Radionuclide bone scintigraphy in the detection of significant complications after total knee joint replacement.

AIM: Post-arthroplasty knee pain is common and clinically it can be difficult to identify those patients with complications requiring active treatment. The aim of this study was to determine the usefulness of(99)Tc(m)-MDP bone scintigraphy.
METHOD: A retrospective study of all patients having a(99)Tc(m)-MDP bone scintigram for a painful knee arthroplasty between 1993 and 1999 was performed. Bone scintigrams were classified as normal or abnormal by a single observer. The results of these investigations were correlated with clinical outcome.
RESULTS: Seventy-five patients with painful knee arthroplasties were referred for investigation. A total of 80 bone scintigrams were performed. The average patient age was 66.2 years (42 female and 33 male). The mean time period between surgery and onset of knee pain was 3 years. A final clinical diagnosis based on arthroscopy, open surgery, and extended clinical follow-up was available for all patients. Forty-three (53.8%) of the scintigrams were normal and 37 (46.3%) abnormal. Two patients with a normal bone scintigram has loose prostheses. Thirteen patients with an abnormal study had normal prostheses on follow-up and these tended to be patients scanned less than a year after surgery. The sensitivity, specificity, positive predictive value and negative predictive value of an unequivocally normal or abnormal bone scintigram was 92.3, 75.9, 64.9 and 95.0%, respectively. The pattern of isotope uptake in the abnormal studies was not specific enough to reliably differentiate aseptic from septic loosening.
CONCLUSION: Radionuclide bone scintigraphy is useful in the assessment of the painful knee arthroplasty. A negative bone scintigram is reassuring and makes loosening or infection unlikely.