract

RATIONALE AND OBJECTIVES: Acute extremity compartment syndrome (AECS) lacks reliable noninvasive diagnostics. This study aimed to validate shear-wave elastography-derived viscoelastic parameters for assessing muscle pathology progress in a rabbit AECS model. METHODS: Forty-eight New Zealand rabbits were randomized into eight groups (control, 4, 6, 8, 12, 24, 48, and 72&#xa0;h post-procedure; n = 6). AECS was induced via ultrasound-guided femoral artery hypoperfusion (75% flow reduction) and calf cuff compression (200&#xa0;mmHg, 2&#xa0;h). Shear-wave speed (SWS) and viscosity (&#x3b7;) of the triceps surae muscle were measured using a programmable ultrasound, with intra-compartmental pressure (ICP) monitored concurrently. Histopathological grading (HGS: 0-9 scale) and ultrastructural staging (USS: 0-4 scale) were performed on hematoxylin and eosin (H&E) or transmission electron microscope (TEM) sections. Apoptosis (TUNEL apoptotic index) and systemic inflammation (plasma TNF-&#x3b1;) were quantified. RESULTS: Histology showed inflammatory cell infiltration, interstitial edema, necrosis, and microenvironmental degeneration in model limbs. HGS strongly correlated with SWS (r = 0.693) and &#x3b7; (r = 0.710, both p < 0.001). &#x3b7; was strongly associated with TNF-&#x3b1; (r = 0.702) and necrosis (r = 0.722), while SWS weakly correlated with inflammation (r = 0.345, p = 0.029). Receiver operating characteristic (ROC) analysis revealed &#x3b7; outperformed SWS in lesions detection (AUC: 0.894 [95% CI: 0.832-0.955] vs. 0.829 [0.749-0.908], p > 0.05). Combined SWS-&#x3b7; metrics improved diagnostic accuracy (AUC = 0.905 [0.845-0.965], p = 0.007 vs. SWS alone). CONCLUSION: SWS and &#x3b7; effectively quantify necrosis and inflammation in AECS progression and offer potential for noninvasive, continuous monitoring.