FDG-PET in patients with painful hip and knee arthroplasty: technical breakthrough or just more of the same

The two major complications of joint replacement are loosening and infection. A reliable differentiation between these pathological processes can be challenging because both are accompanied by similar clinical symptoms. Nuclear medicine examinations are frequently used in the management of patients with painful arthroplasty since they are not impaired by the metallic implants. This report evaluates the pooled data of the major publications in the English literature analyzing the accuracy of the triple-phase bone scan (TPBS), white blood cell imaging (WBC imaging) and positron emission tomography (PET). TPBS yielded the least favorable results with an accuracy of 80% for hip prostheses and 81% for knee arthroplasty. PET finished second with values of 89% (hip) and 83% (knee), respectively. WBC imaging exceeded the results of TPBS and PET, yielding values of 91% (hip) and 84% (knee). Although bested by WBC imaging, PET is still highly attractive since it combines several of the positive aspects of the two other methods. Its accuracy is only slightly lower than that of WBC imaging while at the same time it provides most of the comfort of the bone scan: only one injection, no processing of blood samples and the results are available within 4 h. In conclusion, the data indicate that PET is a highly effective imaging procedure for diagnosing complications of hip and knee arthroplasty. Its only limitations are the restricted availability and the costs. Whether the same holds true for PET/CT has yet to be proven. While the hybrid devices are highly beneficial in oncology, their use in the diagnosis of pathological processes of joint prostheses is questionable due to the CT artifacts induced by the metallic implants. WBC imaging on the other hand has to be considered as gold standard since it yields the highest accuracy of the three diagnostic approaches, especially when combined with bone marrow scintigraphy. In departments where neither the equipment nor the know-how for PET and WBC imaging is available, TPBS is a viable alternative. Compared to the other diagnostic approaches it yields a slightly lower accuracy, but excels in simplicity and cost-effectiveness. Especially in knee prostheses, it nearly reaches the accuracy of WBC imaging and PET (TPBS 81%, WBC imaging 84%, PET 83%).