Accuracy of CT-guided joint aspiration in patients with suspected infection status post-total hip arthroplasty.

OBJECTIVE: To determine the accuracy of guided computed tomography aspiration in the detection of septic hip prosthesis before surgery.
MATERIALS AND METHODS: Sixty-three patients (35 women and 28 men; age range, 29-86 years; mean age, 71 years) with clinically suspected septic hip prosthesis were prospectively studied with independent review board (IRB) approval. Volume and microbiological cultures of aspirated fluid and several computed tomography imaging findings such as periprosthetic fluid collections, prosthetic acetabular malposition, and heterotopic ossification were analyzed. All patients underwent revision surgery and infection was finally diagnosed in 33 patients.
RESULTS: Statistical comparative analysis was performed comparing computed tomography aspiration and surgical findings (95% CI; level of significance at P=0.05 two-sided) with 70% sensitivity, 100% specificity, 84% accuracy, 100% positive predictive value, and 75% negative predictive value. Using Fisher's exact test, the presence of periprosthetic fluid collections (P=0.001), prosthetic acetabular malposition (P=0.025) and aspirated fluid volume (P=0.009) were significantly higher in infected than in non-infected prostheses, whereas heterotopic ossification was not (P=0.429).
CONCLUSION: Computed tomography aspiration is accurate to preoperatively diagnose septic hip prosthesis on the basis of volume and bacterial cultures of aspirated joint fluid. Furthermore, imaging findings such as periprosthetic fluid collections and prosthetic acetabular malposition strongly suggest infected prosthesis.