Use of F-18 Fluoride PET to Differentiate Septic From Aseptic Loosening in Total Hip Arthroplasty Patients

Purpose: The preoperative differentiation of aseptic and septic loosening following a total hip arthroplasty (THA) remains a challenging issue for clinicians to which several molecular imaging techniques have been applied. In our current study, we used F-18 fluoride positron emission tomography (PET) to evaluate THA cases with stable, septic or septic loosened implants to assess the possibility of differentiating these clinical settings using a novel uptake-type classification approach. Materials and Methods: A total of 65 joints were enrolled in this prospective study comprising 27 asymptomatic stable hips (control group), 11 painful hips conservatively treated after THA due to a suspicion of loosening, and 27 painful hips surgically treated after THA. PET imaging was classified into 3 types according to the uptake pattern. The maximum standardized uptake value (SUV(max)) was then measured for each joint. A final diagnosis was made via tissue examinations of surgically treated cases, and by serological and radiographic findings in conservatively treated cases. Results: There were significant differences found between the SUV(max) values for the aseptic and septic loosening THA cases. In the diagnosis of infection with type 3 pattern, the sensitivity and specificity were measured at 0.95 and 0.98 for all cases, and 0.95 and 0.88 for surgically treated cases, respectively. Conclusions: The results of our current study demonstrate that F-18 fluoride PET has considerable potential as a method for differentiating septic from aseptic loosening following a THA. The type classification of the uptake pattern can be performed relatively simply, and quantifications using the SUV(max) values can then provide an objective evaluation.