Combined 99mTc-MDP bone scintigraphy and 99mTc-ciprofloxacin scintigraphy in differentiation of hip and knee prosthesis aseptic loosening and infection: Preliminary study

Background/Aim. Although the number of new primary implantation of hip and knee prostheses every year increases, the rate of failed arthoplasty are nearly the same. The main question is whether it is a aseptic instability or instability is caused by infection. The aim of this preliminary study was attempt with combined 99mTc-ciprofloxacin and 99mTc-methylene diphosphonate (MDP) bone scintigraphy to improve diagnostic accuracy in differentiation of hip and knee prosthesis aseptic loosening and periposthetic joint infection. Methods. Inclusion criteria of patients for this study based on suspected periposthetic joint infection: painful prosthetic joint, restricted joint movements and increased value of erythrocyte sedimentation rate or levels of C-reactive protein. We examined 20 patients with implanted 14 hip and 6 knee prosthesis. All patients also underwent plain radiography of suspected joint. In all patients three-phase 99mTc-MDP bone scintigraphy was performed. Three to five days after bone scan, we performed scintigraphy using 99mTc-ciprofloxacin with calculation of accumulation index. Periposthetic joint infection was confirmed on the basis of microbiological findings. Results. Periprosthetic joint infection was confirmed in fourteen of twenty observed joints, in five of them was present the aseptic loosening and in one patient’s symptoms was not related to the prosthesis (poor biomechanics of prosthetic joints caused by weaknesses of muscle). Estimated sensitvity/specificity for 99mTc-MDP bone scintigraphy alone were 100%/17%; for 99mTc-ciprofloxacin scintigraphy were 85,7%/100%. For results obtained with combined assessment of both methods sensitvity and specificity were 92,3%, 83,3%. Our study confirmed high negative predictive value of 99mTc-MDP bone scan. Negative result of bone scan virtually excludes the possibility of periprosthetic infection. On the other hand, positive findings of 99mTc-MDP scintigraphy cannot with certainty confirm the infection. Conclusion. Combined 99mTc-MDP scintigraphy with 99mTc-ciprofloxacin scintigraphy, significantly increases the ability of differentiation aseptic loosening from periposthetic joint infection.