Evaluating key ultrasound findings and their correlations with hip joint aspiration and prosthetic joint infection diagnosis following total hip arthroplasty.

Objective: To evaluate the association between specific ultrasound findings with the success of hip joint aspiration and the presence of joint infection in patients with hip arthroplasty.

Materials and methods: 138 patients who underwent ultrasound-guided aspiration were analyzed, focusing on hip joint capsular thickness, joint fluid echogenicity, synovial component visualization, and vascularity. These parameters were evaluated for their correlation with technically successful aspiration and infection status, using clinical data and the modified Musculoskeletal Infection Society (MSIS) criteria. Intra- and inter-reader reliability was also assessed for all measured parameters.

Results: Capsular thickness with a cutoff of 10 mm or greater, showed strong associations with technically successful aspiration (p = 0.0001) and joint infection (p = 0.0005), with high intra- and inter-observer reliability. Fluid echogenicity, when categorized as hypoechoic and moderate/heterogeneous, also showed significant associations with technically successful aspiration (p = 0.0001) and joint infection (p = 0.0009). While visualization of the synovial component did not correlate with aspiration outcomes (p = 0.24), it demonstrated a significant association with joint infection (p = 0.0007). Vascularity showed no significant correlation with technically successful aspiration (p = 0.22) or infection (p = 0.05).

Conclusion: Ultrasound is valuable in measuring variables that can be associated with a technically successful aspiration and the presence of prosthetic joint infection in patients with a history of total hip arthroplasty. Capsular thickness, particularly at a 10 mm cutoff, emerged as a sensitive and quantifiable parameter that can improve pre-procedural assessment accuracy. While other findings, such as fluid echogenicity and synovial component visualization showed potential, they are best interpreted alongside other clinical and imaging data.