[Correlation study of superb microvascular imaging on knee osteoarthritis]

To investigate the correlation between superb microvascular imaging (SMI) blood flow grading, ultrasound semi-quantitative scores, and clinical symptom severity in patients with primary knee osteoarthritis (KOA).

A total of 94 knees from 47 patients with primary KOA were evaluated. Ultrasound semi-quantitative scoring and synovial SMI grading were performed for each knee joint. Clinical assessments included the Western Ontario and McMaster Universities osteoarthritis index (WOMAC), visual analog scale (VAS) for pain, and serum biomarkers, such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Correlations between clinical scores and ultrasound parameters were analyzed.

SMI demonstrated a significantly higher synovial blood flow detection rate than power Doppler (PD) (14.9% vs. 9.6%, Z=-2.531, P=0.011). WOMAC stiffness scores showed positive correlations with synovitis, articular cartilage damage, and elevated SMI scores (all P < 0.05). WOMAC function scores were positively correlated with osteophyte severity, synovial thickening, and elevated SMI scores (all P < 0.05). The total WOMAC scores were positively associated with synovitis, synovial thickening, articular cartilage damage, and osteophyte severity (all P < 0.05). However, non-parametric Bootstrap analysis (B=2 000 replicates) revealed no independent associations between SMI blood flow grading, age, or body mass index (BMI) and WOMAC pain, stiffness, function, or total scores (all P>0.05, 95%CI contained zero).

The SMI technique demonstrates significantly higher sensitivity than PD in detecting intensity grade of synovial microvascular flow. While SMI compensates for the limitations of PD in identifying low-grade inflammation, its high sensitivity to low- velocity blood flow did not correlate with symptom severity or WOMAC pain scores. These findings suggest that SMI serves as a valuable tool for visualizing microvascular activity in subclinical synovitis, but its role as a direct indicator of clinical symptom severity in KOA remains limited. Further studies with larger sample sizes are warranted to validate its clinical utility.