Painful infection at the site of hip prosthesis: CT imaging.

Purpose: To prospectively determine the accuracy of computed tomography (CT) in the detection of painful infection at the site of hip prosthesis before surgery.
Materials and Methods: Helical CT examinations of hip prostheses were prospectively performed before surgery after a standard clinical and radiologic examination of 65 patients. CT scans and conventional radiographs were reviewed for periprosthetic bone abnormalities, and CT scans were reviewed for periprosthetic soft-tissue abnormalities (joint distention, fluid-filled bursae, and fluid collection in muscles and perimuscular fat). Patients subsequently underwent revision arthroplasty within 1 month, and infection was diagnosed in 12 (19%) patients.
Results: Infection was detected clinically in 25% of patients. Periprosthetic bone abnormalities did not allow differentiation of infection from complications not related to sepsis, except for periostitis, with 100% specificity but only 16% sensitivity. Soft-tissue findings were accurate for detection of infection, with 100% sensitivity and 87% specificity. Fluid collection in muscles and perimuscular fat had a 100% positive predictive value, and absence of joint distention had a 96% negative predictive value.
Conclusion: CT is accurate in the diagnosis of painful infection at the site of a hip prosthesis on the basis of soft-tissue findings, whereas periprosthetic bone abnormalities are not useful.
(Copyright RSNA, 2002)