Validation of Shear-Wave Elastography for Detecting Kager’s Fat Pad Inflammation: A Pilot Study

Kager’s fat pad (KFP) is inflammation-sensitive due to its anatomical location. This study evaluates the ability of Shear-Wave Elastography (SWE) to visualize Kager’s Fat Pad (KFP) inflammation as diagnosed by Magnetic Resonance Imaging (MRI). This prospective study involved 33 patients (23 control, 10 with disease) having ankle pain who obtained MRI as the gold standard, followed by SWE. Both affected and asymptomatic ankles underwent scanning. MRI was conducted with a 1.5-T scanner with a specialised ankle coil in a neutral position. The SWE was performed in the longitudinal plane with patients in a prone position and the ankle extended at 90 degrees. The inter-observer reliability analysis showed high consistency in SWE measurements, with an ICC of 0.979 for the right KFP and 0.995 for the left KFP. The Mann Whitney U test revealed that the disease group had significantly higher stiffness (26.05 m/s) than the control group (11.21 m/s), z = − 2.256, p < 0.001. The Receiver Operating Characteristic (ROC) analysis proposed a cut-off stiffness value ≥ 3.85 m/s indicate inflamed KFP (AUC = 0.979). SWE demonstrated high reliability and diagnostic accuracy in detecting KFP inflammation, with an optimal shear-wave threshold reliably distinguishes diseased from control group in KFP.