Le protesi dolorose - percorsi diagnostici: bisogna conoscerli tutti

Summary Painful prosthesis are 9% of hip prosthesis, 20% of knee prosthesis and 10 to 16% of shoulder prosthesis. Pain can be immediate, following a first period of normality or can occur after long time. It can follow some significative event like a trauma or particular movement. We have to analyze pain characteristics, post-surgical history or previous infections. It is important to exclude other orthopedic pathologies that can simulate a painful prosthesis (referred pain, bad use of prosthesis, etc.). General clinical parameters have to be evaluated, they are important in the differential diagnosis of a painful prosthesis. The second step is clinical examination. First level instrumental exams are considered blood samples and traditional radiographs in two or more projections. After these steps diagnosis can be still difficult and a second level of instrumental exams have to be considered: scintigraphy, SPECT, FDG-PET and CT. In English literature arthrocentesis with microbiological colture is considered as a first step procedure. In our normal practice is not like this and is performed late in diagnostic investigations. Later studies show the existence of infections by Propionibacterium acnes in shoulder arthroplasty: this bacteria needs a longer incubation period (from 7 to 11 days). Only in knee arthroplasty is possible to perform an arthroscopy to diagnose pathologies like clunk syndrome, tethered patellar syndrome, malalignements, articular blocks or implant wear. If the suspect is related to soft tissues it is possible to perform an MRI using particular settings. Finally also surgeon experience is really important.