The Diagnostic Characteristic and Reproducibility of Bone Scintigraphy Single-Photon Emission Computed Tomography/Computed Tomography for Diagnosing Aseptic Loosening of Uncemented Total Knee Arthroplasty

Abstract

BackgroundThe primary objective of this study was to investigate the diagnostic characteristics of bone scintigraphy single-photon emission computed tomography/computed tomography (BS-SPECT/CT) for diagnosing aseptic loosening after uncemented total knee arthroplasty (TKA), and to evaluate the following aspects: how to manage inconclusive results, the interobserver reliability, and the location of tracer uptake between symptomatic cases with and without aseptic loosening. MethodsIn this study, 180 patients who had uncemented TKA and persistent knee pain suspected of aseptic loosening were included. As part of routine medical care, BS-SPECT/CT was used, and its results were compared with the reference standard, which involved revision surgery for aseptic loosening or a 12-month follow-up without revision or imaging. Inconclusive BS-SPECT/CT results were considered either negative (best-case scenario) or positive (worst-case scenario). Sensitivity, specificity, positive/negative likelihood ratios (LRs), and positive/negative predictive values (PPV and NPV) were calculated. Sensitivity analyses were conducted by comparing the diagnostic characteristics between cases with a follow-up of less and more than 2 years of follow-up. The anatomical distribution of tracer uptake and interobserver reliability were also evaluated. ResultsOf the 180 BS-SPECT/CT scans conducted, 22 were determined positive, 113 negative, and 45 inconclusive. The best-case scenario showed a sensitivity of 66.7%, specificity of 93.8%, +LR 10.8, −LR 0.4, PPV 54.6%, and NPV 96.2%. In contrast, the worst-case scenario had a sensitivity of 94.4%, specificity of 69.1%, +LR 3.1, −LR 0.1, PPV 25.4%, and NPV 99.1%. Sensitivity analyses revealed no relevant differences in characteristics between the 2 TKA-interval groups. The interobserver reliability was fair-to-moderate (κ = 0.39; 95% confidence interval 0.18 to 0.60), with an estimated agreement of 79% (95% confidence interval 70 to 87). Four prosthetic zones had a notably higher proportion of cases with tracer uptake in those with aseptic loosening compared to those without. ConclusionsThe test characteristics of BS-SPECT/CT were deemed appropriate in patients who have complaints of uncemented TKA suspected of aseptic loosening. Inconclusive cases were best categorized as negative, especially in patients who have a short interval between TKA and the first BS-SPECT/CT. Increased tracer uptake in 4 prosthetic zones was observed in cases of aseptic loosening, although interobserver reliability was fair to moderate. Level of EvidenceLevel III, Diagnostic Retrospective Cohort Study.