Introduction

Failing total knee replacement management has included isotope bone scan to identify infection or loosening. BASK guidance suggests bone scans have a poor positive predictive value and are not advised. We assessed isotope bone scanning as a negative predictor to exclude loosening or infection in failing total knee replacement.

Methodology

Retrospective review of consecutive bone scans performed to investigate painful total knee replacements for a one-year period (June 2017 to June 2018). 166 bone scans performed. 33 excluded (no notes or scan for other reasons). Demographic information, age of prosthesis, clinic review date, serological markers, results of aspiration and subsequent intraoperative findings also recorded.

Results

133 patients, mean age 72.7, average age of prosthesis 6.8 years.

45% scans performed showed evidence of infection or loosening.

Of those positive scans, 70% had aspiration and consideration for revision surgery.

73 patients had negative scans. 2 patients had subsequent aspiration and in 1 patient, S. Epidermidis isolated (1 patient had patellar revision and further samples clear of and other patient declined further surgery).

Conclusion

Isotope bone scan had a 97.2% negative predictive value making it a very useful tool to evaluate the failing knee replacement and exclude significant loosening or infection.